We sometimes dream about turning other worlds into habitable ones. Is terraforming worth the try giving the resources needed? Is Mars the obvious choice or should we choose a different world?
Robert Novella (co-founder and vice-president of New England Skeptical Society, co-host of Skeptics’ Guide to the Universe)
I think Terraforming is a no brainer if for no other reason than to have humanity on more than one planet. A worst-case scenario then, like an asteroid strike, would not have to mean the extinction of all life on Earth. It’s definitely worth the effort but the resources required are staggering. We have the technology now to begin the process but it would be just too expensive. The good news is that the resources required will become increasingly less onerous as technology improves.
Ultimately I think we could use a form of molecular nanotechnology to not only perform most of the work but also complete it in a time frame on the scale of decades or less instead of centuries or even millennia. All or most of the raw material required may even already be on the planet. Mars for example already has what we’d need to not not only create the nanomachines but also the oxygen, nitrogen, and carbon dioxide gas to produce a breathable and comfortable atmospheric pressure.
The obvious choices for terraforming in our solar system are Venus and Mars. The low gravity of moons make atmospheric retention an issue. Both these planets are much better options but for every good reason why, there’s also a downside. For example, Venus has 90% of earth’s gravity but its day is 116 earth-days. A day on Mars is very close to earth’s but it’s gravity is only 38%.
I’d have to choose Mars since the energy required to cool Venus and speed its rotation far exceeds what it would take to warm Mars and thicken its atmosphere. The thicker atmosphere would also likely block enough cosmic rays to make that a tolerable problem.
Fraser Cain (publisher at Universetoday.com, co-host of Astronomy Cast)
We’ve actually done a whole series on terraforming as part of the Guide to Space video series we publish on YouTube. We’ve talked about terraforming Mars, Venus, the Moon, Jupiter and even the Sun and black holes (I don’t recommend those last two).
Mars is an interesting target, but one big concern is its low gravity. Can humans survive long term in 30% gravity? Another huge problem is the lack of a geomagnetic field, which would protect future Martians from solar and cosmic radiation.
Although it’s probably harder, Venus sounds like a better target because of its similar size and gravity to Earth. There would be a lot of work to get the dense carbon dioxide out of the air and spin up the planet’s rotation, but the cloud tops of Venus are surprisingly habitable right now. At the right altitude, the temperature and pressure are the same as Earth and our breathable air is a lifting gas. So, future colonists could live in floating cities on Bespin… I mean Venus.
Andrew Rader (SpaceX engineer, MIT PhD, author)
Apart from traveling to another star, I think terraforming is the long-term purpose of branching out into space. Mars is certainly the most suitable because it has all the elements in place, and it’s essentially returning the planet to the way we think it once was. However, it’s probably a more difficult task than people realize, not because of the science behind it, but because of the magnitude of the engineering challenge. It’s easy enough to melt a bit of CO2 ice on Mars and warm up the planet a fraction of a degree, but melting all the polar ice caps to raise the pressure and create a greenhouse effect on Mars is a daunting task. It’s also unclear if melting all the ice would be enough to make Mars a suitable planet to walk around without a space suit (and eventually without a respirator). More intervention may be required.
We may find a simple solution like some kind of self-replicating special microbes or nanobots that we could simply introduce and they would do the rest, but it’s not certain and that also increases other potential dangers like an unstoppable runaway effect. There was even a proposal to seed the Venusian clouds with microbes which could transform Venus into a habitable place – but on Venus, I think we might be stuck in the clouds for a while (which are suitable for floating habitats now). I think it’ll be a long time before we’re truly able to terraform a planet, but that should stop us from experimenting with the concept now. Moreover, there are alternatives to full terraforming. Even partially terraforming Mars by raising the temperature and pressure would be a huge benefit to exploration and settlement, and we can envision enclosed areas of the planet like large dome structures which is effectively terraforming a small section of the planet (AKA “paraterraforming”). If I had to guess, I’d wager Mars will be fully terraformed within the next 1000 years, provided humanity lasts that long.
Nancy Atkinson (Senior Editor for Universe Today, Host of the NASA Lunar Science Institute podcast & a NASA/JPL Solar System Ambassador)
Mars is probably the obvious choice for doing any terraforming (Venus is too hot and crushing while Europa or any other moons of Jupiter or Saturn are too cold) But it would be an incredible proposition to even attempt to try it, and the technology to accomplish such a feat is likely decades away, if not centuries or more. Plus the process itself would likely take hundreds of years to accomplish. I see terraforming as an “emergency” procedure if Earth was somehow becoming inhabitable. Hopefully we won’t have to think about that as a possibility for quite some time!
While Mars has the basic ingredients to do terraforming (water, nitrogen and carbon and oxygen in the form of CO2) there are a few problems to overcome with terraforming Mars. One is that Mars has only trace amounts of atmospheric CO2, and unless there is more CO2 locked up in the polar ice caps than currently estimated, it would be difficult to create as much CO2 as would be needed. You’d have to have huge factories spewing out CO2 to create a greenhouse effect on Mars. This would create a nice thick breathable atmosphere that would also warm up the planet.
The other problem is that Mars lost its magnetic field millennia ago due to a cooling down of its core and mantle. A magnetic field is necessary to shield the planet from the Solar Wind, which otherwise blasts away the atmosphere and any liquid water that might be there. Without a magnetic field, creating a thicker atmosphere or oceans would be an effort in futility.
Nicole Gugliucci (“Noisy astronomer”, blogger, educator, post-doc)
Terraforming a whole planet seems like a huge task that may not have the most gain. After all, it would take quite a lot of resources to build up Mars’ atmosphere, for example, and then to keep replenishing it without a planet-wide protective magnetic field. Unless there is a compelling reason to develop huge tracts of land, I see colonization starting in domes that would connect around a planet like Mars.
Mars seems like an obvious planetary choice for reasons of gravity (less than Earth but potentially still adaptable) and the familiar day-night cycle. One idea I particularly like is to use a hollowed out asteroid as a floating and rotating (to simulate gravity) space colony, but given that so many asteroids may be no more than rubble piles, that may not be feasible at all.
Antonio Paris (Astronaut Candidate, Astronomy Professor, Planetary Scientist, Space Science Author)
For decades, scientists, engineers, and science fiction authors/filmmakers have proposed the idea of combining technology and biology to terraform Mars – in hopes of expanding the human presence in the Solar System. Mars, consequently, is the only other terrestrial planet in the Solar System that has the probability of supporting life – and terraforming seems like a practicable option. Today, planetary scientists argue that the basic elements to revive Mars, such as carbon, nitrogen, and water, exists beneath the Martian soil in sufficient quantities to create an atmosphere and hydrosphere. Recent data by the Mars Global Surveyor satellite, for example, have found indirect traces of water tied up as ice in the polar regions. Moreover, the Mars Reconnaissance Orbiter recently provided convincing evidence that water in the form of liquid flows occasionally on present-day Mars. Terraforming Mars, thus, would focus on introducing a runaway greenhouse effect to thicken and warm the Martian atmosphere, while gradually introducing microbes to bring life to the barren landscape. In principle, terraforming the Red Planet to a Green Planet is essentially restoring the planet back to what it was billions of years ago.
Many in the scientific community, however, remain skeptical of Mars being green again. For example, many scientists believe that radiation, due to Mars’ thin atmosphere and lack of magnetic field, has created an oxidizing agent in the surface, which would destroy any kind of organic molecule or plants. Additionally, the chief hurdle of terraforming Mars is not from a technologically perspective but from a position of commitment. An ambitious project like terraforming Mars would take hundreds or perhaps thousands of years as well as trillions of dollars. No country on Earth, unfortunately, has developed a political or economic system willing to support at great cost an enterprise that will undoubtedly require generations to accomplish. Therefore, the idea of transforming Mars back to a green planet is more science fiction than science – at least for now.
Fraser Cain’s series about terraformation:
How do we terraform Venus
How do we terraform Mars?
Could we terraform Jupiter?
Could we terraform the Moon?
Could we terraform the Sun?
Could we terraform a Black Hole?