Mars Stones And Pebbles Hint At Watery Past
May 30, 2013

More Evidence Hints At Mars’ Wet Past

Lee Rannals for - Your Universe Online

Another piece of evidence has emerged that gives more weight to the argument that the Red Planet could have had a wet history.

NASA's Curiosity rover currently roving around on Mars has snapped images of gravel and pebbles. Researchers writing in the journal Science say that the shapes and sizes of these rounded pebbles clearly show that there has been flowing water on Mars.

Curiosity's stereo camera took photos of a few areas with densely packed pebbles in an area named Hottah. The picture was taken at an angle towards ground-level, giving a slightly distorted view in which the size of the rocks depend on their location in the frame. The scientists had to process this image so the proportions were comparable in order to properly study it.

“Next, we divided the image into smaller fields of 10 mm and analyzed the gravel, which consists of coarse grains of sand around 1/3 mm. We examined the pebbles which are between 4 and 40 mm in greater detail. Altogether we made a thorough analysis of 515 pebbles,” explains Asmus Koefoed, a research assistant in the Mars Group at the Niels Bohr Institute at the University of Copenhagen.

Rocks can be weathered by both wind and water. Those that have been shaped by wind become angular and rough, while rocks that have faced flowing water eventually become smooth and rounded.

“We could see that almost all of the 515 pebbles we analyzed were worn flat, smooth and round. We have classified them according to their geometry, which can be described using a single number -- the ℠Corey shape factor´, where 0 describes rocks that are completely flat like a piece of paper and 1 means they are perfect spheres,” said Koefoed.

The team saw both light and dark rocks in various shades and colors, similar to the original rocks seen on both Earth and Mars. The rocks help scientists get a window into the ancient history on Mars.

“In order to have moved and formed these rounded pebbles, there must have been flowing water with a depth of between 10 cm and 1 meter and a flow rate of about 1 meter per second -- or 3.6 km/h -- slightly faster than a typical natural Danish stream,” said Morten Bo Madsen, head of the Mars research group at the Niels Bohr Institute.

The researchers pointed out that it has not just been sporadic flowing water that evaporates quickly, but prolonged warmer periods where the streams were active. This could have been due to a higher atmospheric pressure on the planet than today.

The new study also challenges another theory about Mars. Scientists have said the warm period on Mars was as far back as 3.5 to 3.7 billion years ago. However, new studies show it may have been only 2 to 3 billion years ago.

Curiosity has been an active rover on the Mars surface, and it recently drilled its second hole. This past weekend Curiosity drilled at its second site known as Cumberland. The rover drilled a 0.6-inch diameter hole about 2.6-inches deep. Once the sample analysis is complete, scientists will be able to compare it with findings from the previous drill site known as John Klein, which lies just nine feet away.