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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