NASA announced Thursday that the Curiosity rover has found evidence of an ancient stream that flowed "vigorously" on Mars. NASA says the stream bed evidence suggests the water flowed in "large volume," and that it was fast-moving and deep.
According to NASA mission scientists, evidence of existence of an ancient stream bed came from analysis of size and shapes of pebbles and gravel near Gale Crater. Scientists consider the find important because it establishes what they consider one of the key prerequisites for life — water.
According to NASA:
"The discovery comes from examining two outcrops, called 'Hottah' and 'Link,' with the telephoto capability of Curiosity's mast camera during the first 40 days after landing. Those observations followed up on earlier hints from another outcrop, which was exposed by thruster exhaust as Curiosity, the Mars Science Laboratory Project's rover, touched down."
According to the The Scientific American, the Martian rock outcrop "Hottah," was named after the Hottah Lake in Canada's Northwest Territories.
The NASA statement explains that stream bed gravels were observed among rocks on the surface of Mars. According to Space.com, photos from Curiosity rover revealed several rocky outcrops with stones cemented into a layer of conglomerate rock. NASA reports: "The science team may use Curiosity to learn the elemental composition of the material, which holds the conglomerate together, revealing more characteristics of the wet environment that formed these deposits."
Image showing the topography around the area where NASA's Curiosity rover landed on Aug. 5 PDT (Aug. 6 EDT).
NASA scientists say the observation that some of the stones were rounded and large suggests they were transported over long distances across the Martian surface by water. According to NASA scientist Rebecca Williams of the Planetary Science Institute in Tucson, Arizona, at a press conference, the stones inside the rock were too big to have been moved by wind and could only have been moved by water. She said: "The consensus of the science team is that these are water-transported gravel in a vigorous stream," she said.
NASA says that Curiosity science co-investigator, William Dietrich, of the University of California, Berkeley, said: "From the size of gravels it carried, we can interpret the water was moving about 3 feet per second, with a depth somewhere between ankle and hip deep." Space.com reports he added: "Plenty of papers have been written about channels on Mars with many different hypotheses about the flows in them. This is the first time we're actually seeing water-transported gravel on Mars. This is a transition from speculation about the size of streambed material to direct observation of it."
NASA/JPL-Caltech/Univ. of Arizona
Map showing the path on Mars of NASA's Curiosity rover toward Glenelg.
According to Space.com, NASA scientists say the flow was comparable to the flows produced by flash floods in desert areas on Earth. The water flowed many billions of years ago, and the evidence from the stream bed is that it flowed over a long period of time. Dietrich said: "I'm comfortable to argue that it's certainly beyond the thousand-year timescale, but we're still gathering data to go further with that."
John Grotzinger, lead scientist at the California Institute of Technology, however, warned that, "The question about habitability goes beyond the simple observation of water on Mars." He said: "Certainly flowing water is a place where micro-organisms could have lived. This particular kind of rock may or may not be a good place to preserve those components that we associate with a habitable environment."
NASA/JPL-Caltech/MSSS and PSI
Images compare the Link outcrop of rocks on Mars (left) with similar rocks seen on Earth (right).
Astrophysicist Niel deGrasse Tyson told The Huffington Post: "As a scientist, it's always a good feeling to obtain confirming evidence for something you had strongly suspected was true. Curiosity has just taken us there. But it's an even better feeling to find evidence that conflicts with long-held ideas. Over its usable life, Curiosity will almost surely take us there too."
Space.com reports that in spite of the new important discovery, Curiosity rover's final destination is Mount Sharp, a 3.4-mile-high (5.5 kilometers) mountain that rises from the Gale Crater. NASA scientists say the mountain's foothills show evidence of ancient flow of water.
Grotzinger said: "A long-flowing stream can be a habitable environment [but] it is not our top choice as an environment for preservation of organics, though. We're still going to Mount Sharp, but this is insurance that we have already found our first potentially habitable environment."
According to NASA, images of the Martian surface taken from space had provided hints that the Martian environment was once wet but the latest find confirms the suspicion.
According to NASA, Curiosity mission is NASA's first astrobiology mission to Mars since the Viking probes of the 1970s. NASA scientists want to investigate the Gale Crater for ancient environmental conditions that can sustain life.