Scientists say they have found significant quantities of methane gas in the Martian atmosphere. More than 90% of the methane on earth is geochemical in origin, which may be an indicator of organic life on Mars.
REUTERS - New observations of the atmosphere on Mars show fairly large amounts of methane along with water vapor in the summertime -- the strongest suggestion yet that living organisms might be producing the gas.
NASA scientists stressed that there is no direct evidence that anything living produced the methane, which could be produced by volcanic activity, could be made by live microbes, or could be left over from long-extinct life.
A report to be carried in Friday's issue of the journal Science details the observations, made using three telescopes in Hawaii. The U.S. space agency was scheduled to hold a briefing later on Thursday to discuss the findings.
"The most compelling question relates to the origin of methane on Mars. The methane we detected is of unknown age -- its origin could be ancient or perhaps recent," Michael Mumma of NASA and colleagues wrote.
The methane appears to have been produced in plumes from certain areas on Mars as temperatures warmed, they said.
"Living systems produce more than 90 percent of Earth's atmospheric methane; the balance is of geochemical origin. On Mars, methane could be a signature of either origin," they added.
On Earth, methane is known as swamp gas and made by decaying plants or found in the burps, belches and other emissions of animals from termites to cattle and people. It is made up of carbon and hydrogen.
"Using high-dispersion infrared spectrometers at three ground-based telescopes, we measured methane and water vapor simultaneously on Mars over several longitude intervals in (northern) early- and late-summer 2003 and near vernal equinox 2006," the scientists said.
Spectrometers can measure gases from afar by the breakdown of signals in light.
Mars is Earth's neighbor, orbiting outside our own orbit around the sun. It is slightly smaller than Earth and colder, with little atmosphere. The atmosphere is mostly carbon dioxide, with a little nitrogen, carbon monoxide, trace amounts of oxygen and water vapor.
Water below the surface
Water exists on Mars, and robot rovers have sampled ice from the surface. Scientists are eager to know how much more water is below the surface and whether it could support life now or in the past.
No known processes produce methane on the surface of Mars, and chemical reactions with compounds on the surface could break it down.
"Thus, the presence of significant methane would require recent release from subsurface reservoirs; the ultimate origin of this methane is uncertain, but it could be either abiotic or biotic," the researchers wrote.
They are not the first team to detect methane on Mars but their observations show the association both with warm temperatures and with water -- which might suggest summer temperatures start some process, either biological or geological.
Bacteria have been found on Earth that use hydrogen as energy and can turn carbon dioxide into methane in a process known as radiolysis.
"These communities thrive at 2-3 km (1.2 to 1.8 miles) depth in the Witwatersrand Basin of South Africa and have been isolated from the surface (and photosynthesis) for millions of years," the researchers wrote.
"It might be possible for analogous biota to survive for eons below the cryosphere boundary on Mars, where water is again liquid, radiolysis can supply energy, and carbon dioxide can provide carbon."
Date created : 2009-01-15