NASA/JPL/US Geological Survey
A closeup of a rock outcrop on Mars' Meridiani Planum. Scientists say the texture and composition of the rocks in this region suggests it was once drenched in water.
The two rovers on Mars continue their pursuit of evidence that water once flowed on the Red Planet.
Earlier this week, scientists said the rocks and soil at Opportunity's landing site did show signs of having been shaped by flowing water. Numerous images from Mars, promptly available to the general public, are proving to be a popular draw for Web users.
NPR's John Ydstie discusses the findings — and some of the photos — with NPR's Joe Palca. Follow along with the Web links at the bottom of the page.