Space

Mars Rounded Pebbles Were Carried for Miles by Ancient River System

Catherine Griffin
First Posted: Oct 15, 2015 09:49 AM EDT

Where did pebbles on Mars come from? They may have just been pushed by a river that existed millions of years ago. Scientists have examined mages of a few rocks and found that their smooth shape may be due to plentiful past water.

In this latest study, the researchers report the first-ever method to quantitatively estimate the transport distance of river pebbles from their shape alone. More specifically, the researchers estimate that the Martian pebbles seen traveled roughly 30 miles from their source. This, in particular, provides additional evidence for the idea that Mars once had an extensive river system.

In order to do this, the researchers developed mathematical models based on the Gomboc shape, which self-rights on a horizontal surface based on shape alone. This, in particular, shows that shape alone can carry vital information on natural history.

"An object's shape can itself tell you a lot," said Gabor Domokos, one of the researchers, in a news release. "If you go to the beach, natural history is written underneath your feet. We started to understand that there is a code that you can read to begin to understand that history."

In order to understand how far a pebble has traveled, though, researchers need to know the initial mass of the pebble. The researchers found that when two particles of similar size bang together, the way in which they influence each other's shape can be reduced to a geometric problem. This means that the researchers could find out the initial mass of the pebbles.

In the end, the scientists found that the pebbles lost about 20 percent of their volume. This meant that they traveled about 30 miles from their source, which is the best evidence yet of large, flowing rivers on the Red Planet in the distant past.

The findings are published in the journal Nature Communications.

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