First, the bad news: There’s still no silver bullet that will make all of Mars habitable.
But every terraforming cloud has a silica lining—and there may yet be hope for making some parts of the Red Planet hospitable to life as we know it.
At least, that’s what the researchers behind a paper published today in the journal Nature Astronomy argue. Their study proposes the installation of a series of shields made of UV-blocking, heat-trapping silica aerogels on select parts of the Martian surface. Such an intervention, the research suggests, could warm up targeted areas enough to support the existence of liquid water, while also blocking harmful radiation—meeting two life-sustaining criteria in one fell swoop.
The technique, which requires both consistent sunlight and a cache of meltable ice, wouldn’t work everywhere. And long before any efforts go extraterrestrial, there are plenty of logistical and ethical considerations that need to be taken into account, including the potential repercussions for yet-undiscovered life that already exists on Mars. But if the findings can be put to use, humans might have a shot at seeding new life on Earth’s ruddiest neighbor.
“This is an exciting demonstration that it’s not impossible to have life on Mars,” says Jennifer Buz, a planetary scientist at Northern Arizona University who was not involved in the study. “There’s a lot that still needs to be worked out....But just showing that this is possible is a big breakthrough.”
Let’s be clear: Mars is no second Earth. One of the Red Planet’s biggest problems is that its surface is so exposed. Unlike the thick, insulating atmosphere that swaddles our own planet, the sparse collection of gases bopping around Mars is simply too thin to keep its surface very warm, leaving a lot of would-be-liquid water locked up in ice. The Martian atmosphere also isn’t very good at blocking UV radiation, which can do serious damage to cells.
To remedy this, some terraforming hopefuls have proposed releasing greenhouse gases like carbon dioxide and water vapor into the Martian atmosphere to thicken it up into a better insulator—essentially, an extraterrestrial echo of the greenhouse effect happening here on Earth. But even if humans were to somehow liberate carbon dioxide from all available sources on Mars, researchers think the planet’s surface still wouldn’t get hot enough to support liquid water. Supplementing the deficiency would require a serendipitous influx of carbon-carrying comets, or human technology powerful enough to infuse the atmosphere with an external source of greenhouse gases—neither of which is likely to happen anytime soon.
But Mars habitability isn’t necessarily an all or nothing pursuit. Even in the absence of global modifications, life could spring up on patches of accommodating real estate, given a few small-scale changes.
That’s where this new study—the brainchild of researchers Robin Wordsworth, Laura Kerber, and Charles Cockell—comes in. “Mars is on the edge of habitability,” Cockell says. “It’s a planet that needs only a bit of a nudge for local environments to be made suitable for life.”
A big part of that nudge, Cockell says, is keeping water in a liquid state. And where there’s ice on the Red Planet, there’s potential for water, given the right amount of heat. So the team zeroed in on ice-rich regions of the Red Planet that had regular exposure to sunlight, and searched for a material that could concentrate heat onto the surface.
Silica aerogel, an ultra-lightweight insulator that’s already been put to use in NASA spacecraft and Mars rovers, fit the bill. In laboratory experiments that mimicked Martian conditions, the team found that inch-thick shields made of silica aerogel generated hotspots of high pressure and temperature beneath them. Scaled up on Mars itself, this could raise surface temperatures by 90 degrees Fahrenheit (50 degrees Celsius)—enough to keep shallow pools of water liquid year-round within a few (Earth) years of installation. And because silica isn’t good at transmitting UV light, the shields would come with the added perk of blocking whatever lay beneath them from damaging radiation.
The team’s models have yet to leave the lab, but Wordsworth says a clear next step is to test the silica aerogels’ warming effects in Mars-like environments here on Earth, like the Antarctic. If all goes well, the team hopes to eventually bring a small sample of the technology to Mars, and scale up from there. Silica is abundant on the Red Planet, Cockell says, which could make a Martian manufacturing plant a tantalizing possibility in the distant future.
A smattering of shields wouldn’t change Mars on a global scale, and would still leave certain ice-poor or sun-starved areas, like the equator or poles, uninhabitable. But unlike proposals of the past, this new idea “is actionable...something that could be done within a few decades,” Kerber says. It’s also pretty low-maintenance: Once the shields go up, they’d just keep doing their thing, leaving open the possibility that they could eventually shelter burgeoning colonies of bacteria or small plants.
In the short term, silica aerogels could also have exciting applications for harvesting water from the Martian surface—something that could make a splash in the realm of space exploration, says Bethany Ehlmann, a planetary scientist at Caltech who was not involved in the study.
But ultimately, the researchers’ sights remain set on life. Tiled onto self-contained structures, the aerogels might someday serve as building material for greenhouses or habitation domes. “The really fundamental things that make Mars uninhabitable are low temperatures and UV radiation,” Wordsworth says. “The silica aerogel removes those two most onerous constraints.”
Meeting these two criteria alone, however, by no means guarantees life, says Germán Martínez, a planetary scientist at the Lunar Planetary Institute in Houston who was not involved in the study. “The approach is excellent… but while these conditions are necessary, they are not sufficient.” A few especially hardy microbes might be able to get by with these two ingredients alone, he adds. More complex life—like photosynthesizing plants—would probably need a boost from nutrients like nitrogen, which is also in short supply on Mars.
But before humans can even think about introducing any Earth-based organisms to the Red Planet, there needs to be a better understanding of how even small-scale modifications would affect any life forms currently stirring on the Martian surface, should they exist, Ehlmann says. Wordsworth agrees, and notes that, should the research progress, measures would need to be taken to minimize this kind of contamination.
Someday, Mars may yet be livable for us Earthlings. We just need to stay alert to the possibility that something (or someone) else may have beat us to the punch.