A recent study has found that Martian pebbles once rolled dozens of miles down a river, providing more evidence that the Red Planet was once covered in oceans, lakes and rivers.
While new evidence suggests that Mars may harbor a tiny amount of liquid water, it exists today as a largely cold and arid planet. Three billion years ago, however, the situation may have been much different.
In 2012 the Mars Curiosity rover beamed images back to Earth containing some of the most concrete evidence that water once flowed in abundance on the planet. Small, remarkably round and smooth pebbles suggested that an ancient riverbed had once carried these rocks and abraded them as they traveled.
To Douglas Jerolmack, a geophysicist at the University of Pennsylvania, and his collaborator Gabor Domokos, a mathematician at Budapest University of Technology and Economics, Curiosity’s findings raised a fundamental geological question: Can we use shape alone to interpret the transport history of river pebbles — on Mars, Earth or any planet?
In a new report, Jerolmack, Domokos and colleagues report the first-ever method to quantitatively estimate the transport distance of river pebbles from their shape alone. The researchers’ estimate that the Martian pebbles traveled roughly 30 miles from their source, providing additional evidence for the idea that Mars once had an extensive river system, conditions that could support life.
Determining how far pebbles have traveled could also be useful for studies on Earth, for example in identifying sources of river-transported resources, such as gold.
Jerolmack noted that the study is not only exciting for what it implies about Mars but for opening up a new realm of possibility to quantify what before could only be described qualitatively.
The study appears in Nature Communications.