'Dandruff' could contaminate Phoenix landing site

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http://www.nature.com/news/2008/080606/full/news.2008.878.html

Published online 6 June 2008 | Nature | doi:10.1038/news.2008.878

'Dandruff' could contaminate Phoenix landing site
Dead microbes and skin flakes from Earthlings may scupper the search for organic molecules.
Eric Hand

Could Phoenix’s search for organic molecules on Mars be foiled by dandruff from Earth? After a successful landing last month on the planet’s northern plains, the NASA spacecraft is busily scraping through the martian dirt. Next week, the mission team plans to use one of its premier instruments, the Thermal and Evolved Gas Analyzer (TEGA), to test its first baked soil sample for molecules containing carbon.

The search for the organic building blocks of life has been a major selling point for Phoenix; many press accounts have eagerly, yet mistakenly, foreshortened the mission’s raison d’etre to ‘the search for life’. Yet some mission scientists say that it is the science goal least likely to succeed, partly because TEGA is so sensitive that it may end up sensing only contamination from Earth.

“We will see organics, for sure, because we’re bringing them,” says Aaron Zent, a mission scientist from NASA’s Ames Research Center in California. Likely contaminants include skin flakes, dead microbes and volatile lubricants. “The problem with an instrument so sensitive is all you detect is your own schmutz,” says Zent.

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But the advantages end there. NASA spent about US$800 million, in 1975 dollars, on the Vikings, which were encased entirely in a biological shield prior to launch. And NASA is spending almost US$2 billion for a 2009 launch of the Mars Science Laboratory, which will be able to 'bake out' its ovens – ridding them of contamination upon arrival at Mars – before ingesting samples.

The $420 million Phoenix mission, by comparison, is low-budget, built from parts recycled from a cancelled mission — the Mars Surveyor Lander — that had been kept in a warehouse – and how much dust those parts gathered is a worry. “We’re doing a quick and dirty organic analysis,” says TEGA lead scientist William Boynton, of the University of Arizona in Tucson. “We’re kind of doing it on a shoestring.”

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