Leonard David's INSIDE OUTER SPACE

Curiosity’s location as of Sol 3420. Distance driven at that Sol, 17.04 miles/27.42 kilometers.
Credit: NASA/JPL-Caltech/Univ. of Arizona

NASA’s Curiosity Mars rover at Gale Crater is now wrapping up Sol 3422 duties.

Lauren Edgar, a planetary geologist at USGS Astrogeology Science Center in Flagstaff, Arizona, reports that the robot is investigating the different surface expressions of the Greenheugh pediment. Last weekend’s drive put the rover next to some “gator-back terrain.”

Curiosity Right B Navigation Camera image acquired on Sol 3421, March 22, 2022.
Credit: NASA/JPL-Caltech

That’s some evenly spaced ridges with a blocky expression, Edgar adds. A recent one sol (Sol 3421) plan is focused on a close encounter with one of these ridges through contact science and remote sensing.

Sedimentary structures

Edgar explains that the Chemistry and Camera (ChemCam) Laser Induced Breakdown Spectroscopy (LIBS) observation of “Scandal Beck” is to assess the chemistry of the blocky outcrop.

Curiosity Chemistry & Camera (ChemCam) Remote Micro-Imager (RMI) photo taken on Sol 3421, March 22, 2022.
Credit: NASA/JPL-Caltech/LANL

“Then we’ll acquire 2 long-distance RMI [Remote Micro-Imager] mosaics to investigate the stratigraphy exposed in Gediz Vallis ridge. Afterwards, Mastcam will take two large mosaics to look at the sedimentary structures exposed in the “gator-back” ridge and characterize the erosion of these blocks,” Edgar notes.

Curiosity Front Hazard Avoidance Camera Right B image taken on Sol 3422, March 23, 2022.
Credit: NASA/JPL-Caltech

The rover was then slated to also take a Navcam dust devil survey now that Curiosity has entered the dusty season on Mars. In the afternoon, the plan called for the Mars Hand Lens Imager (MAHLI) to take a closer look at the grain size of these rocks at the target “Calder,” followed by an overnight Alpha Particle X-Ray Spectrometer (APXS) integration to learn about its chemistry.

Curiosity Mars Hand Lens Imager (MAHLI) photo produced on Sol 3422, March 23, 2022.
Credit: NASA/JPL-Caltech/MSSS

Good vantage point

Early the next morning Mastcam, Edgar reports, the script calls for the rover to acquire a mosaic of Gediz Vallis ridge “to document this feature from our good vantage point and morning lighting conditions.”

Prior to arriving on the Greenheugh pediment, the team had been intrigued by the “washboard texture” preserved on its surface, as identified in orbital images.

“Now that we’re here,” Edgar concludes, “it’s quite surprising to see how rugged it is, and the informal description of this “gator-back terrain” seems very fitting!”

Textural transition

In an earlier report, Mark Salvatore, a planetary geologist at the University of Michigan, explains that after Curiosity made a drive of roughly 49 feet (15 meters) to the west along the top of the Greenheugh Pediment, the robot was in position at an interesting textural transition within the pediment’s surface units.

Curiosity Mast Camera Left image acquired on Sol 3420, March 21, 2022.
Credit: NASA/JPL-Caltech/MSSS

“Quite a large amount of the pediment is dominated by a washboard-like pattern at the surface that can be easily observed from orbit, while the region Curiosity ascended onto the pediment surface is rugged yet lacks those clear washboard-like features,” Salvatore observes. “With this latest drive, Curiosity is now positioned at the transition between these two surface units, and the team is continuing to assess the traversability of these units.”

Landscape ahead

With this new vantage point, the plan is for Curiosity to characterize the different morphological features observed on top of the pediment. Several Mastcam imaging sequences were designed to characterize the washboarding that is observed in the landscape ahead of the rover.  

The terrain’s small-scale roughness and oriented ventifacted rocks led the Science Team to informally refer to these textures as “gator-back terrain.”

Curiosity was on tap to also perform two ChemCam LIBS analyses on two different targets – a smooth outcrop target named “Macmerry” and a rougher knobby target named “Ochiltree.”

Planned drive to the west

After a ChemCam passive sky observation around midday on sol 3419, Curiosity, the plan called for the rover to unstow its arm to conduct an APXS integration on the outcrop target named “Blackadder” and an overnight APXS measurement to characterize the martian atmosphere.

On sol 3420, Curiosity was scheduled to complete Mastcam and ChemCam observations (including a long-distance remote imaging mosaic) before embarking on a planned drive of roughly 115 feet (35 meters) to the west to continue the investigation of the pediment and the interesting surface textures found on its surface, Salvatore reports.