Curiosity's Mars Crater was Once a Vast Lake
The mountain that NASA's Mars rover Curiosity is exploring appears to have once been a lake.
The mountain that NASA's Mars rover Curiosity is exploring appears to have been the site of a large lake, one that likely filled and drained over tens of millions of years, scientists said Monday.
The discovery is based on data collected by Curiosity over the past 2.5 years, including findings of sediment beds of sandstones that are inclined toward Mount Sharp, a three-mile high mound rising from the center of a 96-mile wide impact crater.
"We can see a whole series of beds, of sandstones, with some pebble beds in there, that are actually inclined at a large scale toward the south," Curiosity scientist Sanjeev Gupta, with Imperial College in London, told reporters on a conference call.
Scientists believe that means that not only did Mount Sharp not exist at the time, but that Curiosity's Gale Crater landing site was once -- and possibly many times over -- a shallow lake.
Similar inclined beds are found on Earth at the mouths of river channels where they feed into lakes, Gupta said.
The research indicates that Mount Sharp formed from sediments deposited in the center of the lakebed over millions of years. The sediments would have been carried in rivers originating from the crater rim highlands -- which may have been capped in snow or ice -- and ending in the waters that filled the crater basin. Scientists suspect that winds later eroded the deposits, eventually creating the mountain.
"We are beginning to think that maybe Mount Sharp formed in a series of episodes involving sedimentation and erosion, stacked by different processes," said lead Curiosity scientist John Grotzinger, with the California Institute of Technology in Pasadena.
Scientists suspect there were many cycles of wet and dry times at Gale Crater and that the cycle continued for millions or tens of millions of years, boosting chances that conditions were suitable for microbial life.
"The size of the lake in Gale Crater and the length of time and series that water was showing up implies that there may have been sufficient time for life to get going and thrive," said NASA's Mars Exploration Program scientist Michael Meyer.
Curiosity landed inside Gale Crater to assess if the planet most like Earth in the solar system has or ever had the chemical ingredients and conditions for life. It found a life-friendly habitat almost immediately and spent the next 14 months driving to the base of Mount Sharp for additional studies and more ambitious experiments to try to find places where organic carbon may have been preserved.
Scientists have not yet released companion chemical data on the lakebed deposits.
This illustration depicts a lake of water partially filling Mars' Gale Crater, receiving runoff from snow melting on the crater's northern rim.
On Friday (Dec. 20), NASA's Mars Science Laboratory team announced that they were monitoring Curiosity's wheels. The rover's six wheels appear to have sustained accelerated damage as the one-ton rover drives over the rocky terrain inside Gale Crater. Although the aircraft-grade aluminum is designed to withstand some dents and holes, some of the rips and gashes in between the wheels' treads are causing concern. In this selection of "before and after" photos from Curiosity's raw image archive, we've pulled some photos taken by Curiosity's robotic-arm mounted MAHLI camera. The dates and the day (sol) of Curiosity's mission are noted.
Curiosity's middle-right wheel is shown here 34 days (sols) after the mission touched down in Gale Crater. Some red dust can be seen lightly covering the wheel. Very few dents are evident.
Note: Some minor contrast and brightness adjustments have been made to the raw imagery.
454 sols later, significant wear and tear can be seen on the same wheel. On the top, a gash in the aluminum skin is evident.
Close up and comparison of the gash in the aluminum wheel skin as seen on sol 488 (Dec. 20).
Curiosity's front-right wheel as seen on sol 177 of the mission.
The same front-right wheel as seen 311 sols later. Note the punctures on the inside of the wheel.
Until now we've seen minor damage to Curiosity's wheels, likely well within the wear expected for nearly 3 miles of roving. But the rover's front-left wheel is exhibiting one of the larger gashes with a long flap of aluminum bending toward the inside of the wheel. Shown here is the wheel in sol 177 when only minor dings and scratches can be seen.
By sol 488, the same wheel is dented and damaged, but of most concern is the large hole that is forming near the bottom of the photo.
The same wheel, zoomed in and compared between sol 177 and sol 488. Arrows indicate the spreading of the crack through the wheel's skin, along the tread.