Scientists Find Possibility of Ancient Coastline on Mars

WASHINGTON — Scientists studying polar areas of Mars have found features that might once have been an ancient coastline.

The theory that the Red Planet once had water has long been of interest to scientists, and a group led by James W. Head III of Brown University searched data collected by Mars Global Surveyor for confirmation. The Surveyor satellite began orbiting Mars in 1997.

They found a geological feature extending around the northern third of the planet like a bathtub ring. This, they speculate in today’s issue of the journal Science, could be evidence that ocean waves once lapped at a coast there.

There are terraces parallel to the ring in many places, as often occur under oceans on Earth, and the area within the ring has fewer meteor craters than other parts of the planet, possibly indicating an area protected by a layer of water.

However, while this information lends support to the theory that water once existed on the planet, scientists will still need chemical or other evidence to confirm it.

The researchers estimate that the ocean could have been as much as 3,000 feet deep at a time when Mars was warmer and water could exist in liquid form. The planet began cooling about a billion years ago, they said, and the atmosphere thinned, allowing much of the water to escape.

There remains the possibility, however, that some water is still present on Mars as a form of permafrost below the surface.