Is there life elsewhere in the universe? It's a question that has long intrigued astronomers and science fiction buffs alike, and now the National Aeronautics and Space Administration has launched its most ambitious attempt yet to find the answer.
Curiosity, NASA's 1-ton wheeled rover vehicle, blasted off from the Kennedy Space Center on Saturday for the 346 million-mile journey to Mars, where it will spend two years roaming the Red Planet's surface in search of tell-tale organic compounds that could signal the presence of life there, either now or in the distant past. If successful, the rover will demonstrate NASA still has the right stuff to explore the mysteries of space, even after the temporary suspension in July of its human spaceflight program.
More than a century has passed since the Italian astronomer Giovanni Schiaparelli observed what he thought were long, straight lines traversing the Martian surface. Schiaparelli called the markings canali, an Italian word that means "channels" such as the grooves carved out by streams and riverbeds on Earth. Unfortunately, the term was mistakenly translated into English as "canals," which implies structures built by intelligent creatures. And for a brief period during the late 19th and early 20th centuries, the error caused no end of scientific mischief.
Percival Lowell, a wealthy American amateur astronomer who built his own observatory to study Schiaparelli's canali, speculated the markings indicated the presence of an advanced civilization that had constructed an elaborate system of viaducts to bring water from Mars' perpetually frozen poles to its more habitable mid-latitudes. Lowell popularized his enthusiasm for the subject through books and articles that made the image of little green men a staple of countless science fiction novels and movies, but the whole fanciful theory collapsed when later investigators proved the markings he observed were nothing more than optical illusions.
NASA sent Mariner 4, its first space probe to Mars, whizzing past the planet in 1965. It photographed Mars' surface but found no evidence of either life or liquid water there (though subsequent orbital images suggest that water might still flow in some places on the planet). Mariner was followed in1976 by the two Viking landers, which were designed to search for life chemistry in soil samples. But they, too, failed to find evidence of life.
However, NASA's most recent probes, Spirit and Opportunity, launched in 2003, did find that conditions on Mars may have been conducive to life in the distant past. Since Mars is smaller than Earth and presumably cooled earlier than our own planet, it's even possible that life developed there first, and that microbial life forms blasted into space by asteroid impacts later landed on Earth, seeding life here.
Now Curiosity, the largest, most complex lander ever dispatched to Mars, is carrying an array of sophisticated instruments — some of which were designed and constructed at Maryland's Goddard Space Flight Center — that may finally allow scientists to determine whether the chemical building blocks necessary for life ever coalesced into actual life forms there. One of its main objectives will be to search for methane gas that has been detected in the thin Martian air. Since sunlight quickly breaks down methane molecules, scientists believe the methane in Mars' atmosphere must be of relatively recent origin, possibly from microorganisms able to withstand the harsh conditions on the planet's surface.