The Mars Exploration Rovers Update: Opportunity Makes Tracks on Magical Mystery Tour of Different Rocks

Opportunity continued exploring the south trough of Perseverance in May, still looking for evidence that explains just how this one-of-a-kind valley meandering through Endeavour Crater’s rim formed, and, along the way, helped the Mars Exploration Rover (MER) mission chalk up yet another first, linking with three relay orbiters in one Martian day or sol to send a pipeline of data home.

The veteran robot field geologist – the longest-lived robot on Mars, 14.4 years and counting – has been taking a kind of magical mystery tour of the rocks in the south trough for more than two months. “The rocks vary and what’s interesting is these outcrops change in texture and in color as we go from north to south,” said MER Deputy Principal Investigator Ray Arvidson, of Washington University St. Louis (WUSTL). 

“We’re trying to look at all the different kinds of rocks in this complicated zone that might be fault-controlled, investigating what’s causing patterns we see in terms of the material properties, and working to understand the nature of each one,” he added. 

Opportunity began the merry month on Mars studying a pitted rock, formerly known as vesicular, then roved on, to an outcrop of bright, tan-colored, tabular rocks. “We were intrigued by these pitted rocks and at first called them vesicular,” said Arvidson. “Vesicular rocks are characterized by these little cavities known as vesicles that are formed when you have a magma or lava that degasses and leaves holes. But now the science team is beginning to think that maybe the pits are caused by some kind of chemical corrosion,” he explained.

There is nothing too weird or particularly exotic about these pitted rocks or the bright, tan-colored tabular rocks, Arvidson said. That is to say, they all look pretty much like Earth rocks, but they harbor evidence and clues of what happened here at Endeavour billions of years ago. 

“It’s still all a work in progress,” said Arvidson. Even so, the thinking about Perseverance Valley (PV) continues to evolve toward a fractured tale from the ancient past, evidence for which MER Athena Science Team members Larry Crumpler, of the New Mexico Museum of Natural History and Science, and Rob Sullivan, of Cornell University, presented at the Lunar & Planetary Science Conference in March. “It just seems PV is the continued exposure, with erosion, of a deep-seated fault,” Arvidson offered. 

Opportunity also had plenty of other assignments that kept her busy throughout the month. The robot looked to the night sky with her Panoramic Camera (Pancam) to try and freeze-frame the transits of the Martian moons, Phobos and Deimos. “There were a few chances to get Phobos, including one at sunrise,” said MER Athena Science Team member Mark Lemmon, Associate Professor, Atmospheric Sciences at Texas A&M University. “Sadly, even with the extra power we have these days, that one was not do-able.” 

The other chances were do-able however, and the rover and the team delivered. “It was nice to get the Deimos one, especially,” Lemmon said. “They are more rare due to the orbit geometry.”

On Earth, MER’s Principal Investigator Steve Squyres, of Cornell, and Project Manager John Callas appeared before a Senior Review on May 2^ndat the Jet Propulsion Laboratory (JPL) to propose an eleventh mission extension that would keep Opportunity roving through 2019. Beginning in 2020, NASA is to shift to granting mission extensions every threeyears as opposed to every two years; hence, this extension would be for just one year.

“We presented. It was well received. And we’ll wait to hear what they say,” summed up Callas, who oversees the mission from JPL, the NASA center and birthplace of all the space agency’s Mars rovers. “We did put forward a compelling science case, but at the same time we told them that the budget is very difficult and that there are risks associated with the budget they are proposing for us,” Callas said. “I’m trying to identify where the risks are in the project and mitigate those given our situation. But the reality is, with a smaller budget, no matter what you do there are going to be risks.”

Opportunity and the MER operations team roved Mars comfortably for years on a frills-free $14 million annual budget. For the tenth mission extension (2017-2018), the budget was cut to a little less than $13 million. The maximum funding to be allotted for 2019 is further reduced to about $12 million, according to one source. While it may not seem like a lot – and in the grand financial scheme of planetary exploration it isn’t – there is almost no doubt that this budget cut will impact operations, primarily by shrinking the ops team.

Therefore, assuming the missionis granted this extension for 2019, MER’s greatest challenge will be ensuring the care and feeding of Opportunity continues with the same kind of attention and integrity that led to the mission becoming a legend in its own time.

The 2019 budget will likely mean that the MER ops team will also be forced to work fewer days in a given month and thus have less interaction with Opportunity. “That is the main nob that I can turn,” said Callas. “We still have to plan every sol for the rover. The question is how many times a week do we do that? Right now, we’re moving between three and five times a week depending on how Earth time and Mars time line up. But we may have to go to just three times a week.”

That could present problems. The equation is fairly simple. Fewer people = less expertise on the project = less scrutiny = potentially less discovery of challenges. With a crew of part-timers who are balancing MER work with other missions, there is the risk those individuals could lose focus or “situational awareness.” The bare bones budget also likely means mission ops loses continuity. “Those all introduce risks into the operations process,” Callas said.

The frustrating factor is that the amount of money in question, a couple million dollars, to keep this heralded mission – one of NASA’s most popular in all its 60 years – and this beloved little record-setting, textbook changing, pioneering golfcart-sized robot healthy and roving on, is really a drop in the bucket in terms of the entire Mars Program.

“There weren’t many comments and it ended early,” said Arvidson, who listened in to the presentation telephonically. “Hopefully that’s a good sign.”

Meanwhile, back on Mars, Opportunity kept on showing her MER mettle. “I sound like a broken record again,” said MER Chief of MER Engineering, Bill Nelson, of JPL. “But Opportunity is busy and doing wonderfully well with good energy and moderate internal temperatures.”

“The vehicle is well behaved and is currently moving on a slope of about 24 degrees,” added JPL Rover Planner Paolo Bellutta, at month’s end. “Lately, we are driving mostly cross-slope with the vehicle tilted to the left and pointed due south. The rover is very stable, even when using the Rock Abrasion Tool (RAT) for brushing. When we apply some force to the Martian surface, we barely notice any change in vehicle attitude.  She seems to be glued to the road like a Porsche.” 

Wait, a Porsche?

“Yes,”responded Bellutta, who has been overseeing the charting of the Opportunity’s paths for a decade, since Victoria Crater. “I know, the speedis not the same. Oppy moves at a top speed of 135 mph – that is meters per hour, not miles.”

The rover has also been conducting relay tests with the Trace Gas Orbiter (TGO), now in its commissioning phase. Part of the ExoMars program led by ESA and the Russian Roscosmos State Corporation, TGO is a much-needed and welcomed addition to the Mars communications constellation. The new orbiter boasts an advanced Electra radio relay payload provided by NASA, which nearly doubles the performance of the Mars Reconnaissance Orbiter’s (MRO’s) radio. [The ESA spacecraft reached its final orbit in February after a year of 'aerobraking. The ExoMars rover is slated to land in 2021.]

“TGO represents a significant step forward in our Mars relay infrastructure, replenishing on-orbit capability as our NASA orbiters, Odyssey, MRO, and MAVEN, operate well beyond their primary mission lifetimes,” said Chad Edwards, the longtime manager of the Mars Relay Network Office who recently moved on to managing the Program Formulation Office at JPL, where he is now focusing on future mission concepts. 

Opportunity had TGO commissioning relay passes on every sol from Sols 5076 to 5085, 5087, and from 5089 to 5092, “and several more,” said MER Mission Manager Scott Lever, of JPL. “We exceeded 200 megabits of downlinked data two times in recent weeks. We’re now entering a regime where we will occasionally get the right timing in a sol to use a nap to aid in data management and science acquisition volume. So far, so very good,” he said.

“Recently, we had one of our largest data returns from a single sol maybe ever in the mission, more than 200 megabits of data, in three relays with MRO, TGO, and of course, Mars Odyssey,” said Callas. “We have great energy levels, so we can service all these relay passes. This represents a great increase in our science return.”

In fact, the straw of data suddenly turned into a pipeline in May. “The rover’s downlink data volumes in May “increased by about 50%, which lets Science maximize imaging each sol,” said Nelson. 

“If TGO continues as is and it appears this is their intention, it will become known as a relay workhorse in the Mars community,” Lever offered. “The orbit inclination provides for several consecutive weeks with 5 or 6 contacts per week, followed by about three weeks where the contacts are at undesirable times in the night. The orbit shape is approximately 380 kilometers (236.12 miles) by 410 kilometers (254.76 miles), which gives us very nice short ranges for the UHF link. We are instant fans of TGO, and look forward to future relay service,” he said. “I think the MER scientists are feeling the impact.”

Indeed they are. “We are pleasantly surprised at how well TGO is doing in increasing our downlink capacity,” confirmed Arvidson. “This is especially important, because we lost Flash a few years ago and must rely on RAM to store our data.” [Flash, is non-volatile memory that allows the robot to store data overnight, while Radom Access Memory (RAM) is volatile memory and data disappears when Opportunity shuts down.]

TGO officially begins communications relay duty in mid-July, following this commissioning phase. This newbie orbiter will provide communication relay for Opportunity and Curiosity, ahead of the arrival of InSight lander later this year, and for its ExoMars rover and surface science platform in March 2021. Preliminary relay tests with NASA's rovers were conducted in November 2016, shortly after the orbiter's arrival at Mars. “We expect TGO to be a great addition to ongoing Mars exploration,” said Callas.  

On May 22^nd, the spring equinox in the southern hemisphere of the Red Planet came and went, so Opportunity is now officially basking in the warmth of her eighth Martian spring and is producing robust energy.  Although the sky was a bit dustier than in the last couple of months, the solar powered robot’s arrays are still pretty clean and she continued to produce impressive power throughout the month, more than two-thirds her capability as determined on landing when she was “new” and has sparkling arrays.

In coming sols, Opportunity will probably bump to a “blue-purple” rock, “which might have hematite,” said Arvidson. “We’re trying to get at the compositions of these different rocks that are mainly juxtaposed it appears by faulting. It’s all about how the valley was put together and whether or not wind or maybe groundwater has been involved in shaping it.” 

The rover will also likely return to a spot near the pitted rock Allende, where she smushed up the soil and possibly broke or at least moved another pitted rock as she struggled to climb up the nearly 25-degree slope. In images that Opportunity took with her Pancam, utilizing the system’s 13-filter, multispectral capabilities, the scientists saw some intriguing colors, “colorful fragments that are now sitting on the surface, mixed in with the soil,” as Arvidson described the scene. “It has kind of greenish, whitish, brownish, and darkish kind of debris where the pitted rocks used to be.”

A stereoscopic, panoramic imaging system, Pancam is comprised of two digital cameras mounted on a mast 1.5 meters (4.92 feet) abovethe Martian surface. Itsmultispectral capabilities enable the scientists to characterize and distinguish between different mineralogical units of targets.

“A lot of the color differences in the scene are not associated with definable spectral characteristics that I could assign any kind of mineral ID to,” said MER Athena Science Team member Bill Farrand, Senior Research Scientist
 at the Space Science Institute. “So it is colorful, but a little frustrating from a Pancam perspective in terms of interpretations.”

But, that “disturbed soils” site, Arvidson suggested, could be a “goldmine.” 

Deep Dive into May 

Opportunity, still about halfway down Perseverance Valley, had maneuvered into position on the near 25-degree slope over the pitted rock named Allende in late April, and woke up to May and an agenda full of assignments, raring to go. 

With 45.15 kilometers (28.06 miles) on her odometer, the robot maintained a still impressive solar array dust factor of 0.787 and was producing a hardy 642 watt-hours of power, nearly two-thirds her full capability after landing with pristine solar panels. The sky was typically hazy for this time of the Martian year and the atmospheric opacity or Tau was recorded at 0.641. 

On Sol 5072 (May 1, 2018), Opportunity deployed her Instrument Deployment Device (IDD) or robotic arm and focused the Microscopic Imager (MI) on the rock that the team named Allende, after a stop along the El Camino Real de Tierra Adentro, the old, 2,560-kilometer (about 1,591-mile) trade route between Mexico City and San Juan Pueblo, New Mexico, the current naming theme for targets and sites inside Perseverance Valley. 

The robot field geologist took a two-by-two set of image frames, each with five stacks of images per frame, plus an offset stereo frame. In addition, she placed her Alpha Particle X-ray Spectrometer (APXS) on the chosen target spot on Allende for a multi-hour integration to determine the rock’s chemical composition. 

The following sol, 5073 (May 2, 2018), Opportunity offset the APXS by 1 centimeter (0.39 inch) for another multi-hour integration so the science team could analyze spatial trends. The rover also used her Panoramic Camera (Pancam) to take close-up, color stereo images to fill out the investigation of Allende.

There’s no new news yet about these pitted rocks, formerly known as vesicular. “I have no idea what these rocks are,” said Arvidson. “We called them vesicular. Vesicular is what happens when you have a magma or lava that degasses and leaves holes. But now people are beginning to think – well, maybe they’re pitted and the pits are just due to kind of chemical corrosion,” he explained.

Back in April, on Sol 5058 (April 16, 2018) as Opportunity was trying to reach some pitted rocks farther upslope from Allende, she wound up possibly breaking up a pitted rock and churning up patch of soil. Inside the mess, said Arvidson was “beautiful colorful debris,” lying in front of the rover. The scene is relatively flat, where the robot wouldn’t have to risk doing IDD work on irregular rock surfaces. “But it’s broken up,” he said. “It’s the target I want to look at more.”

But, the colorful debris would have to wait. “With the investigation of Allende finished, the rover turned to her next objective, the tabular rocks that for weeks had been of interest to the science team. “It has to do with ease of mobility and low risk for slip. So we gave the RPs, the tabular rocks, the purple rocks, the disrupted soil / colorful debris and worked with them to schedule all these places,” said Arvidson.

On Sol 5074 (May 3, 2018), Opportunity backed up about 1.847 meters (6.059 feet) to set up for an approach to a tabular rock target named Inde, which the team chose to check out up close. The rover moved forward 3.180 meters (10.433 feet) to approach the rock outcrop on Sol 5076 (May 5, 2018).

Opportunity spent the rest of the first week of May at this new location, taking both Navigation Camera (Navcam) and Pancam panoramas to establish the context of this rocky scene for the scientists. 

On Sol 5078 (May 7, 2018), the rover wrapped the first week of May with an overnight atmospheric argon measurement with her APXS, part of a mission-long study that is revealing some very interesting findings about the Red Planet’s atmosphere.

Scott VanBommel, a postdoc at WUSTL and a young MER scientist who also serves on tactical shifts as APXS PUL/PDL, has been researching Opportunity’s APXS argon data since his undergraduate years. Advised by MER Athena Science Team member and APXS Lead Scientist Ralf Gellert, he defended his doctoral thesis, titled “Expanding the Capability of the Alpha Particle X-ray Spectrometer Including Quantification of Fine-Scale Chemistry and Atmospheric Monitoring,” and earned his PhD from the University of Guelph late last year.

Designed to analyze the chemical composition of rocks and soils, the APXS was not calibrated to take measurements of atmospheric argon. However, early on in the mission it was proposed that Opportunity’s APXS could be used to measure the atmosphere. “Because of the composition of the atmosphere and how this instrument works, the only peak that we could get would be from argon,” said VanBommel, who joined the MER team in 2014. 

Over the years, Opportunity has tallied thousands of hours worth of argon measurements, providing solid ground-truth data for the Mars community. “Arguably, it’s the largest amount of data from one single probe – six, seven Mars years worth of acquired data that can provide bounds to the climate models and further improve our understanding of how the air mass is moving and the potential affects on local and global weather and climate on Mars,” he said.

Originally conceived as a dive into data, when VanBommel looked at the scientific aspect of the data in terms of the argon peak area and how it changes with time of the year and temperature, he found there was some pretty interesting science that could be done. “By combining all these measurements, we can start to see the condensation flow in the atmosphere by following this argon gas as a tracer of what’s going on – that’s what the paper was about,” he said.

It is important to note that very few spacecraft on Mars have monitored the atmosphere and how it moves. “So much of what we know about climate on Mars and how the air mass moves around is from extrapolating from these data points in global climate models,” noted VanBommel. As it turns out, his findings agree “quite nicely” with what local climate models would predict in terms of the argon-mixing ratio. “We also saw something that hasn’t been documented or observed before near the equator and that’s kind of the highlight of the research,” he said. 

From her position near the planet’s equator, Opportunity has been measuring argon as the atmosphere flows north to south and south to north during various times of the Martian year. “We have lots of measurements from orbit where we see significant argon enrichment, especially at the southern pole during southern winter,” said VanBommel. “When southern winter approaches, it gets very cold and the carbon dioxide (CO₂) from the atmosphere gets deposited onto the surface and the argon, which is non-condensable just like nitrogen, will remain the atmosphere and is enriched, and measurements from orbit see this significant enrichment.”

During the Martian spring, there is a concentration of CO₂from the southern polar cap and the air mass moves northward. “Opportunity at the equator can see this rise in argon that is observed prior to the rise in pressure that is observed by Curiosity in this case,” VanBommel said. “This is because when you have that atmosphere that is enriched in argon at the southern pole, once you have that condensation of CO₂, you have a pressure gradient during this air mass northward and we can see the enrichment from orbit at high latitudes to near the poles. But as we get closer to the equator it enters the uncertainty of the orbital measurements.”

“We think we’re seeing a spike in the data kind of at southern spring,” he continued. “So right when that air mass is moving northward, we think we’re seeing the burst, a little blip of that enriched argon that was at the southern pole during southern winter moving northward as it’s dispersed through Mars.”

Interestingly, VanBommel found no correlation between dust storms and the spike, as he “informally” calls it. “The spike varies in amplitude and timing from year to year, but when it’s most prominent there was no dust storm event ongoing,” he said.

VanBommel’s work led to another paper, “Seasonal Atmospheric Argon Variability Measured in the Equatorial Region of Mars by the Mars Exploration Rover Alpha Particle X‐Ray Spectrometers: Evidence for an Annual Argon‐Enriched Front,” which he wrote along with Gellert and MER Athena Science Team members Ben Clark and Doug Ming. It was published in the Journal of Geophysical Research - Planets in February 2018.

The real power in the data is not in a single measurement, but in all the many measurements complementary to each other. “With the atmospheric modeling, we’ve actually used this research to provide improved guidance as to when we should take these measurements and how often, keeping in mind the power limitations of a solar-powered rover,” said VanBommel, who plans to continue this work.

Although Opportunity’s twin succumbed at some point, it’s presumed, in 2010, Spirit played a role in this research. “Spirit helped calibrate Opportunity,” said VanBommel. 

When Spirit was stuck and had plenty of power to burn, she took almost daily overnight, long duration APXS measurements. “Since they were long duration, they are great statistics, because day after day after day the atmosphere doesn’t really change that much, he said. “So this provided us with our calibration data with which we could test various models on. From there, we could apply could apply that to the Opportunity dataset that spans six, seven Mars years,” he said.

So the death of Spirit was what made the calibration in this study with Opportunity possible. “My undergrad project and Master’s project involved the Spirit dataset, so really my whole career and introduction to Mars research, I owe to Spirit,” VanBommel acknowledged. “It’s kind of a mixed bag of emotions there.”

As the second week of May began on Sol 5079 (May 8, 2018), Opportunity began work on the close-up, in situ investigation of Inde. The robot used her MI to take the pictures needed for a mosaic of the target, then, following the current scientific protocol, placed the APXS on the same target spot for a multi-hour integration to analyze the elemental chemistry.

Two sols later, 5081 (May 10, 2018), Opportunity moved the APXS about 1 centimeter (0.39 inch) to collect an offset measurement on Inde, relative to the previous sampling. While performing contact measurements, the rover also took targeted, multispectral images of the rocks with her Pancam. “Inde is kind of a rough looking rock that wants to be purple but not as purple as the purplish rock. Nothing unusual,” said Arvidson.

Then on Sol 5082, Oppy and the team got lucky and captured a shot of the Deimos transit at about 11:45 Hybrid Local Solar Time (HLST). Once that and the work on Inde was “in the can,” the rover, on Sol 5083 (May 12, 2018), bumped about 1.862 meters(6.108 feet) to other tabular rock targets soon to be christened La Joya 1 and La Joya 2. As usual, the robot then took a multi-frame Navcam panorama for the team’s “site awareness” and future drive planning. 

But there was a rub, err rock, a small rock under the right-front wheel. That raised some concern about the rover’s stability if she were to use her IDD. So, as the third week of May bloomed on Sol 5086 (May 15, 2018), Opportunity was commanded to rotate the right-front wheel backward about 45 degrees, turning just 0.013 meters (0.511 inch). Voila! The movement ejected the pebble and put the rover’s right front wheel firmly on the ground along with the other five.

The following sol, 5087 (May 16, 2018), Opportunity performed a "salute" with her IDD to move it out of the way of the Pancam so she could take 13-filter targeted images of La Joya and thepitted rocks and disturbed soil she smushed up to create colorful debris in April. 

During the next three sols, the robot took more 13-filter imagery of La Joya, working in an APXS argon integration on Sol 5088 (May 17, 2018), a Pancam low sun survey on Sol 5089 (May 18, 2018), and finishing with more Pancams for a tabular rock panorama on Sol 5090 (May 19, 2018). 

Opportunity then hunkered down over the surface target labeled La Joya 1 on Sol 5091 (May 20, 2018) to take the usual close-up pictures her MI, following that with the routine multi-hour APXS integration to glean its chemical make-up. 

The rover had two relay passes that sol, Odyssey as usual and ESA’s TGO, which significantly increased the amount of data the rover could send home that day. Truncating to round whole numbers, Lever tallied the total – 217 megabits of data with the combined downlink! “That is 147 megabits of real data, and 70 megabits of fill data.” The rover could have collected more data than she’s been used to since her non-volatile Flash memory drive was taken out of commission several years ago.  

The following sol, 5092 (May 21, 2018), Oppy took more Pancams for a tabular rock panorama, as well as some targeted 13-filter Pancam images, and continued the APXS chemical sleuthing on La Joya 1.

As the fourth week of May began on Sol 5093 (May 22, 2018), Opportunity, in preparation for a future Rock Abrasion Tool (RAT) brush and grind, conducted a preload test to be sure the rover would be stable enough on the sloped terrain to safely use the. Instrument. The test results were positive, showing the rover to be stable and able to perform any future surface contact activities. 

The robot then focused on MI imaging of La Joya 2, an offset target on a dark part of the rock. “It’s either a rock embedded in the outcrop or just a different color, we’re not sure,” said Arvidson. 

Opportunity would later place her APXS on La Joya 2, but before the integration, Phobos was set to transit Mars at about 14:45 HLST, and the team wanted to make a ‘movie’ of the crossing. It was, “the best measurement opportunity,” said Lemmon. “The annular eclipse makes the position measurement quite precise.” 

Even so, until he sees the image, Lemmon still gets “a little nervous,” as he put it. “I check the downlink right away to make sure things went as planned.” Not too surprisingly, they did.

Experience and precision planning have allowed for the shots to become technically easier to capture, said Lemmon. “In the past, we've had to contend with errors in the onboard clock that led to pointing errors and we had to figure out what to tell the rover to get it to do what we want in some cases. But that is all fixed up, and this time it was quite straightforward,” he said.

That same sol, the robot hero scored another first. “Looks like we broke 200 megabits again on Sol 5093 with three different orbiters combined, MRO, TGO, Odyssey,” said Lever. “Wouldn’t it be nice if this got boring?”

On Sol 5094 (May 23, 2018), Opportunity continued adding to the tabular rock panorama and continued the APXS integration on La Joya 2. But the following sol, 5095 (May 24, 2018), the Deep Space Network’s Station 54 was “red,” said Nelson. That meant no new sequence could be uplinked, so the rover executed the standard run-out, with autonomous wakeup and shutdown around X-band and UHF passes.

Opportunity took more images for the tabular rock panorama on Sol 5096 (May 25, 2018) and on Sol 5097 (May 26, 2018) she brushed La Joya 1, and again took more images to add to the tabular rock panorama.

The plan for Sol 5098 (May 27, 2018) included more MI imaging of La Joya 1. But that was not to be. “It was halted by fault protection,” said Nelson. “When the gyro's vehicle attitude estimate changes from right to left (or vice versa) about a heading of 180 degrees, the small change is treated by the flight software as a rotation of virtually 360 degrees. That violates the small heading change allowed and IDD fault protection then stops all IDD activity,” he explained.

“This is a known issue,” Nelson added. “Individual gyro measurements of the rover's orientation will jitter. Integration of these measurements tends to cancel out the jitter, but the change between individual measurements can be – and in this case was – enough to trip the fault protection.”

Opportunity carried on with another APXS argon measurement and more remote sensing on the tabular rock panorama. “There’s nothing unusual about the tabular rocks,” Arvidson said. “They’re not particularly high in silica or other stuff, just kind of within the family of other rocks we’ve been seeing on the rim.”

Nevertheless, the rover spent the next two sols, 5099 and 5100 (May 28 and 29, 2018), collecting more images to add to the tabular rock panorama, as well as some site imaging and a Pancam horizon survey on Sol 5099, and some sky radiance thumbnails, more site survey imaging, and Pancam twilight imaging on Sol 5100. 

Opportunity devoted her Sol 5101 (May 30, 2018) to completing the Pancam survey of the current site. Then, the following sol, 5102 (May 31, 2018), she wrapped the month quietly, still hunkered over La Joya, taking a break from science activities, because of “very poor UHF data returns,” said Nelson.

As May began fading to June, the robot, with 45,161.04 meters or 45.161 kilometers (28.061 miles) on her odometer, was still producing upwards of 650 watt-hours of power with a dust factor hovering around 0.774. Tau was recorded at 0.667. 

The plan for June includes an investigation of a set of “blue-purple rocks,” as Arvidson described them, located “about a meter or about southeast from our current location,” said Bellutta. The rocks,basically part of the overall tabular rocks area of PV, aren’t really blue or purple but are so-called because they appear blue, purple, or blue-purple in the false color images that the Pancam team processes for the scientists to better see the different constituents in the scenes.

From there,Opportunity may drive “either to the southern margin and come back to do the disrupted soil/colorful debris scene, which is presently about 2-2.5 meters behind and to the left or northeast of the vehicle’s current location, said Bellutta. Or,after the blue-purple rock, she may go straight back to the disrupted soil site. “It’s all going to get done before we continue downhill,” Arvidson said.

“There’s a whole set of outcrops that run up and down Perseverance Valley and as you head south from where we are, there seems to be almost a layered structure in these outcrops, so we need to investigate the different kinds of rocks that are in the vicinity of Allende and Inde,” he added.

From the looks of the rover’s findings in the valley so far, Perseverance is appearing more and more to have been fault controlled. “An enormously energetic event formed Endeavour, so you have the impact and a lot of shock and a lot of melting and big chunks of real estate were probably twisted and turned and put into the rim,” Arvidson theorized. “My guess now is that PV is a deep-seated fault and the patterns we’re seeing are basically a huge chunk of Mars that has been put into the rim as ejecta, and then faulted between Cape Byron and Cape Tribulation, andexposed by the faulting shortly after the crater formed.”

As Arvidson sees it, Perseverance has since been eroded by some combination of groundwater and wind, which is exposing more of it, though he is quick to point out that not allteam members share the same view. 

Other views will be covered in future MER Updates. And, as always, with time and more research in Perseverance, the truth, as Shakespeare would say, will out.