This Material May Make Human Habitation on Mars Possible
Silica aerogel traps heat and allows light in while blocking ultraviolet radiation, making it a good candidate for building human settlements
Earlier this week, NASA administrator Jim Bridenstine said a crewed mission to Mars in 2033 is still in the realm of possibility, and the technological innovations needed to get to the red planet are moving ahead. Landing astronauts on Mars is just the first step; many people hope humans can establish a permanent settlement on the planet, and, eventually, colonize the world. But that would mean transforming the cold, dry, nearly airless planet into a habitable place for humans, a process that would be significantly more difficult than just getting to Mars. A new study, however, proposes using silica aerogel as a cheap way to warm up things up and make patches of the planet friendly to human life.
According to a Harvard press release, back in 1971, Carl Sagan floated the first plausible scenario for terraforming Mars, or transforming the planet into a place humans could live. By vaporizing the planet’s northern polar ice caps, he suggested, the water vapor and CO2 released into the atmosphere could create a greenhouse effect, raising temperatures enough for liquid water to exist on the surface of the planet. But just last year, a study in Nature Astronomy found that even if humans used all the available CO2 available from water, minerals and the soil to spike the atmosphere, it would only produce an atmosphere with about 7 percent of the pressure of the atmosphere on Earth. So unless we have a technological breakthrough, humans won’t be terraforming Mars anytime soon.
Instead of trying to modify the whole planet at once, however, researchers at Harvard and NASA decided to look at whether it’s possible to modify smaller sections of the planet. “We wanted to think about something that's achievable on a decadal time scale rather than something that would be centuries in the future—or perhaps never, depending on human capabilities,” Harvard’s Robin Wordsworth, lead author of the study in Nature Astronomy, tells Mike Wall at Space.com.
Their solution was inspired by a phenomenon already found in the Martian polar ice caps. Made of water and CO2, researchers believe some sections of the ice act as a solid state greenhouse, allowing sunlight through and trapping heat underneath. The warm spots show up as dark smudges on the ice. “We started thinking about this solid-state greenhouse effect and how it could be invoked for creating habitable environments on Mars in the future,” Wordsworth says in the release. “We started thinking about what kind of materials could minimize thermal conductivity but still transmit as much light as possible.”
The team landed on silica aerogel, a 97 percent porous material that allows light through but is an insulator that slows the conduction of heat. Through modeling and experiments, they found that a layer of the gel, just 2 to 3 centimeters thick, would be enough to allow light through to power photosynthesis while blocking out hazardous ultraviolet radiation, and it could raise temperatures above the melting point of water.
By laying the stuff on the ground, humans on Mars could warm up the ground by 90 degrees, and the material could also be used to build domes, greenhouses or self-contained biospheres. “Spreading it over a larger area would make the solid-state greenhouse effect more efficient, as the proportional amount of heat emitted from the sides would be less, but you could still get substantial warming in a greenhouse,” Wordsworth tells Wall. “Whether you place the layer on or above the surface does not have a huge influence on the basic physics of the effect.”
The aerogel would perform almost anywhere on the planet between 45 degrees north latitude and 45 degrees south, though areas with subsurface water and a little wind to blow the dust off the dome would be best.
As opposed to terraforming, which would involve changing the entire planet, using the aerogel would be scalable and reversible. “The nice part is that the other ways you can think of to terraform a planet are so far out there,” coauthor Laura Kerber of NASA’s Jet Propulsion Laboratory tells Ryan F. Mandelbaum at Gizmodo. By comparison, this looks like a practical solution.
It also addresses some of the thornier ethical questions that come with altering the environment of an entire planet. “If you’re going to enable life on the Martian surface, are you sure that there’s not life there already? If there is, how do we navigate that?” Wordsworth asks in the release. “The moment we decide to commit to having humans on Mars, these questions are inevitable.”
The next step is to test out the viability of the aerogel by deploying it on Earth in a dry, cold area like Antarctica or Chile. If it works, the material or at least equipment to produce it from Martian resources, may be in the cargo bay of some of the first flights to Mars.