Lessons from Martian Climate Change

Water flows on Mars, NASA announced September 28. “Using an imaging spectrometer on [the Mars Reconnaissance Orbiter], researchers detected signatures of hydrated minerals on slopes,” NASA reports. I first heard about this surface water from an August 19 video from Comic-Con (see minute 9:40), in which NASA representatives discuss Mars and The Martian film; some evidence for this water has been around for several years.

This is huge news with respect to potential human missions to Mars as well as to the potential for discovering life on Mars.

But how did Mars get so dry in the first place, and what does that phenomenon teach us about Earth?

I was somewhat amused to read the following Tweet: “‘Mars suffered climate change and lost its surface water.’ There are words to scare the s**t out of all living humans.” I agree with that sentiment, but not for the reasons the Tweeter presumably had in mind.

What the Tweeter probably thought was something like this: “Mars experienced climate change that would have been catastrophic for any life present and that likely prevented new life from developing. Earth, too, is experiencing some climate change, largely because of human activity, and this could lead to catastrophic results such as we see on Mars.”

Obviously, such a take on Martian climate change is a little silly. Mars lost almost all of its greenhouse gasses; Earth is gaining greenhouse gases. (Due mostly to human activity, carbon dioxide has risen from around 300 parts per million of the atmosphere, or 0.03 percent of the atmosphere, to 400 parts per million, or 0.04 percent.) Outside the realm of pure fantasy, not even the most hysterically alarmist predictions about Earth’s climate change predict a future remotely as dire as what happened on Mars.

But the extreme changes on Mars do offer a warning to humans. We’ll come back to that.

First, let’s review in brief what happened on Mars. As the geography of Mars makes evident, water once flowed in great abundance on Mars. But then Mars lost most of its atmosphere and the oceans boiled away. Why? Apparently Mars just didn’t have enough mass to hang on to its air, especially given the violence of meteor impacts, and the atmosphere dissipated. (Another theory I’d heard, that Mars’s weak magnetic field allowed solar winds to blow off the atmosphere, appears not to be much of a factor.)

The main lesson of Martian climate change, then, is that for the most part the universe is extremely hostile to life, and even places most hospitable to life may not stay that way. If life evolved on Mars, it was either killed off or driven underground by purely natural causes.

The Earth is not magically immune from such potential natural catastrophes. Indeed, less-severe natural catastrophes, ranging from earthquakes to hurricanes to volcanic eruptions, happen fairly routinely. Asteroid collisions have dramatically impacted the evolution of life on Earth—and a sufficiently large asteroid could destroy all life on Earth. At one point, humanity “damn near went extinct” due to an ice age likely caused by a supervolcano.

The lesson I take from this is that, to ensure the survival and expansion of our species long-term, humans absolutely must colonize space—and Mars is a great place to begin.

Andy Weir, author of The Martian novel, shares this view:

I want us to have a self-sufficient, human population somewhere other than Earth, because, twenty-five years of being a computer programmer has taught me the value of backing things up. And, as long as our entire species is on one planet, we risk extinction. It’s not very likely, but it could happen. It could be plague, it could be a war, it could be a meteor strike or something like that. But, if we’re on two planets, it is practically impossible for us to die.

Similarly, in Welcome to Mars, Buzz Aldrin writes, “The pioneers who settle Mars will . . . ensure the long-term survival of life in our solar system. Earth faces challenges. If there were a disaster, Mars would give us a place to get resources or to make a new home” (p. 6).

Speaking of climate change, Aldrin has some intriguing ideas for pursuing human-made climate change on Mars:

Giant mirrors in orbit could direct . . . sunshine to heat Mars’s polar ice caps. A temperature increase of just a few degrees would thaw the carbon dioxide frozen there. . . . As the temperature rises, more carbon dioxide is released. . . . If the mirrors aren’t enough, we can knock an asteroid out of its orbit to slam into Mars. Some asteroids are rich in ammonia, another greenhouse gas. An impact would produce a lot more heat and carbon dioxide, too. Once it is warm enough for water on the surface, plants can grow. (pp. 88–89)

I’m not sure how well that would work long-term, especially given Mars’s apparent difficulty keeping its atmosphere. But, one way or another, humans can make Mars hospitable to life.

Sure, human activity brings with it certain risks, harms, and trade-offs. But these risks are nothing compared to the risks of humans not acting to expand and improve human life on Earth and, eventually, beyond.