It’s been an eventful few weeks for Curiosity on Mars. From sols 981 to 986, Curiosity’s human pilots tried and failed to drive the rover southward to a wide exposure of the geologic contact between Pahrump and Washboard rock units, experiencing several days of slipping and high tilts as they scrambled for purchase on the sloping walls of the sand-filled valley below Logan Pass. So they turned and retraced their steps to the area they explored last month -- Logan’s Run -- and quickly found a ramp that took them up the slope to a beautiful geological amphitheater named Marias Pass. The time spent trying to enter Logan Pass wasn’t entirely wasted; the ChemCam team managed to install an upgrade to their software that is now permitting them to work around the loss of their autofocus laser.
Marias Pass is where they will remain throughout the three weeks of conjunction, as Mars passes behind the Sun as seen from Earth, making radio transmissions unreliable. The USGS Astrogeology blogs (embedded below) supply lots of detail on the challenges of the attempted southward drive, so I’ll focus instead on what we saw from the rover at Marias Pass, as well as the ChemCam upgrade.
Let’s begin by getting oriented. I’ve always relied heavily on Phil Stooke’s route maps for orienting myself to Curiosity’s landing site, but they are missing one piece of information that is getting increasingly important for the rover’s mission on Mars: topography. So I asked Peter Grindrod to make me a contour map, and I tweaked the results, and dropped Phil’s route map on top of it, and it’s really fun to see how they’ve been driving Curiosity:
You can see how they kept to valleys for the most part, avoiding areas with lots of sand ripples. But they got bogged down in the pass between Jocko Butte and Apikuni Mountain. They changed tactics on sol 991: instead of driving through a notch in the topography (a local low) they charged up a topographic bump between Apikuni Mountain and Mount Shields, which evidently gave the wheels the purchase they needed to get up the slope to Marias Pass. They got a couple of very good looks at the pass on sols 991 and 992 before crossing a flat area to another slope, where they’re now exploring rocks in situ.
Marias Pass is just gorgeous. Here are two panoramic views. I’m trying a new way of sharing the panoramas. These use a site for 360-degree panorama viewing called round.me, which also has a VR panorama viewing app for iOS. The app allows you to use Google Cardboard to view the pans, so you can just turn your head and see the landscape around you. It’s pretty neat.
Here is the view from sol 992, looking at Marias Pass from a distance:
And here is Curiosity’s current view, as of sol 997.
"It's everything we hoped for," Project Scientist Ashwin Vasavada told me. They began with systematic examination of the different rock types exposed here. As expected, they can access both the Pahrump material, which they've seen a lot of before, and the Stimson unit above it, which they had not. The Stimson unit is what I've been calling the Washboard unit; they named it after the outcrop in the hill that they were trying to get to, even though they're now no longer headed for that hill. Such is life on Mars. It is chock full of beautiful crossbeds. Ashwin told me that they'd hit both units with all the instruments -- APXS, MAHLI, and ChemCam -- but that they ran out of time to complete the work before conjunction.
But there was a surprise waiting for them. Seen up close with MAHLI, the base of the Stimson unit is quite pebbly. They looked at that unit very closely before going in to conjunction:
Those rounded grains look like pebbles that must have been rolled in a stream, but if I've done my math correctly, the so-called pebbles are only about 1 millimeter across. That's just sand-sized. Earth's winds would have no trouble moving such small particles. On Mars, I'm not sure whether wind or water is the more likely scenario for transporting grains of this size. Wind usually does an extremely good job of sorting particles by size, and this deposit shows two distinctly different grain sizes. So I'm not sure what this rock is telling us; I'll have to wait for the professionals to weigh in with their opinions. It is interesting that some of the rounded grains are very light-colored. On Earth, I'd assume they were quartz. On Mars, I wouldn't expect quartz. Maybe albite? I am very glad that ChemCam is back in action and can hopefully tell us more about the composition of this rock. (More on that below.)
The Curiosity team isn’t only interested in the rocks; they’re interested in the relationships between the rocks. Does one unit grade into another – does it record a continuous history? Is that grainy bit just part of Stimson, or it is a distinct unit? Is there an unconformity between the units, representing an unknown amount of time elapsed between the two? If an unconformity is there, what’s the nature of the unconformity? Was the lower layer eroded before the upper layer was deposited? What do the veins do across the layer boundaries? Ashwin told me that the location where Curiosity is currently parked is not quite right to investigate these relationships. But just beyond the rover's reach to the left is an outcrop where it looks like Curiosity can see Pahrump, Stimson, and grainy interlayer all in contact, so after conjunction they will likely bump over there to investigate more closely.
Ashwin told me that the team is "really having fun now" that they are investigating such a varied and interesting package of rocks. This is exactly the kind of work Curiosity was sent to Mars to do. Sometimes there are driving challenges, but it's no different from the challenges faced by Spirit as she climbed Husband Hill. The rover planners are enjoying themselves too, walking the line between keeping the rover safe and trying to get the scientists where they want to go.
And it sure doesn't hurt that the views are beautiful! The Mastcam panoramas recorded from Curiosity's position were only partially downlinked before conjunction; it may be a while before we can get the full view in color. But do explore those round.me panoramas that I embedded above.
ChemCam laser back in action
ChemCam is well known as Curiosity's laser blaster, but the instrument actually contains two lasers. One was used to detect the best-focus distance to a zappable rock target, and the other was used for the actual zapping. But late last year, the focus laser died. The ChemCam team developed a workaround that involved making a guess at the range to the target and then zapping using five slightly different focal distances that bracketed the guessed range. Only one of those observations would be in focus, and the rest of the data would be thrown away before transmission to Earth.
The workaround has enabled them to continue using ChemCam, but because it has increased the time it takes to make a single observation by a factor of five, it has substantially cut the number of observations they could make. In the past, ChemCam would often shoot “rasters,” arrays of evenly spaced observations (often 1x5 or 3x3) that allowed them to understand not only the composition of a target but also the local variability in composition.
The software update now has ChemCam using its camera for focus: they take nine images with the camera, an onboard algorithm finds the best focus position, and then the instrument uses that to focus the final camera and laser position. As of sol 989 they have resumed performing raster observations, like this 3-by-3 array on a rock target named “Spokane” on sol 989 and this 1-by-5 array on a rock (maybe Hoodoo?) on sol 992. As conjunction approached, ChemCam was being put to heavy use exploring the varied and fascinating rock facies in Marias Pass.
Mars is now quite close to the Sun, as seen from Earth. It's entered the field of view of SOHO's LASCO C2 camera; you can watch it cross the Sun with animated SOHO data. Of course Mars is actually no nearer the Sun than its orbit ever takes it! Even though I know that, its' still a little scary to see solar activity apparently blasting in Mars' direction. There are a lot of spacecraft there, riding out conjunction.
Throughout conjunction, Curiosity will continue to gather environmental data with its REMS, RAD, and DAN instruments, and will uplink image data as usual when orbiters fly overhead. As far as rover downlink is concerned, there is very little difference between conjunction operations and ordinary operations; it will continue to talk to orbiters at every opportunity. Unlike the previous conjunction (in April 2013, sols 236-261), the orbiters will relay data to Earth for the entire three weeks, as a test of the reliability of conjunction communications. So even though new image data are not being acquired until June 21, we are continuing to see transmission of older images to Earth. Just in case solar radio noise messes up the signal, the orbiters will be holding all the rover data transmitted during conjunction in a buffer and retransmitting it a few days before the end of conjuction. Ashwin told me that the Mastcam team worked hard to prioritize the backlog of images stored aboard the rover to select roughly 5 Gigabits of images to be transmitted during this period, a mix of never-transmitted data and re-transmission of particularly important images with lossless compression.
Following are the USGS blogs for the period covered in this update:
Sol 978-979 update by Ryan Anderson: Jocko Chute (6 May 2015)
The sol 976 drive was successful and we are close to “Jocko Chute” (our informal name for the saddle point west of Jocko Butte). In the sol 978 plan, we have a ChemCam LIBS observation of a patch of exposed bedrock called “Big Salmon”, followed by lots of Mastcam images. There is a 14x3 mosaic of some hills in the direction of our drive, some single frame high-resolution images of the targets “Silvertip”, “White_Coyote”, and part of the wall of “Logan Pass”. There is also a stereo Mastcam image of an outcrop called “White Horse” and a 4x2 mosaic of Jocko Butte.
Once all that is done, we will drive toward “Logan Pass” and do our standard post-drive imaging so we can see our new surroundings. On sol 979 ChemCam has a few calibration observations of targets on the rover, and then Mastcam has an overnight observation of Phobos as it is eclipsed by Mars. The idea of this observation is to take pictures of Phobos when it is illuminated by the sun, and then when it is illuminated just by light passing through Mars’ atmosphere, and compare them to figure out how much dust is in the atmosphere.
Sols 980-982 by Ryan Anderson: Dodging Sand, Updating ChemCam (8 May 2015)
The Sol 978 drive stopped after going only a couple meters instead of the expected ~19 meters because Curiosity detected that its wheels were slipping in the sand. The rover periodically takes pictures of its surroundings while driving to make sure that it is actually moving forward and its wheels are not just spinning in place. This was a lesson learned years ago when the Opportunity rover got itself stuck in a sand ripple by spinning its wheels. Curiosity currently is in no danger of getting stuck: in the weekend plan we will just back up slightly and drive around the worst of the sand.
On Sol 980, before we drive, ChemCam and Mastcam will analyze two targets, “Silver Valley” and “Snowslip” and Navcam will watch for clouds above Mt. Sharp. Then on sol 981, Mastcam will take some pictures of the crater rim and the sun to measure the amount of dust in the atmosphere. After that comes the drive and our standard post-drive images so we can see our new surroundings. Mastcam will also take a 7x2 mosaic of Logan Pass right after driving.
In the afternoon of Sol 981, ChemCam will turn on so that its software can be updated. I’ve really been looking forward to this update, which will allow ChemCam to automatically focus using its camera, bringing us back to almost-normal operations!
On sol 982 there won’t be much activity, just some maintenance activities for REMS.
Sol 983 update by Ken Herkenhoff: More sand traps (11 May 2015 )
The Sol 981 drive got the rover around the troublesome ripples and to the desired location, which gave us a good view of the terrain ahead. Unfortunately, the images taken from the new location show more sandy ripples between the rover and the sharp transition between bright and dark rocks that we would would like to examine close up.
So the plan for Sol 983 is to go around the ripples to the right and search for a safe path ahead. But first, ChemCam will test its new focusing software, using the RMI to find the best focus position for LIBS analyses of the onboard calibration targets. The biggest challenge for me as SOWG Chair today was prioritizing data for downlink, as the data volume expected via MRO is much less than usual. We will probably receive the images most urgently needed to plan the next drive, but not the results of the ChemCam software tests. This will delay the return of ChemCam to "normal" operations. But the near-term focus will likely be on driving, so there will be few opportunities for ChemCam observations anyway.
Sol 984 update by Ken Herkenhoff: Slippery sand (13 May 2015)
The MSL tactical team took a day off yesterday to allow Earth and Mars time to synch up; planning is no longer restricted and we will be working every day the rest of this week (including Saturday). Despite efforts to avoid sandy areas, the Sol 983 drive stopped short when the rover detected that it was slipping too much. So after taking some Mastcam images of the areas that are being considered for upcoming contact science, the rover will back up and drive around the sand and up onto a low ridge to the southwest of our current location. The slopes on the flank of the ridge are steeper than those that the rover has traversed before, but it will probably be easier to climb them than to drive across the sandy ripples. Overnight, CheMin will perform an instrument calibration activity.
Sol 985 update by Ken Herkenhoff: High Tilt (14 May 2015)
Once again, excessive wheel slippage prevented MSL from driving as far as planned, so the tactical team decided to take a break from driving to allow various options to be studied in more detail. The rover is tilted 21 degrees, the highest tilt of the mission so far, on the flank of a small ridge. The vehicle is high enough on the ridge that the terrain to the southwest is visible in Sol 984 Navcam images, allowing more complete evaluation of a traverse in that direction.
The Sol 985 plan includes ChemCam observations of a nearby rock called "Una" to test the newly-installed ChemCam autofocus software. Of course we are hoping this test goes well and that ChemCam will return to more normal operations soon. Mastcam will also observe Una, as well as the ripples and small rocks near the rover, and outcrops toward the south. The usual atmospheric monitoring observations round out the plan.
Sol 986 update by Ryan Anderson: Finding a Path (15 May 2015)
We’ve been having trouble with the path we originally wanted to take through the sand toward the interesting geology at “Mt. Stimson”, so in today’s plan we are going to take a careful look around to identify better routes. Mastcam has a 13x3 mosaic in the direction we want to go, as well as a 5x3 mosaic of Mt. Stimson and a 2x2 mosaic to fill a gap in a previous mosaic.
While Mastcam tries to spot a path through the sand, ChemCam is busy testing out its new focusing software, which seems to be working well. ChemCam has an autofocus observation of a target called “Yellowjacket”, and a z-stack observation of the same target to compare the results.
After that, we have a short backwards drive to get us from our current highly tilted location to more level ground. After the drive, Navcam will provide a 360 degree view of our new location, and Mastcam will do a “clast survey” to document the sand and pebbles at our new location.
Finally, Mastcam has some night-time imaging of another Phobos eclipse.
Sol 987-989 update by Ryan Anderson: Back at Jocko Butte (18 May 2015)
The backwards drive on sol 986 was successful, and over the weekend, Curiosity drove back toward “Jocko Butte”. Before the drive on sol 987, ChemCam had a 5x1 observation of the target “Mill”, accompanied by a Mastcam image. Mastcam also took a small 2x2 mosaic of our tracks.
The drive back toward Jocko Butte was about 43 m, bringing our total odometry to 10,697 m. After the drive, Navcam and Mastcam took images to allow for targeted science and contact science, and Navcam also had an atmospheric observation. On sol 988, we had several “untargeted” observations, including some Mastcam measurements of the amount of dust in the atmosphere, a Mastcam “clast survey” observation, and a MAHLI image of the ground at our new location.
In today’s plan for sol 989, there is a ChemCam 3x3 observation on the target “Spokane”, and an accompanying APXS observation. (And can I just say how nice it is to be able to rapidly analyze nine spots on a target with ChemCam again?) Sol 989 also has a number of arm settling tests with MAHLI that we want to get done before the upcoming conjunction (several weeks when the sun is between the Earth and Mars, cutting off communications). These tests help us to see how long it takes for vibrations in the rover’s arm to disappear enough to allow good MAHLI images. Finally, APXS will be placed back on Spokane for an overnight measurement.
After sol 989, we will be driving again, though where exactly we will go is still being discussed. We want to get to the stratigraphic contact at the base of “Mt. Stimson”, but it is proving to be difficult to reach so we are also considering alternatives.
Sol 990 update by Ken Herkenhoff: ChemCam Autofocus Software (19 May 2015)
Testing of the new ChemCam automatic focusing software continues to go well--the instrument is returning well-focused data of the quality we got used to early in the mission. The MAHLI test data acquired on Sol 989 are also looking good; here's an image of the penny in the MAHLI calibration target on the rover.
Having completed the most urgent arm activities needed before conjunction, MSL is ready to drive again. The Sol 990 plan begins with a Navcam search for dust devils, ChemCam and Mastcam observations of "Pinedale," and a Right Mastcam image of the APXS target "Spokane." Then the rover will drive west in search of a route up the hill toward the southwest and acquire the post-drive data needed to plan the next drive and targeted science observations.
Sol 991 update by Lauren Edgar: Taking the high road (20 May 2015)
After assessing a few different drive paths to deal with the challenging terrain, the team decided to drive uphill to avoid crossing the ripples near Jocko Butte. On Sol 990, Curiosity drove 52 m back towards Mt. Shields, which puts our total odometry at 10,533 m.
The goal of today’s plan is to climb uphill towards an interesting geologic contact. It’s the same contact that we would have seen in Logan Pass, but the path through “Marias Pass” looks a little bit shorter. Today’s plan also includes ChemCam and Mastcam observations of the target “Petty,” and Mastcam documentation of “Apikuni Mountain” and Mt. Shields to characterize the local geology. After the drive we’ll acquire some standard imaging to help with future targeting.
Hopefully the climb will give Curiosity a good workout, and we’ll get to see some exciting features when we get there!
Sols 993-996 update by Lauren Edgar: A long weekend at Marias Pass (22 May 2015)
On Sol 992 Curiosity took a short drive into Marias Pass to get a better look at the terrain ahead. The 6 m drive on Sol 992 brought our total odometry to 10,562 m. It also put Curiosity in a great position for targeted science over the long holiday weekend.
The 4 sol plan includes some large Mastcam mosaics to characterize the terrain and the contact between the Stimson and Pahrump units. The plan also includes ChemCam and Mastcam observations on the targets “Hoodoo,” “Pinehaven,” “Red Sleep,” and “Red Horn” to assess the composition of the bright outcrop and veins. On Sol 995, Curiosity will bump closer to the outcrop, to prepare for possible contact science next week. Curiosity will also acquire several Mastcam observations of Deimos and stars to assess the nighttime atmospheric opacity. Sol 996 will be a “REMS-a-palooza” devoted entirely to extended environmental monitoring.
Sol 997 update by Lauren Edgar: Preparing for contact science (26 May 2015)
Curiosity spent the weekend characterizing the terrain and bedrock exposed in Marias Pass. Curiosity drove 33 m further into Marias Pass, bringing our total odometry to 10,596 m. The drive set us up perfectly to investigate the contact between two different types of bedrock – the underlying Pahrump unit and the overlying Stimson unit.
Today’s plan is focused on characterizing the contact in this new location, and then bumping even closer to the outcrop to prepare for contact science later this week. Now that ChemCam is back in action with its autonomous focusing capability, the plan includes two ChemCam rasters on the targets “Mission” and “Missoula” to assess the chemistry on either side of the contact. The plan also includes some Mastcam mosaics to document the sedimentary structures, and a Navcam observation to search for dust devils. Then Curiosity will bump closer to the outcrop, and will acquire images for future targeting. Overnight, Curiosity will acquire Mastcam images of Phobos to study aerosols in the atmosphere of Mars.
Sol 998 update by Lauren Edgar: Contact Science at Marias Pass (27 May 2015)
A short bump on Sol 997 put Curiosity in a great position to investigate a few different rock units in Marias Pass, using the instruments on the rover’s arm. The 2.5 m drive brings our total odometry to 10,599 m. With the upcoming solar conjunction (Mars will be on the opposite side of the sun from the Earth, so we can’t communicate with the rover for most of the month of June), Curiosity is now parked for the next few weeks. But we are parked in front of a beautiful outcrop that shows the contact between the underlying Pahrump unit and the overlying Stimson unit.
The goal of today’s plan is to characterize the Stimson unit. First, Curiosity will acquire ChemCam and Mastcam on part of the Stimson unit called “Ronan” (the large block in the top part of this Mastcam image) as well as a coarse-grained block named “Big_Arm.” Then we’ll acquire several MAHLI images on “Ronan.” Next, Curiosity will brush “Ronan” to remove the dust, and will then take MAHLI images of the brushed area to get a better look at the grain size and textures. And finally, we’ll place APXS on the target to investigate the bulk chemistry of “Ronan.” Tomorrow’s plan will likely include similar observations on the Pahrump unit.
Sol 999 update by Ken Herkenhoff: Last MAHLI images before conjunction (28 May 2015)
Today is the last day we can plan MAHLI activities before the operational stand-down for solar conjunction, to ensure that we have time to confirm that MAHLI's dust cover is safely closed. So we worked to include as many MAHLI images as possible in the Sol 999 plan, making for a rather hectic day for me as MAHLI uplink lead.
The plan includes a full set of MAHLI images of a potential DRT target called "Big Arm." The target dubbed "Wallace" was selected for brushing by the DRT, followed by a full set of MAHLI images of the brushed spot. The APXS will then be placed on Wallace for overnight integration. Mastcam multispectral observations of the brushed Ronan target and some rocks broken by one of the wheels (dubbed "Seeley") are also planned--we want to image them before any dust is deposited on those clean surfaces.
Sols 1000-1002 update by Ken Herkenhoff: Photometry (29 May 2015)
We're planning 3 sols of MSL activities today, starting with Sol 1000! As we continue to prepare for solar conjunction, arm motion is allowed in this plan, but no contact science. The plan starts with ChemCam and Mastcam observations of a platy rock called "Newland" and a Navcam search for dust devils. Then the first of several Mastcam/Navcam photometry observations is planned. The goal of these images of patches of ground east and west of the rover is to measure reflectivity at various times of day and compare the results with models of the physical properties of the surface. The arm will then be moved to a position that allows imaging in front of the rover, including a large Mastcam stereo mosaic of the nearby outcrops. The rover will wake up early on Sol 1001 for another photometry observation, which will be repeated later that morning before Mastcam and Chemcam observations of "Big Arm 2," a potential contact science target. Three more photometry observations are planned late in the afternoon, before the arm is tucked away for conjunction. On Sol 1002, Mastcam will observe the Sun during the day, and Phobos after dusk. It's been a good day for me so far as SOWG Chair--not too hectic but certainly not boring!
Sols 1003-1004 update by Ken Herkenhoff: Last tactical planning before solar conjunction (1 June 2015)
Today is the last day of MSL tactical operations until after solar conjunction, so this will probably be the last MSL update for a few weeks. Ryan Anderson and I are both on shift as payload uplink lead today, but because the instruments we're representing (ChemCam and MAHLI/MARDI, respectively) are already standing down in preparation for conjunction, our efforts have been focused on planning for the resumption of activities after conjunction. We don't know precisely when tactical planning will resume, as the ability to communicate with spacecraft as Mars passes behind the Sun depends on variable solar activity. The expectation is that the next tactical planning day will be June 25th (Sol 1026), but the schedule probably won't firm up until that week.
The Sol 1003 plan starts with Mastcam images of the Sun to measure the amount of dust in the atmosphere, followed by another set of Mastcam/Navcam photometry images to extend the experiment started on Sol 1000. Then Mastcam will take images of various targets near the rover, to be compared with images of the same targets taken after conjunction to look for changes caused by winds. Later in the afternoon, the photometry and change-detection imaging will be repeated, and Mastcam will acquire a stereo mosaic of "Apikuni Mountain." Then the focus motors of both Mastcams will be moved to their "home" positions for conjunction and Navcam will search for clouds above MSL. The Sol 1004 plan includes only the usual RAD and REMS observations, a preview of the plan for the next few weeks. During the break from tactical operations, the science team will have more time to analyze the wealth of data the rover has returned over the past 1000 sols.