A Material Way Of Making Mars Habitable
Editorials News | Jul-30-2019
People have long dreamed of remodeling the Martian climate so that it ishabitable for humans. Carl Sagan was the first outside the field ofscience fiction to propose terraformation. In a 1971 article, Sagan suggested that the vaporization of the ice sheets of the North Pole"would produce ~ 10 sg cm-2 of atmosphere on the planet, higher global temperatures through the greenhouse effect and a much higher probability of liquid water".
Sagan's work inspired other researchers and futurists to take the idea of terra forming seriously. The key question was: are there enough greenhouse gasesand water on Mars to increase its atmospheric pressure to levels similar to those on Earth?
In 2018, a couple of NASA-funded researchers from the University of Colorado, Boulder and the University of Northern Arizona found thatprocessing all available sources on Mars would only increaseatmospheric pressure to approximately 7 percent of Earth, far below what is needed to make the planet habitable.
Terraforming Mars, it seemed, was an impossible dream to fulfill.Now,researchers at Harvard University, NASA's Jet Propulsion Laboratoryand the University of Edinburgh have a new idea. Instead of trying tochange the entire planet, what would happen if I adopted a more regional approach?
The researchers suggest that the Martian surface regions could become habitable with a material, the silica airgel, which mimics theEarth's atmospheric greenhouse effect. Through modeling andexperiments, the researchers show that a silica airgel shield two to three centimeters thick could transmit enough visible light forphotosynthesis, block dangerous ultraviolet radiation and raise temperatures below the melting point of the Water permanently, all without the need for any internal heat source.
The article is published in Nature Astronomy
"This regional approach to making Mars habitable is much more feasible thanglobal atmospheric modification," said Robin Wordsworth,Assistant Professor of Environmental Sciences and Engineering at theJohn A. Paulson School of Engineering and Applied Sciences at Harvardand the Department of the earth. and planetary science. "Unlikeprevious ideas to make Mars habitable, this is something that can besystematically developed and tested with the materials and technologywe already have."
"Mars is the most habitable planet in our Solar System, in addition to Earth," said Laura Kerber, Scientific Researcher at NASA's Jet Propulsion Laboratory. "But it remains a hostile world for manytypes of life. A system to create small islands of habitability wouldallow us to transform Mars in a controlled and scalable way."
The researchers were inspired by a phenomenon that already occurs on Mars.
Unlike the polar ice sheets on Earth, which are made of frozen water, thepolar ice caps on Mars are a combination of ice water and frozen CO2.Like its gaseous form, frozen CO2 allows sunlight to penetrate whiletrapping heat. In the summer, this solid-state greenhouse creates hotspots under the ice.
"We started thinking about this solid-state greenhouse effect and how itcould be invoked to create habitable environments on Mars in thefuture," said Wordsworth. "We began to think what kind ofmaterials could minimize thermal conductivity but still transmit asmuch light as possible."
The researchers landed on silica airgel, one of the most insulatingmaterials ever created.
Silica aerogels are 97 percent porous, which means that light moves throughthe material, but interconnected nano layers of infrared silicondioxide radiation significantly reduce heat conduction. Theseaerogels are used in several engineering applications today,including NASA's Mars exploration rovers.
"The silica airgel is a promising material because its effect is passive,"Kerber said. "It would not require large amounts of energy orthe maintenance of moving parts to maintain a hot area for longperiods of time."
Using models and experiments that mimicked the Martian surface, theresearchers showed that a thin layer of this material increased theaverage temperatures of the mid-latitudes on Mars to Earth-liketemperatures.
"Distributedin a large enough area, you would not need any other technology orphysics, you would only need a layer of these things on the surfaceand underneath you would have permanent liquid water,"Wordsworth said.
Thismaterial could be used to build housing domes or even self-containedbiospheres on Mars.
"Thereare a lot of fascinating engineering questions that arise from this,"Wordsworth said.
Next,the team aims to test the material in climates similar to those on Mars on Earth, such as the dry valleys of Antarctica or Chile.
Wordsworthpoints out that any discussion on how to make Mars habitable forhuman beings and life on Earth also raises important philosophicaland ethical questions about planetary protection.
"Ifyou are going to allow life on the Martian surface, are you surethere is no life there anymore? If there is, how can we navigatethat?" Wordsworth asked. "At the moment we decided tocommit to having humans on Mars, these questions are inevitable.
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