Two critical puzzle pieces for life on Mars, separated by 32 years of conjecture and thousands of miles of terrain, are coming together to yield new clues for a “Genesis 2.0″ on the Red Planet.
The evidence is tied together by one thread: Perchlorate.
Perchlorate is a highly oxidized chlorate and is commonly used as a powerful rocket fuel. Perchlorate is so rich in oxygen it could also fuel Martian metabolisms. It is also a strong antifreeze that could be used by alien microorganism to combat low temperatures on Mars.
To everyone’s surprise NASA’s Phoenix Mars Lander — our first extraterrestrial visitor to Mars’ north polar regions — found perchlorate in soil samples analyzed in 2008. What’s more, the anomalous results from biology experiments conducted by the NASA Viking landers in 1976 may be explained by perchlorate in the Martian soil.
“This oxidizer may be at the root of an exotic Martian biology,” says astrobiologist Chris McKay of NASA’s Ames Research Center. “It is the most important astrobiology discovery on Mars since the Viking experiments. It will cause us to rethink everything we knew about Mars chemistry because everything we thought we knew is wrong. Perchlorate is my favorite molecule for Mars biology.”
In 1976 the Gas Chromatograph Mass Spectrometers (GCMS) on twin Viking landers failed to find any organic compounds on Mars when they heated soil samples to 350 degrees Fahrenheit. For 34 years this has been a compelling argument against life on the surface of Mars.
But it was also very curious that the Viking GCMS failed to find any organics at all. Meteorites should have peppered the surface with carbon-based compounds. But if perchlorates were in the soil it would have destroyed all organics when heated in the GCMS.
Exotic chlorine chemistry would also have triggered a false positive in the Viking labeled release experiments which tried to nurture Mars bugs to metabolize buy being fed a radioactively spiked liquid nutrient. But wetting the soil made it outgas like an Alka-Seltzer tablet, mimicking metabolism. In 34 years the experiment’s results has never been successfully duplicated in earthly labs.
McKay, who has done extensive field research in the dry valleys of Antarctica as well as the bone dry Atacama plateau in Chile, believes that the Martian north polar regions could have been an oasis for microorganisms 5 million years ago. Back then Mars had extreme seasons because its axis was tilted 45 degrees rather than the 25 degrees it is today. This meant that the northern polar region got double the sunlight than it does today.
The northern pole has some of the lowest elevations on Mars and so air pressure may have been dense enough back then for perchlorate-rich liquid water to remain stable. It would have been sandwiched between the dust top coating and a hard ice-rock mix underneath the surface. Microbes may have flourished in a rich film of liquid water, like their cousins on Earth who live in a similarly thin sandwich in the high Antarctic dry valleys.
“The polar temperatures back then (about 15 degrees Fahrenheit) are within the range of biological possibility,” McKay says enthusiastically. He envisions Mars microbes extracting oxygen from the perchlorate and eating iron oxides in the soil.
NASA’s nuclear-powered rover the Mars Science Laboratory named Curiosity (look out you Martian cats!) has an experiment called the Sample Analysis at Mars (SAM) instrument. It will wash out organics if they exist in the Martian soil without the need for heating it. If there is a positive detection after it lands in 2012 it will end a three-decade long search for organic compounds on Mars.
The ultimate dream is to do a Mars sample return mission to bring microorganisms to Earth labs (with a price tag running as high as $10 billion a rock). McKay favors a quicker, cheaper technology demonstrator mission, like the 1997 Mars Pathfinder landing. A small probe would touch down, scoop up a soda can full of soil, and scoot back to the Earth.
To trace the history of life on the Red Planet, “ultimately you want to go to Mars and drill down 500 feet into the soil and rock,” says McKay. This is very hard to do with robots that barely might penetrate down just couple of feet (unless NASA builds Transformers — not the electrical device but a real-life version of the 1980s Hasbro toy robots). It would call for brawny Mars astronauts who could jiggle the drilling apparatus and give it some good old-fashioned elbow grease. (At last we have a role for Bruce Willis in space!)
It is also the most compelling scientific reason to save up the $1 trillion to eventually send humans to Mars. The realization that the solar system had a “Second Genesis” might bolster a view that what we call “life” is a property matter acquires at a certain threshold of its organization. This would mean that physical laws in a hospitable environment, rather than some unique and abrupt discontinuity in cosmic evolution, directs life processes across the galaxy.
The mantra for the manned Mars mission might be, “drill baby, drill!”
Images (from top): A view from the Phoenix Mars Lander in 2008 (NASA/JPL/Univ. of Ariz.); trenches dug by one of the Viking landers in 1976 (NASA/JPL); a trench dug by Phoenix (NASA/JPL/Univ. of Ariz.); permafrost in terrestrial polar regions are not dissimilar to the ones found in Martian polar regions (NASA).