Space.com (September 3, 2010)
"Samples of Mars dirt collected by NASA's Viking Mars landers back in the 1970s may have contained carbon-based chemical building blocks of life as we know it, a new study suggests.
"During their missions, the two Viking landers vaporized Martian dirt and scrutinized the samples for signs of organic - or carbon-based - molecules that could serve as the raw ingredients for life. At the time, all they found were chlorine compounds attributed to contamination, but the new research suggests the Viking probes' heat-treatment may have generated these chlorine compounds from naturally occurring Martian organics, destroying them in the process.
" 'This doesn't say anything about the question of whether or not life has existed on Mars, but it could make a big difference in how we look for evidence to answer that question,' study co-author Chris McKay, of NASA's Ames Research Center in Moffett Field, Calif., said in a statement...."
There's a decent amount of detail in the Space.com article about how the Viking lander experiments worked, what they were supposed to show - and maybe why they didn't show any signs of organic compounds.
It's a little more complicated than this: but essentially, it looks like the Viking life experiments were (unintentionally) designed to obliterate organic compounds - and then perform detailed tests on what was left.
One indication, the Lemming thinks, that the Viking life experiment results are - dubious - is that if the Viking landers had touched down on Earth: they probably wouldn't have detected anything organic here, either.
"...The Viking landers performed several different tests on Martian surface material in 1976. They found no compelling evidence for life, or even for the existence of organic molecules.
"But subsequent studies have questioned what these tests actually showed. Researchers replicating Viking's methods on Earth, for example, failed to detect signs of life in Earth soil teeming with microbes...."
My hat's off to folks who develop chemical tests that can be performed by robotic systems small, light, and durable enough to make it to Mars - but I'm also glad that a Phoneix spacecraft had a microscope on board. (May 26, 2008) Martian microbes, if there are any, may not look quite like the Terrestrial varieties: but I'm guessing that they act more-or-less like their counterparts here.
- "Mars, Mud Volcanoes, and the Search for Life"
(August 20, 2010)
- "New Look at the Lost Ocean of Barsoom"
(June 15, 2010)
- "Life on Mars: Reality Check"
(April 30, 2010)
- "Life on Ceres? Could Be"
(March 5, 2009)
- "Martian Methane Media Madness"
(January 19, 2009)
- "Phoenix Mars Mission: This Time, They Brought a Microscope"
(May 26, 2008)
- "Phoenix Attempts Landing on Mars Tomorrow"
(May 24, 2008)