Planetary Engineering of Mars to Make It Habitable Won't Work, NASA Study Finds

The idea of geoengineering Mars to make it hospitable for Earth's plants and animals, including humans, has long been a staple of science fiction.

Tech magnate Elon Musk and others have also proposed "terraforming" the red planet to enable human colonization there.

However, an article published in the journal Nature Astronomy, has poured cold water on the concept, suggesting that the planet lacks sufficient carbon dioxide (CO2) to make terraforming a viable possibility with current technology.

Proponents of terraforming Mars have put forward a number of different strategies that focus on techniques to release greenhouse gases stored in Mars's rocks and polar ice caps to thicken the atmosphere. This would trap heat and create sufficient conditions for water to remain on the surface—an essential ingredient for life. People living on a terraformed Mars such as this wouldn't need spacesuits, although they would still require breathing gear.

The current Martian atmosphere consists mostly of carbon dioxide. However, it is too thin and cold to support liquid water on the surface. The water would quickly evaporate or freeze at the current pressure.

Authors of the article, Bruce Jakosky and Christopher Edwards, from the University of Colorado Boulder and Northern Arizona University respectively, examined the possibilities of terraforming Mars using CO2—the only greenhouse gas present in sufficient quantities on the planet to create significant warming.

"There is a large group of people who are interested in the concept," Jakosky told Newsweek. "The rationales include having a backup planet in case the Earth gets too mucked up to live here, and expanding our civilization out beyond the Earth. My own view is that, if we can develop the capability of changing the Mars environment to be more like Earth, we can actually "terraform" the Earth and keep it livable!"

The researchers looked at the most recent data collected by Mars rovers as well as information gathered by spacecraft that have been studying the planet for the past 20 years, to work out the total amount of potentially accessible surface and subsurface carbon dioxide and the effects this gas would have on the Martian atmosphere. They also took into account the continuous leaking of gas from the Martian atmosphere into space.

Day breaks on Mars in this computer-generated image. The idea of geoengineering Mars to make it hospitable for Earth’s plants and animals, including humans, has long been a staple of science fiction. NASA/JPL-Caltech

Their results showed that the readily accessible carbon dioxide would only triple the planet's atmospheric pressure. This might sound like a significant amount, but the change is 50 times smaller than what would be required to make Mars habitable. In fact, such a change would only raise the temperature by around 50 degrees Fahrenheit, which is not that helpful when the average temperature on the planet is around -81 degrees Fahrenheit.

"Our results suggest that there isn't enough CO2 that, even if you put it into the atmosphere, it would provide much greenhouse warming; and, in addition, that it is very difficult to mobilize it and put it into the atmosphere," Jakosky said. "The bottom line is that terraforming Mars is not possible with today's technology."

The most accessible CO2, for example, is in the polar regions. It could be released into the atmosphere just by heating the polar ice caps—perhaps by darkening them so that they absorbed more light or, as Elon Musk has suggested, by using nuclear explosives. However, the researchers found that not much CO2 was available in these regions.

"Other places include CO2 trapped in carbon-bearing minerals (carbonates), but this requires heating to 300 degrees Celsius (572 degrees Fahrenheit) to get the CO2 out, and would essentially require something akin to strip mining the deposits to process them," Jakosky said.

Another source is "adsorbed gas", the gas accumulated on the surface of solid materials, which may by the most abundant CO2 on Mars. Unfortunately, it is both distributed globally and can only be mobilized after heating the atmosphere.

"If you add it all up, it's still only maybe 5 % of the amount of CO2 that would be required, even if you could put it back into the atmosphere," he said. "Unfortunately for this problem, most of the CO2 has been lost to space over time, stripped away by the solar wind."

This doesn't mean that terraforming Mars would never be possible, he stresses. But it would require doing something like mass-manufacturing a high-efficiency greenhouse gas—for example, CFCs such as freon—on Mars that would trap sunlight and warm the planet.

This article has been updated to include additional comments from Bruce Jakosky.