海角大神

Could a huge magnet turn the Red Planet green?

Martian climate simulations suggest a relatively simple plan could restore Mars's ancient atmosphere, and more. 

With all the excitement over far-away exoplanets, it can be easy to overlook the other habitable-zone planet right in Earth's backyard.聽

Despite its occasionally just-right temperature for surface water, we don鈥檛 often think of Mars as a thriving incubator, in no small part because our rusty neighbor聽lacks many of Earth鈥檚 comforts, including a life-giving atmosphere, mild temperatures, and a protective magnetic field. 聽

But if NASA鈥檚 Director of Planetary Science Jim Green and his team have their way, the Red Planet might someday look a little greener. Taking the stage at the聽Planetary Science Vision 2050 Workshop, Dr. Green outlined a new way of thinking about how to make Mars a little more like home by bringing back a life-supporting atmosphere and temperatures with an artificial version of the planet's lost magnetic field.

The plan is to plop a giant magnet at one of the spots where the gravitational pulls from the sun and Mars balance in such a way that a 聽arises, allowing it to stay put relative to the sun and Mars. If the magnet were strong enough, the team鈥檚 simulations predict it could block the 鈥渨ind鈥� of charged particles that stream out from the sun, which the NASA's MAVEN orbiter has determined is blowing away what remains of the Martian atmosphere at about two pounds per second. Such a move could let Mars鈥檚 natural gas emissions slowly rebuild its ancestral atmosphere, aiding any future efforts to 鈥渢erraform鈥� the planet to make its environment more Earthlike.

鈥淢ars is an arid and cold world,鈥� the team writes in the accompanying paper. While the average temperature hovers around a chilly 80 degrees F. below, some days can reach a . Such temperatures could melt ice, but with an atmosphere well over a hundred times thinner than Earth鈥檚, the water would boil off into space before it could be of much use to a thirsty Martian explorer.

But ancient Mars was a different story, a relatively lush atmosphere protecting a giant ocean covering as much as a third of the surface. 鈥淲e now know Mars has lost between over its history,鈥� said Green in a talk last Wednesday. He suggests applying a modern understanding of the sun and solar wind to Martian climate models could pave the way to a new understanding of how to terraform the Red Planet. 聽

鈥淎re there things that we can do that can help mitigate some of these extremes on Mars and provide a better environment for science and exploration to coexist on the surface?鈥� he asked.

That鈥檚 where the magnet comes in. According to his team鈥檚 simulations, placing an Earthlike magnetosphere between Mars and the sun could produce some 鈥減retty good鈥� shielding from the solar wind, whose energy breaks up molecules in the atmosphere and . Specifically, they predict total stripping could drop by a factor of ten, facilitating an eventual recovery.

A greatly enhanced atmosphere would afford humanity numerous benefits, including the ability to take advantage of 鈥渁ir braking鈥� to land larger spaceships on the surface, a shield against most cosmic and solar particle radiation, and the possibility of for plant production, the team writes.

It could even mean a partial return of the ancient ocean, one seventh of which remains on the planet, locked up at the poles. Various schemes, from , aim to melt the polar ice caps, and for good reason. Along with all that ice sits an even more valuable terraforming material, frozen carbon dioxide.

While rising CO2 levels threaten to make life more difficult on our planet, they鈥檇 be a boon for Martian settlers. 鈥淲e as a species have learned how to make a planet hotter, and it would not take a lot to sublimate the CO2 in the polar caps (perhaps 4 degrees [of warming]). Once you do that the atmosphere would have a positive feedback due to the CO2 and get even hotter,鈥� writes Luther Beegle, head of an on NASA鈥檚 2020 Mars rover, in an email to 海角大神.

As the CO2 joined the magnetically swaddled infant atmosphere, warmer weather could someday start to restore that ancient ocean. 鈥淵ou could conceivably get up to the point where the water would melt. The temperature on Mars does get above zero occasionally, so you would get more and more times like that,鈥� Dr. Beegle says.

But scientists suspect it wouldn鈥檛 happen overnight. 鈥淎t current loss rates driven by the sun and solar wind as measured by MAVEN, it would take about 2 billion years to remove the present atmosphere鈥�. If we put up an artificial magnetosphere, it would be very intriguing in terms of physics. 聽But it would have minimal effect on the thickness of the atmosphere, the global temperature, or the behavior of the polar caps. At least not for billions of years,鈥� says Bruce Jakosky,聽principal investigator of the MAVEN mission.

Even if scientists could accelerate the timescale, future settlers won鈥檛 be going for evening strolls on the gains of this plan alone. The magnetic shielding may be able to thicken the atmosphere and start to melt the ice caps, but it wouldn鈥檛 introduce any breathable oxygen into the primarily CO2 mix.

Still, it鈥檇 be a good start. Beegle, who calls the proposal 鈥渢echnically feasible, if you wanted to terraform the surface and were willing to spend large sums of money to do so,鈥� points out that a lack of breathable air and comfortable temperatures don鈥檛 stop people from summiting Everest. Even without space suits.

But he has other objections. Green suggests a thicker, warmer atmosphere would smooth human endeavors on Mars, including scientific exploration, but Beegle isn鈥檛 so sure. With the exception of a few rovers, Mars鈥檚 pristine environment remains mostly untarnished, but if we start tinkering with the planet鈥檚 climate, it might not stay that way.

鈥淎s soon as we start mucking around with the surface, we change things perhaps to the point where it would be impossible to determine if life ever started on Mars. When we first send humans we are going to contaminate the site that they land at, because humans bring a ton of microbiology with them. If we also start heating the atmosphere, it would result in unpredictable consequences.鈥�

Those who think a future on Mars is might not lose much sleep over a few microbes, but if delaying a centuries- (or billions of years) long plan a couple decades threatens the whole undertaking, we might not have much of a shot in the first place.聽

After all, turning Mars from red to green is a colossal task, prompting some to wonder why it鈥檚 sometimes pitched as a Plan B to keeping the Earth green.

As Neil Degrasse Tyson told The Guardian: 鈥淚f you had the power of geoengineering to terraform Mars into Earth, then you have the power of geoengineering to .鈥�