How silica aerogel could help make Mars habitable
A team of researchers from Harvard University, NASA’s Jet Propulsion Lab, and the University of Edinburgh believe silica aerogel may be the key material that could make the surface of Mars habitable for Earthlings.
Because silica aerogel mimics Earth’s greenhouse gas effect, which could therefore increase Mars’ atmospheric pressure to Earth-like levels, the researchers believe this one material could make life on Mars possible.
In fact, through modelling and experiments, the team found that a two- to three-centimeter-thick shield of silica aerogel could filter enough visible light photosynthesis while blocking harmful ultraviolet radiation. This shield would also raise temperatures above the melting point of water without the need for an internal heat source.
These findings are published in Nature Astronomy.
“This regional approach to making Mars habitable is much more achievable than global atmospheric modification,” said Robin Wordsworth, Assistant Professor of Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Department of Earth and Planetary Science. “Unlike the previous ideas to make Mars habitable, this is something that can be developed and tested systematically with materials and technology we already have.”
“Mars is the most habitable planet in our Solar System besides Earth,” added Laura Kerber, Research Scientist at NASA’s Jet Propulsion Laboratory. “But it remains a hostile world for many kinds of life. A system for creating small islands of habitability would allow us to transform Mars in a controlled and scalable way.”
The research team decided to draw inspiration from a phenomenon that already occurs on the surface of Mars. The planet’s polar ice caps are a mix of frozen water and CO2. Even when frozen, CO2 allows sunlight to penetrate and traps its heat under the surface. Then, in the summer, the greenhouse effect causes pockets of warming under the icy surface.
“We started thinking about this solid-state greenhouse effect and how it could be invoked for creating habitable environments on Mars in the future,” said Wordsworth. “We started thinking about what kind of materials could minimize thermal conductivity but still transmit as much light as possible.” They decided to test out silica aerogel, which is 97% porous, meaning light can penetrate the material, but heat is trapped underneath.
“Silica aerogel is a promising material because its effect is passive,” said Kerber. “It wouldn’t require large amounts of energy or maintenance of moving parts to keep an area warm over long periods of time.”
“Spread across a large enough area, you wouldn’t need any other technology or physics, you would just need a layer of this stuff on the surface and underneath you would have permanent liquid water,” said Wordsworth.
The researchers posit that the material could be used to build habitation domes or self-contained biospheres on the surface of Mars. They plan to test silica aerogel in Mars-like climates on Earth, like in Antarctica or Chile.
Even with this discovery, the ethics surrounding the colonization of Mars raises philosophical and ethical questions about planetary protection, Wordsworth said.
“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,” asked Wordsworth. “The moment we decide to commit to having humans on Mars, these questions are inevitable.”
Image Credit: Harvard SEAS