The idea of terraforming Mars has long been debated by the scientific community.
Ever since Carl Sagan was the first — outside of science fiction — to seriously propose the idea, the feasibility of the method has been a cause for contention.
Now, a new paper outlining a more localized approach to changing Mars' climate shows that the debate is far from over — and that scientists won't give up on finding ways to make the Red Planet habitable for future humans.
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Carl Sagan's Mars dream
As far back as 1961, Carl Sagan released a paper outlining a way to change Venus' climate. In the following years, the famous science popularizer started to focus solely on the terraforming of Mars — he felt it was our most viable hope for colonizing another planet in our solar system.
Sagan's work inspired many other scientists to seriously consider the likelihood that we could change a whole planet's climate in order to inhabit it as a plan B for human civilization.
The problem with terraforming Mars
One key question is at the root of the terraforming proposal: are there enough greenhouse gases and water sources on Mars that we can manipulate to increase the planet's atmospheric pressure to Earth-like levels?
In 2018, two NASA-funded scientists from the University of Colorado, Boulder and Northern Arizona University came to the conclusion that there are not.
Processing all of the available resources on Mars, they wrote, would only increase the planet's atmospheric pressure to about 7 percent that of Earth — a lot less than the necessary amount to make the planet habitable.
A more localized approach?
The 2018 findings put a serious damper on any scientists inspired by the idea of terraforming Mars. Sadly, with our current technology, going to Mars in the 2030s and completely changing the planet's atmosphere looks impossible.
And yet, this only emboldened researchers to look for new methods.
Now, scientists from Harvard University, NASA's Jet Propulsion Lab, and the University of Edinburgh have presented a new idea that might see Sagan's dream live on in a different form.
Instead of changing the entire makeup of Mars' atmosphere, what if you could take a more localized, regional approach?
Silica aerogel: extremely high insulation domes
In their paper — published today, July 15, in Nature Astronomy — the researchers outline how regions of the Red Planet could be made habitable. To do this, they would use silica aerogel, one of the highest insulation materials found on Earth.
The scientists ran experiments on models they created using the material. By testing it on Mars-like conditions on Earth, they found that a large dome with a 2 to 3 cm thick shield of silica aerogel could enable an atmospheric greenhouse effect.
What's more, the conditions would largely be created naturally in this confined space — no need for artificial conditions like in a spacecraft, or in the space domes of science fiction.
Biospheres and livable Earth-like environments
Silica aerogel would allow the transmitting of enough visible light for photosynthesis. Used as a dome, it would also block hazardous ultraviolet radiation while raising temperatures permanently above the melting point of water — all of this without an internal heat source.
The material is 97 percent porous; so light moves through it while its nanolayers of silicon dioxide greatly slow the conduction of heat. This means that biospheres and large livable areas could, in theory, be created under a relatively thin layer of this silica aerogel, the scientists say.
"Silica aerogel is a promising material because its effect is passive," said Laura Kerber, Research Scientist at NASA's Jet Propulsion Laboratory, in a press release. "It wouldn't require large amounts of energy or maintenance of moving parts to keep an area warm over long periods of time."
The research team's next steps involve them testing the material in Mars-like climates on Earth, like the dry valleys of Antarctica and deserts of Chile.
Inspired by Mars observations
Silica aerogel is already used on the Red Planet today, on NASA's Mars Exploration Rovers. The researchers drew from this, as well as a phenomenon that already occurs on the Martian planet.
Mars' polar ice caps are made from frozen CO2 — not only frozen water, like on Earth. Frozen CO2 allows sunlight to penetrate it while also trapping in the heat, much in the same way as its gaseous form does on Earth.
This creates a solid-state greenhouse effect that creates pockets of warming under the CO2-infused Martian 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," said Robin Wordsworth, Assistant Professor of Environmental Science and Engineering at Harvard.
"We started thinking about what kind of materials could minimize thermal conductivity but still transmit as much light as possible."
The ethics of colonizing Mars
"There's a whole host of fascinating engineering questions that emerge from this," Wordsworth says.
And what of the ethical questions?
"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. "The moment we decide to commit to having humans on Mars, these questions are inevitable."
For now, all we know is that SpaceX and NASA aim to get humans to Mars by the 2030s.
If we get to a point where we need to seriously ponder the ethics of Mars on the Red Planet, it will be thanks to a technological achievement like no other — one that may just involve huge livable silica aerogel biodomes.