Could we one day terraform Mars to give it an atmosphere, new seas, and a generally habitable environment where people could settle without special protection? According to a new NASA study, don't hold your breath. By the most generous estimate, there isn't enough material on the Red Planet to even begin to provide it with a minimal atmosphere – much less make it suitable for colonization.
The idea of colonizing Mars is very attractive, but it keeps coming up against the fact that Mars is about as friendly to life as the Moon. The atmosphere is made up almost entirely of carbon dioxide and is less than a hundredth as dense as the Earth's. Though there is water trapped in the polar ice caps and in permafrost, as well as in what may be a newly discovered subglacial lake, any water on the surface would quickly evaporate. The result is that the surface of Mars is a thousand times drier than the driest spot on Earth.
Add to this the arctic temperatures at night even at the equator and the constant bombardment of UV and cosmic radiation, as well as weird soil chemistries that break down organic molecules with ease, and the picture for human settlement is a depressing one. As things stand, any potential colonists would face a lifetime for themselves and their descendants that would condemn them to living inside entirely artificial environments.
An alternative to this is terraforming. It's an idea that's been around for over a century and the basic concept is to alter the environment on Mars to make it more like Earth's. Though this might seem a bit daunting, we have evidence that billions of years ago ancient Mars had a large ocean, rivers, lakes, and rainfall. If it could be done once, why not again? Melt the water at the poles or in the permafrost, free up the carbon dioxide in the ice caps and the crust, and build up enough of an atmosphere to support liquid water and start the greenhouse process to warm the surface. Everything else would be just tweaking, like introducing plants to produce oxygen.
The problem is that there are many ideas that are very good in theory and work very well in the laboratory, but when you run the numbers in the real world, they turn out to be non-starters. You could, for example, run a fleet of aircraft carriers off used chip shop oil, but what if there aren't enough chip shops to supply enough oil?
According to the NASA-sponsored study, that is what Martian terraforming is up against. Using the most recent data from Mars orbiters and landers, the team led by Bruce Jakosky of the University of Colorado, Boulder has determined that there isn't nearly enough water or carbon dioxide on Mars to do the job.
By looking at how much water there is on Mars as well as carbon dioxide ice and carbon-bearing minerals in the crust of the planet, the researchers calculate that even if a mining and processing effort covering the entire planet was carried out, it wouldn't nearly be enough. In addition, greenhouse substitutes, like chlorofluorocarbons or other fluorine-based compounds (even if there were enough available) would break down too quickly to do any good.
The team says that the Martian atmospheric pressure is about 0.6 percent that of Earth. Because Mars is farther from the Sun than the Earth, for water to exist as a liquid on Mars, that pressure would have to be raised to almost Earth normal. The depressing thing is, that the math says that Mars can't manage anywhere near that.
The study shows that, based on present data, turning the ice caps into water vapor would only raise the pressure to 1.2 percent Earth normal. If the surface dust of the planet was all dug up by strip mining and heated to release carbon dioxide, that would provide only another four percent pressure. Even by deep mining carbon-bearing mineral deposits, the yield would bring the pressure to less than five percent. Even strip mining the planet to a depth of 100 yards (91 m) would bring it up by not much more.
Another source of carbon dioxide would be minerals deep in the crust, but these would take a huge amount of energy to extract and then they'd have to be heated to over 300° C (272° F) – as would any minerals mined on the surface. Even if all of this could be done, it wouldn't be nearly enough, contributing to a total pressure of only 6.9 percent of Earth normal. Worse, Mars has no magnetic field to speak of and no volcanic activity to supplement the terraforming effort, so the atmosphere would be continuously stripped away by the solar winds with nothing to replace the loss.
While the team concedes that it may be possible to bring in the necessary materials from off world, they point out that this would require many thousands of asteroids and comets, which presents another set of problems. They therefore conclude that terraforming Mars will only happen in the far-flung future when as yet unknown technologies have been developed.
The research was published in Nature Astronomy.
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