A new study suggests that Mars’s 3.5-mile high Mount Sharp formed as strong winds carried dust and sand into the crater in which it rests. If true, Gale Crater probably never contained a lake, which would totally suck, because that’s one of the main reasons why NASA sent Curiosity there in the first place.
Gale Crater is about 96 miles (154 km) in diameter and is estimated to be about 3.5 to 3.8 billion years old. It has a really unique feature — an enormous mound of sedimentary debris extending to a height equivalent to that of Alaska’s Mt. McKinley. Formally, it’s known as Aeolis Mons, but everyone just calls it Mount Sharp.
The going theory about its formation, which has now been put in serious doubt owing to the new study, is that it is the eroded remnant of sedimentary layers that once filled the crater — layers of silt that were originally deposited on a massive lakebed.
Consequently, the area may have once featured vast reservoirs of water. NASA scientists figured that Mt. Sharp would be a fantastic geological structure for Curiosity to study — especially as far as Martian habitability is concerned.
But if the new research is correct, the mound will yield no such clues.
A SWEET Hypothesis
According to researchers based at Princeton University and the California Institute of Technology, Mt. Sharp likely emerged as strong winds carried dust and sand into the hole over the course of millions of years — a process driven by a wind feedback effect. The researchers, a team consisting of Edwin Kite, Kevin Lewis, and other, are calling it the slope wind enhanced erosion and transport (SWEET) hypothesis.
During the day, air rises from the crater as the surface is pounded by sunlight. But then, when things cool down at night, it sweeps back down its steep walls. These slope winds, or katabatic winds, would have been strong along the crater’s walls, but weak at the crater’s center, which is where the debris would have slowly accumulated.
Image: Air would have flowed up the crater rim (red arrows) and the flanks of Mt. Sharp (yellow) in the morning when the surface warmed, and reversed in the cooler late afternoon. Blue indicates the more variable wind patterns on the crater floor, the X marks Curiosity's landing site.
What’s more, previous theories about the mound’s formation don’t add up. There’s no way, say the researchers, that previously proposed processes could have resulted in sedimentary strata that outwardly dips the way it does from the mound’s center.
Image: The various layers of sediment that make up the mound did not extend to the crater wall and also display a consistent tilt, or "dip," away from the center of the mound. The yellow star shows Curiosity's initial location.
Not a Total Loss — and Not By a Longshot
NASA chose the Gale Crater site for a number of reasons, and not merely because it may have been the site of an ancient lake. Indeed, back in December Curiosity found traces of clay, water molecules and even organic compounds. To suggest that landing in Gale Crater was a complete mistake would be totally unfair.
Moreover, as the researchers themselves admit, a body of water could have existed in the moat surrounding the base of Mt. Sharp. And even if the bulk of the material was deposited by wind, the area will continue to produce valuable information about the region’s geological, and possibly biological, past.
But if the new SWEET hypothesis is true, Gale Crater could ultimately prove to be less than ideal. As the authors write in the paper, the region has limited organic carbon preservation potential.
"The quest to determine whether Mars could have at one time supported life might be better directed elsewhere,” noted study co-author Kevin Lewis through a statement.
Read the entire study at Geology: "Growth and form of the mound in Gale Crater, Mars: Slope wind enhanced erosion and transport.”
Photo of Curiosity via NASA; inset images via Kevin Lewis.