June 20, 2018

Mountain-climbing Mars rover sends back low-angle selfie

This low-angle self-portrait of NASA's Curiosity Mars rover from Aug. 5 shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin" on lower Mount Sharp. Credit: NASA/JPL-Caltech/MSSS
This low-angle self-portrait of NASA’s Curiosity Mars rover from Aug. 5 shows the vehicle at the site from which it reached down to drill into a rock target called “Buckskin” on lower Mount Sharp. Credit: NASA/JPL-Caltech/MSSS

NASA’s Curiosity Mars rover has recorded itself in another of its famous self-portraits as the mobile robot analyzes bore samples recently collected from a rock slab, the first use of the drill since a short circuit halted use of the device in February.

This time, the rover selfie comes from a lower viewing angle and shows Curiosity looming over a bore hole left from a drill into a block of Martian rock July 30 at a site dubbed “Buckskin.”

A camera mounted on the end of the rover’s robotic arm captured dozens of individual frames of the rover and its surroundings. Scientists normally use the arm-mounted camera — called the Mars Hand Lens Imager, or MAHLI — to detect features in close-up views of Martian rocks.

But the robot arm can double as a selfie stick, and the camera scans across the rover to collect multiple views that image analysts on Earth can stitch together into a self-portrait. The wrist joint on the rover’s arm keeps the appendage out of frame in all of the images used in the mosaic, but the arm’s shadow is visible on the ground.

The sample collected July 30 is the seventh specimen gathered from boring into rock with the rover’s percussive drill, and the first since a glitch sidelined the drill in February.

“We were pleased to see no repeat of the short circuit during the Buckskin drilling and sample transfer,” said Steven Lee, deputy project manager for Curiosity at NASA’s Jet Propulsion Laboratory. “It could come back, but we have made changes in fault protection to continue safely drilling even in the presence of small shorts. We also improved drill percuss circuit telemetry to gain more diagnostic information from any future occurrences.”

Scientists hope to analyze the samples with Curiosity’s internal instruments, which comprise a miniature laboratory with ovens, lasers and other high-tech devices, to find out why the region around the Buckskin drill site contains higher levels of silica and hydrogen than other terrain explored by the rover.

“Curiosity initially noted the area with high silica and hydrogen on May 21 while climbing to a site where two types of sedimentary bedrock lie in contact with each other,” NASA said in a statement. “Such contact zones can hold clues about ancient changes in environment, from conditions that produced the older rock type to conditions that produced the younger one.”

The Martian outcrop where pale rock meets darker overlying rock near the middle of this May 21, 2015, view is an example of a geological contact. Such contacts can reveal clues about how environmental conditions that produced one type of rock were related to conditions that produced the other. Credit: NASA/JPL-Caltech
The Martian outcrop where pale rock meets darker overlying rock near the middle of this May 21, 2015, view is an example of a geological contact. Such contacts can reveal clues about how environmental conditions that produced one type of rock were related to conditions that produced the other. Credit: NASA/JPL-Caltech

Curiosity began its fourth Earth year on the red planet Aug. 6, and its plutonium power source is expected to provide stable electrical supplies for the next few years, according to Ashwin Vasavada, the rover’s project scientist at JPL.

“We think we have at least two, three, or four very productive years left, and then several more years after that as the power source degrades,” Vasavada said in remarks to the NASA Advisory Council on July 28.

A radioisotope thermoelectric generator, or RTG, aboard the rover produce electricity from the radioactive decay of plutonium carried to Mars on the spacecraft. The power source degrades a few percent each year, according to Vasavada.

“It was sized to allow a particular pace of operations that match both our payload and the frequency that our team can staff operations and communicate with the rover,” Vasavada told Spaceflight Now. “In large part, it comes down to the ability to run down our battery each sol (Martian day) and recharge it overnight. When that is no longer possible, we need to either spread out how often we command the rover or do less each command cycle, and not run the battery down as far.”

Specific activities that require large amounts of electricity, such as long drives and use of Curiosity’s ovens which heat up soil samples for scientific examination, may have to be spread out over multiple days in the future as the power levels run down.

Curiosity also has more demands on its power source than other plutonium-powered probes, such as NASA’s Cassini spacecraft and Voyager missions. The extreme temperature swings on Mars require the rover to control its temperature with thermal control loops that pump fluid through the spacecraft, and Curiosity also carries survival heatters.

“Even so, we expect to have enough energy for survival for at least 10 years,” Vasvada told Spaceflight Now on Thursday.

Curiosity completed its two-year prime mission phase in 2014.

Rover managers plan to propose another two-year extension to Curiosity’s operations on Mars next year. Further extensions, if approved by NASA, will also come in two-year increments under the agency’s senior review process.

Curiosity arrived at the base of Mount Sharp, a peak the size of Mount Rainier at the center of the rover’s landing site at Gale Crater, in September 2014. The robot’s first stop at the foot of the mountain is in a geologic deposit named the Murray Formation, thought to be near the boundary between separate rock units comprising Mount Sharp and the floor of Gale Crater.

Farther up the mountain, Curiosity will encounter a ridge that shows the chemical signature of hematite, a clay-bearing mineral that forms in watery environments, in data obtained from Mars orbit.

“It will take us another few months, at least, to get through the 150-meter (500-foot) thick broad sloping Murray Formation,” Vasavada told the advisory committee in late July. “Then we get to a ridge that as a lot of hematite mineralogy, another clay-bearing rock (type).”

A stretch goal for the rover is to make it to a boundary between clay and sulfate geologic units believed to be between 6 and 8 kilometers (4-5 miles) ahead.

“If we get to this boundary of the sulfate-clay area, that’s how we’re sort of timing our mission,” Vasavada said.

As of this week, Curiosity has logged 11.1 kilometers (6.9 miles) of driving since it landed in 2012.

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