The rover planners executed another great drive to park us in front of a megaripple in order to study its physical and chemical characteristics, which we can compare and contrast to the sands we investigated during our recent Bagnold dune campaign.

As the geology (GEO) theme group lead today, my job was to make sure we planned the highest priority observations of the megaripple, and positioned ourselves to successfully complete all the desired observations of the megaripple in the upcoming weekend plan. Working with my fellow GEO group members and all the individual instrument teams is one of the most satisfying parts of the job, as everyone brings their experience and capabilities together to build a plan that gets the most science out of the rover each sol. We certainly put Curiosity to work, planning MAHLI and APXS observations of the target "Schoolhouse Ledge" along the ripple crest, and the target "Man of War Brook" along the flank of the ripple. To keep the structure of the ripple crest pristine for MAHLI imaging, we shot ChemCam across another part of the ripple crest, the target "Gilpatrick Ledge". We also used ChemCam to interrogate the target "The Gorge", located inside the wheel scuff the rover planners purposely cut into the ripple to expose its interior structure. GEO planned a Mastcam observation using filters at specific wavelengths of light that help constrain what iron-bearing minerals are present within the sands. The target for this observation was "Cobbosseecontee Lake", which one of our Maine-dwelling team members insisted was not challenging to say (it is actually pretty phonetic…)! Even with our focus on the megaripple, there was still time to image the rocks around us with Mastcam, including an expanse of well-layered bedrock south of us called "Amphitheater Valley". Last but not least, GEO started a series of MARDI images - one image acquired each evening we are parked at the megaripple - to look for wind-induced changes. These change detection images help the team understand if (or how) wind activity and direction are changing as we leave the Bagnold dunes. Speaking of winds, the environmental (ENV) theme group planned a dust devil survey to look for those telltale signs of wind activity. ENV also acquired a long DAN passive observation, and regular RAD and REMS measurements.

Continuing the steady march up Mt. Sharp, Curiosity drove 18.3 m to bring us closer to a series of features being called megaripples, which are darker and larger ripples than were seen on the Bagnold Dunes. Touch-and-go was again the option for this plan (see Sols 1684 and 1685), and GEO made use of it with contact science on two targets, "Newport Ledge" and "Sugarloaf Mountain." These two targets are the closest two rocks protruding above the sand in the Navcam image above. MAHLI will target Newport Ledge to gauge grain size and distribution. A series of observations by APXS and ChemCam on Newport Ledge will continue to investigate the variations in the Murray bedrock over the course of the ascent up Mt. Sharp. Mastcam will target Newport Ledge and Sugarloaf Mountain to look at stratification and layering. After a drive that should take Curiosity to the edge of the megaripples, ChemCam will perform an AEGIS activity, and Navcam will document the new surroundings.

In working as the ENV theme lead today, I planned a pair of afternoon dust observations with Mastcam, looking in the direction of the sun and towards the crater rim (a line-of-sight extinction). As usual, REMS will capture the top of the hour five-minute observations and hour-long blocks of environmental measurements. In addition, a two-hour block of high-resolution data for the humidity sensor will be taken in the early morning. The high-resolution capture of humidity data is only sparingly used because it requires the ground temperature and wind sensors to be turned off as the heat they generate interferes with the humidity measurements. A DAN passive and post-drive active measurement will be acquired as well.

Planning rover science activities is a dynamic process. Unlike yestersol's plan, the Geology Theme Group decided to include an APXS and MAHLI "touch-and-go" in the plan, carrying out valuable contact science on the layered Murray bedrock. A touch-and-go, and in this case with a small APXS raster, is an option often available tactically to the Geology Theme Group that enables contact science to be carried out prior to a drive. Touch-and-go contact science activities, when appropriate, let the science team acquire the most information on a target without bringing a sample onboard the rover to instruments like CheMin and SAM. What makes these touch-and-go activities so valuable is that they have minimal impact to the drive distance for that day, allowing Curiosity to continue its ultimate goal of characterizing the geologic units of Mt. Sharp.

In this case, the APXS integration spots, dubbed "Harding Ledge" were also targeted with the ChemCam instrument to provide cross-correlation between the two instruments. Harding Ledge is a light toned, layered portion of the Murray bedrock. Some additional Mastcam documentation images were taken of the various targets in today's workspace to ensure proper context for the chemistry measurements is available for future investigations.

While yestersol's successful drive ended a bit prematurely due to the rough terrain the rover encountered, a new drive of ~20 meters is in the plan for today. At Curiosity's next parking spot before the sun sets, the rover will acquire a host of standard imaging to help with targeting in the next sol's plan.

Today was a day of tradeoffs. Should Curiosity focus on driving to get to a higher priority target sooner, or conduct contact science at the current location? Ultimately the Geology Theme Group decided to forgo the "touch-and-go" option, in which contact science is carried out prior to driving, and instead focused on using that time to increase the drive distance. With today's drive, the hope is to make it about 50 meters down the road along the strategically planned path informally known as the "Mt. Sharp Ascent Route." At the end of today's drive, the plan is for the rover to end up within about 2 meters of an intriguing gray hued target, having made significant progress towards a "megaripple" of high interest for helping to further our understanding of Martian aeolian processes. Megaripples are thought to form when the wind regime is not strong enough to move larger particles but still strong enough to move some of the smaller particles by saltation (that is, by bouncing short distances across the surface). Previously, Curiosity has visited several locations associated with the Bagnold Dunes where the rover is conducting a detailed assessment of variability and properties of the dune field as a whole.

Before Curiosity drives, away several ChemCam activities were planned including observations on the targets "Cow Ledge" and "Carter Cove." The "Carter Cove" target is located on the darker, more knobby, layered outcrop in the upper left of the accompanying Navcam image. Both of these targets are aimed at refining our understanding of the compositional and textural variability present in the Murray formation. Additionally, Mastcam documentation images of these targets will be acquired along with the documentation of the autonomously selected AEGIS target acquired after the previous sol's drive. An extension of an existing Mastcam mosaic was also planned, to provide additional context along a section of the exposed Murray outcrop.

Following the drive, we planned some standard imaging to help with targeting in the next sol's plan as well as a ChemCam AEGIS target, designed to autonomously measure bright patches of outcrop in the Navcam scene. All in all, a good day's work on Mars.

After a drive of almost 29 meters, we are parked at a site suitable for a busy plan full of contact science on the Murray formation. GEO focused mainly on characterizing nearby flagstone - "Duck Brook Bridge" was like the typical Murray formation that was tan in color, and "Cliffside Bridge" and "Waterfall Bridge" were more coarse-grained and gray. ChemCam will observe all of those targets, and APXS will measure both Duck Brook Bridge and Waterfall Bridge, with a long integration on Duck Brook Bridge. Mastcam observations will support that targeted science in addition to obtaining mosaics of fine-scale laminations on the "Stanley Brook Bridge" contact and alternating layering on "Chasm Brook Bridge." In the final targeted science block on Sol 1682, ChemCam will observe "Amphitheater Bridge" and nodule-rich "Cobblestone Bridge." A major component of the plan is the MAHLI full-wheel imaging that is periodically done to ascertain the state of the rover wheels. This is being done slightly earlier than usual in preparation for traction control driving (see Sol 1646 for more). Finally, after a drive, ChemCam will perform an AEGIS activity, and the usual post-drive imaging will be performed.

I worked the ENV STL role today and was busy planning a morning imaging suite for Sol 1683. In the suite, Navcam will search for clouds looking both directly above (zenith movie) and across the horizon (supra-horizon movie). Mastcam will measure the amount of dust in the atmosphere in two directions: in the direction of the sun and towards the crater rim - called a line-of-sight (LOS) extinction. Each of these measurements will be repeated in the afternoon to determine what, if any, diurnal changes occur. A 360 degree dust devil search like the one pictured above from Sol 1675 looking towards Mt. Sharp will be captured on Sol 1681. There do not appear to be dust devils in that image, but other sets of enhanced images have been more fruitful. Finally, a Navcam LOS extinction measurement will be taken for comparison with Mastcam. Normal REMS and RAD measurements as well as several DAN passive measurements and one DAN active were planned.

After a 30 meter drive on Sol 1679, we find ourselves near diverse outcrops of the Murray formation. We plan to drive on today across the Murray formation towards Vera Rubin Ridge.

I helped the ENV (Environmental) group to train a new ESTLK (ENV Science Theme Lead and Keeper-of-the-Plan) today. Unlike the GEO group, ENV combines the two roles into one to reduce staffing and because the required duties are lighter in ENV. The ENV plan was relatively straightforward as we are in unrestricted sols, which allow for planning (and driving) every day of the week. This makes time for science, a precious commodity, so ENV frequently cuts back on opportunistic science as long as the regular cadence of recurring ENV observations can be maintained. To stay on the usual cadence, ENV planned a Navcam zenith movie and supra-horizon movie, like the clear-sky image pictured above from Sol 1675. The normal complement of background RAD measurements, hourly REMS observations, plus 8 hour-long blocks of extended REMS observations were included. One long DAN passive observation, along with a post-drive DAN active observation were planned.

Unlike the previous few sols, GEO decided to forgo a touch-and-go (see Sol 1679) to instead sample the large array of outcrops of the Murray formation. Four ChemCam 5x1 rasters, with accompanying Mastcam images, were planned on several targets, including laminated bedrock "Trenton Bridge," bedrock targets "Brown's Brook" and "Beach Cliff," and a pebble named "Norwood Cove." A Mastcam mosaic of the sedimentary structures at "Birch Spring" was also planned. Finally, Navcam requested a single frame to complete the 360 mosaic acquired on Sol 1679. After the drive, which is expected to be about 30 m, a ChemCam AEGIS activity plus Mastcam deck monitoring were included with the ENV activities mentioned above.

MSL drove another 33 meters on Sol 1677, and again is surrounded by rocky outcrops partly covered by dark sand. Although Rover Planner support was available for "touch and go" contact science, the GEO science theme group decided that the limited reachable outcrop did not warrant contact science, and that driving is the top priority for this plan. APXS data were successfully acquired on Sol 1677, so are not urgently needed in this new location. The plan for Sol 1678 therefore focuses on remote sensing, with ChemCam 10x1 rasters on "Hancock Point," a darker exposure of bedrock, and "Crocker Mountain," a more normal-looking bedrock exposure. Mastcam context imaging of these targets will be followed by mosaics of nearby exposures that show sedimentary structures. Because the drive plan is likely to end up with bedrock in the arm workspace, we added a 3x2 Left Mastcam mosaic of the workspace to the post-drive imaging block, in case we can plan a touch and go tomorrow. Two ChemCam AEGIS activities and a Navcam zenith movie are planned after the drive. Thanks to the efficient work done by the science theme groups, planning went very smoothly today, making it an easy day for me as SOWG Chair.

Our drive yestersol went as planned and added another 28.3 meters to Curiosity's odometer. The science team was pleased to see that more interesting outcrop would be reachable by Curiosity's arm from our new location, so we decided to plan contact science followed by an afternoon drive in the Sol 1679 plan. We call sols like this "Touch and Go" sols. Curiosity will be examining interesting color variations in the rock target "Maple Spring" using MAHLI and APXS. We also had a few minutes left in the morning to allow us to take ChemCam observations of Maple Spring that will complement our contact science observations. After the morning science, Curiosity will go for an afternoon drive, followed by some post-drive imaging, environmental science observations, and automated targeting of the ChemCam instrument using the AEGIS (Autonomous Exploration for Gathering Increased Science) software.

I didn't participate a lot in the science team planning discussions today because I was staffed as a Surface Properties Scientist (SPS). In this role, I work closely with Rover Planners (RPs) as they design a sol's drive, lending my geologist's eye to provide feedback on the traversability of the terrain ahead. In particular, I look for any potential mobility hazards that might include wheel-damaging rocks, sand that could lead to high slip, or any other features that might pose a problem for our mobility system. I've often found it's useful to take a glance in our rearview mirror, or Rear Hazcam to be precise, to look at our tracks to understand how much we sank in the sand and how thick the sand cover is. It's also important to check out the terrain around us in 3D using stereo red-blue anaglyphs or, even better, virtually walk along our planned drive path using augmented reality in a Microsoft HoloLens running OnSight. I'm looking forward to seeing where we end up tomorrow!

AEGIS press release:
https://mars.nasa.gov/news/nasa-mars-rover-can-choose-laser-targets-on-its-own

HoloLens press release:
https://mars.nasa.gov/news/mixed-reality-technology-brings-mars-to-earth

This morning we woke up to fresh images from Curiosity that showed our surroundings after an ~17 m Sunday afternoon drive. I always really enjoy days like this because, even after 1,676 sols and just under 16.1 kilometers of driving, it still thrills me to look at images from unexplored areas of Mars. Immediately after inspecting the data, the science team jumped into planning by debating whether we wanted to spend the morning of Sol 1677 doing remote sensing, or if we wanted to spend the time doing contact science with the arm, all before an early afternoon drive continuing up Mt. Sharp.

A big part of the science team strategy for exploring the Murray formation, the group of rocks that are the lowest and oldest in Mt. Sharp, has been to systematically characterize their changing chemistry and mineralogy. Understanding how these properties vary with elevation gives us insight into changing conditions in the geologic processes that deposited and altered these rocks during burial. Because two of Curiosity's wheels were perched on rocks during Friday's planning, we were unable to safely use the arm to measure their chemistry using the APXS (Alpha Particle X-Ray Spectrometer). Since we had the opportunity to make these measurements again today and since the rover wheels were in good contact with the underlying terrain, we easily agreed we would shorten our remote sensing block and instead use the morning time to take advantage of the opportunity for contact science.

The area directly in front of the rover was filled mostly with sand, but we were pleased to find there was a small patch of Murray bedrock that we were able to reach with the arm and that wasn't filled with white veins. While veins and filled fractures are extremely interesting and frequently targeted for study, their presence in the field of view of the APXS makes it more difficult to understand the changing chemistry of the primary Murray bedrock. We named our contact science target "Casco Bay" and planned both MAHLI and APXS observations of it. We also managed to have enough time in the plan for a little bit of remote sensing, and used that to take ChemCam observations of Casco Bay that will complement the contact science measurements. We also planned to take several Mastcam color images to help us document the geologic context of our surroundings. Environmental science also requested a dust devil movie plan. After our morning science block, we planned another drive to continue our way up Mt. Sharp.

In the Sol 1673 drive, the rover planners aimed us for a nice curb of Murray bedrock which we could investigate with targeted science (with Mastcam and ChemCam) and contact science (with APXS, MAHLI and the dust removal tool (DRT)) over the weekend. The rover has to be sitting stably on the terrain for us to conduct contact science, with none of the six wheels in danger of slipping off a rock as we deploy the arm and turret. The arm and turret together are over 2 m in length and 95 kg in mass, providing a lever arm significant enough to move even our 900 kg rover! When placing APXS in contact with a rock, or MAHLI 1 cm away from a rock, the last thing you want is for the rover to move. While the rock in our workspace was indeed enticing, the rover planners found that two of our wheels were partially perched on rock slabs like those in the workspace, precluding us from using APXS and getting MAHLI any closer than 10 cm to any target in the workspace.

With these constraints in place, the science team set out to make lemonade. GEO planned three ChemCam rasters, with the "Back Cove" and "Lookout Point" targets selected to survey the chemistry and grain size of the Murray bedrock, and the "South Brother" target aimed at one of the gray, non-Murray pebbles seen dotting the bedrock surface in the workspace. We imaged both "Back Cove" and "Lookout Point" with MAHLI from 10 cm, the former with a single image, and the latter with a 3x2 mosaic that also captured multiple Murray layers around "Lookout Point". Mastcam also imaged the three ChemCam targets, and acquired mosaics of the Murray bedrock structures both in front of and along the starboard side of the rover. Since we would be in place for multiple sols, GEO planned two Mastcam images of the sandy target "Grant Cove", one image on Sol 1674 and the second on Sol 1675, to look for wind-induced changes.

ENV kept busy, obtaining their weekly morning imaging suite paired with afternoon observations to determine diurnal variability in cloud cover and the amount of dust in the atmosphere using both Mastcam and Navcam. ENV took advantage of the ability to use MAHLI, as well, acquiring an image of the REMS UV sensor. This is done periodically to determine the amount of dust covering the UV photodiodes, because the longer Curiosity remains in the Martian environment, the more dust settles on the detectors. The increased dust covering the photodiodes affects the REMS UV dust measurements of the atmosphere, so images of the sensors allow for recalibration of the observation. Accurate measurements from REMS are important for comparison to the Mastcam and Navcam dust measurements.

Once all these great observations are wrapped up, Curiosity will drive further up the slopes of Mt. Sharp, picking her way across the rough terrain toward yet another intriguing Murray bedrock patch. What surprises await? Check back next week to find out!