Silica airgel could make March habitable

People have long dreamed of reshaping the Martian climate to make it liveable for humans. Carl Sagan was the first outside the field of science fiction to offer terraforming. In a 1971 article, Sagan suggested that vaporization of the northern polar ice caps "would produce about 10 sg cm-2 of atmosphere on the planet, higher global temperatures through the greenhouse effect and a significantly increased probability of liquid water ".

Sagan's work has inspired other researchers and futurists to take the idea of ​​terraforming seriously. The key question was: is there enough greenhouse gas and water on Mars to increase its atmospheric pressure to levels similar to those of the Earth?

In 2018, two researchers from the University of Colorado, Boulder and Northern Arizona University, funded by NASA, discovered that treating all available sources on Mars would increase atmospheric pressure to about 7% of that of the Earth, far below what is needed to make the planet habitable.

Terraformer Mars, it seemed, was an unreachable dream.

Researchers at Harvard University, NASA's Jet Propulsion Lab and the University of Edinburgh now have a new idea. Rather than trying to change the entire planet, if you take a more regional approach?

The researchers suggest that areas of the Martian surface could be made habitable with a material, silica airgel, reproducing the Earth's atmospheric greenhouse effect. With the help of models and experiments, the researchers showed that a silica airgel shield two to three centimeters thick could transmit enough visible light for the photosynthesis, block dangerous ultraviolet rays and raise the temperature permanently below the melting point of water, all without any need for any internal heat source.

The article is published in Nature Astronomy.

"This regional approach to making Mars liveable is far more achievable than a global atmospheric modification," said Robin Wordsworth, an assistant professor of environmental science and engineering at the school of Toronto. Engineering and Applied Sciences Harvard John A. Paulson (SEAS) and Earth Department. and planetary science. "Unlike previous ideas to make Mars habitable, it's something that can be developed and tested systematically with the materials and technology that we already have."

"Mars is the most habitable planet in our solar system, apart from Earth," said Laura Kerber, researcher at NASA's Jet Propulsion Laboratory. "But it remains a hostile world for many types of life, and a system of creating small islands of habitability would allow us to transform Mars in a controlled and evolutionary way."

The researchers were inspired by a phenomenon that is already occurring on Mars.

Unlike the ice caps of the Earth, composed of frozen water, the polar ice caps on Mars are a combination of ice water and frozen CO2. Like its gaseous form, frozen CO2 allows sunlight to penetrate while capturing heat. In summer, this greenhouse effect in the solid state creates pockets of warming under the ice.

"We started thinking about this greenhouse effect in the solid state and how it could be invoked to create habitable environments on Mars in the future," said Wordsworth. "We started thinking about the types of materials that could minimize thermal conductivity while transmitting as much light as possible."

The researchers landed on silica airgel, one of the most insulating materials ever created.

Silica aerogels are 97% porous, which means that light travels through the material, but interconnected nanocoats of infrared radiation to silicon dioxide significantly slow the conduction of heat. These aerogels are used in several engineering applications, including Mars exploration rovers of NASA.

"Silica airgel is a promising material because its effect is passive," said Kerber. "This would not require large amounts of energy or maintenance of moving parts to keep a hot zone for long periods."

By using models and experiments that mimic the Martian surface, researchers have shown that a thin layer of this material increases the mean temperatures of the mid-latitudes of Mars to temperatures similar to those of the Earth.

"Spread out on a large enough surface, you do not need any other technology or physics, you just need a layer of this material on the surface and under which you will have the advantage. permanent liquid water, "said Wordsworth.

This material could be used to build housing domes or even standalone biospheres on Mars on Mars.

"The result is a host of fascinating engineering questions," said Wordsworth.

The team then aims to test the material in climates similar to those of Mars, such as the dry valleys of Antarctica or Chile.

Wordsworth points out that any discussion of making Mars habitable for humans and for life on Earth also raises important philosophical and ethical questions about the protection of the planet.

"If you want to allow life on the Martian surface, are you sure that there is no life there yet? There are, how can we navigate in that, "asked Wordsworth. "By the time we decide to commit to having humans on Mars, these issues are inevitable."