Rover rolls where stream flowed on Mars

CALTECH (US) — NASA’s Curiosity rover is currently exploring the site where a stream flowed with force across the surface of Mars.

The finding, announced by members of the project’s science team this week at the Jet Propulsion Laboratory (JPL), offers new information about a once wet environment in Gale Crater, the ancient impact crater where the rover touched down in early August.

This set of images compares the Link outcrop of rocks on Mars (left) with similar rocks seen on Earth (right). The image of Link, obtained by NASA’s Curiosity rover, shows rounded gravel fragments, or clasts, up to a couple inches (few centimeters), within the rock outcrop. (Credit: NASA/JPL-Caltech/MSSS and PSI)

A close-up view of Hottah reveals more details of the outcrop. Broken surfaces of the outcrop have rounded, gravel clasts, such as the one circled in white, which is about 1.2 inches (3 centimeters) across. Erosion of the outcrop results in gravel clasts that protrude from the outcrop and ultimately fall onto the ground, creating the gravel pile at left. This image mosaic was taken by Curiosity’s 100-millimeter Mastcam telephoto lens on its 39th Martian day, or sol, of the mission (Sept. 14, 2012 PDT/Sept. 15 GMT). (Credit: NASA/JPL-Caltech/MSSS)

In this image from NASA’s Curiosity rover, a rock outcrop called Link pops out from a Martian surface that is elsewhere blanketed by reddish-brown dust. (Credit: NASA/JPL-Caltech/MSSS)

Using Curiosity’s mast camera to analyze two rock outcrops known as Hottah and Link, the team has identified a tilted block of an ancient streambed—a layer of conglomerate rock, which is made up of stones of different sizes and shapes cemented together.

“Curiosity’s discovery of an ancient streambed at Gale Crater provides confirmation of the decades-old hypothesis that Mars once had rivers that flowed across its surface,” says John Grotzinger, the mission’s project scientist and a geology professor at the California Institute of Technology (Caltech).

“This is the starting point for our mission to explore ancient, potentially habitable environments, and to decode the early environmental history of Mars,” adds Grotzinger.

“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,” says Curiosity science co-investigator William Dietrich of the University of California, Berkeley, according to a report from JPL. “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.”

The sizes of the gravels in the conglomerate rock suggest that the stream once flowed at a rate of about a meter per second. The discovery marks the first time scientists have identified gravel that was once transported by water on Mars.

In coming weeks and months, the team plans to use all of Curiosity’s analytical instruments to study these types of rocks.

And Grotzinger points out, “Finding geological evidence for past water is a prerequisite to beginning geochemical measurements that inform analysis of ancient potentially habitable environments. Curiosity has the most sophisticated and comprehensive suite of geochemical instruments ever flown to Mars.”

Source: Caltech