NASA’s Mars Curiosity rover is on a mountain, more than three miles high, that is built out of sedimentary rock in the enormous Gale Crater of the Red Planet. How exactly that mountain, officially dubbed Aeolis Mons but called Mount Sharp, got to be there is somewhat a of a mystery, writes Kenneth Chang for the New York Times. On Earth, mountains push up as erupting volcanos or as collisions between the plates of the crust. "Mars lacks plate tectonics, and volcanoes do not spew out of sedimentary rock. So how did this 18,000-foot mountain form?" Chang asks.
Curiosity is slowly crawling up the side of the mountain, passing layers and layers of sedimentary rock to find the answer. And along the way, the rover has found many signs that Gale Crater once contained large freshwater lakes, explains Rachel Feltman for the Washington Post. New images from Curiosity show that patterns seen in lake-floor sediment and signs of rivers flowing down the crater rim.
The discovery that there was once water on Mars isn’t actually new. For Aeon, Lee Billings writes:
Every mission sent to Mars seeking water has found it and, as a result, we now know that our neighboring world used to be a warmer, wetter, more habitable place. Billions of years ago, that all changed, as the planet cooled and lost most of its air and water, and settled into a quiet senescence. But present-day Mars still harbors a slumbering aquasphere, locked in the ground as ice, which may stir every so often, erupting to the surface in evanescent briny flows.
But the latest findings indicate that the water of that warmer, wetter time may have stuck around long enough to create conditions favorable for life.
"If our hypothesis for Mount Sharp holds up, it challenges the notion that warm and wet conditions were transient, local, or only underground on Mars,” Ashwin Vasavada, Curiosity’s deputy project scientist at NASA's Jet Propulsion Laboratory in Pasadena said in a NASA press release. “A more radical explanation is that Mars' ancient, thicker atmosphere raised temperatures above freezing globally, but so far we don't know how the atmosphere did that."
Gale Crater was shaped by millions or possibly tens of millions of years of flowing rivers, deltas and large lakes, reports Marc Kaufman for the New York Times. The layers of Mount Sharp alternate between deposits laid by wind, rivers and lakes. It seems the cycles slowly built the mountain up and carved away deposits around the edge of the crater. Now we have a sedimentary mountain rising out of the crater floor.
Curiousity can keep scratching and drilling away, but it’s ill-equipped to determine if life once lived in the shifting environment of lakes, rivers and sculpted mountain. To answer that question, Kenneth S. Edgett of Malin Space Science Systems, which helped build an orbiter to investigate Mars’ geology, says we will need more than robots and satellites. “I’d like to think it would take only a few months,” to solve the questions raised by Mount Sharp, he told the Times, “with a few people on the ground.”