Methane concentrations revealing a plume in Mars’ northern
hemisphere during its summer season. Credit: NASAMethane on Mars? Really? What does that mean?
We’ve known about the existence of methane gas on Mars for several years now, from independent observations. Further observations have led to the detection of “plumes” or clouds of methane gas apparently emanating from specific locations on Mars. One plume is estimated to contain 19,000 metric tons of the stuff.
Why is this exciting news? If you know anything about the source of most of Earth’s atmospheric methane gas, you already know the answer: possible life. Not, I should say, necessarily life on Mars, but maybe a strong piece of evidence in that direction.
On Earth, methane (CH4) is produced by living organisms—mostly by the activity of microbes, but some by the digestive processes in larger organisms (yes, like humans, and cows). Methane is the major constituent of natural gas, which fuels gas powered ovens and heaters in homes, as well as natural gas power plants. Methane is also produced by decaying organic matter—that’s where “swamp gas” comes from.
On Mars, methane gas cannot exist for long in the atmosphere; it is relatively quickly broken down by solar radiation. So, the methane detected in Mars’ atmosphere must be replenished by something, continually.
So the big question right now is, where is the methane coming from? Under the surface of Mars, almost certainly. By biological processes—life—underground? Could be. By non-biological means? Could be, too; methane can be produced through inorganic chemical processes. We don’t know yet. The next step in finding out more will be the Mars Science Laboratory, a large rover scheduled to be launched to Mars sometime in the near future.
In one form or another, humans have been trying to see, or find, life on Mars for a long time. Percival Lowell squinted at Mars’ small, blurry disk through his 24-inch telescope in Flagstaff, and perceived markings he saw to be vast canal complexes, ostensibly built by a desert Martian civilization thirsty for water harvested from their planet’s polar ice caps. This led to much of the science fiction relating to life on Mars in the 20th Century.
Earth-bound telescopes noted seasonal changes in Mars’ color and brightness, and some attributed this to possible seasonal growth of Martian vegetation—though it was later found that these variations were the effects of seasonal planet-wide dust storms.
The Viking landers’ primary mission in the 1970’s was to search for life. They didn’t find any by scratching around Mars’ surface and testing the soils there.
The 1990’s saw the controversy over microscopic structures in meteorites found on Earth but determined to have originated on Mars. Some argued that these structures were fossils of Martian microbes that lived on Mars long ago. Whether these findings were in fact fossils and not just geologic structures was never conclusive.
The determination that liquid water once flowed on the surface of Mars, and still exists under its surface at least as ice, is pretty much scientific fact today. Evidence of past liquid flows have been imaged and mapped from space, and the Phoenix lander found water ice in the north polar regions last year. And there’s the rover Opportunity that has confirmed gray hematite, a mineral that forms in the presence of water.
It’s almost certain that there are no Martian cows grazing the rusty desert plains out there. But there seems to be a lot of evidence for the possibility that something is going on below Mars’ surface—perhaps the presence of liquid water, perhaps the presence of some form of life. We don’t know yet, but it sure feels like we’re onto something here….