by Timothy N. Titus, Ph.D
U.S.G.S. Astrogeology Team
Speculations about life on Mars have always caused great interest and controversy. Recently, several Internet articles have been posted describing the discovery of Martian Surface Organisms in the south polar region of Mars.
As a research scientist working on the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) Team, I have spent the last four years analyzing data from this Martian region. The data reveal a region active with interesting and intriguing physical phenomena, but does not suggest the existence of life.
Hungarian scientists have reported evidence of life in the Martian southern polar region. They claim that the dark spots observed during the southern spring are living organisms, similar to those found at the south pole of Earth.
This comparison of the Martian southern polar cap to the Earth's Antarctica is highly inaccurate and misleading since the two regions have little in common.
Antarctica has an abundant supply of water ice at a mean winter surface temperature of between -40°F (-40°C) and -94°F (-70°C).
The Martian seasonal cap is almost entirely dry ice at a surface temperature of -195°F (-126°C). The near absence of water, even in the form of ice, and the frigid surface temperatures make the current existence of life unlikely.
Early in the MGS Mission, we discovered a region of Mars seasonal south polar cap that remains dark in the spring, while the rest of the polar cap is bright. [ Titus et al., 1998, Kieffer et al., 1999, Kieffer et al.,2000] This dark region remains cold enough for dry ice to continue to exist.
Dramatic changes of appearance of many ices can result from minor or no change in the basic material, similar to the disparity between the appearance of snow and "black ice" on Earth. Studies of thermal spectra from this Martian region suggest that the dark dry ice is either a clear transparent slab or dirty and coarse grained. The formation of these Martian dark ice regions is an annual event, occurring each Martian southern spring.
The dark spots at issue, occurring on crater floors inside the cryptic region, have been under study by several scientists at NASA, the U.S. Geological Survey, and Malin Space Science Systems. All of our studies suggest these dark spots are formed from the natural defrosting process of the seasonal cap. The dark spots are either exposed soil or dark dry ice [e.g. Edgett et al., 2000, Bridges et al. 2001].
The Hungarian report is riddled with glaring scientific errors. The report claims according to the Hungarian researchers that during harsh Martian winters, when temperatures plummet to minus 200 degrees Celsius (minus 328 Fahrenheit), these so-called Mars Surface Organisms are protected by a thick blanket of ice which then melts as the planet's early summer temperatures climb to just above zero.
Firstly, the polar cap surface temperatures, even in the dead of winter, do not drop below -195°F (-126°C), which is the temperature at which dry ice and gaseous CO2 can co-exist under Martian pressures.
Secondly, the Martian southern polar cap consists of dry ice (solid CO2), not water ice. In the spring time, the dry ice does not melt, but sublimates, transitioning directly to gas. The temperature at which this occurs is -195°F (-126°C), not zero degrees, as suggested by the Hungarian article.
And thirdly, water ice does exist on Mars, but sublimates around -100°F (-73°C), due to the low atmospheric pressure of 6.1 mbars. Earth has a surface pressure of 1000 mbars.
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Why Microbes Matter
Houston - Sept. 4, 2001
One of the most frequent questions that I have encountered when talking with people about astrobiology is, "If there are microorganisms on Mars, so what? Why should I be interested in the Martian equivalent of bacteria?" Here is my answer:
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