Can Mars Be Made Habitable in Our Lifetime?

It's a very poorly kept secret in the world of science. For many of us who study Mars, Kim Stanley Robinson's 1990s trilogy, which describes the colonization and eventual terraforming of the Red Planet, was particularly influential. But rereading these books in 2019, I noticed that much of what he imagined looks pretty far-fetched-we're still a long way from landing the first human on Mars, and terraforming the planet to make it habitable seems like a very distant dream .

Serious scientific ideas for transforming Mars into an Earth-like planet have been put forward before, but they require vast industrial capabilities and make assumptions about the total amount of accessible carbon dioxide (CO₂the planet has been criticized as unrealistic. When we started thinking about this problem a few years ago, therefore, we decided to take a different approach. One thing you'll learn quickly when you study It's never been so hard that it's never been so much earth-it has always been a unique and alien world. So when we're thinking about how to make Mars habitable in the future, we should also take inspiration from the Red Planet itself.

One natural process on Mars-the so-called solid-state greenhouse effect-is of particular interest, as it's capable of intensely heating layers of ice in Mars's polar caps every summer. This effect occurs when visible light is transmitted to the interior of a thermally insulating material, after which the heat becomes trapped and dramatic warming can occur.

Inspired by this process, a question for the first time in the classroom (we never know how to help with research!) Mars by thin layers of translucent solid material on the surface. To do our experiments we used silica aerogel, an exotic[AQ: Please clarify “exotic” in this context. Silica aerogels are the most commonly studied class of aerogels, so a different word might be preferable if you are trying to suggest that they have unusual properties in comparison with more everyday materials.] material that's incredibly insulating, very low density (it's over 97 percent air) and almost transparent to visible light, making it an ideal candidate for creating strong solid-state greenhouse warming.

Silica aerogel is already used by NASA to insulate the insides of Mars rovers, among other things. As we show in our paper[AQ: This is your first reference to your paper. Would you like to link to it here, or provide more details (e.g., journal title, if published)?] via a combination of experiments, modeling and first-principles theory, we found that a two-to-three-centimeter-thick layer of this layer would be sufficient to keep the layer beneath permanently warm enough to grow algae or plants and to block most hazardous UV radiation. If we're happy to start locally, making Mars habitable is more likely to be done.

What are the next steps? Well, our paper demonstrates that the basic physics of this idea is sound, but there is still a lot of room for improvement in the future. Silica aerogel is quite fragile, so to allow for robust shields and control interior pressure it would need to be modified or combined with some other materials. There's also the question of how to supply silica air on Mars. It's very light, which is favorable for transporting it from Earth, but eventually we'd like to make it on the surface.

One standard industrial approach involves high-pressure CO₂ drying step, which could use CO₂ supplied from the atmosphere. However, it is notable that some organisms on Earth are incredibly proficient at manipulating silica on nanometer scales (glass sponges and diatom phytoplankton are just two examples). Speculatively, it is possible that they would eventually be able to produce silica-aerogel-like materials themselves, leading to a biosphere that helps to sustain its own livable environment.

In practical terms, we will focus on improving the range and sophistication of our laboratory experiments and performing initial tests in the field. Mars is unique, but there are some inhospitable locations on Earth that are rather like it, including the Atacama Desert in Chile and the Dry Valleys in Antarctica. If we can demonstrate the feasibility of our site, we will be able to demonstrate that it can work for us on the Martian surface.

After that, the most important hurdle will be planetary protection: any plans to put life on it. This will be more easily done with the regional, scalable approach we are proposing that in any global terraforming scenario, but it is still a major issue that requires very much consideration in the future.

We're still a long way from making viable self-sufficient habitats on other planets. But for the first time, our research opens up a plausible path to success in the future, rather than centuries, if we choose to do so. And we think that's something worth getting excited about.