Washington

NASA seems to have trouble keeping secrets, when it comes to Mars.

Four years ago, it was claims of fossil life in a Martian rock that set the media in a spin, after word leaked out ahead of publication in the journal Science.

Splash down? These layered patterns on the surface of Mars could have been caused by water. Credit: NASA/JPL/MALIN SPACE SCIENCE SYSTEMS

Now, in an uncanny echo of these events, a NASA press conference originally planned for Thursday 7 December was hastily pulled forward to the Monday after news services ran the story that scientists Michael Malin and Ken Edgett of Malin Space Science Systems in San Diego had found evidence for ancient lakes on Mars.

Malin and Edgett report in the 8 December issue of Science on layered outcrops that appear to be sedimentary rocks in several natural basins. The outcrops, which are between 4.3 billion and 3.5 billion years old, are possible evidence that surface water was widespread in the planet's distant past.

The researchers caution that water may not be the only explanation for the images returned by NASA's Mars Global Surveyor. It is also possible, for example, that atmospheric pressure was once higher on Mars than it is today, causing winds to spread dust around the surface.

Layered deposits were discovered on Mars in the 1970s, but have never been seen in so much detail. The lake sediments — if the evidence holds up — would have important implications for any future fossil hunts. “These discoveries give us some direction on where to go,” said Jim Garvin, NASA's programme scientist for Mars exploration.