While news about finding evidence of water on Mars has dominated the media in recent weeks, research on other aspects of the Red Planet have also been released that could just as well be as big of a discovery as the former.
An international team of researchers from the University of Pennsylvania and the Budapest University of Technology and Economics (BME) have discovered smooth and rounded rocks on the Martian surface that suggest these pebbles could have rolled for several miles down a river.
The scientists believe that this provides evidence that ancient waterways on Mars were stable and not merely streams that were short-lived.
The small, round Martian stones were found by NASA's Curiosity rover near its landing point located at the Gale Crater in 2013. Agency scientists previously identified these rocks as similar to those typically found in rivers systems on Earth, which become rounded as they roll, slide and hop down riverbeds and hit other rocks.
A recent study has found that these Martian rocks rolled in the river for a considerable amount of time, a discovery that should help NASA researchers to reconstruct the environment of ancient Mars and determine the planet's former potential to support living organisms.
"We believe liquid water is a principal ingredient for life," Douglas Jerolmack, a Pennsylvania geophysicist and co-author of the study, said.
"Knowing whether pebbles in a river moved one kilometer or 100 kilometers (around 62 miles) could tell us how stable water was on the surface of ancient Mars."
Rolling Martian Stones
Through the use of a mathematical model, the Pennsylvania scientists were able to determine how blocky rocks become smoother and rounder as parts of them begin to be chipped off because of erosion.
The researchers then examined the shape of the pebbles on Mars in order to find out the amount of mass each rock lost as a result of erosion.
Applied mathematician and study co-author Gábor Domokos, from BME, explained how the shape of an object can reveal different information about it.
He said that they were able to identify a specific code that can help researchers understand the natural history objects such as the sand typically found on a beach.
The researchers tested their model by rolling fragments of limestone in a drum and documented the changes in mass and shape. They discovered that the pattern of changes observed in the rocks closely resembled their model.
The team then traveled to a Puerto Rican mountain river to study the local rocks.
Jerolmack said they took note of large, angular rock formations that appear to break off from the walls of the river located at the headwaters, and then they proceeded with studying the rocks found downstream.
He said that take out thousands of stones out every few hundred meters to document their weight and take images of their silhouette.
The researchers noticed that the pattern of changes in the rocks once again resembled their model.
Jerolmack and his colleagues also studied rock samples found in an alluvial fan, which is a fan-shaped sediment deposit that is formed as stream flows. The rocks were retrieved from a canyon in New Mexico that mirrored the location on Mars where the round pebbles were located.
This finding suggests that the shape of the Martian rocks could help the researchers determine the distance that these stones have traveled.
Domokos said that their study is the first of its kind to attempt to identify the history of an object based solely on its shape.
The researchers compared their recorded rock images with the rounded pebbles discovered the Curiosity Mars mission and calculated that the Martian rocks had lost around 20 percent of their original mass.
Considering the reduced gravity on Mars, which is around 40 percent less compared to Earth's own gravity, the team found that the rounded stones had traveled an estimated 50 milometers, or 30 miles, from the their place of origin, which is believed to be the Gale Crater's northern rim.
The scientists noted that their study could also help fellow researchers in examine river-borne particles found on other planet systems and moons such as Saturn's massive satellite Titan.
The findings of the international study are featured in the journal Nature Communications.