Mars is conventionally described as a cold, lifeless world that's a giant barren desert, because the surface explorations we've made via Mars Rovers pretty much demonstrate that. But NASA's recently released data about Methane on Mars is providing fodder for excitement, and speculation.
"Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so our discovery of substantial plumes of methane in the northern hemisphere of Mars in 2003 indicates some ongoing process is releasing the gas," said Dr. Michael Mumma of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "At northern mid-summer, methane is released at a rate comparable to that of the massive hydrocarbon seep at Coal Oil Point in Santa Barbara, California."
Scientists using Earth-based telescopes at NASAS's University of Hawaii site and the W. M. Keck telescope at Mauna Kea, Hawai, with spectrometers attached to them (spectrometers <a href="http://www.nasa.gov/images/content/303598main_mjmumma_vid_01_1280_01.jpg" separate light into various bandwidths, or colors) could see plumes of methane. They've now collected several years' worth of observations, and have been able to isolate dark areas, drop outs, in the spectrum, where methane absorbed reflected sunlight from Mars' surface. The team found methane in the atmosphere of Mars by carefully observing the planet over several Mars years (and all Martian seasons) with NASA's Infrared Telescope Facility, run by the University of Hawaii, and the W. M. Keck telescope, both at Mauna Kea, Hawaii. They spotted multiple "plumes" of methane—one of which released about 19,000 metric tons of the gas.
Dr. Geronimo Villanueva of the Catholic University of America, Washington, D.C said that the methane plumes were emitted during Mar's spring and summer, when the planet was warmer. The first embedded image in this post shows spectrometer data about the plumes; click the image for a larger image with explanatory call-outs.
Over the last four years NASA has announced that gullies on Mars were probably the result of meltwater from glaciers that existed a few million years ago, and that sediment deposits appeared to have been deposited by flowing water, as were stains. Together, these all suggest that Mars in its ancient past had had surface ice and/or flowing water.
The methane plumes seen by the scientists are over areas that demonstrate evidence of ground ice, or flowing water, in Mars' ancient history. Plumes appeared over the Northern hemisphere of Mars, especially in the areas east of Arabia Terra, over the Nili Fossae ara, and over the south-east quadrant of the ancient volcano called Syrtis Major (about 745 miles) across.
Because Methane doesn't last in the Martian atmosphere, and because the observations go back to 2003, the constant presence suggests that there's a process that is continuously releasing the gas—or, as the press release puts it, that Mars "is still alive."
Methane is most likely being released by either a natural geologic process. Iron oxidation, for instance, releases methane as a by-product. Alternatively, it's possible that ancient methane trapped in ice "cages" called clathrates might now be released. The far more interesting possibility is that microorganisms far below Mar's hostile surface are alive and well, and outgassing methane much like microorganisms on Earth, who release methane as a byproduct of their digestive processes. In fact 90% of the methane on Earth is from biological processes; the remaining 10% is derived from geologic processes.
Dr. Michael Mumma of NASA's Goddard Space Flight Center in Greenbelt, Md observed that there are microorganisms on Earth living from 1.2 to 1.9 miles below the planets surface, under the Witwatersrand basin of South Africa. Natural radioactivity divides water molecules into their constituent molecular hydrogen, and oxygen. The microorganisms then use the hydrogen as an energy source. According to Mumma, a similar process might work on Mars. Microorganisms might survive, for billions of years, hidden beneath the now permanent permafrost on Mars, in the warmer sub-surface where water is liquid, and radiation supplies energy, and carbon dioxide serves as as source for carbon.
Similar microorganisms on Mars, might be living far below the surface where the ambient temperature is much much warmer, warm enough that there could be liquid water. With energy from radiation, and carbon from carbon dioxide, such microbial life could possibly survive for billions of years, protected from the harsh surface environment. The methane they release could escape to the surface via fissures or vents in the deeper canyons and craters. (The plumes' shape and height suggest that they originate from very specific sites.) In the image linked in this paragraph artist Susan Twardy of NASA suggests that water below the surface of Mars, internal heat from the planets' core and carbon dioxide would react to release methane.
Carl Pilcher of NASA's Astrobiology Institute notes that similar microbes that produced methane from hydrogen and carbon dioxide were one of the earliest forms of life on Earth. It's worth noting too that there are microbes on Earth that consume methane.
There's a NASA video here that explains all this in very practical, clear terms, and talks a little bit about future Mars missions. For you academic types, the journal Science has the article here.
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In 2011 NASA's Mars Science Laboratory will launch. The mission will send a sophisticated, adaptive next-generation rover with a variety of tools for close, mobile examination of Mars, above and below the planet's surface. The idea is to explore one of four potential Mars sites, each of which suggest that they were wet in Mars' distant past. The rover will check for signs of an environment that could have supported microbial life, and attempt to record and preserve and data it finds.
Personally, I can't wait.