Tipped-over Mars could explain ocean riddle, say scientists

0 Comments | AFP, June, 2007

PARIS (AFP) — Scientists firing the latest salvo of opinions over the mystery of Mars' water say they have new evidence to back the theory that a mighty ocean once washed over much of the Red Planet's surface.

The theory -- derived from photos snapped by orbiters and geological and chemical data sent home by US rovers Spirit and Opportunity -- is that as much as a third of Mars' surface was once covered by water.

The cornerstone of this idea is that there are remarkable "shoreline" features visible in a ring thousands of kilometers (miles) long on the planet's northern hemisphere lowlands.

But there's a big problem: these intriguing features are at widely different altitudes, with elevation varying by several thousand metres (thousands of feet) instead of...