Scientists Find Strong Evidence of Primitive Life on MarsBy Kathy Sawyer
The Washington Post
British scientists Thursday announced they had found strong new evidence that primitive life once existed on ancient Mars, along with tantalizing hints that similar organisms may even survive today.
The team of planetary geochemists analyzed two different meteorites that fell to Earth from Mars, including the same rock in which an American team last summer reported similar evidence, and a second sample billions of years younger.
The finding comes just as the American and Russian space agencies are preparing to launch a series of robot explorers to the fourth planet from the sun, where water once flowed. Scientists said the new evidence increases the odds that the robots will find signs of life.
The evidence in the second rock indicates life could have existed on Mars just 600,000 years ago. "Geologically speaking, this is sufficiently recent for there to be a good chance that life might still exist in protected areas on our planetary neighbor," the team concluded in a report presented at a meeting in London at the Royal Society hosted by the British minister of science.
The new findings both corroborate and go beyond the earlier evidence, according to Michael Meyer, who heads NASA's exobiology program.
The British team reported the presence of organic compounds - complex organic molecules of the sort required for carbon-based life - in both Mars rocks. While the American team also found organic material, the British added a second configuration, or form, of it, scientists said.
Using a different technique from the American team, they also tied this material in some instances to a second line of evidence - the signature of "microbially produced methane" similar to that produced by bacteria that flourish in cows stomachs and other places on Earth.
The new findings, based on the ratios of isotopes (varying atomic weights of the same chemical substance) in the meteorites' organic material, matched the ratios contained in some of the oldest fossils found on Earth, also of bacteria, according to the British team of Colin Pillinger, Ian Wright and Monica Grady of the Open University.
The news elated the American team that announced evidence of extraterrestrial life on Aug. 7, producing headlines around the world but also a barrage of skepticism.
"We are pleased that an international group of this stature has gone to work on the problem," said Everett Gibson Jr. of NASA's Johnson Space Flight Center, a leader of the U.S. team that also included David S. McKay of JSC and Richard N. Zare of Stanford University.
After arduous study of minuscule fissures in the surface of their Mars rock, the American group found a chain of several different pieces of evidence, including what could be fossils of ancient bacteria 100 times smaller than any known on Earth. Each of their findings individually could be explained by non-biological causes but, taken together, they said the accumulation pointed strongly to biological activity on Mars 3.5 billion years ago.
The second Mars meteorite is of particular significance to scientists who study Mars rocks. Found in Antarctica in 1979, it is known as Elephant Moraine 79001 - (EETA 79001, for short) - after its location. About a dozen Mars rocks have now been identified.