A new analysis of spacecraft photography of Mars appears to show that in its earliest history, much of the planet was a land of lakes and shallow seas, and this left distinct layers of sedimentary rock where a fossil record of Martian life, if it ever existed, is most likely to be preserved.
The discovery, scientists said, provided some of the most striking evidence yet that Mars, though cold and arid now, was once a warmer world with a denser atmosphere and presumably substantial amounts of flowing and standing water. And where there has been liquid water, scientists say, there could have been life.
In a statement issued on Monday by NASA, Dr. Michael C. Malin, principal investigator for photography on the Mars Global Surveyor spacecraft, announced: "We see distinct, thick layers of rock within craters and other depressions for which a number of lines of evidence indicate that they may have formed in lakes or shallow seas. We have never before had this type of irrefutable evidence that sedimentary rocks are widespread on Mars."
Malin added that the latest photographs showed that "early Mars was very dynamic and may have been a lot more like Earth than many of us had been thinking."
Malin and Dr. Kenneth S. Edgett, both with Malin Space Science Systems in San Diego, which operates the spacecraft camera for the National Aeronautics and Space Administration, have also written a formal report of their analysis to be published in Friday's issue of the journal Science. In the article, they described pictures from the Mars Global Surveyor that showed outcrops of horizontal sedimentary layers that they estimated date from the earliest period of preserved Martian history, between 4.3 billion and 3.5 billion years ago.
Some of the layering had been observed by earlier spacecraft, but never in such detail or over such a broad expanse of Mars.
On the Net: NASA: Exploring Mars