While Opportunity was resting her sprained left ankle in and waiting for help to get her wheel back on the straight and narrow in June 2017, she kept working, taking pictures of the scene all around her for the Sprained Ankle Panorama. Seán Doran, a designer, animator, and filmmaker in the U.K., processed the raw images the rover sent home into this partial view of the full panorama to come. Doran contributes to The Planetary Society’s Amateur Space Images Archive. More of his work can be found on Twitter and Flickr.
The following day, July 7th – the 14th anniversary of Opportunity’s launch from Cape Canaveral – the rover drove again, cruising right up onto the gentle north-facing knoll or slope where she could soak up the Sun while waiting out solar conjunction. Between adjusting to new driving techniques and the team’s urgent desire to get the rover parked before conjunction, the mission’s grand entrance into Perseverance turned out to be a quiet event, greeted with as many sighs of relief as cheers. But it opened the doorway to the historic science campaign inside Perseverance Valley that was about to begin.
After settling in, Opportunity took images of the valley walls, the continuations of the troughs or channels and rocks and outcrop with interesting features and the site’s morphology for as far as she could see with her cameras, peering as far down into the valley as she could. With Mars soon to move behind the Sun, the team had to prepare for the two-week communications blackout during the celestial event. “It’s kind of like we’ve just walked into Town Square on Main Street USA at Disneyland and haven’t yet gotten to Space Mountain or Tomorrow Land,” said Callas.
The Earth-Mars solar conjunction occurs every 26 months or so when the orbits of Earth and Mars place them on opposite sides of the Sun, making communications between the two planets so risky that NASA instructs all Mars missions to institute a two-to-three-week communications blackout period. “Out of caution, we don’t send any commands to the rover during this period,” said Chad Edwards, the Manager of the Mars Relay Network Office at JPL. “We don't want to take a chance that one of our spacecraft would act on a corrupted command.” So aside from brisk communication check-ins, Opportunity would be incommunicado for the latter half of July, but working on assignments the team sent up in previous weeks.
As the blackout began, the veteran explorer got to work on autopilot, as programmed. But then, the unexpected happened.
On July 23rd, JPL engineers received data that Opportunity had suddenly rebooted and as a result put herself into safe mode. “We believe the re-set of the rover's computer happened on Friday, July 21st during the morning X-band communication session, and that stopped the stored master sequence of commands,” said Nelson.
Opportunity is designed to autonomously protect herself when things go awry by switching into safe mode, a kind of auto mode that puts the rover in a safe and stable state. Opportunity was power positive, thermally stable, and would continue to honor the scheduled X-band and UHF relay communication passes through the remainder of solar conjunction. “We like to say safe mode is safe,” said Edwards. “Right now, that is the safest state the rover can be in.” Still, this was not in the plan.
The communication blackout ended August 1st. The MER ops team promptly recovered Opportunity and got her back online. The rover soon roved onward, vicariously taking the MER team, along with a global contingent of mission observers all around Earth, downhill into Perseverance and into a brand new journey on this legendary expedition of the Red Planet.
Over the edge into the valley
NASA / JPL-Caltech / Cornell / ASU / S. Atkinson
OVER THE EDGE INTO THE VALLEY
After driving over the edge of the rim crest and into Perseverance Valley on July 6, 2017, the robot took the image on the right with her rear Hazard Camera. A frequent image contributor to The MER Update, Stuart Atkinson processed this view from the raw ‘snaps’ the rover sent home.
As usual during Martian winters, Opportunity maintained energy and maximized power production on her jaunts downhill by using the “lily pad” method, which enables the solar-powered rover to soak up as much of the winter sunshine as possible for power production. The team first used this strategy, during Spirit’s winter climb up Husband Hill in 2005. Essentially, the robot drives from one north-facing slope to another where she can position herself and her solar deck to the north where the Sun rises and falls in the sky during the Martian winters.
The rover’s prime directive in Perseverance is to take extensive imagery of the valley interior as she roves through it. These hundreds of images will be used to create a digital elevation model (DEM) that will reveal Perseverance in all its Martian glory in a simulated 3D view. “We’ll drive downhill at about 20 meters a clip and then spend time at each of those places doing 360-imaging with Navcam and targeted Pancam imaging, and when targets present themselves do some close-up work,” said Arvidson.
During the third week of August, Opportunity drove downhill or east to the second science stop, a small rise along the southern ‘wall’ or side of the valley, located about a third of the way down the valley. The second of seven tentatively planned science stops on a route that extends from the valley top to the bottom and the floor of Endeavour, this site is known simply as station 2
The work was easy enough for this ’bot and Opportunity was willing. But the deep freeze of the Martian winter was real and the robot had to use more and more energy just to stay warm. To meet operational demands, the rover began devoting two or more sols per week just to recharge her batteries.
Compounding the power situation is the fact that Opportunity lost use of her Flash or long-term memory a couple years ago. Since then, the robot has had to store her day’s work in RAM and offload it that same sol to Mars Odyssey, her mainstay communication orbiter, or the Mars Reconnaissance Orbiter (MRO), before she shuts down for the night, because RAM is volatile memory that doesn’t save data.
Nevertheless, with the support of her human colleagues on Earth, Opportunity was getting the job done. “The rover is doing fine, the team is doing a great job, and we’re just going to keep at it,” said Squyres then.
Stars from Mars
NASA / JPL-Caltech / Cornell / ASU
STARS FROM MARS
Late in the evening on July 9, 2017, Opportunity focused her Pancam eyes, looked to the night sky, and took some pictures of the stars. This really is a picture of stars from Mars taken by the longest-lived rover ever to explore the Red Planet. How cool is that?
As the calendar turned to September, Opportunity was producing enough energy to survive and to work but the amount of energy she needed just to keep warm continued to increase as old man winter dipped the rover’s external temperatures to -90 degrees Celsius [-130 Fahrenheit], slowing the rover’s pace. “Winter is setting in and we’re getting cold,” said Nelson.
The ops engineers even considered turning on a back-up, never-before-used battery heater to help out their robot colleague in the Martian field. In the meantime, the robot braved the brutal temps and succeeded in completing her assignments at station 2. “We are imaging and we have even looked at a couple of targets, pebbles within reach,” said Project Scientist Matt Golombek, of JPL. “But things are slow going, because we’re approaching the dead of winter.”
The day of the least amount of sunshine, what planetary scientists call minimum insolation, would hit on Halloween. Then the winter solstice (in the southern hemisphere of Mars where Endeavour and Opportunity are located) would follow on November 20th, still a ways off.
So ‘slow’ was better than ‘no,’ and the scientists liked what they saw in the images trickling in from Opportunity. “The morphology of the valley is quite interesting,” Golombek said. “There’s a little more diversity of rocks here than what I think we expected.”
During the final sols of September, Opportunity worked on completing her imaging and APXS assignments on the station 2 target named Bernalillo, while the MER ops team members discussed sending the rover back uphill to an area near the first way station. The scientists had spotted some interesting bedrock the rover had driven through in her exit images. It looks to be a contact – “two different colored, bedrock units in direct proximity,” said Golombek – where, perhaps, two epochs of Mars collide. And one of the bedrock units has some particularly puzzling features.
A new mission
NASA / JPL-Caltech / Cornell / ASU / S. Atkinson
A NEW MISSION
A new mission dawned at Endeavour Crater in August as Opportunity drove deeper into Perseverance Valley and into distinctive, challenging terrain. Stuart Atkinson processed this artistic vision from the raw image that Opportunity sent home. An author, astronomy outreach educator, and contributor to The Planetary Society’s Amateur Space Images Archive, Atkinson has followed this rover’s journey for years. See his The Road to Endeavour.
With winter nipping at her wheels, a very dusty Opportunity roved into October and finished up the requested work at station 2, and then began the journey back uphill, to the contrasting outcrops. The MER team members named the site La Bajada, following the naming theme of stops 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. “There is something different between the bright, flattish rocks on the northern side and the lumpy, darker rocks on the southern side, so it is probably a geologic contact,” said Arvidson. “But we went back uphill because the northern or light-toned outcrop has some features that look like they were etched.”
The etching or scouring appeared to be small erosional tails, geological signs of an erosive force but they seemed to be pointing up hill. Since the favored theory is that Perseverance as a whole was carved by water in some form, and since water doesn’t flow up hill, at least not a hill as steep as the grade of this valley, the scientists wanted to check out these little tails even though they were but centimeters in scale. The objective was to get the rover in a secure and safe position over one of these etched rocks and check it out with her Microscopic Imager (MI) and her chemical sniffing Alpha Particle X-ray Spectrometer (APXS).
Backing upslope in Perseverance would be easier said than done. Admittedly, Opportunity is getting on in years and has a few driving limitations, but nothing that would stop her from this assignment. “The biggest trouble,” said Stroupe, “is this terrain is very steep.”
While pumpkins were populating planet Earth, the rover struggled dutifully to reach the chosen etched rock. She even popped two wheelies during her roboculean efforts. “The key point right now,” said Squyres, “is Opportunity is performing beautifully as we ask it to do some very complicated things.”
Once all six wheels were firmly back on Martian ground, the robot field geologist got to studying Mesilla, a target spot on a northern, light-toned outcrop rock with ‘tails’ to tell. As the robot worked, Mars delivered its October surprise.
Forever 9/11 memorial
NASA / JPL-Caltech / Cornell / ASU
FOREVER 9/11 MEMORIAL
The cable guard on Opportunity's Rock Abrasion Tool (RAT), built and operated by Honeybee Robotics, is made from metal from the World Trade Center. The rover took the view above, which shows the American flag that was affixed to the shields, with two different cameras on the 10th anniversary of the attacks on the World Trade Center, Sep. 11, 2011. “I was a grad student at Washington University St. Louis then and working as the MER documentarian,” said MER Deputy Project Scientist Abby Fraeman, of JPL-Caltech. “I still remember almost every detail of that planning day. It’s still one of my top five favorite images of the mission because of all it represents.”
Just as MER Power Team Lead Jennifer Herman, of JPL, had cautiously suggested might happen in the weeks earlier, the planet produced a gust or two or three of gentle winds that lifted up from the floor of the crater and cleared some of the accumulated dust from the rover’s solar arrays. “We've had a little dust cleaning,” Herman confirmed. “And we are hoping for more.”
The winter cold continued to slow ‘life’ on Mars, but Opportunity pressed on. She spent November sleuthing the scenes with her cameras for any visual clues or evidence that could reveal what carved this unique valley feature billions of years ago, what formed its braided grooves or channels, and what scoured its outcrops. The rover used her robotic arm or Instrument Deployment Device (IDD) to focus up close on Mesilla with her MI and then APXS.
From flowing water to a muddy debris flow, to ice and ice melting into water, or water coming out of fractures, wind, or a combination of these forces, the MER scientists were still considering multiple hypotheses to explain how the valley and its distinctive features were formed. Perched over Mesilla, the rover scored a small, partial win for wind.
“It was the Battle of La Bajada,” Squyres said. “In the end, the team absolutely nailed it. We have a mosaic that very clearly shows multiple erosional tails pointing up hill … one of the most difficult and beautiful microscopic image mosaics in the history of this project. And we made a fundamental finding, one that was enabled by some very, very tough driving.”
Significant as this finding was, it revealed nothing about how the valley itself was created. There was a lot more work to do. From La Bajada, Opportunity headed back down the valley and onto another north-facing slope or lily pad.
During the ensuing two weeks, the solar powered robot soaked up as much winter sunlight as possible, and with a little more help from the Martian winds, Opportunity made it through winter solstice without incident, despite outside temperatures that dropped to -96.12 (-141.01 Fahrenheit). “We passed the winter solstice on November 20th and power levels have been improving,” Callas confirmed. “We’ve had some dust-cleaning events, which is helping increase power.”
La Bajada
NASA / JPL-Caltech / Cornell / ASU
LA BAJADA
La Bajada captured the MER scientists’ attentions because it is a possible contact zone, where one rock ‘contacts’ another. The site features two different bedrock units in direct proximity separated by rubbley terrain: the southern outcrop is darker in tone and lumpy with rocks; the northern outcrop is flatter and lighter toned, and features ‘telltail’ clues of being scoured by an erosive force that MER Principal Investigator Steve Squyres, MER Deputy P.I. Ray Arvidson, and others believe is wind, a fundamental finding.
Opportunity worked through the Thanksgiving holiday, mostly on taking images of everything around, while her human colleagues took a break. Then, the robot trundled farther into the valley to another north-facing slope, stopping about 15 meters away from where a large trough splits, the bifurcation zone, as the geologists define it.
From her vantage point, the robot snapped away, visually documenting the fork in the road just downhill. “Opportunity is in good health and everybody on the team seems to be as well,” said Squyres. We’ve got a lot to be thankful for this year.”
Opportunity spent the first week and a half of December conducting an extensive Pancam color stereo imaging campaign, taking large panoramas almost every sol. The skies overhead were lightly hazy, Tau registering 0.417, typical for winter. With a solar array dust factor of 0.624, the rover’s power production was on the increase and the robot was boasting energy levels hovering around 400 watt-hours of energy.
Winter however is not over. Opportunity did have to devote her Sol 4933 (December 9, 2017) to recharging. Then, the following sol, the rover took off, driving 8.4 meters (27.55 feet), approximately east, down the valley to a modest energy lily pad just uphill from the fork in the road.
Beyond this point, the trough or channel splits into a left and right or north and south fork, leaving a hummock or mesa or island in between. From this stop, the rover and her team can see right into both forks. “We wanted to image this hummock or mesa, because there are hypotheses that it might be a gravel bar from an ancient river or something else and we wanted to create a mosaic that covers the north fork and the south fork,” said Arvidson.
October surprise #2
NASA / JPL-Caltech / S. Atkinson
OCTOBER SURPRISE #2
Opportunity hiked up this slope on the northern outcrop of La Bajada, slippery with soils and rubble, to get to targets on a bright outcrop that showed signs of having been etched or scoured by some force. As the ‘bot finished her climb on October 25, 2017, she popped her second wheelie of the month, this time with her rear left wheel. It brought a little excitement to the doldrums of winter. Author, astronomy outreach educator, and contributor to The Planetary Society’ Amateur Space Images Archive, Stuart Atkinson processed this view from raw images that the rover sent home. Atkinson has followed this rover’s journey for years in his The Road to Endeavour blog.
There’s no shortage of weird geological Martian things to check out here. The trough where the rover sat for most of December is distinctive in its own right, marked with “a crazy pattern in the regolith,” as Arvidson described it. “It looks like ripples with tops that are a concentration of the little rock pebbles, kind of shaped in what I call stone stripes that are lined uphill and downhill. We’re not quite sure what’s done this, so it’s really interesting,” he said.
Being there and given the holidays were rushing in, when Opportunity wasn’t shooting the scene around her, she investigated a target spot on one of the ripples topped with little rocks, which the team named Carrizal. On Sol 4941 (December 17, 2017), the robot geologist took the pictures needed for a MI mosaic, and then placed her APXS on that target.
Opportunity also continued imaging the hummock and the fork scene through the Christmas break from her vista point just ‘upstream’ of the ‘fork,’ and worked in some other assignments too, including a color twilight panorama with her Pancam on Sol 4942 (December 18, 2017). “Once we’re done with the holidays, we’ll move on down the valley,” said Squyres.
Telling ‘tails’
NASA / JPL-Caltech
TELLING ‘TAILS’
At La Bajada, Opportunity used her Microscopic Imager (MI) to take these pictures of the erosional tails on the target Mesilla. These digital images are part of the final visual evidence that led MER scientists to the fundamental finding that these rocks have been etched by an erosional force, which, most on the team strongly believe, is wind. As MER Deputy Principal Investigator Ray Arvidson put it: “We’ve nailed the fact that wind has modified the rocks on the centimeters to tens of centimeters scale."
But down – where? The team has been scrutinizing the rover’s images to decide which fork to take. Although team members have been quoting Yogi Berra’s advice: “When you come to a fork in the road, take it,” decision time is near. “Everybody’s keen on going to the north where it looks like there is more variety, which is going to tell you more about process,” Arvidson said. The team is scheduled to decide in the New Year.
Most of the MER scientists are still confident that Perseverance was forged and shaped by water. The question that remains is: can they find the evidence to prove that? “There is a lot of room there is a lot of leeway as to what the water to rock ratio was,” Squyres said. “Was it a muddy debris flow? Was it a clear flowing stream? There is a lot of uncertainty there. That’s what we’re working on.”
At the fork in the road
NASA / JPL-Caltech
AT THE FORK IN THE ROAD
As Opportunity trekked deeper into Perseverance Valley In December 2017, the rover came to a “fork in the road,” where she stopped for the winter holiday break. While the human crew mostly took time off, the robot field geologist worked. She used her Navigation Camera to take the raw images that Stuart Atkinson processed into this version of her view across the fork in the road.
The answers or at least some of them are here somewhere. “It could be in the shape of the hummock or island and what’s been happening to the rocks there,” ventured Arvidson. For Squyres, what’s interesting is “the stuff on either side of it,” as he put it. “Because what’s on either side is the valley. If the valley weren’t there, it would be all hummock or mesa,” he said.
All in all, 2017 was another very good year for Opportunity and the MER team. “Mars is never dull,” said Bellutta. “It keeps you on your toes all the time. The year went by quickly and I am glad that we are on the other side of Winter 8.”
Come January 24, 2018 Opportunity and the team will check off their 14th Earth year of surface ops, and then keep on roving into Year 15. “Mechanically, things have been holding together really well lately,” said Squyres. “Knock on wood but we’ve been doing pretty well. We’re past the solstice and the power is starting to come back up. The skies have been pretty clear and the solar array is fairly clean. We’re ready.”
Perseverance Valley orbital view
NASA / JPL-Caltech / University of Arizona
PERSEVERANCE VALLEY ORBITAL VIEW
In this image taken by the HiRISE Camera onboard Mars Reconnaissance Orbiter, Perseverance Valley is clearly visible, just left of center top, meandering below the notch or cut in the rim. This view was processed in false color and then stretched 2X VE so the MER scientists can better see the valley and the grooves or channels that branch from it, thus the valley is not as steep as it appears here. The rover and the MER scientists are currently studying this unique geological formation that cuts east-to-west into the western rim of the 22-kilometer (13.7-mile) diameter Endeavour Crater seeking to determine how it formed.
Spirit Remains Silent at Troy
Stuck in the sandy edge of a shallow hidden crater along one side of Home Plate, Spirit phoned home on Sol 2210 (March 22, 2010) just before she went into a planned hibernation.
The robot that came to known as the-little-rover-that-could had worked for more than six Earth years and drove 7,730.50 meters (4.80 miles) in some of the harshest Martian terrain the mission will ever encounter. She was the first rover to climb a mountain, the first robot to take pictures of dust devils on the surface of Mars, and the first to find evidence for near-neutral water on Mars. In those 6+ years, Spirit literally defined MER mettle.
For the next year, NASA-JPL radiated more than 1,300 commands to Spirit as part of the recovery effort to elicit a response, any response. Hearing nothing in all that time, NASA officially concluded recovery efforts on May 25, 2011. The remaining, pre-sequenced ultra-high frequency (UHF) relay passes scheduled with the Odyssey orbiter completed June 8, 2011. No one has heard from Spirit since.
