Terraforming Mars might be impossible due to a lack of carbon dioxide

Stages for terraforming Mars. Credit: Wikimedia Commons.

Terraforming Mars has long been a dream of science fiction authors, making Mars our second home, in an environment where humans no longer need to put on a space suit, and the easiest way to do that would be to use carbon dioxide already on Mars to create a new atmosphere, however, now researchers say that will be impossible. 

In order to terraform Mars to make it into a habitable world, two important things are need it, raising both its temperature and pressure by adding an atmosphere made of heat-trapping greenhouse gases, and the only ones found on Mars are carbon dioxide and water vapour, but now days, they are frozen.  

“If there is enough carbon dioxide, we could warm up Mars in 100 years once we start,” says Chris McKay at NASA’s Ames Research Center in California. “We know how to warm up a planet – we’re doing it on Earth. The fundamental question is, is there enough stuff?” 

The Nili Fossae carbonate plains, this site is part of the largest known carbonate-rich deposit on Mars. Credit: NASA/JPL-Caltech/JHUAPL/Univ. of Arizona

It seems that there is not enough. Two scientist, Bruce Jakosky at the University of Colorado, Boulder, and Christopher Edwards at Northern Arizona University employed the results from several spacecraft to build an inventory of all the carbon dioxide on Mars to figure out whether, if we moved all of it from the ground into the atmosphere, we could create high enough temperatures and pressures for life. 

A question of pressure 

At this moment, Mars has an atmospheric pressure of about six millibars – that is tiny when compared to the one bar at sea level on Earth. “We would need something like a million ice cubes of carbon dioxide ice that are a thousand kilometres across in order to do get to one bar,” says Jakosky. 

With an atmospheric pressure of one bar, the temperature would be just above 0°C, allowing water to be liquid, and making life possible, on the surface of the red planet. However, the atmosphere wouldn’t be breathable, but humans could get by with breathing masks, without the need for a full pressurized space suits, and plants could grow freely, slowly building up oxygen over the course of the next few centuries. 

A terraformed Mar. ESO/M. Kornmesser

However, Jakosky and Edwards found that there’s probably only enough carbon dioxide in the Martian polar ice caps, dust and rocks to raise the pressure to 20 millibars at most. So we can’t terraform Mars with existing technology, because there simply isn’t enough carbon dioxide. “It’s not that terraforming itself isn’t possible, it’s just that it’s not as easy as some people are currently saying,” says Jakosky. “We can’t just explode a few nukes over the ice caps.” 

Difficulty 

There is also the possibility that there could be reservoirs of carbon deep under the surface that could make the job easier, says Robin Wordsworth at Harvard University. “If you could develop the technology to look for those and extract it, that might get you close to the bar,” he says. “But it’d be kind of a fishing expedition – there’s no guarantee that these things exist.” 

Without enough carbon, we would have to warm up Mars some other way, perhaps by making chlorofluorocarbons (CFCs) or bombarding the planet with comets or asteroids. That’s going to be difficult, and it will still not be enough to truly make Mars a home. For that, we need nitrogen – and we’re still not sure how much of that Mars has. 

“If there’s not enough carbon dioxide, terraforming would take thousands of years or more but it’s still possible,” says McKay. “If there’s not enough nitrogen, you need Star Trek. You need warp drive and tractor beams, you need to pull nitrogen from the atmosphere of Jupiter. It becomes science fiction.” 

Sources: newscientist, Wikipedia, Nature Astronomy, DOI: 10.1038/s41550-018-0529-6