Evidence suggests early Mars was warmer and wetter

Scientists are generally in agreement that water once flowed on Mars. The nature of those flows and the conditions that made them possible are less obvious, however.

New evidence may offer some clarity. Researchers in Italy have discovered a region of sedimentary rock southern hemisphere of Mars, just north of a massive impact crater known as Hellas Basin. Its presence suggests a warm, young Mars hosted water across an expanded geological timescale -- not simply during brief episodes of warming.

Until now, most researchers believed the smooth plains north of Hellas Basin featured rocks formed by volcanic activity. But astronomers from the University of Chieti-Pescara suggest the plains feature sedimentary rock.

The researchers are backed by evidence captured by Mars Express and the Mars Reconnaissance Orbiter. Images of small craters and instances of erosion on the plains have revealed layers of flat, light-colored rock.

"To create the kind of sedimentary plains we found at Hellas, we believe that a generally aqueous environment was present in the region some 3.8 billion years ago," researcher Francesco Salese said in a news release. "Importantly, it must have lasted for a long period of time -- on the order of hundreds of millions of years."

The new images also revealed planar stratification and cross-bedding, characteristics of sedimentary rock. Furthermore, the probes identified the presence of significant amounts of clay.

"These characteristics suggest that the rock didn't form from lava flow deposits but rather from sedimentary processes, which implies that the region once experienced warm and wet conditions for a relatively long time," explained Salese. "When the layered rock was deposited -- during the Noachian period, around 3.8 billion years ago -- its surroundings must have been soaked in water, with intense liquid circulation.

The findings have significant implications for the search for evidence of life on Mars. The evidence suggests early Mars was a much more life-friendly place than previous studies. Clay-rich sedimentary rock is also an ideal medium in which to look for ancient signs of life.