Traces of life on Martian surface may have been bleached away
London: A Martian meteorite found in Antarctic ice suggests that the surface of the Red Planet is riddled with chemicals related to those used in household bleach.
This supports the idea that carbon-bearing compounds - strong indicators of life - may have been broken down by chemical reactions, suggesting that scientists need to dig deeper into Mars to search for traces of any past inhabitants.
"We're speculating that you perhaps cannot find organics on the surface of Mars. You have to be below the surface or inside sedimentary rocks," New Scientist quoted Sam Kounaves of Tufts University in Medford, Massachusetts as saying.
Kounaves and colleagues studied a Martian meteorite called EETA 79001, collected in 1979 in Antartica where it fell 12,000 years ago.
When the team cut it open to study the stuff inside, they found a white substance nestled in the meteorite that turned out to contain a form of nitrate, a chemical that some earthly bacteria use as fuel.
By comparing the ratio of isotopes found in it with those on Earth, the team determined it's Martian not a contaminant, Kounaves told New Scientist at a meeting of the American Association for the Advancement of Science in Boston, Massachusetts, last week.
The team also found small amounts of chloride minerals in the rock, and are confident these are from Mars.
The Phoenix Mars lander had earlier found related compounds called perchlorates, which can also be fuel for microorganisms, in Martian soil.
Chemical reactions can produce perchlorates from chlorides, but an intermediate step is the formation of oxychlorines - a class of highly oxidising chemicals that includes household bleach.
Then ultraviolet light from the sun and cosmic rays can convert perchlorates back into oxychlorines. When these bleaching agents contact even a little bit of water, they will break down any organic compounds present.
The finding suggests that NASA's Curiosity rover have to drill beneath the Martian surface to find traces of past life.
Good news is Curiosity has brought along a drill.
Although it can only get 6.4 centimetres deep, scientists say it may be enough to find any organics preserved in rocks below, shielded from the oxychlorine-forming processes.