Mars Pebble Discovery Indicates Ancient Flowing Stream

Posted on May 31, 2013

Scientists have completed analysis of pebble-containing slabs that NASA's Mars rover Curiosity investigated last year. Scientists say the rocks are part of ancient, flowing streambed on Mars. The images above compare the Mars pebbles to rocks from a sedimentary conglomerate formed of gravel fragments in a stream on Earth. You can see a larger version of the image here.

NASA says these rocks are the first ever found on Mars that contain streambed gravels. The researchers estimate that the stream carried the gravels for at least a few miles.

Rebecca Williams of the Planetary Science Institute, Tucson, Ariz., lead author of a report in Science, said in a statement, "We completed more rigorous quantification of the outcrops to characterize the size distribution and roundness of the pebbles and sand that make up these conglomerates. We ended up with a calculation in the same range as our initial estimate last fall. At a minimum, the stream was flowing at a speed equivalent to a walking pace -- a meter, or three feet, per second -- and it was ankle-deep to hip-deep."

Three separate areas were examined. They include Goulburn, which is immediately adjacent to the rover's Bradbury Landing touchdown site. The other two, Link (pictured above) and Hottah (pictured below), are about 165 and 330 feet (50 and 100 meters) to the southeast.

Williams says, "These conglomerates look amazingly like streambed deposits on Earth. Most people are familiar with rounded river pebbles. Maybe you've picked up a smoothed, round rock to skip across the water. Seeing something so familiar on another world is exciting and also gratifying."

The researchers say in Science that the finding "provides the clearest view yet on the nature of early martian rivers and should provide momentum for Curiosity's mission moving forward."

More from Science Space & Robots