Gone With the Martian Wind

NASA's Mars rover Spirit catches a bevy of dust devils race across Gusev Crater. Credit: NASA/JPL/Cornell. Click to enlarge.



Mars is a very windy place—so windy, in fact, that bright, oxidized martian soil is being scoured away by martian winds and dust devils to reveal darker, sub-surface soil with the end result of making the whole planet warmer. Mars is experiencing its own brand of climate change. Is this related to planet earth’s greenhouse gas driven climate change? No. Is understanding the process important for our understanding of how planets evolve and change over time? Absolutely.

In early April of this year, a young Carl Sagan Center Principal Investigator named Lori Fenton, together with her colleagues at NASA Ames Research Center and the USGS in Flagstaff Arizona, published an article in the journal Nature revealing the phenomenon of the rise in the martian global temperature over the past 20 years. The rise, less that 2° for both surface and air temperature, is still significant from a geologic perspective.

The mechanism for the warming is due to the change in brightness, or “albedo” of the martian surface. The light, bright, oxidized martian surface soil reflects a significant amount of solar radiation, tending to keep Mars cool, just as wearing white on a hot summer’s day is cooling. The darker, more absorbent subsurface soil, revealed after a windstorm or dust devil passes through on Mars, retains more heat, just as wearing dark clothes will on that same hot summer’s day here on earth. The result of more exposed dark soil is that the temperature of Mars has gone up between one and two degrees over the last two decades.

Such a change is very intriguing and has never before been seen on any planet. The martian atmosphere is significantly thinner than that on earth. It’s similar to what is found on our home planet at about 100,000 feet. Even so, the winds that result from the movement of even such a thin atmosphere are clearly strong enough to have a profound impact on the planet. Comparative planetologists and climate modelers will be monitoring Mars closely for the next 20 years and beyond, trying to discern if there is some sort of pattern to the changes and if the trend seems to be continuing. The truth is, we have only begun to monitor and record such data and are just beginning to track changes as they unfold.

Mars dust devils have been in space news before now. In fact, the Mars Rover twins, Spirit and Opportunity, owe their lives to the quixotic martian winds. Gusts of wind and dust devils pass over the solar arrays on the intrepid robotic explorers just often enough to scour away the ubiquitous martian dust from the surface of their mission prolonging solar arrays and sweep away the dust build-up, allowing the 4 year old batteries to recharge. This helpful process was completely unforeseen.

With new high resolution instruments on Mars, thanks to the Mars Reconnaissance Orbiter, and advanced landers and rovers in the pipeline with Phoenix Scout and Mars Science Laboratory due to launch in the next few years, we will continue to get information on martian winds and weather and discover just what else is gone with the wind.

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