Evidence of Water Found on Mars

NASA’s Curiosity rover found evidence for an ancient, flowing stream on Mars at a few sites, including the rock outcrop pictured here, which the science team has named “Hottah.” (NASA)

The Curiosity rover has discovered an ancient stream bed that suggests water, possibly lots of it, once flowed on Mars.

In a new study,  scientists say their findings represent the first on-site evidence of sustained water flow on the Martian landscape. The discovery also supports the theory Mars would have once been able to host life.

Dawn Sumner, a co-author of the study, said  she and her colleagues used very basic geologic principles in making their discovery.  While examining high-resolution photographs of multiple outcrops of pebble-rich slabs  shot by Curiosity, they noticed some rounded pebbles.

“On the first day of my sedimentary class, I have the students measure grain size and the rounding,” said Sumner, who is a University of California-Davis geologist and professor. “It’s simple, and it’s important.”

Sumner said the pebbles’ rounded shape and granular size, along with other characteristics, can only form when pebbles are transported through water over long distances.

The pebbles, which were likely deposited more than two billion years ago, were discovered at three locations on Mars, known as Goulburn, Link and Hottah, which are located between the north rim of the planet’s Gale Crater and the base of a mountain located in the crater called Mount Sharp, about a quarter mile away from where Curiosity landed last summer.

In the foreground is the gravelly area around Curiosity’s landing site in Gale Crater. Mt. Sharp is seen in the distance. (NASA)

Sumner is also a co-investigator for the Mars Science Laboratory team and played an important role in selecting Gale Crater as Curiosity’s landing site.  She also helped coordinate the first scientific interpretations of what the rover saw during its first few days on the Red Planet, by controlling it with a computer to take photographs of its surroundings.

“The main reason we chose Gale Crater as a landing site was to look at the layered rocks at the base of Mount Sharp, about five miles away,” she said. “We knew there was an alluvial fan in the landing area, a cone-shaped deposit of sediment that requires flowing water to form. These sorts of pebbles are likely because of that environment. So while we didn’t choose Gale Crater for this purpose, we were hoping to find something like this.”

You can hear Dr. Sumner talk about her team’s discovery and the role geology is playing in the Curiosity’s goal of determining the “habitability” of Mars on this weekend’s radio edition of Science World – see right column for times and audio links.