NASA’s Curiosity rover samples linear active dune on Mars
As NASA’s Curiosity Mars rover travels uphill from a band of rippled sand dunes, it carries with it a sample of dark sand for later analysis that will complete the rover’s examination of those dunes. The rover studied four sites near a linear dune from early February until early April to compare those to what it had found during its examination of crescent-shaped dunes in late 2015 and early 2016.
Curiosity’s two-phase investigation of the Bagnold Dunes is the first study of active dunes on a world other than Earth.
One of the questions this Martian dune campaign is seeking to answer is how winds shape dunes that are relatively close together, on the same side of the mountain, into different patterns. Another question is whether Martian winds sort grains of sand in ways that affect the distribution of mineral compositions, which would have implications for the study of Martian sandstones.
“At these linear dunes, the wind regime is more complicated than at the crescent dunes we studied earlier,” said Mathieu Lapotre of Caltech, in Pasadena, California, who helped lead the Curiosity science team’s planning for the dune campaign. “There seems to be more contribution from the wind coming down the slope of the mountain here compared with the crescent dunes farther north.”
The linear dunes are uphill and about a mile (about 1.6 kilometers) south of the crescent dunes. Both locations are part of a swath of dark sand called Bagnold Dunes, which stretches several miles in length. This dune field is on the northwestern flank of Mount Sharp, the mountain at the center of Gale Crater that Curiosity is climbing.
“There was another key difference between the first and second phases of our dune campaign, besides the shape of the dunes,” Lapotre said. “We were at the crescent dunes during the low-wind season of the Martian year and at the linear dunes during the high-wind season. We got to see a lot more movement of grains and ripples at the linear dunes.”
Because the wind-sensing capability of Curiosity’s Rover Environmental Monitoring Station (REMS) is no longer functioning, the rover team now uses change-detection pairs of images taken at different times to assess wind strength and direction. Two of the six wind sensors on the rover’s mast were found to be inoperable when it landed in 2012. The other four provided wind information during the rover’s prime mission and the first two-year extended mission. The REMS instrument still provides other Mars-weather data daily, including temperatures, humidity, and pressure.
One reason the rover team chose to drive further uphill before finishing the analysis of the scooped sand sample is the status of Curiosity’s rock-sampling drill, which has not been used on rock since it experienced a problem with the drill feed mechanism five months ago. Engineers are assessing how the use of vibration to deliver samples may be affecting the drill feed mechanism, which is used to move the drill bit forward and backward. High winds at the linear dune sight were also complicating the process of pouring sand into the entry ports for the rover’s laboratory instruments.
“A balky brake appears to be affecting drill feed mechanism performance,” said Curiosity Deputy Project Manager Steven Lee, of NASA’s Jet Propulsion Laboratory, Pasadena, California. “In some cases, vibration has been observed to change feed effectiveness, so we’re proceeding cautiously until we better understand the behavior. In the meantime, the engineering team is developing several methods to improve feed reliability.”
Video courtesy of NASA
Jim Sharkey is a lab assistant, writer and general science enthusiast who grew up in Enid, Oklahoma, the hometown of Skylab and Shuttle astronaut Owen K. Garriott. As a young Star Trek fan he participated in the letter-writing campaign which resulted in the space shuttle prototype being named Enterprise. While his academic studies have ranged from psychology and archaeology to biology, he has never lost his passion for space exploration. Jim began blogging about science, science fiction and futurism in 2004. Jim resides in the San Francisco Bay area and has attended NASA Socials for the Mars Science Laboratory Curiosity rover landing and the NASA LADEE lunar orbiter launch.