NASA’s Perseverance rover successfully landed on Mars on Feb. 18, 2021. Perseverance is currently exploring the delta front of Jezero Crater on Mars. We last reported the rover’s progress in the June 2022 EXPLORER. As of Aug. 22, 2022, Sol 536, Perseverance has traveled 7.4 miles and drilled twelve core samples. The rover has returned more than 313,000 raw images that are publicly available in the mission multimedia catalog.
Jezero Delta Front Science Campaign
Perseverance reached the flat lying sedimentary rocks at Enchanted Lake in April 2022. For Katie Stack Morgan, geologist and deputy project scientist for the Perseverance Mars rover, the first close-up image of layered rocks at the base of Jezero Crater’s ancient river delta grabbed her imagination.
“These are the layered rocks that we came for!” she said.
The Perseverance team and legions of enthusiasts on Earth have waited years to get this close to the Jezero river delta. These rocks could hold evidence of ancient life on Mars. The search began in earnest with the rover inspecting many outcrops of deltaic rocks, looking for the best spot to bring its coring tool to bear to get precious core samples that will be returned to Earth on a future mission.
The rover team selected the Hawksbill Gap channel of the Jezero delta to ascend and begin the long-awaited delta sampling campaign. On May 17, 2022, SOL 441, Perseverance began the climb up the 3.5-billion-year-old Jezero delta front to characterize the delta rocks and to drill more core samples. The core samples will be cached at the base of the delta to be retrieved and returned to Earth on a later mission in the early 2030s.
On June 12, the Perseverance rover took a photo with an Earth-like feel of a Wild West movie. On the left side of the picture, a basketball-sized boulder is unexpectedly balanced on a tilted slab of sedimentary rock. In the center of the picture, another rock slab juts out from a layered reddish stack of delta sediments resembling an open-mouthed snakehead. Are there bad guy’s hiding behind that cliff?
In late June, the rover team reported that as amazing and as tantalizing as the ancient delta rocks are, none had been perfect for a coring attempt. Like Goldilocks’ dilemma, some were too soft, some too brittle and some too jagged.
Perseverance scientists and engineers work together using a suite of the rover’s instruments to glean rock elemental distributions and mineralogy and to detect organic molecules as potential biomarkers. The rover team brought the RAT, rock abrasion tool, to bear on rocks at several locations to test the rock competency. Remember that the first core was lost months ago, wasting one of the rover’s 43 precious core sample tubes. The rocks at Hogwallow Flats appeared to be very fine-grained. That is intriguing to mission scientists since fine-grained rocks may have the best chance at preserving evidence of life.
Fine-grained rocks are more likely to contain more clay minerals than coarser-grained rocks with abundant sand, pebbles and gravel. Clay minerals have charged surfaces that can attract and hold organic molecules. Ancient, complex organic molecules can then be protected from damage by radiation in the Martian environment. Hopefully, the organics were preserved over geologic time, waiting to be analyzed in laboratories back on Earth.
On June 18, the RAT tool tested a rock at Hogwallow Flats and it completely crumbled. The team persisted. After all, the rover is called Perseverance!
On June 23, Perseverance attempted to sample a layered boulder named Betty’s Rock. It has layers of both coarse-grained and fine-grained sediment. Rover operators were frustrated trying to maneuver around the jagged layers and awkward shape of this rock to make proper contact for sampling. Then nearby, the team found a flat, layered slab called Skinner Ridge Rock, similar to Betty’s Rock, but seemed optimal for coring.
“We plan to bump the rover over to this target, study its composition, and hopefully collect a sample,” a team spokesperson said in a NASA statement. “This process will take several sols (days on Mars) to complete, but we all have our fingers crossed for success.”
Between June 29 and July 7, Perseverance adeptly ran measurements, ran an abrasion test and drilled a core sample on Skinner Ridge rock. The core sample was inspected to ensure its integrity then stowed as the ninth core sample in the rover’s cache.
As of Aug. 22, Perseverance is in Hawksbill Gap of the main delta front of Jezero Crater on Mars.
NASA officials told reporters that core samples 11 and 12 in Hawksbill Gap are from a sedimentary rock that might contain biomarkers, or indications of life. These are the best tantalizing clues that Perseverance can deliver. The truth will have to wait until samples can be sent back to Earth. Only Earth-based labs can deliver the detailed analysis required to claim that life may have existed on Mars.
While Perseverance is exploring the Jezero delta it has also been busy scouting
for locations where the planned Mars Sample Return Mission can land a spacecraft and collect the cached sample tubes from Perseverance. The sites being considered are close to the delta and are in relatively flat, lander-friendly terrain.
The Mars Sample Return Mission is a strategic partnership between NASA and the European Space Agency. They have announced that the architecture of their planned Sample Return Mission has changed to simplify and increase the likelihood of success. The current plan assumes that Perseverance will still be functioning to deliver the sample cache to the Sample Retrieval Lander. Two Ingenuity-class helicopters will be included to provide a secondary capability to retrieve the samples.
Mars Sample Return Mission will retrieve the sample cache, launch to orbit to dock with an Earth return spacecraft. When the samples are safely retrieved on Earth, they will be analyzed in detail to look for signs of past microscopic Martian life and to determine if the Martian surface is safe for humans to explore. The planned launch dates for the Earth Return Orbiter is in fall 2027 and the Sample Retrieval Lander in summer 2028. The samples are expected to arrive on Earth in 2033.
Ingenuity Nails Flight, Settles Down for Winter
In our last update in the June EXPLORER, we saw that the Ingenuity Mars helicopter made its 26th flight on April 18 and found Perseverance’s backshell and parachute where it was jettisoned in Jezero Crater. Flights 27 and 28 followed on April 23 and 29, respectively. Then for the next six weeks, Ingenuity rested to to help survive the cold Martian winter when there isn’t sufficient solar power to keep its electronics warm overnight. The JPL team discovered this when Ingenuity stopped responding to commands relayed by the Perseverance rover.
Now, at night, JPL controllers have Ingenuity power itself off. This resets the mission clock so it doesn’t know when to check in with Perseverance. Then each morning, the rover searches for Ingenuity’s weak signal to check on its condition.
In early June, it was discovered that Ingenuity had a dead inclinometer sensor. JPL uploaded a software workaround using redundant accelerometers. Then, on June 11, Ingenuity completed a successful Flight 29, putting it in a better communication location with Perseverance. The next flight will have to wait until warmer weather on Mars, perhaps by late August.
Curiosity Rover Geochemical Discoveries at Gale Crater
On the other side of Mars, NASA’s Curiosity rover has been operating in Gale Crater since 2012. For the past year, Curiosity has been exploring in a picturesque transition from a clay-rich area to a sulfate-rich area. The clay-rich and the sulfate-rich areas offer clues about Mars’ ancient wet climate. The transition zone might provide the record of a major change in Mars’ climate billions of years ago. The clay-rich zone formed when lakes and streams dominated Gale Crater. Higher on Mount Sharp in the transition zone, Curiosity found that the wet climate dried out and arid sand dunes formed above the lake sediments.
In our last update in the EXPLORER, we reported that Curiosity’s tunable laser spectrometer measurements from six sample locations found anomalously light δ13C values of less than 70 parts per thousand. Enrichment in carbon-13 on Earth is associated with biological processes but the measurements are not proof of biological processes at work in Gale Crater.
On June 27, 2022, in the Proceedings of the National Academy of Sciences, NASA geochemist Jennifer Stern and her team reported measurements from the Curiosity rover of high organic carbon concentrations in 3.5-billion-year-old lacustrine mudstones of Mars. The measurements were made in Curiosity’s Sample Analysis at Mars instrument, which heats powdered rock to increasingly higher temperatures. Oxygen is introduced to convert the organic carbon to carbon dioxide. That is measured to get the total organic carbon in the sample for the first time.
This is another clue – but not proof – of possible past biological processes.
“Total organic carbon is one of several measurements that help us understand how much material is available as feedstock for prebiotic chemistry and potentially biology,” said Stern. “We found at least 200 to 273 parts per million of organic carbon. This is comparable to or even more than the amount found in rocks in very low-life places on Earth, such as parts of the Atacama Desert in South America, and more than that has been detected in Mars meteorites.”
