Uranus & Neptune May Keep “Hitler’s Acid” Stable Under Massive Pressure

Uranus and Neptune, the Solar System’s ice giant planets. Credit: Wikipedia Commons

“Hitler’s acid” is a colloquial name used to refer to Orthocarbonic acid – a name which was inspired from the fact that the molecule’s appearance resembles a swastika. As chemical compounds go, it is quite exotic, and chemists are still not sure how to create it under laboratory conditions.

But it just so happens that this acid could exist in the interiors of planets like Uranus and Neptune. According to a recent study from a team of Russian chemists, the conditions inside Uranus and Neptune could be ideal for creating exotic molecular and polymeric compounds, and keeping them under stable conditions.

The study was produced by researchers from the Moscow Institute of Physics and Technology (MIPT) and the Skolkovo Institute of Science and Technology (Skoltech). Titled “Novel Stable Compounds in the C-H-O Ternary System at High Pressure”, the paper describes how the high pressure environments inside planets could create compounds that exist nowhere else in the Solar System.

Professor Artem Oganov – a professor at Skoltech and the head of MIPT’s Computational Materials Discovery Lab – is the study’s lead author. Years back, he and a team of researchers developed the worlds most powerful algorithm for predicting the formation of crystal structures and chemical compounds under extreme conditions.

Known as the Universal Structure Predictor: Evolutionary Xtallography (UPSEX), scientists have since used this algorithm to predict the existence of substances that are considered impossible in classical chemistry, but which could exist where pressures and temperatures are high enough – i.e. the interior of a planet.

With the help of Gabriele Saleh, a postdoc member of MIPT and the co-author of the paper, the two decided to use the algorithm to study how the carbon-hydrogen-oxygen system would behave under high pressure. These elements are plentiful in our Solar System, and are the basis of organic chemistry.

Until now, it has not been clear how these elements behave when subjected to extremes of temperature and pressure. What they found was that under these types of extreme conditions, which are the norm inside gas giants, these elements form some truly exotic compounds.

As Prof. Oganov explained in a MIPT press release:

“The smaller gas giants – Uranus and Neptune – consist largely of carbon, hydrogen and oxygen. We have found that at a pressure of several million atmospheres unexpected compounds should form in their interiors. The cores of these planets may largely consist of these exotic materials.”

Under normal pressure – i.e. what we experience here on Earth (100 kPa) – any carbon, hydrogen or oxygen compounds (with the exception of methane, water and CO²) are unstable. But at pressures in the range 1 to 400 GPa (10,000 to 4 million times Earth normal), they become stable enough to form several new substances.

These include carbonic  acid, orthocarbonic acid (Hitler’s acid) and other rare compounds. This was a very unusual find, considering that these chemicals are unstable under normal pressure conditions. In carbonic acid’s case, it can only remain stable when kept at very low temperatures in a vacuum.

At pressures of 314 GPa, they determined that carbonic acid (H²CO³) would react with water to form orthocarbonic acid (H4CO4). This acid is also extremely unstable, and so far, scientists have not yet been able to produce it in a laboratory environment.

This research is of considerable importance when it comes to modelling the interior of planets like Uranus and Neptune. Like all gas giants, the structure and composition of their interiors have remained the subject of speculation due to their inaccessible nature. But it could also have implications in the search for life beyond Earth.

According to Oganov and Saleh, the interiors of many moons that orbit gas giants (like Europa, Ganymede and Enceladus) also experience these types of pressure conditions. Knowing that these kinds of exotic compounds could exist in their interiors is likely to change what scientist’s think is going on under their icy surfaces.

“It was previously thought that the oceans in these satellites are in direct contact with the rocky core and a chemical reaction took place between them,” said Oganov. “Our study shows that the core should be ‘wrapped’ in a layer of crystallized carbonic acid, which means that a reaction between the core and the ocean would be impossible.”

For some time, scientists have understood that at high temperatures and pressures, the properties of matter change pretty drastically. And while here on Earth, atmospheric pressure and temperatures are quite stable (just the way we like them!), the situation in the outer Solar System is much different.

By modelling what can occur under these conditions, and knowing what chemical buildings blocks are involved, we could be able to determine with a fair degree of confidence what the interior’s of inaccessible bodies are like. This will give us something to work with when the day comes (hopefully soon) that we can investigate them directly.

Who knows? In the coming years, a mission to Europa may find that the core-mantle boundary is not a habitable environment after all. Rather than a watery environment kept warm by hydrothermal activity, it might instead by a thick layer of chemical soup.

Then again, we may find that the interaction of these chemicals with geothermal energy could produce organic life that is even more exotic!

Further Reading: MIPT, Nature Scientific Reports

The post Uranus & Neptune May Keep “Hitler’s Acid” Stable Under Massive Pressure appeared first on Universe Today.

Friendly Giants Have Cozy Habitable Zones Too

Artist's impression of a red giant star. Credit:NASA/ Walt Feimer

It is an well-known fact that all stars have a lifespan. This begins with their formation, then continues through their Main Sequence phase (which constitutes the majority of their life) before ending in death. In most cases, stars will swell up to several hundred times their normal size as they exit the Main Sequence phase of their life, during which time they will likely consume any planets that orbit closely to them.

However, for planets that orbit the star at greater distances (beyond the system’s “Frost Line“, essentially), conditions might actually become warm enough for them to support life. And according to new research which comes from the Carl Sagan Institute at Cornell University, this situation could last for some star systems into the billions of years, giving rise to entirely new forms of extra-terrestrial life!

In approximately 5.4 billion years from now, our Sun will exit its Main Sequence phase. Having exhausted the hydrogen fuel in its core, the inert helium ash that has built up there will become unstable and collapse under its own weight. This will cause the core to heat up and get denser, which in turn will cause the Sun to grow in size and enter what is known as the Red Giant-Branch (RGB) phase of its evolution.

This period will begin with our Sun becoming a subgiant, in which it will slowly double in size over the course of about half a billion years. It will then spend the next half a billion years expanding more rapidly, until it is 200 times its current size and several thousands times more luminous. It will then officially be a red giant star, where it will measure approximately 2 AU in diameter, thus reaching beyond Mars’ current orbit.

As we explored in a previous article, planet Earth will not survive our Sun becoming a Red Giant – nor will Mercury, Venus or Mars. But beyond the “Frost Line”, where it is cold enough that volatile compounds – such as water, ammonia, methane, carbon dioxide and carbon monoxide – remain in a frozen state, the remain gas giants, ice giants, and dwarf planets will survive. Not only that, but a massive thaw will set in.

In short, when the star expands, its “habitable zone” will likely do the same, encompassing the orbits of Jupiter and Saturn. When this happens, formerly uninhabitable places – like the Jovian and Cronian moons – could suddenly become inhabitable. The same holds true for many other stars in the Universe, all of which are fated to become Red Giants as they near the end of their lifespans.

However, when our Sun reaches its Red Giant Branch phase, it is only expected to have 120 million years of active life left. This is not quite enough time for new lifeforms to emerge, evolve and become truly complex (i.e. like humans and other species of mammals). But according to a recent research study that appeared in The Astrophysical Journal – titled “Habitable Zone of Post-Main Sequence Stars” – some planets may be able to remain habitable around other red giant stars in our Universe for much longer – up to 9 billion years or more in some cases!

To put that in perspective, nine billion years is close to twice the current age of Earth. So assuming that the worlds in question also have the right mix of elements, they will have ample time to give rise to new and complex forms of life. The study’s lead author, Professor Lisa Kaltennegeris, is also the director of the Carl Sagan Institute. As such, she is no stranger to searching for life in other parts of the Universe. As she explained in a Cornell University press release, which coincided with the publication of the study:

“When a star ages and brightens, the habitable zone moves outward and you’re basically giving a second wind to a planetary system. Currently objects in these outer regions are frozen in our own solar system, like Europa and Enceladus – moons orbiting Jupiter and Saturn… Long after our own plain yellow sun expands to become a red giant star and turns Earth into a sizzling hot wasteland, there are still regions in our solar system – and other solar systems as well – where life might thrive.”

Using existing models of stars and their evolution – i.e. one-dimensional radiative-convective climate and stellar evolutionary models – for their study, Kaltenegger and Ramirez were able to calculate the distances of the habitable zones (HZ) around a series of post-Main Sequence (post-MS) stars. Ramses M. Ramirez – a research associate at the Carl Sagan Institute and co-author of the paper – explained the research process to Universe Today via email:

“We used stellar evolutionary models that tell us how stellar quantities, mainly the brightness, radius, and temperature all change with time as the star ages through the red giant phase. We also used a  climate model to then compute how much energy each star is outputting at the boundaries of the habitable zone. Knowing this and the stellar brightness mentioned above, we can compute the distances to these habitable zone boundaries.”

At the same time, they considered how this kind of stellar evolution could effect the atmosphere of the star’s planets. As a star expands, it loses mass and ejects it outward in the form of solar wind. For planets that orbit close to a star, or those that have low surface gravity, they may find some or all of their atmospheres blasted away. On the other hand, planets with sufficient mass (or positioned at a safe distance) could maintain most of their atmospheres.

“The stellar winds from this mass loss erodes planetary atmospheres, which we also compute as a function of time,” said Ramirez. “As the star loses mass, the solar system conserves angular momentum by moving outwards. So, we also take into account how the orbits move out with time.” By using models that incorporated the rate of stellar and atmospheric loss during the Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) phases of star, they were able to determine how this would play out for planets that ranged in size from super-Moons to super-Earths.

What they found was that a planet can stay in a post-HS HZ for eons or more, depending on how hot the star is, and figuring for metallicities that are similar to our Sun’s. As Ramirez explained:

“The main result is that the maximum time that a planet can remain in this red giant habitable zone of hot stars is 200 million years. For our coolest star (M1), the maximum time a planet can stay within this red giant habitable zone is 9 billion years. Those results assume metallicity levels similar to those of our Sun. A star with a higher percentage of metals takes longer to fuse the non-metals (H, He..etc) and so these maximum times can increase some more, up to about a factor of two.”

Within the context of our Solar System, this could mean that in a few billion years, worlds like Europa and Enceladus (which are already suspected of having life beneath their icy surfaces) might get a shot at becoming full-fledged habitable worlds. As Ramirez summarized beautifully:

“This means that the post-main-sequence is another potentially interesting phase of stellar evolution from a habitability standpoint. Long after the inner system of planets have been turned into sizzling wastelands by the expanding, growing red giant star, there could be potentially habitable abodes farther away from the chaos. If they are frozen worlds, like Europa, the ice would melt, potentially unveiling any preexisting life. Such pre-existing life may be detectable by future missions/telescopes looking for atmospheric biosignatures.”

But perhaps the most exciting take-away from their research study was their conclusion that planets orbiting within their star’s post-MS habitable zones would be doing so at distances that would make them detectable using direct imaging techniques. So not only are the odds of finding life around older stars better than previously thought, we should have no trouble in spotting them using current exoplanet-hunting techniques!

It is also worth noting that Kaltenegger and Dr. Ramirez have submitted a second paper for publication, in which they provide a list of 23 red giant stars within 100 light-years of Earth. Knowing that these stars, all of which are in our stellar neighborhood, could have life-sustaining worlds within their habitable zones should provide additional opportunities for planet hunters in the coming years.

And be sure to check out this video from Cornellcast, where Prof. Kaltenegger shares what inspires her scientific curiosity and how Cornell’s scientists are working to find proof of extra-terrestrial life.


Further Reading: The Astrophysical Journal

The post Friendly Giants Have Cozy Habitable Zones Too appeared first on Universe Today.

Enceladus’ Jets Selectively Power-Up Farther From Saturn

Icy water vapor geysers erupting from fissures on Enceladus. Credit: NASA/JPL

A crowning achievement of the Cassini mission to Saturn is the discovery of water vapor jets spraying out from Enceladus‘ southern pole. First witnessed by the spacecraft in 2005, these icy geysers propelled the little 515-kilometer-wide moon into the scientific spotlight and literally rewrote the mission’s objectives. After 22 flybys of Enceladus during its nearly twelve years in orbit around Saturn, Cassini has gathered enough data to determine that there is a global subsurface ocean of salty liquid water beneath Enceladus’ frozen crust—an ocean that gets sprayed into space from long “tiger stripe” fissures running across the moon’s southern pole.  Now, new research has shown that at least some of the vapor jets get a boost in activity when Enceladus is farther from Saturn.

By measuring the changes in brightness of a distant background star as Enceladus’ plumes passed in front of it in March 2016, Cassini observed a significant increase in the amount of icy particles being ejected by one particular jet source.

Named “Baghdad 1,” the jet went from contributing 2% of the total vapor content of the entire plume area to 8% when Enceladus was at the farthest point in its slightly-eccentric orbit around Saturn. This small yet significant discovery indicates that, although Enceladus’ plumes are reacting to morphological changes to the moon’s crust due to tidal flexing, it’s select small-scale jets that are exhibiting the most variation in output (rather than a simple, general increase in outgassing across the full plumes.)

“How do the tiger stripe fissures respond to the push and pull of tidal forces as Enceladus goes around its orbit to explain this difference? We now have new clues!” said Candice Hansen, senior scientist at the Planetary Science Institute and lead planner of the study. “It may be that the individual jet sources along the tiger stripes have a particular shape or width that responds most strongly to the tidal forcing each orbit to boost more ice grains at this orbital longitude.”

The confirmation that Enceladus shows an increase in overall plume output at farther points from Saturn was first made in 2013.

Whether this new finding means that the internal structure of the fissures is different than what scientists have suspected or some other process is at work either within Enceladus or in its orbit around Saturn still remains to be determined.

“Since we can only see what’s going on above the surface, at the end of the day, it’s up to the modelers to take this data and figure out what’s going on underground,” said Hansen.

Sources: Planetary Science Institute and NASA/JPL

The post Enceladus’ Jets Selectively Power-Up Farther From Saturn appeared first on Universe Today.

How Do We Terraform Saturn’s Moons?

The  moons of Saturn, from left to right: Mimas, Enceladus, Tethys, Dione, Rhea; Titan in the background; Iapetus (top) and irregularly shaped Hyperion (bottom). Some small moons are also shown. All to scale. Credit: NASA/JPL/Space Science Institute

Continuing with our “Definitive Guide to Terraforming“, Universe Today is happy to present our guide to terraforming Saturn’s Moons. Beyond the inner Solar System and the Jovian Moons, Saturn has numerous satellites that could be transformed. But should they be?

Around the distant gas giant Saturn lies a system of rings and moons that is unrivaled in terms of beauty. Within this system, there is also enough resources that if humanity were to harness them – i.e. if the issues of transport and infrastructure could be addressed – we would be living in an age a post-scarcity. But on top of that, many of these moons might even be suited to terraforming, where they would be transformed to accommodate human settlers.

As with the case for terraforming Jupiter’s moons, or the terrestrial planets of Mars and Venus, doing so presents many advantages and challenges. At the same time, it presents many moral and ethical dilemmas. And between all of that, terraforming Saturn’s moons would require a massive commitment in time, energy and resources, not to mention reliance on some advanced technologies (some of which haven’t been invented yet).

The Cronian Moons:

All told, Saturn system is second only to Jupiter in terms of its number of satellites, with 62 confirmed moons. Of these, the largest moons are divided into two groups: the inner large moons (those that orbit close to Saturn within its tenuous E-Ring) and the outer large moons (those beyond the E-Ring). They are, in order of distance from Saturn, Mimas, Enceladus, Tethys, Dione, Rhea, Titan, and Iapetus.

These moons are all composed primarily of water ice and rock, and are believed to be differentiated between a rocky core and an icy mantle and crust. Among them, Titan is appropriately named, being the largest and most massive of all the inner or outer moons (to the point that it is larger and more massive than all the others combined).

In terms of their suitability for human habitation, each one present its own share of pros and cons. These include their respective sizes and compositions, the presence (or absence) of an atmosphere, gravity, and the availability of water (in ice form and subsurface oceans), And in the end, it is the presence of these moons around Saturn that makes the system an attractive option for exploration and colonization.

As aerospace engineer and author Robert Zubrin stated in his book Entering Space: Creating a Spacefaring Civilization, Saturn, Uranus and Neptune could one day become “the Persian Gulf of the Solar System”, due to their abundance of hydrogen and other resources. Of these systems, Saturn would be the most important, thanks to its relative proximity to Earth, low radiation, and excellent system of moons.


Possible Methods:

Terraforming one or more of Jupiter’s moons would be a relatively straightforward process. In all cases, this would involve heating the surfaces through various means – like thermonuclear devices, impacting the surface with asteroids or comets, or focusing sunlight with orbital mirrors – to the point that surface ice would sublimate, releasing water vapor and volatiles (such as ammonia and methane) to form an atmosphere.

However, due to the comparatively low amounts of radiation coming from Saturn (compared to Jupiter), these atmospheres would have to be converted to a nitrogen-oxygen rich environment through means other than radiolysis. This could be done by using the same orbital mirrors to focus sunlight onto the surfaces, triggering the creation of oxygen and hydrogen gas from water ice through photolysis. While the oxygen would remain closer to the surface, the hydrogen would escape into space.

The presence of ammonia in many of the moon’s ices would also mean that a ready supply of nitrogen could be created to act as a buffer gas. By introducing specific strains of bacteria into the newly created atmospheres – such as the Nitrosomonas, Pseudomonas and Clostridium species – the sublimated ammonia could be converted into nitrites (NO²-) and then nitrogen gas.

Another option would be to employ a process known as “paraterraforming” – where a world is enclosed (in whole or in part) in an artificial shell in order to transform its environment. In the case of the Cronian moons, this would involve building large “Shell Worlds” to encase them, keeping the newly-created atmospheres inside long enough to effect long-term changes.

Within this shell, a Cronian moon could have its temperatures slowly raised, the water-vapor atmospheres could be exposed to ultra-violet radiation from internal UV lights, bacteria could then be introduced, and other elements added as needed. Such a shell would ensure that the process of creating of an atmosphere could be carefully controlled and none would be lost before the process was complete.


With a diameter of 396 km and a mass of 0.4×1020 kg, Mimas is the smallest and least massive of these moons. It is ovoid in shape and orbits Saturn at a distance of 185,539 km with an orbital period of 0.9 days. The low density of Mimas, which is estimated to be 1.15 g/cm³ (just slightly higher than that of water), indicates that it is composed mostly of water ice with only a small amount of rock.

As a result of this, Mimas is not a good candidate for terraforming. Any atmosphere that could be created by melting its ice would likely be lost to space. In addition, its low density would mean that the vast majority of the planet would be ocean, with only a small core of rock. This, in turn,  makes any plans to settle on the surface impractical.


Enceladus, meanwhile, has a diameter of 504 km, a mass of 1.1×1020 km and is spherical in shape. It orbits Saturn at a distance of 237,948 km and takes 1.4 days to complete a single orbit. Though it is one of the smaller spherical moons, it is the only Cronian moon that is geologically active – and one of the smallest known bodies in the Solar System where this is the case. This results in features like the famous “tiger stripes” – a series of continuous, ridged, slightly curved and roughly parallel faults within the moon’s southern polar latitudes.

Large geysers have also been observed in the southern polar region that periodically release plumes of water ice, gas and dust which replenish Saturn’s E-ring. These jets are one of several indications that Enceladus has liquid water beneath it’s icy crust, where geothermal processes release enough heat to maintain a warm water ocean closer to its core.

The presence of a warm-water liquid ocean makes Enceladus an appealing candidate for terraforming. The composition of the plumes also indicate that the subsurface ocean is salty, and contains organic molecules and volatiles. These include ammonia and simple hydrocarbons like methane, propane, acetylene, and formaldehyde.

Ergo, once the icy surface was sublimated, these compounds would be released, triggering a natural greenhouse effect. Combined with photolysis, radiolysis, and bacteria, the water vapor and ammonia could also be converted to a nitrogen-oxygen atmosphere. The higher density of Enceladus (~1.61 g/cm3) indicates that it has a larger than average silicate and iron core (for a Cronian moon). This could provide materials for any operations on the surface, and also means that if the surface ice were to be sublimated, Enceladus would not consist mainly of incredibly deep oceans.

However, the presence of this liquid salt-water ocean, organic molecules and volatiles also indicates that the interior of Enceladus experiences hydrothermal activity. This energy source, combined with organic molecules, nutrients, and the prebiotic conditions for life, means that is possible that Enceladus is home to extraterrestrial life.

Much like Europa and Ganymede, these would probably take the form of extremophiles living in environments similar to Earth’s deep-ocean hydrothermal vents. As a result, terraforming Enceladus could result in the destruction of the natural life cycle on the moon, or release life forms that could prove harmful to any future colonists.


At 1066 km in diameter, Tethys is the second-largest of Saturn’s inner moons and the 16th-largest moon in the Solar System. The majority of its surface is made up of heavily cratered and hilly terrain and a smaller and smoother plains region. Its most prominent features are the large impact crater of Odysseus, which measures 400 km in diameter, and a vast canyon system named Ithaca Chasma – which is concentric with Odysseus and measures 100 km wide, 3 to 5 km deep and 2,000 km long.

With a mean density of 0.984 ± 0.003 grams per cubic centimeter, Tethys is believed to be comprised almost entirely of water ice. It is not currently known whether Tethys is differentiated into a rocky core and ice mantle. However, given the fact that rock accounts for less 6% of its mass, a differentiated Tethys would have a core that did not exceed 145 km in radius. On the other hand, Tethys’ shape – which resembles that of a triaxial ellipsoid – is consistent with it having a homogeneous interior (i.e. a mix of ice and rock).


Because of this, Tethys is also off the terraforming list. If in fact it has a tiny rocky interior, treating the surface to heating would mean that the vast majority of the moon would melt and be lost to space. Alternately, if the interior is a homogeneous mix of rock and ice, then all that would remain after melting occurred would be a cloud of debris.


With a diameter and mass of 1,123 km and 11×1020 kg, Dione is the fourth largest moon of Saturn. The majority of Dione’s surface is heavily cratered old terrain, with craters that measure up to 250 km in diameter. With an orbital distance of 377,396 km from Saturn, the moon takes 2.7 days to complete a single rotation.

Dione’s mean density of about 1.478 g/cm³ indicates that it is composed mainly of water ice, with a small remainder likely consisting of a silicate rock core. Dione also has a very thin atmosphere of oxygen ions (O+²), which was first detected by the Cassini space probe in 2010. While the source of this atmosphere is currently unknown, it is believed that it is the product of radiolysis, where charged particles from Saturn’s radiation belt interact with water ice on the surface to create hydrogen and oxygen (similar to what happens on Europa).

Because of this tenuous atmosphere, it is already known that sublimating Dione’s ice could produce an oxygen atmosphere. However, it is not currently known if Dione possesses the right combination of volatilizes to ensure that nitrogen gas can be created, or that a greenhouse effect will be triggered. Combined with Dione’s low density, this makes it an unattractive target for terraforming.


Measuring 1,527 km in diameter and 23×1020 kg in mass, Rhea is the second largest of Saturn’s moons and the ninth largest moon of the Solar System. With an orbital radius of 527,108 km, it is the fifth-most distant of the larger moons, and takes 4.5 days to complete an orbit. Like other Cronian satellites, Rhea has a rather heavily cratered surface, and a few large fractures on its trailing hemisphere.

With a mean density of about 1.236 g/cm³, Rhea is estimated to be composed of 75% water ice (with a density of roughly 0.93 g/cm³) and 25% of silicate rock (with a density of around 3.25 g/cm³). This low density means that although Rhea is the ninth-largest moon in the Solar System, it is also the tenth-most massive.

In terms of its interior, Rhea was originally suspected of being differentiated between a rocky core and an icy mantle. However, more recent measurements would seem to indicate that Rhea is either only partly differentiated, or has a homogeneous interior – likely consisting of both silicate rock and ice together (similar to Jupiter’s moon Callisto).

Models of Rhea’s interior also suggest that it may have an internal liquid-water ocean, similar to Enceladus and Titan. This liquid-water ocean, should it exist, would likely be located at the core-mantle boundary, and would be sustained by the heating caused from the decay of radioactive elements in its core. Interior ocean or not, the fact that the vast majority of the moon is composed of ice water makes it an unattractive option for terraforming.


As already noted, Titan is the largest of the Cronian moons. In fact, at 5,150 km in diameter, and 1,350×1020 kg in mass, Titan is Saturn’s largest moon and comprises more than 96% of the mass in orbit around the planet. Based on its bulk density of 1.88 g/cm3, Titan’s composition is half water ice and half rocky material – most likely differentiated into several layers with a 3,400 km rocky center surrounded by several layers of icy material.

It is also the only large moon to have its own atmosphere, which is cold, dense, and is the only nitrogen-rich dense atmosphere in the Solar System aside from Earth’s (with small amounts of methane). Scientists have also noted the presence of polycyclic aromatic hydrocarbons in the upper atmosphere, as well as methane ice crystals. Another thing Titan has in common with Earth, unlike every other moon and planet in the Solar System, is atmospheric pressure. On the surface of Titan, the air pressure is estimated to be around 1.469 bars (1.45 times that of Earth).

The surface of Titan, which is difficult to observe due to persistent atmospheric haze, shows only a few impact craters, evidence of cryovolcanoes, and longitudinal dune fields that were apparently shaped by tidal winds. Titan is also the only body in the Solar System beside Earth with bodies of liquid on its surface, in the form of methane–ethane lakes in Titan’s north and south polar regions.

With an orbital distance of 1,221,870 km, it is the second-farthest large moon from Saturn, and completes a single orbit every 16 days. Like Europa and Ganymede, it is believed that Titan has a subsurface ocean made of water mixed with ammonia, which can erupt to the surface of the moon and lead to cryovolcanism. The presence of this ocean, plus the prebiotic environment on Titan, has led some to suggest that life may exist there as well.

Such life could take the form of microbes and extremophiles in the interior ocean (similar to what is thought to exist on Enceladus and Europa), or could take the even more extreme form of methanogenic life forms. As has been suggested, life could exist in Titan’s lakes of liquid methane just as organisms on Earth live in water. Such organisms would inhale dihydrogen (H²) in place of oxygen gas (O²), metabolize it with acetylene instead of glucose, and then exhale methane instead of carbon dioxide.

However, NASA has gone on record as stating that these theories remain entirely hypothetical. So while the prebiotic conditions that are associated with organic chemistry exist on Titan, life itself may not. However, the existence of these conditions remains a subject of fascination among scientists. And since its atmosphere is thought to be analogous to Earth’s in the distant past, proponents of terraforming emphasize that Titan’s atmosphere could be converted in much the same way.

Beyond that, there are several reasons why Titan is a good candidate. For starters, it possess an abundance of all the elements necessary to support life (atmospheric nitrogen and methane), liquid methane, and liquid water and ammonia. Additionally, Titan has an atmospheric pressure one and a half times that of Earth, which means that the interior air pressure of landing craft and habitats could be set equal or close to the exterior pressure.

This would significantly reduce the difficulty and complexity of structural engineering for landing craft and habitats compared with low or zero pressure environments such as on the Moon, Mars, or the Asteroid Belt. The thick atmosphere also makes radiation a non-issue, unlike with other planets or Jupiter’s moons.


And while Titan’s atmosphere does contain flammable compounds, these only present a danger if they are mixed with sufficient enough oxygen – otherwise, combustion cannot be achieved or sustained. Finally, the very high ratio of atmospheric density to surface gravity also greatly reduces the wingspan needed for aircraft to maintain lift.

With all these things going for it, turning Titan into a livable world would be feasible given the right conditions. For starters, orbital mirrors could be used to direct more sunlight onto the surface. Combined with the moon’s already dense and greenhouse gas-rich atmosphere, this would lead to a considerable greenhouse effect that would melt the ice and release water vapor into the air.

Once again, this could be converted into a nitrogen/oxygen-rich mix, and more easily than with other Cronian moons since the atmosphere is already very rich in nitrogen. The presence of nitrogen, methane and ammonia could also be used to produce chemical fertilizers to grow food. However, the orbital mirrors would need to remain in place in order to ensure the environment did not become extremely cold again and revert to an icy state.


At 1,470 km in diameter and 18×1020 kg in mass, Iapetus is the third-largest of Saturn’s large moons. And at a distance of 3,560,820 km from Saturn, it is the most distant of the large moons, and takes 79 days to complete a single orbit. Due to its unusual color and composition – its leading hemisphere is dark and black whereas its trailing hemisphere is much brighter – it is often called the “yin and yang” of Saturn’s moons.


With an average distance (semi major axis) of 3,560,820 km, Iapetus takes 79.32 days to complete an single orbit of Saturn. Despite being Saturn’s third-largest moon, Iapetus orbits much farther from Saturn than its next closest major satellite (Titan). Like many of Saturn’s moons – particularly Tethys, Mimas and Rhea – Iapetus has a low density (1.088 ± 0.013 g/cm³) which indicates that it is composed primary of water ice and only about 20% rock.

But unlike most of Saturn’s larger moons, its overall shape is neither spherical or ellipsoid, instead consisting of flattened poles and a bulging waistline. Its large and unusually high equatorial ridge also contributes to its disproportionate shape. Because of this, Iapetus is the largest known moon to not have achieved hydrostatic equilibrium. Though rounded in appearance, its bulging appearance disqualifies it from being classified as spherical.

Because of this, Iapetus is not a likely contender for terraforming. If in fact its surface were melted, it too would be an ocean world with unrealistically deep seas, and this water would likely be lost to space.

Potential Challenges:

To break it down, only Enceladus and Titan appear to be viable candidates for terraforming. However, in both cases, the process of turning them into habitable worlds where human beings could exist without the need for pressurized structures or protective suits would be a long and costly one. And much like terraforming the Jovian moons, the challenges can be broken down categorically:

  1. Distance
  2. Resources and Infrastructure
  3. Hazards
  4. Sustainability
  5. Ethical Considerations

In short, while Saturn may be abundant in resources and closer to Earth than either Uranus or Neptune, its really very far. On average, Saturn is approximately 1,429,240,400,000 kms away from Earth (or ~8.5 AU the equivalent of eight and a half times the average distance between the Earth and the Sun). To put that in perspective, it took the Voyager 1 probe roughly thirty-eight months to reach the Saturn system from Earth. For crewed spacecraft, carrying colonists and all the equipment needed to terraform the surface, it would take considerably longer to get there.

These ships, in order to avoid being overly large and expensive, would need to rely on cryogenics or hibernation-related technology in order to be smaller, faster and more cost-effective. While this sort of technology is being investigated for crewed missions to Mars, it is still very much in the research and development phase. What’s more, a large fleet of robotic spaceships and support craft would also be needed to build the orbital mirrors, capture asteroids or debris to use as impactors, and provide logistical support to crewed spaceships.

Unlike the crewed vessels, which could keep crews in stasis until their arrival, these ships would need to have advanced propulsion systems to ensure that they were able to make the trips to and from the Cronian moons in a realistic amount of time. All of this, in turn, raises the crucial issue of infrastructure. Basically, any fleet operating between Earth and Saturn would require a network of bases between here and there to keep them supplied and fueled.

So really, any plans to terraform Saturn’s moons would have to wait upon the creation of permanent bases on the Moon, Mars, the Asteroid Belt, and the Jovian moons. In addition, building orbital mirrors would require considerable amounts of minerals and other resources, many of which could be harvested from the Asteroid Belt or from Jupiter’s Trojans.

This process would be punitively expensive by current standards and (again) would require a fleet of ships with advanced drive systems. And paraterraforming using Shell Worlds would be no different, requiring multiple trips to and from the Asteroid Belt, hundreds (if not thousands) of construction and support craft, and all the necessary bases in between.

And while radiation is not a major threat in the Cronian system (unlike around Jupiter), the moons have been subject to a great deal of impacts over the course of their history. As a result, any settlements built on the surface would likely need additional protection in orbit, like a string of defensive satellites that could redirect comets and asteroids before they reached orbit.

Fourth, terraforming Saturn’s moons presents the same challenges as Jupiter’s. Namely, every moon that was terraformed would be an ocean planet And whereas most of Saturn’s moons are untenable due to their high concentrations of water ice, Titan and Enceladus are not that much better off. In fact, if all of Titan’s ice were melted, including the layer that is believed to sit beneath its interior ocean, its sea level would be up to 1700 km in depth!

Not only that, but this sea would surround a hydrous core, which would likely make the planet unstable. Enceladus would not fair any better, as gravity measurements by Cassini have shown that the density of the core is low, indicating that the core contains water in addition to silicates. So in addition to a deep ocean on its surface, its core might also be unstable.

And last, there are the ethical considerations. If both Enceladus and Titan are home to extra-terrestrial life, than any efforts to alter their environments could result in their destruction. Barring that, melting the surface ice could cause any indigenous life forms to proliferate and mutate, and exposure to them could prove to be a health hazard for human settlers.


Once again, when faced with all of these considerations, one is forced to ask, “why bother?” Why bother altering the natural environment of the Cronian moons when we could settle on them as is, and use their natural resources to usher in an age of post-scarcity? Quite literally, there is enough water ice, volatiles, hydrocarbons, organic molecules, and minerals in the Saturn system to keep humanity supplied indefinitely.

What’s more, without the effects of terraforming, settlements on Titan and Enceladus would probably be a lot more tenable. We could also fathom building settlements on the moons of Tethys, Dione, Rhea, and Iapetus as well, which would prove much more beneficial in terms of being able to harness the system’s resources.

And, as with Jupiter’s moons of Europa, Ganymede, and Callisto, foregoing the act of terraforming would mean there would be an abundant supply of resources that could be used to terraform other places – namely, Venus and Mars. As has been argued many times over, the abundance of methane, ammonia, and water ices in the Cronian system would be very useful in helping to turn “Earths twins” into “Earth-like” planets.

Once again, it would seem that the answer to the question “can/should we?” is a disappointing no.

We have written many interesting articles about terraforming here at Universe Today. Here’s The Definitive Guide To Terraforming, How Do We Terraform Mars?, How Do We Terraform Venus?, How Do We Terraform the Moon?, and How Do We Terraforming Jupiter’s Moons?

We’ve also got articles that explore the more radical side of terraforming, like Could We Terraform Jupiter?, Could We Terraform The Sun?, and Could We Terraform A Black Hole?

Astronomy Cast also has good episodes on the subject, like Episode 61: Saturn’s Moons.

For more information, check out NASA’s Solar System Exploration page on Saturn’s Moons and the Cassini mission page.

And if you like the video, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

The post How Do We Terraform Saturn’s Moons? appeared first on Universe Today.

NASA Invests In Radical Game-Changing Concepts For Exploration

Artist's concept of some of the Phase I winners of the 2016 NIAC program. Credit: NASA

Every year, the NASA Innovative Advanced Concepts (NIAC) program puts out the call to the general public, hoping to find better or entirely new aerospace architectures, systems, or mission ideas. As part of the Space Technology Mission Directorate, this program has been in operation since 1998, serving as a high-level entry point to entrepreneurs, innovators and researchers who want to contribute to human space exploration.

This year, thirteen concepts were chosen for Phase I of the NIAC program, ranging from reprogrammed microorganisms for Mars, a two-dimensional spacecraft that could de-orbit space debris, an analog rover for extreme environments, a robot that turn asteroids into spacecraft, and a next-generation exoplanet hunter. These proposals were awarded $100,000 each for a nine month period to assess the feasibility of their concept.

Of the thirteen proposals, four came from NASA’s own Jet Propulsion Laboratory, with the remainder coming either from other NASA bodies, private research institutions, universities and aerospace companies from around the country. Taken as a whole, these ideas serve to illustrate of the kinds of missions NASA intends to purse in the coming years, as well as the cutting-edge technology they hope to leverage to make them happen.

As Jason Derleth, the Program Executive of the NASA Innovative Advanced Concepts (NIAC) Program, told Universe Today via email:
“The NASA Innovative Advanced Concepts (NIAC) program is one of NASA’s early stage technology development programs. At NIAC, we concentrate on mission studies that demonstrate the benefit of new technologies that are on the very edge of science fiction, but while still remaining firmly rooted in science fact.”

Those proposals that are deemed feasible will be eligible to apply for a Phase II award, which consists of up to $500,000 of additional funding and two more years of concept development. And as with previous years, those concepts that were selected for Phase I were highly representative of NASA’s research and exploration goals, which include missions beyond Low-Earth Orbit (LEO) to near-Earth asteroids, Mars, Venus, and the outer Solar System.

“All 13 of these new NIAC studies are innovative, interesting, and groundbreaking in their own fields,” said Derleth. “There are a mix of NASA researchers, universities, and industry-led studies, all chosen by a process meant to identify and fund the ones with the most impact to our efforts to push the envelope in aerospace technology.”

For example, the Jet Propulsion Laboratory’s submissions included a mission that would send a probe back to Venus to explore its atmosphere in greater depth. Known as the Venus Interior Probe Using In-situ Power and Propulsion (VIP-INSPR), this small solar-powered craft would use hydrogen harvested from Venus’ atmosphere – which would be isolated through electrolysis – for altitude control at high altitudes (in a balloon), and as a back-up power source at lower altitudes.

Within Venus’ atmosphere, solar power is no longer a viable option (due to low solar intensity) and primary batteries tend to survive for only an hour or two. What’s more, radioisotope thermoelectric generators (RTGs) – like those that powered the Voyager missions – were dismissed as inefficient for the purposes of a Venus probe.

VIP-INSPR will address these problems by refilling hydrogen on one end of its structure and providing power on the other, thus enabling sustained exploration of the Venusian atmosphere. This is a creative solution to addressing the challenge of keeping a probe powered as it enters Venus’ thick atmosphere, and is sure to have applications beyond the exploration of just Venus.

Similarly, another concept from the JPL involves sending a next-generation rover to Venus, known as the Automaton Rover for Extreme Environments (AREE). This rover seeks to build on the accomplishments of the Soviet Venera and Vega programs, which were the only missions to ever successfully land rovers on Venus’ hostile surface.

Unfortunately, those probes that successfully landed only survived for 23 to 127 minutes before their electronics failed and they could no longer send back information. But by using an entirely mechanical design and a hardened metal structure, the AREE could survive for weeks or months, long enough to collect and return valuable long-term scientific data.

In essence, they proposed reverting back to an ancient concept, using analog gears instead of electronics to enable exploration of the most extreme environment within the Solar System. Beyond Venus, such a probe would also be useful in such hostile environments as Mercury, Jupiter’s radiation belt, and the interior of gas giants, within volcanoes, and perhaps even the mantle of Earth.

Then there is the Icy-moon Cryovolcano Explorer (ICE), another JPL submission which, it is hoped, will one-day explore icy, volcanically-active environments like Europa and Enceladus. The concept of an autonomous underwater vehicle (AUV) is something that has been explored a lot in recent years, but the task of getting such a vehicle to Jupiter or Saturn and beneath the surface of one of their moons presents many challenges.

The ICE team addresses these by designing a surface-to-subsurface robotic system that consists of three modules. The first is the Surface Module (SM), which will remain on the surface after the craft has landed, providing power and communications with Earth. Meanwhile, the Descent Module (DM) will use a combination of roving, climbing, rappelling and hopping to descend into a volcanic vent. Once it reaches the subsurface ocean, it will launch the AUV module, which will explore the subsurface ocean environment and seek out any signs of life.

Last, but not least, the JPL also proposed the Electostatic-Glider (E-Glider) for this year’s NIAC program. This proposal calls for the creation of an active, electrostatically-powered spacecraft to explore airless bodies. Basically, near the surface of comets, asteroids and the Moon, the environment is both airless and full of electrically-charged dust, due to the Sun’s photoelectric bombardment.

A glider equipped with a pair of thin, charged appendages could therefore use the interactions with these particles to create electrostatic lift and propel itself around the body. These appendages are also articulated to direct the levitation force in the whatever direction is most convenient for propulsion and maneuvering. It would also be able to land by simply retracing these appendages (or possibly using thrusters or an anchor).


Beyond NASA, other concepts that made the cut include the Tension Adjustable Novel Deployable Entry Mechanism (TANDEM). In a novel approach, the TANDEM consists of a tensegrity frame with a semi-rigid deployable heat shield composed of 3-D woven carbon-cloth. The same infrastructure is used for every part of the mission, with the shield providing protection during entry, and the frame providing locomotion on the surface.

By reusing the same infrastructure, TANDEM seeks to be the most efficient system ever proposed. The use of tensegrity robotics, which is a largely unexplored concept at present, also provides numerous potential benefits during entry and descent. These include the ability to adjust its shape to achieve an optimal landing, and the ability to reorient itself and charge its aerodynamic center if it gets overturned.

What’s more, conventional tensegrity locomotion depends largely on the actuation of outer cables, which requires mechanical devices in each strut to reel in the cables. However, such a system can prove impractical when used in extreme environments, since it requires that each strut be protected from the environment. This can make the vehicle overly-heavy and contribute to higher launch costs.

The TANDEM, in contrast, relies on only inner cable actuation, which allows the locomotion mechanisms to be housed in the central payload module. Taken together, this means that the TANDEM concept can allow for landings in new locations (opening up the possibility for new missions), can traverse significantly rougher terrain than existing rovers, and provide a higher level of reliability, safety and cost-effectiveness to surface missions.

From the private sector, Made In Space was awarded a Phase I grant for their concept of Reconstituting Asteroids into Mechanical Automata (RAMA). In brief, this concept boils down to using analog computers and mechanisms to convert asteroids into enormous, autonomous mechanical spacecraft, which is likely to have applications when it comes to diverting Potentially-Hazardous Asteroids (PHAs) from Earth, or bringing NEOs closer to Earth to be studied.

The concept was designed with recent developments in additive manufacturing (3-D printing) and in-situ resource utilization (ISRU) in mind. The mission would consist of a series of technically simple robotic components being sent to an asteroid, which would then convert elements of it into very basic parts of spacecraft subsystems – such as guidance, navigation and control (GNC) systems, propulsion, and avionics.

Such a proposal offers cost-saving measures since it eliminates the need to launch all spacecraft subsystems into space. It also offers an affordable and scalable way for NASA to realize future mission concepts, such as the Asteroid Redirect Mission (ARM), the New Frontiers Comet Surface Sample Return, and other Near Earth Object (NEO) applications. If all goes according to plan, Made In Space believes that it will be able to create a space mission that utilizes 3-D printing and ISRU within 20 to 30 years.

Another interesting concept is the Direct Fusion Drive (DFD), which was proposed by Princeton Satellite Systems Inc. Based on the Princeton Field-Reversed Configuration (PFRC) fusion reactor, which is under development at the Princeton Plasma Physics Laboratory, this mission would involve sending a 1000 kg lander to Pluto within 4 to 6 years. By comparison, the New Horizons space probe took roughly 9 years to reach Pluto and didn’t have the necessary fuel to slow down or make a landing.

NASA’s Ames Research Center also proposed a mission that would rely on bioprinting and an end-to-end recycling system to turn Mars’ own atmosphere into replacement electronics. Under the guidance of Dr. Lynn Rothschild, this revolutionary idea calls for small living cells to be printed out in a gel which will then consume resources (like the local atmosphere) and excrete metals, or plastics, or other useful materials.

With this kind of technology, the mass of missions could be significantly reduced, and replacement electronics could be created on-site to address failures or breakdowns. This proposal will not only enhance the likelihood of mission success, but could also have immediate applications to environmental issues here on Earth (not the least of which is the problem of e-waste).

The other winning proposals can be read about here, and include a probe that will analyze the molecular composition of “cold targets” in the Solar System (such as asteroids, comets, planets and moons), a 2-dimensional brane craft that could merge with orbital debris to deorbit it, and the Nano Icy Moons Propellant Harvester (NIMPH) – a proposed Europa mission that would involve Cubesat-sized microlanders harvesting water from the moon’s interior ocean.

There is also the NASA Kennedy Space Center’s Mars Molniya Orbit Atmospheric Resource Mining craft, which would use resources in Mars orbit to make travel to the Red Planet more affordable for future missions. And last, but not least, there was the exoplanet-hunter proposed by Nanohmics Inc., which would use a technique known as stellar echo imaging to provide more detailed imaging of exoplanets than existing techniques.

All in all, this year’s Phase I awards represent a good smattering of the research goals NASA intends to pursue in the coming years. These include, bu are not limited to, studying NEOs, returning to Venus, more missions to Mars and Pluto, and exploring the exotic environments of the outer Solar System. Only time will tell which missions will move from science fiction into the realm of science fact, and which ones will have to be put aside for later consideration.


Further Reading: NASA, NIAC 2016 Phase I Selections

The post NASA Invests In Radical Game-Changing Concepts For Exploration appeared first on Universe Today.

The Definitive Guide To Terraforming

Artist's impression of the terraforming of Mars, from its current state to a livable world. Credit: Daein Ballard

Terraforming. Chances are you’ve heard that word thrown around before, most likely in the context of some science fiction story. However, in recent years, thanks to renewed interest in space exploration, this word is being used in an increasingly serious manner. And rather than being talked about like a far-off prospect, the issue of terraforming other worlds is being addressed as a near-future possibility.

Whether it’s Elon Musk claiming that humanity needs a “backup location” in order to survive, private ventures like MarsOne looking to send humans on a one-way mission to colonize the Red Planet, or space agencies like NASA and the ESA discussing the prospect of long-term habitability on Mars or the Moon, terraforming is yet another science fiction concept that appears to be moving towards science fact.

But just what does terraforming entail? Where exactly could we go about using this process? What kind of technology would we need? Does such technology already exist, or do we have to wait? How much in the way of resources would it take? And above all, what are the odds of it actually succeeding? Answering any or all of these questions requires that we do a bit of digging. Not only is terraforming a time-honored concept, but as it turns out, humanity already has quite a bit of experience in this area!

Origin Of The Term:

To break it down, terraforming is the process whereby a hostile environment (i.e. a planet that is too cold, too hot, and/or has an unbreathable atmosphere) is altered in order to be suitable for human life. This could involve modifying the temperature, atmosphere, surface topography, ecology – or all of the above – in order to make a planet or moon more “Earth-like”.

The term was coined by Jack Williamson, an American science fiction writer who has also been called “the Dean of science fiction” (after the death of Robert Heinlein in 1988). The term appeared as part of a science-fiction story titled “Collision Orbit”, which was published in the 1942 editions of the magazine Astounding Science Fiction. This is the first known mention of the concept, though there are examples of it appearing in fiction beforehand (see below).

Terraforming in Fiction:

Science fiction is filled with examples of altering planetary environments to be more suitable to human life, many of which predate the scientific studies by many decades. For example, in H.G. Wells’ War of the Worlds, he mentions at one point how the Martian invaders begin transforming Earth’s ecology for the sake of long-term habitation.

In Olaf Stapleton’s Last And First Men (1930), two chapter are dedicated to describing how humanity’s descendants terraform Venus after Earth becomes uninhabitable; and in the process, commit genocide against the native aquatic life in the process. By the 1950s and 60s, owing to the beginning of the Space Age, terraforming began to appear in many works of science fiction.

For example, in Farmer in the Sky (1950), Robert A. Heinlein offers a vision of how Ganymede is being transformed into an agricultural settlement. This was a very significant novel, in that it was the first novel where the concept of terraforming is presented as a serious and scientific matter, rather than the subject of mere fantasy.

In 1951, Arthur C. Clarke wrote the first novel in which the terraforming of Mars was presented in fiction. Titled The Sands of Mars, the story involves Martian settlers heating up the planet by converting Phobos into a second sun, and growing plants that break down the Martians sands in order to release oxygen. In his seminal book 2001: A Space Odyssey, and 2010: Odyssey Two, Clarke presents a race of ancient beings (“Firstborn”) turning Jupiter into a second sun so that Europa will become a life-bearing planet.

Poul Anderson also wrote extensively about terraforming in the 1950s. In his 1954 novel, The Big Rain, Venus is altered through planetary engineering techniques over a very long period of time. The book was so influential that the term term “Big Rain” has since come to be snyonimous with the terraforming of Venus.  This was followed in 1958 by the Snows of Ganymede, where the Jovian moon’s ecology is made habitable through a similar process.

In Issac Asimov’s Robot series, colonization and terraforming is performed by a powerful race of humans known as “Spacers”, who conduct this process on fifty planets in the known universe.  In his Foundation series, humanity has effectively colonized every habitable planet in the galaxy and terraformed them to become part of the Galactic Empire.

In 1984, James Lovelock and Michael Allaby wrote what is considered by many to be one of the most influential books on terraforming. Titled The Greening of Mars, the novel explores the formation and evolution of planets, the origin of life, and Earth’s biosphere. The terraforming models presented in the book actually foreshadowed future debates regarding the goals of terraforming.

In the 1990s, Kim Stanley Robinson released his famous trilogy that deals with the terraforming Mars. Known as the Mars TrilogyRed Mars, Green Mars, Blue Mars – this series centers on the transformation of Mars over the course of many generations into a thriving human civilization. This was followed up in 2012 with the release of 2312, which deals with the colonization of the Solar System – including the terraforming of Venus and other planets.

Countless other examples can be found in popular culture, ranging from television and print to films and video games.

Study Of Terraforming:

In an article published by the journal Science in 1961, famed astronomer Carl Sagan proposed using planetary engineering techniques to transform Venus. This involved seeding the atmosphere of Venus with algae, which would convert the atmosphere’s ample supplies of water, nitrogen and carbon dioxide into organic compounds and reduce Venus’ runaway greenhouse effect.

In 1973, he published an article in the journal Icarus titled “Planetary Engineering on Mars“, where he proposed two scenarios for transforming Mars. These included transporting low albedo material and/or planting dark plants on the polar ice caps to ensure it absorbed more heat, melted, and converted the planet to more “Earth-like conditions”.

In 1976, NASA addressed the issue of planetary engineering officially in a study titled “On the Habitability of Mars: An Approach to Planetary Ecosynthesis“. The study concluded that photosynthetic organisms, the melting of the polar ice caps, and the introduction of greenhouse gases could all be used to create a warmer, oxygen and ozone-rich atmosphere. The first conference session on terraforming, then referred to as “Planetary Modeling”, was organized that same year.

And then in March of 1979, NASA engineer and author James Oberg organized the First Terraforming Colloquium – a special session at the Tenth Lunar and Planetary Science Conference, which is held annually in Houston, Texas. In 1981, Oberg popularized the concepts that were discussed at the colloquium in his book New Earths: Restructuring Earth and Other Planets.

In 1982, Planetologist Christopher McKay wrote “Terraforming Mars”, a paper for the Journal of the British Interplanetary Society. In it, McKay discussed the prospects of a self-regulating Martian biosphere, which included both the required methods for doing so and ethics of it. This was the first time that the word terraforming was used in the title of a published article, and would henceforth become the preferred term.

This was followed by James Lovelock and Michael Allaby’s The Greening of Mars in 1984. This book was one of the first to describe a novel method of warming Mars, where chlorofluorocarbons (CFCs) are added to the atmosphere in order to trigger global warming. This book motivated biophysicist Robert Haynes to begin promoting terraforming as part of a larger concept known as Ecopoiesis.

Derived from the Greek words oikos (“house”) and poiesis (“production”), this word refers to the origin of an ecosystem. In the context of space exploration, it involves a form of planetary engineering where a sustainable ecosystem is fabricated from an otherwise sterile planet. As described by Haynes, this begins with the seeding of a planet with microbial life, which leads to conditions approaching that of a primordial Earth. This is then followed by the importation of plant life, which accelerates the production of oxygen, and culminates in the introduction of animal life.

In 2009, Kenneth Roy – an engineer with the US Department of Energy – presented his concept for a “Shell World” in a paper published with the Journal of British Interplanetary Sciences. Titled “Shell Worlds – An Approach To Terraforming Moons, Small Planets and Plutoids“, his paper explored the possibility of using a large “shell” to encase an alien world, keeping its atmosphere contained long enough for long-term changes to take root.

These and other concepts where a world is enclosed (in whole or in part) in an artificial shell in order to transform its environment is also known as “paraterraforming”.

Potential Sites:

Within the Solar System, several possible locations exist that could be well-suited to terraforming. Consider the fact that besides Earth, Venus and Mars also lie within the Sun’s Habitable Zone (aka. “Goldilocks Zone”). However, owing to Venus’ runaway greenhouse effect, and Mars’ lack of a magnetosphere, their atmospheres are either too thick and hot, or too thin and cold, to sustain life as we know it. However, this could theoretically be altered through the right kind of ecological engineering.

Other potential sites in the Solar System include some of the moons that orbit the gas giants. Several Jovian (i.e. in orbit of Jupiter) and Cronian (in orbit of Saturn) moons have an abundance of water ice, and scientists have speculated that if the surface temperatures were increased, viable atmospheres could be created through electrolysis and the introduction of buffer gases.

There is even speculation that Mercury and the Moon (or at least parts thereof) could be terraformed in order to be suitable for human settlement. In these cases, terraforming would require not only altering the surface, but perhaps also adjusting their rotation. In the end, each case presents its own share of advantages, challenges, and likelihoods for success. Let’s consider them in order of distance from the Sun.

Inner Solar System:

The terrestrial planets of our Solar System present the best possibilities for terraforming. Not only are they located closer to our Sun, and thus in a better position to absorb its energy, but they are also rich in silicates and minerals – which any future colonies will need to grow food and build settlements. And as already mentioned, two of these planets (Venus and Mars) are located within Earth’s habitable zone.

The vast majority of Mercury’s surface is hostile to life, where temperatures gravitate between extremely hot and cold – i.e. 700 K (427 °C; 800 °F) 100 K (-173 °C; -280 °F). This is due to its proximity to the Sun, the almost total lack of an atmosphere, and its very slow rotation. However, at the poles, temperatures are consistently low -93 °C (-135 °F) due to it being permanently shadowed.

The presence of water ice and organic molecules in the northern polar region has also been confirmed thanks to data obtained by the MESSENGER mission. Colonies could therefore be constructed in the regions, and limited terraforming (aka. paraterraforming) could take place. For example, if domes (or a single dome) of sufficient size could be built over the Kandinsky, Prokofiev, Tolkien and Tryggvadottir craters, the norther region could be altered for human habitation.

Theoretically, this could be done by using mirrors to redirect sunlight into the domes which would gradually raise the temperature. The water ice would then melt, and when combined with organic molecules and finely ground sand, soil could be made. Plants could then be grown to produce oxygen, which combined with nitrogen gas, would produce a breathable atmosphere.

As “Earth’s Twin“, there are many possibilities and advantages to terraforming Venus. The first to propose this was Sagan with his 1961 article in Science. However, subsequent discoveries – such as the high concentrations of sulfuric acid in Venus’ clouds – made this idea unfeasible. Even if algae could survive in such an atmosphere, converting the extremely dense clouds of CO² into oxygen would result in an over-dense oxygen environment.

In addition, graphite would become a by-product of the chemical reactions, which would likely form into a thick powder on the surface. This would become CO² again through combustion, thus restarting the entire greenhouse effect. However, more recent proposals have been made that advocate using carbon sequestration techniques, which are arguably much more practical.


In these scenarios, chemical reactions would be relied on to convert Venus’ atmosphere to something breathable while also reducing its density. In one scenario, hydrogen and iron aerosol would be introduced to convert the CO² in the atmosphere into graphite and water. This water would then fall to the surface, where it cover roughly 80% of the planet – due to Venus having little variation in elevation.

Another scenario calls for the introduction of vast amounts of calcium and magnesium into the atmosphere. This would sequester carbon in the form of calcium and magnesium carbonites. And advantage to this plan is that Venus already has deposits of both minerals in its mantle, which could then be exposed to the atmosphere through drilling. However, most of the minerals would have to come from off-world in order to reduce the temperature and pressure to sustainable levels.

Yet another proposal is to freeze the atmospheric carbon dioxide down to the point of liquefaction – where it forms dry ice – and letting it accumulate on the surface. Once there, it could be buried and would remain in a solid state due to pressure, and even mined for local and off-world use. And then there is the possibility of bombarding the surface with icy comets (which could be mined from one of Jupiter’s or Saturn’s moons) to create a liquid ocean on the surface, which would sequester carbon and aid in any other of the above processes.

Last, there is the scenario in which Venus’ dense atmosphere could be removed. This could be characterized as the most direct approach to thinning an atmosphere which is far too dense for human occupation. By colliding large comets or asteroids into the surface, some of the dense CO² clouds could be blasted into space, thus leaving less atmosphere to be converted.

A slower method could be achieved using mass drivers (aka. electromagnetic catapults) or space elevators, which would gradually scoop up the atmosphere and either lift it into space, or fire it away from the surface. And beyond altering or removing the atmosphere, there are also concepts that call for reducing the heat and pressure by either limiting sunlight (i.e. with solar shades) or altering the planet’s rotational velocity.

The concept of solar shades involves using either a series of small spacecraft or a single large lens to divert sunlight from a planet’s surface, thus reducing global temperatures. For Venus, which absorbs twice as much sunlight as Earth, solar radiation is believed to have played a major role in the runaway greenhouse effect that has made it what it is today.

Such a shade could be space-based, located in the Sun–Venus L1 Lagrangian Point, where it would not only prevent some sunlight from reaching Venus, but also serve to reduce the amount of radiation Venus is exposed to. Alternately, solar shades or reflectors could be placed in the atmosphere or on the surface. This could consist of large reflective balloons, sheets of carbon nanotubes or graphene, or low-albedo material.

Placing shades or reflectors in the atmosphere offers two advantages: for one, atmospheric reflectors could be built in-situ, using locally-sourced carbon. Second, Venus’ atmosphere is dense enough that such structures could easily float atop the clouds. However, the amount of material would have to be large and would have to remain in place long after the atmosphere had been modified. Also, since Venus already has highly reflective clouds, any approach would have to significantly surpass its current albedo (0.65) to make a difference.

Also, the idea of speeding up Venus’ rotation has been floating around as a possible means of terraforming. If Venus could be spun-up to the point where its diurnal (day-night) cycle were similar to Earth’s, the planet might just begin to generate a stronger magnetic field. This would have the effect of reducing the amount of solar wind (and hence radiation) from reaching the surface, thus making it safer for terrestrial organisms.

The Moon:
As Earth’s closest celestial body, colonizing the Moon would be comparatively easy compared to other bodies. But when it comes to terraforming the Moon, the possibilities and challenges closely resemble those of Mercury. For starters, the Moon has an atmosphere that is so thin that it can only be referred to as an exosphere. What’s more, the volatile elements that are necessary for life are in short supply (i.e. hydrogen, nitrogen, and carbon).

These problems could be addressed by capturing comets that contain water ices and volatiles and crashing them into the surface. The comets would sublimate, dispersing these gases and water vapor to create an the atmosphere. These impacts would also liberate water that is contained in the lunar regolith, which could eventually accumulate on the surface to form natural bodies of water.

The transfer of momentum from these comet would also get the Moon rotating more rapidly, speeding up its rotation so that it would no longer be tidally-locked. A Moon that was sped up to rotate once on its axis every 24 hours would have a steady diurnal cycle, which would make colonization and adapting to life on the Moon easier.


There is also the possibility of paraterraforming parts of the Moon in a way that would be similar to terraforming Mercury’s polar region. In the Moon’s case, this would take place in the Shackleton Crater, where scientists have already found evidence of water ice. Using solar mirrors and a dome, this crater could be turned into a micro-climate where plants could be grown and a breathable atmosphere created.

When it comes to terraforming, Mars is the most popular destination. There are several reasons for this, ranging from its proximity to Earth, its similarities to Earth, and the fact that it once had an environment that was very similar to Earth’s – which included a thicker atmosphere and the presence of warm, flowing water on the surface. Lastly, it is currently believed that Mars may have additional sources of water beneath its surface.

In brief, Mars has a diurnal and seasonal cycle that are very close what we experience here on Earth. In the former case, a single day on Mars lasts 24 hours and 40 minutes. In the latter case, and owing to Mars similarly tilted axis (25.19° compared to Earth’s 23°), Mars experiences seasonal changes that are very similar to Earth’s. Though a single season on Mars lasts roughly twice as long, the temperature variation that results is very similar – ±178 °C (320°F) compared to Earth’s ±160 °C (278°F).

Beyond these, Mars would need to undergo vast transformations in order for human beings to live on its surface. The atmosphere would need to be thickened drastically, and its composition would need to be changed. Currently, Mars’ atmosphere is composed of 96% carbon dioxide, 1.93% argon and 1.89% nitrogen, and the air pressure is equivalent to only 1% of Earth’s at sea level.

Above all, Mars lacks a magnetosphere, which means that its surface receives significantly more radiation than we are used to here on Earth. In addition, it is believed that Mars once had a magnetosphere, and that the disappearance of this magnetic field led to solar wind to stripping away Mars’ atmosphere. This in turn is what led Mars to become the cold, desiccated place it is today.

Ultimately, this means that in order for the planet to become habitable by human standards, it’s atmosphere would need to be significantly thickened and the planet significantly warmed. The composition of the atmosphere would need to change as well, from the current CO²-heavy mix to an nitrogen-oxygen balance of about 70/30. And above all, the atmosphere would need to be replenished every so often to compensate for loss.

Luckily, the first three requirements are largely complimentary, and present a wide range of possible solutions. For starters, Mars’ atmosphere could be thickened and the planet warmed by bombarding its polar regions with meteors. These would cause the poles to melt, releasing their deposits of frozen carbon dioxide and water into the atmosphere and triggering a greenhouse effect.

The introduction of volatile elements, such as ammonia and methane, would also help to thicken the atmosphere and trigger warming. Both could be mined from the icy moons of the outer Solar System, particularly from the moons of Ganymede, Callisto, and Titan. These could also be delivered to the surface via meteoric impacts.

After impacting on the surface, the ammonia ice would sublimate and break down into hydrogen and nitrogen – the hydrogen interacting with he CO² to form water and graphite, while the nitrogen acts as a buffer gas. The methane, meanwhile, would act as a greenhouse gas that would further enhance global warming. In addition, the impacts would throw tons of dust into the air, further fueling the warming trend.


In time, Mars’ ample supplies of water ice – which can be found not only in the poles but in vast subsurface deposits of permafrost – would all sublimate to form warm, flowing water. And with significantly increased air pressure and a warmer atmosphere, humans might be able to venture out onto the surface without the need for pressure suits.

However, the atmosphere will still need to be converted into something breathable. This will be far more time-consuming, as the process of converting the atmospheric CO² into oxygen gas will likely take centuries. In any case, several possibilities have been suggested, which include converting the atmosphere through photosynthesis – either with cyanobacteria or Earth plants and lichens.

Other suggestions include building orbital mirrors, which would be placed near the poles and direct sunlight onto the surface to trigger a cycle of warming by causing the polar ice caps to melt and release their CO² gas. Using dark dust from Phobos and Deimos to reduce the surface’s albedo, thus allowing it to absorb more sunlight, has also been suggested.

In short, there are plenty of options for terraforming Mars. And many of them, if not being readily available, are at least on the table…

Outer Solar System:

Beyond the Inner Solar System, there are several sites that would make for good terraforming targets as well. Particularly around Jupiter and Saturn, there are several sizable moons – some of which are larger than Mercury – that have an abundance of water in the form of ice (and in some cases, maybe even interior oceans).

At the same time, many of these same moons contain other necessary ingredients for functioning ecosystems, such as frozen volatiles  – like ammonia and methane. Because of this, and as part of our ongoing desire to explore farther out into our Solar System, many proposals have been made to seed these moons with bases and research stations. Some plans even include possible terraforming to make them suitable for long-term habitation.

The Jovian Moons:
Jupiter’s largest moons, Io, Europa, Ganymede and Callisto – known as the Galileans, after their founder (Galileo Galilei) – have long been the subject of scientific interest. For decades, scientists have speculated about the possible existence of a subsurface ocean on Europa, based on theories about the planet’s tidal heating (a consequence of its eccentric orbit and orbital resonance with the other moons).

Analysis of images provided by the Voyager 1 and Galileo probes added weight to this theory, showing regions where it appeared that the subsurface ocean had melted through. What’s more, the presence of this warm water ocean has also led to speculation about the existence of life beneath Europa’s icy crust – possibly around hydrothermal vents at the core-mantle boundary.

Because of this potential for habitability, Europa has also been suggested as a possible site for terraforming. As the argument goes, if the surface temperature could be increased, and the surface ice melted, the entire planet could become a ocean world. Sublimation of the ice, which would release water vapor and gaseous volatiles, would then be subject to electrolysis (which already produces a thin oxygen atmosphere).


However, Europa has no magnetosphere of its own, and lies within Jupiter’s powerful magnetic field. As a result, its surface is exposed to significant amounts of radiation – 540 rem of radiation per day compared to about 0.0030 rem per year here on Earth – and any atmosphere we create would begin to be stripped away by Jupiter. Ergo, radiation shielding would need to be put in place that could deflect the majority of this radiation.

And then there is Ganymede, the third most-distant of Jupiter’s Galilean moons. Much like Europa, it is a potential site of terraforming, and presents numerous advantages. For one, it is the largest moon in our Solar System, larger than our own moon and even larger that the planet Mercury. In addition, it also has ample supplies of water ice, is believed to have an interior ocean, and even has its own magnetosphere.

Hence, if the surface temperature were increased and the ice sublimated, Ganymede’s atmosphere could be thickened. Like Europa, it would also become an ocean planet, and its own magnetosphere would allow for it to hold on to more of its atmosphere. However, Jupiter’s magnetic field still exerts a powerful influence over the planet, which means radiation shields would still be needed.

Lastly, there is Callisto, the fourth-most distant of the Galileans. Here too, abundant supplies of water ice, volatiles, and the possibility of an interior ocean all point towards the potential for habitability. But in Callisto’s case, there is the added bonus of it being beyond Jupiter’s magnetic field, which reduces the threat of radiation and atmospheric loss.

The process would begin with surface heating, which would sublimate the water ice and Callisto’s supplies of frozen ammonia. From these oceans, electrolysis would lead to the formation of an oxygen-rich atmosphere, and the ammonia could be converted into nitrogen to act as a buffer gas. However, since the majority of Callisto is ice, it would mean that the planet would lose considerable mass and have no continents. Again, an ocean planet would result, necessitated floating cities or massive colony ships.

The Cronians Moons:
Much like the Jovian Moons, Saturn’s Moons (also known as the Cronian) present opportunities for terraforming. Again, this is due to the presence of water ice, interior oceans, and volatile elements. Titan, Saturn’s largest moon, also has an abundance of methane that comes in liquid form (the methane lakes around its northern polar region) and in gaseous form in its atmosphere. Large caches of ammonia are also believed to exist beneath he surface ice.

Titan is also the only natural satellite to have a dense atmosphere (one and half times the pressure of Earth’s) and the only planet outside of Earth where the atmosphere is nitrogen-rich. Such a thick atmosphere would mean that it would be far easier to equalize pressure for habitats on the planet. What’s more, scientists believe this atmosphere is a prebiotic environment rich in organic chemistry – i.e. similar to Earth’s early atmosphere (only much colder).

As such, converting it to something Earth-like would be feasible. First, the surface temperature would need to be increased. Since Titan is very distant from the Sun, and already has an abundance of greenhouse gases, this could only be accomplished through orbital mirrors. This would sublimate the surface ice, releasing ammonia beneath, which would lead to more heating.

The next step would involve converting the atmosphere to something breathable. As already noted, Titan’s atmosphere is nitrogen-rich, which would remove the need for introducing a buffer gas. And with the availability of water, oxygen could be introduced by generating it through electrolysis. At the same time, the methane and other hydrocarbons would have to be sequestered, in order to prevent an explosive mixture with the oxygen.

But given the thickness and multi-layered nature of Titan’s ice, which is estimated to account for half of its mass, the moon would be very much an ocean planet- i.e. with no continents or landmasses to build on. So once again, any habitats would have to take the form of either floating platforms or large ships.

Enceladus is another possibility, thanks to the recent discovery of a subsurface ocean. Analysis by the Cassini space probe of the water plumes erupting from its southern polar region also indicated the presence of organic molecules. As such, terraforming it would be similar to terraforming Jupiter’s moon of Europa, and would yield a similar ocean moon.

Again, this would likely have to involve orbital mirrors, given Enceladus’ distance from our Sun. Once the ice began to sublimate, electrolysis would generate oxygen gas. The presence of ammonia in the subsurface ocean would also be released, helping to raise the temperature and serving as a source of nitrogen gas, with which to buffer the atmosphere.

In addition to the Solar System, extra-solar planets (aka. exoplanets) are also potential sites for terraforming. Of the 1,941 confirmed exoplanets discovered so far, these planets are those that have been designated “Earth-like. In other words, they are terrestrial planets that have atmospheres and, like Earth, occupy the region around a star where the average surface temperature allows for liquid water (aka. habitable zone).

The first planet confirmed by Kepler to have an average orbital distance that placed it within its star’s habitable zone was Kepler-22b. This planet is located about 600 light years from Earth in the constellation of Cygnus, was first observed on May 12th, 2009 and then confirmed on Dec 5th, 2011. Based on all the data obtained, scientists believe that this world is roughly 2.4 times the radius of Earth, and is likely covered in oceans or has a liquid or gaseous outer shell.


In addition, there are star systems with multiple “Earth-like” planets occupying their habitable zones. Gliese 581 is a good example, a red dwarf star that is located 20.22 light years away from Earth in the Libra constellation. Here, three confirmed and two possible planets exist, two of which are believed to orbit within the star’s habitable zone. These include the confirmed planet Gliese 581 d and the hypothetical Gliese 581 g.

Tau Ceti is another example. This G-class star, which is located roughly 12 light years from Earth in the constellation Cetus, has five possible planets orbiting it. Two of these are Super-Earths that are believed to orbit the star’s habitable zone – Tau Ceti e and Tau Ceti f. However, Tau Ceti e is believed to be too close for anything other than Venus-like conditions to exist on its surface.

In all cases, terraforming the atmospheres of these planet’s would most likely involve the same techniques used to terraform Venus and Mars, though to varying degrees. For those located on the outer edge of their habitable zones, terraforming could be accomplished by introducing greenhouse gases or covering the surface with low albedo material to trigger global warming. On the other end, solar shades and carbon sequestering techniques could reduce temperatures to the point where the planet is considered hospitable.

Potential Benefits:

When addressing the issue of terraforming, there is the inevitable question – “why should we?” Given the expenditure in resources, the time involved, and other challenges that naturally arise (see below), what reasons are there to engage in terraforming? As already mentioned, there is the reasons cited by Musk, about the need to have a “backup location” to prevent any particular cataclysm from claiming all of humanity.

Putting aside for the moment the prospect of nuclear holocaust, there is also the likelihood that life will become untenable on certain parts of our planet in the coming century. As the NOAA reported in March of 2015, carbon dioxide levels in the atmosphere have now surpassed 400 ppm, a level not seen since the the Pliocene Era – when global temperatures and sea level were significantly higher.

And as a series of scenarios computed by NASA show, this trend is likely to continue until 2100, and with serious consequences. In one scenario, carbon dioxide emissions will level off at about 550 ppm toward the end of the century, resulting in an average temperature increase of 2.5 °C (4.5 °F). In the second scenario, carbon dioxide emissions rise to about 800 ppm, resulting in an average increase of about 4.5 °C (8 °F). Whereas the increases predicted in the first scenario are sustainable, in the latter scenario, life will become untenable on many parts of the planet.

As a result of this, creating a long-term home for humanity on Mars, the Moon, Venus, or elsewhere in the Solar System may be necessary. In addition to offering us other locations from which to extract resources, cultivate food, and as a possible outlet for population pressures, having colonies on other worlds could mean the difference between long-term survival and extinction.

There is also the argument that humanity is already well-versed in altering planetary environments. For centuries, humanity’s reliance on industrial machinery, coal and fossil fuels has had a measurable effect Earth’s environment. And whereas the Greenhouse Effect that we have triggered here was not deliberate, our experience and knowledge in creating it here on Earth could be put to good use on planet’s where surface temperatures need to be raised artificially.

In addition, it has also been argued that working with environments where there is a runaway Greenhouse Effect – i.e. Venus – could yield valuable knowledge that could in turn be used here on Earth. Whether it is the use of extreme bacteria, introducing new gases, or mineral elements to sequester carbon, testing these methods out on Venus could help us to combat Climate Change here at home.

It has also been argued that Mars’ similarities to Earth are a good reason to terraform it. Essentially, Mars once resembled Earth, until its atmosphere was stripped away, causing it to lose virtually all the liquid water on its surface. Ergo, terraforming it would be tantamount to returning it to its once-warm and watery glory. The same argument could be made of Venus, where efforts to alter it would restore it to what it was before a runaway Greenhouse Effect turned it into the harsh, extremely hot world it is today.

Last, but not least, there is argument that colonizing the Solar System could usher in an age of “post-scarcity”. If humanity were to build outposts and based on other worlds, mine the asteroid belt and harvest the resources of the Outer Solar System, we would effectively have enough minerals, gases, energy, and water resources to last us indefinitely. It could also help trigger a massive acceleration in human development, defined by leaps and bounds in technological and social progress.

Potential Challenges:

When it comes right down to it, all of the scenarios listed above suffer from one or more of the following problems:

  1. They are not possible with existing technology
  2. They require a massive commitment of resources
  3. They solve one problem, only to create another
  4. They do not offer a significant return on the investment
  5. They would take a really, REALLY long time

Case in point, all of the potential ideas for terraforming Venus and Mars involve infrastructure that does not yet exist and would be very expensive to create. For instance, the orbital shade concept that would cool Venus calls for a structure that would need to be four times the diameter of Venus itself (if it were positioned at L1). It would therefore require megatons of material, all of which would have to be assembled on site.

In contrast, increasing the speed of Venus’s rotation would require energy many orders of magnitude greater than the construction of orbiting solar mirrors. As with removing Venus’ atmosphere, the process would also require a significant number of impactors that would have to be harnessed from the outer solar System – mainly from the Kuiper Belt.

In order to do this, a large fleet of spaceships would be needed to haul them, and they would need to be equipped with advanced drive systems that could make the trip in a reasonable amount of time. Currently, no such drive systems exist, and conventional methods – ranging from ion engines to chemical propellants – are neither fast or economical enough.

To illustrate, NASA’s New Horizons mission took more than 11 years to get make its historic rendezvous with Pluto in the Kuiper Belt, using conventional rockets and the gravity-assist method. Meanwhile, the Dawn mission, which relied relied on ionic propulsion, took almost four years to reach Vesta in the Asteroid Belt. Neither method is practical for making repeated trips to the Kuiper Belt and hauling back icy comets and asteroids, and humanity has nowhere near the number of ships we would need to do this.

The Moon’s proximity makes it an attractive option for terraforming. But again, the resources needed – which would likely include several hundred comets – would again need to be imported from the outer Solar System. And while Mercury’s resources could be harvested in-situ or brought from Earth to paraterraform its northern polar region, the concept still calls for a large fleet of ships and robot builders which do not yet exist.

The outer Solar System presents a similar problem. In order to begin terraforming these moons, we would need infrastructure between here and there, which would mean bases on the Moon, Mars, and within the Asteroid Belt. Here, ships could refuel as they transport materials to the Jovian sand Cronian systems, and resources could be harvested from all three of these locations as well as within the systems themselves.

But of course, it would take many, many generations (or even centuries) to build all of that, and at considerable cost. Ergo, any attempts at  terraforming the outer Solar System would have to wait until humanity had effectively colonized the inner Solar System. And terraforming the Inner Solar System will not be possible until humanity has plenty of space hauler on hand, not to mention fast ones!

The necessity for radiation shields also presents a problem. The size and cost of manufacturing shields that could deflect Jupiter’s magnetic field would be astronomical. And while the resources could be harvest from the nearby Asteroid Belt, transporting and assembling them in space around the Jovian Moons would again require many ships and robotic workers. And again, there would have to be extensive infrastructure between Earth and the Jovian system before any of this could proceed.

As for item three, there are plenty of problems that could result from terraforming. For instance, transforming Jupiter’s and Saturn’s moons into ocean worlds could be pointless, as the volume of liquid water would constitute a major portion of the moon’s overall radius. Combined with their low surface gravities, high orbital velocities and the tidal effects of their parent planets, this could lead to severely high waves on their surfaces. In fact, these moons could become totally unstable as a result of being altered.

There is also several questions about the ethics of terraforming. Basically, altering other planets in order to make them more suitable to human needs raises the natural question of what would happen to any lifeforms already living there. If in fact Mars and other Solar System bodies have indigenous microbial (or more complex) life, which many scientists suspect, then altering their ecology could impact or even wipe out these lifeforms. In short, future colonists and terrestrial engineers would effectively be committing genocide.

Another argument that is often made against terraforming is that any effort to alter the ecology of another planet does not present any immediate benefits. Given the cost involved, what possible incentive is there to commit so much time, resources and energy to such a project? While the idea of utilizing the resources of the Solar System makes sense in the long-run, the short-term gains are far less tangible.

Basically, harvested resources from other worlds is not economically viable when you can extract them here at home for much less. And real-estate is only the basis of an economic model if the real-estate itself is desirable. While MarsOne has certainly shown us that there are plenty of human beings who are willing to make a one-way trip to Mars, turning the Red Planet, Venus or elsewhere into a “new frontier” where people can buy up land will first require some serious advances in technology, some serious terraforming, or both.

As it stands, the environments of Mars, Venus, the Moon, and the outer Solar System are all hostile to life as we know it. Even with the requisite commitment of resources and people willing to be the “first wave”, life would be very difficult for those living out there. And this situation would not change for centuries or even millennia. Like it not, transforming a planet’s ecology is very slow, laborious work.


So… after considering all of the places where humanity could colonize and terraform, what it would take to make that happen, and the difficulties in doing so, we are once again left with one important question. Why should we? Assuming that our very survival is not at stake, what possible incentives are there for humanity to become an interplanetary (or interstellar) species?

Perhaps there is no good reason. Much like sending astronauts to the Moon, taking to the skies, and climbing the highest mountain on Earth, colonizing other planets may be nothing more than something we feel we need to do. Why? Because we can! Such a reason has good enough in the past, and it will likely be sufficient again in the not-to-distant future.

This should is no way deter us from considering the ethical implications, the sheer cost involved, or the cost-to-benefit ratio. But in time, we might find that we have no choice but to get out there, simply because Earth is just becoming too stuffy and crowded for us!

We have written many interesting articles about terraforming here at Universe Today. Here’s Could We Terraform the Moon?, Should We Terraform Mars?, How Do We Terraform Mars?, How Do We Terraform Venus?, and Student Team Wants to Terraform Mars Using Cyanobacteria.

We’ve also got articles that explore the more radical side of terraforming, like Could We Terraform Jupiter?, Could We Terraform The Sun?, and Could We Terraform A Black Hole?

Astronomy Cast also has good episodes on the subject, like Episode 96: Humans to Mar, Part 3 – Terraforming Mars

For more information, check out Terraforming Mars  at NASA Quest! and NASA’s Journey to Mars.

The post The Definitive Guide To Terraforming appeared first on Universe Today.

Retro Travel Posters Show Us The Future

Visitors to Jupiter view the Jovian auroras from balloons. Image: NASA/JPL.

One of the greatest things about being a space enthusiast is all of the discoveries that come out on an almost daily basis. One of the saddest things about being a space enthusiast is all of the discoveries and destinations that are so close, just beyond the horizon of our lifespan.

Will we colonize other planets? Sure, but most of us living will be gone by then. Will we spend time in glorious, gleaming space habitats? Obviously, but we’ll just be epitaphs by then. Sentient, alien species that gift us faster-than-light travel and other wonders? Maybe, but not before my bucket list has its final item checked off.

Citizen space travel? Hmmmm, tantalizingly within reach.

But now, new retro style posters from NASA, designed by the team at Invisible Creature, are making us feel nostalgic about things that haven’t even happened yet, and are helping us leave behind gloomy thoughts of being born at the wrong time.

The Grand Tour celebrates a time when our probes toured the planets, using gravity assist to propel them on their missions.

“Grandpa, do you remember the Grand Tour, when spacecraft used gravity assist to visit other worlds?”

“I sure do. Gravity assist. Those were the days. Swooping so close to Jupiter, you could feel the radiation killing your hair follicles. Only to be sling-shotted on to the next planet.”

“But why didn’t you just use a quantum drive to bend space time and appear at your destination?”

“Quantum drives! Those things ain’t natural. And neither is bending space-time. Give me a good old-fashioned chemical rocket any time.”

“Oh Grandpa.”

Visit the Historic Sites of Mars recalls a time when space pioneers colonized and terraformed Mars.

“Grandpa, what was Mars like in the Early Days?”

“You mean before it was terraformed? Very tough times.”

“Because conditions were so difficult? And food was hard to grow?”

“No. Because of the protesters.”

“Protesters? On Mars?”

“Yup. Every time we found a good spot for a Bacterial Production Facility (BPF), it seemed like there was an expired old rover in the way. The protesters didn’t think we should move ’em. Part of our heritage.”

“So what did you do Grandpa?”

“We created a network of computers that everybody would stare at all day. After that, nobody noticed what we did anymore.”

“Oh Grandpa.”

Visit Beautiful Southern Enceladus invites vacationers to visit Saturn’s sixth largest moon to view the ice geysers there.

“Grandpa, did you ever visit Enceladus?”

“I sure did. A beautiful, haunting place.”

“Was it scary? With all of the ice geysers erupting unpredictably?”

“On no. I always knew when one was going to erupt.”

“What? How did you know?”

“My arthritis would flare up.”

“Oh Grandpa.”

Other Posters

NASA has a growing collection of other posters. You can see them here.

SpaceX has their own posters, which you can see here. They also have cool t-shirts with the same designs.

The post Retro Travel Posters Show Us The Future appeared first on Universe Today.