Methane discovery provides new evidence of life on Mars
Alien bugs could be responsible for strong plumes of methane gas detected on Mars, it emerged today.
Scientists say the emissions, as large as some of those seen on Earth, could have either a geological or biological source.
Life is responsible for more than 90% of the Earth’s atmospheric methane.
Experts believe there is a good chance that microbial organisms produced the gas on Mars too.
The bugs that made it may have vanished millions of years ago, leaving the methane frozen under the planet’s surface.
But another possibility is that some hardy organisms still survive on the Red Planet, living underground without sunlight and using hydrogen from water for energy. Similar microbes exist on Earth.
Methane produced by the action of water on hot carbon bearing rocks, as occurs in volcanic regions on Earth, is the alternative explanation.
Whatever the source is, scientists agree that something is replenishing the methane.
The gas cannot remain for long in the atmosphere. Sunlight breaks methane down within a few hundred years, and strong oxidising chemicals in Martian dust are likely to make it last even less time.
The discovery, reported today in the journal Science, was made using three large telescopes in Hawaii to scan 90% of the Martian surface for seven years.
Specific wavelengths of infrared light indicated the presence of methane.
The plumes occurred over specific locations in the planet’s northern hemisphere in early and late summer 2003.
One of them contained an estimated 19,000 metric tons of methane.
That is comparable with the amount produced at Coal Oil Point, a massive hydrocarbon seep off the Californian coast at Santa Barbara, where liquid petroleum and methane escapes through cracks in the Earth’s surface.
The scientists, led by Dr Michael Mumma from the American space agency Nasa’s Goddard Space Flight Centre in Greenbelt, Maryland, said the Martian methane could be breaking out through the walls of craters or canyons from underground reservoirs.
They wrote: “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. Both geochemical and biological origins have been explored, but no consensus has emerged.”
Signs of methane in the Martian atmosphere were detected in 2004 by the European Mars Express orbiter.
Initially it was assumed that comets containing methane were delivering the gas from space.
But British expert Professor Fred Taylor, head of atmospheric, oceanic and planetary science at Oxford University, says this could not explain plumes appearing at specific locations at certain times of the year.
“Most methane is biologically produced,” he said. “If its focused it’s much more likely to be coming from the interior of the planet, and therefore its quite hard to think of a non-biological source.
“It could be that some kind of chemistry nobody understands is occurring. You can make methane inorganically in a chemistry lab quite easily.
“This paper doesn’t settle anything finally. What it says is ’come and have a look’. We need to go there.”
Prof Taylor said the methane may have been produced by living organisms long ago, like coal and oil on the Earth today.
Or it could be the result of volcanic activity that occurred when Mars was still young. The ancient deposits could be releasing the gas to this day.
But Dr Mumma’s team has not ruled out the possibility of Martian life surviving under the planet’s surface.
The scientists drew attention to colonies of organisms that live up to three kilometres underground in the Witwatersrand Basin, a gold mining region of South Africa.
The bugs use hydrogen obtained from the break down of water by radiation (radiolysis) as an energy source and live off carbon dioxide.
“It might be possible for analogous biota to survive for eons below the cryosphere (frozen) boundary on Mars, where water is again liquid, radiolysis can supply energy, and CO2 (carbon dioxide) can provide carbon,” wrote the researchers.
“Gases accumulated in such zones might be released to the atmosphere if pores or fissures open seasonally, connecting these deep zones to the atmosphere at scarps, crater walls or canyons.”
Prof Taylor said both organic and inorganic sources of methane were likely to require warmth.
Two of the most prominent methane “hotspots” were over regions of past Martian volcanic activity, Syrtis Major and nearby Nili Fossae.
“Regions that used to be volcanic are most likely still to be warm below the surface,” said Prof Taylor.
