The search for water on Mars has gone on for almost as long as humanity has been traveling beyond our own planet. While tantalizing hints have been uncovered at various stages in this search, NASA’s latest baby, the Curiosity rover, has finally unearthed conclusive evidence that flowing water once existed on the red planet.
The rover has supplied the first-ever images of rocks containing ancient stream bed gravel, showing that water not only existed on Mars at one point, but actively flowed across its surface. The gravel is smoothed in a fashion that indicates water flowed over it, and some of it is so large that it could only have been moved by water, not by wind.
NASA Science quotes Curiosity science co-investigator William Dietrich of the University of California, Berkeley, as saying:
“From the size of the gravels it carried, we can interpret the water was moving about three feet per second, with a depth somewhere between ankle and hip deep. Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is a transition from speculation about the size of stream bed material to direct observation of it.”
The location of this momentous discovery is between the north rim of Gale Crater and the base of Mount Sharp, NASA Science reports. The stream bed gravel was uncovered when the rover examined two outcroppings, known as “Hottah” and “Link,” and NPR reports that Curiosity’s landing site was specifically chosen because the area looked like a place where a canyon stream had spilled water out onto a plain.
Mars Science Laboratory Project Scientist John Grotzinger of the California Institute of Technology in Pasadena compared Hottah visually to “jack-hammered slabs of a city sidewalk” but explained that it is actually a tilted block of an ancient stream bed.
Andrew Knoll, a planetary sciences professor at Harvard University, heralds the discovery as a peek into the ancient past of the red planet.
“Something happened on Mars that simply doesn’t happen today,” he said. “And that is, there was water flowing at high rates over the Martian surface. That’s really what they’ve found.”
While previous rovers have found evidence that water once existed on the planet, Knoll explained that these discoveries were of groundwater that would bubble up from time to time, not of a flowing stream like the Curiosity has uncovered.
The Curiosity’s main mission, according to NPR, is to search for evidence that Mars was once capable of supporting life. The discovery of this stream bed is a tantalizing hint that the possibility may very well have existed at one point, and that humanity and Earth are not as alone as we once thought.