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By Denise Chow

Before humans can colonize Mars, we’ll need to figure out a way to make it a bit more hospitable. But a surprising new study suggests that “terraforming” Mars into an Earthlike planet — an idea at the heart of many science fiction novels and films — simply isn’t possible with today's technology.

The study, published July 30 in the journal Nature Astronomy, seems to throw cold water on those fictional terraforming schemes — along with some real-world ideas that sound like make-believe: In 2015, SpaceX CEO Elon Musk said we could warm Mars and give it a thicker atmosphere capable of supporting agriculture by detonating nuclear warheads over the planet’s icy poles.

There’s no doubt that Mars' thin atmosphere and its soil and icy polar regions contain carbon dioxide. But the new research indicates that there’s not enough of it for us to be able to trigger a sort of runaway greenhouse effect that would turn the red planet into a green one.

“The bottom line is that there just isn’t very much there, and it’s hard to put very much back into the atmosphere,” said Bruce Jakosky, a professor of geological sciences at the University of Colorado, Boulder and the study's lead author. “Our conclusion is we can’t do it with today’s technology.”

Jakosky and his collaborator, Christopher Edwards, an assistant professor of planetary science at Northern Arizona University in Flagstaff, came up with an estimate for the total amount of carbon dioxide on Mars by looking at data collected by space probes over the past two decades. They concluded that the polar ice caps contain the most accessible stores of carbon dioxide, but that melting the caps — for example, by somehow covering them with sunlight-absorbing dust — wouldn't produce enough gaseous carbon dioxide to terraform the planet.

NASA's Mars Reconnaissance Orbiter captured this image of snow and ice covering dunes in Mars' northern hemisphere.NASA / AFP - Getty Images file

And tapping the carbon dioxide in Martian soil would likely require heating and strip-mining the entire planet — things the researchers concluded aren't feasible.

Astronomer Caleb Scharf, director of the Columbia Astrobiology Center at Columbia University in New York City, said in an email to NBC News MACH that while it might be premature to conclude that we know the full extent of carbon dioxide on Mars, the study was “nicely done.”

“We may have to simply accept that Mars will remain an alien environment, and what we could do with currently feasible terraforming is simply to bring it to a state that makes habitation easier, but not easy,” Scharf said in the email. “And of course all of this is likely moot, since the chances of us launching a full-scale terraforming effort on Mars anytime soon seem pretty remote.”

But some experts are not so willing to throw in the towel.

Robert Zubrin, an aerospace engineer and founder of the Mars Society, disagrees with the study’s conclusions. He said the researchers “grossly underestimated” the amount of carbon dioxide on the planet.

In a 1993 paper, Zubrin calculated that there is enough carbon dioxide in Martian soil that, if it were released, could create an atmosphere comparable to the air atop Mount Everest.

Zubrin acknowledges that efforts to terraform Mars are unlikely to happen anytime soon, but he remains optimistic. “I’m a 21st century engineer grappling with a 22nd century problem,” he said. “There’s no question that it can be done. The question is: how hard is it, and at what point do humans get the industrial capability to do it?”

Musk also seems unconvinced by the new research. Several hours after the paper was published, he tweeted, “There’s a massive amount of CO2 on Mars adsorbed into soil that’d be released upon heating. With enough energy via artificial or natural (sun) fusion, you can terraform almost any large, rocky body.”

But Jakosky said the study was never meant to sound the death knell for terraforming Mars. “Our results are not the be all and end all,” he said. “It’s the best estimate today of where that gas is on the planet. But this isn’t a dead end. It’s really just a next step in the process.”

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