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Curiosity update, sols 748-763: Driving and Drilling at Pahrump Hills

Posted By Emily Lakdawalla

29-09-2014 17:57 CDT

Topics: pretty pictures, mission status, Mars, Curiosity (Mars Science Laboratory)

The biggest news on Curiosity of late is that the rover has drilled her fourth full drill hole on Mars! Drilling happened at a site called "Confidence Hills" on sol 759 (September 25, 2014). The previous drill sites were John Klein, on sol 182; Cumberland, on sol 279; and Windjana, on sol 621. This is Curiosity's first drill hole into what the science team thinks are Mount Sharp rocks.

Drill hole at Confidence Hills, Curiosity sol 759

NASA / JPL / MSSS

Drill hole at Confidence Hills, Curiosity sol 759
Curiosity took this photo of the drill hole at Confidence Hills on sol 759 (September 24, 2014) with its Mars Hand Lens Imager (MAHLI). The hole is 1.6 centimeters in diameter and about 6.7 centimeters deep. It is a merged-focus image product combining information from multiple images that MAHLI took from a position 5 centimeters away from the target as the camera stepped through different focal distances.

But I'm getting ahead of the story. When I last wrote about Curiosity, it was sol 747, and the rover had finally descended into Owens Valley; she was less than 200 meters' drive from her drilling target at Pahrump Hills. On the way to Pahrump Hills, she passed by some absolutely amazing-looking outcrops of rock. This update is being written days later than I had initially planned because I spent so much time examining and playing with those images.

To set the stage, let's step back to sol 746. Curiosity was sitting atop a low outcrop at a spot called Jubilee Pass. The view takes in the ripple-filled Owens Valley in front of the rover, and the bright smudge of Pahrump Hills in the distance.

Curiosity Navcam panorama from Jubilee Pass, sol 746 (September 11, 2014)

NASA / JPL / Jan van Driel

Curiosity Navcam panorama from Jubilee Pass, sol 746 (September 11, 2014)
Curiosity took this photo on sol 746 as she prepared to cross Owens Valley. She sits in Jubilee Pass; outcrops associated with Jubilee Pass stretch across the whole panorama. In the distance, beyond a ripple field, is Panamint Butte. Beyond that is a light-colored patch, Pahrump Hills.

On the extreme right of this panorama, there is a curious-looking crack through the outcrop that caught the attention of the science team. So, before driving on sol 747, they took a large, detailed panorama of the outcrop. To me, this is the most exciting part. I have attempted to place a scale bar on it to give a sense of the size of this feature, but the scale bar could be off by 50% (either short or long), and of course the scale of the image changes as you go from the bottom (which is closer to the rover) to the top (which is farther).

Outcrop near Jubilee Pass, Curiosity sol 747

NASA / JPL / MSSS / Emily Lakdawalla

Outcrop near Jubilee Pass, Curiosity sol 747
Mosaic of several Mastcam-R pictures taken on sol 747 (September 12, 2014) of an outcrop near Jubilee Pass. The color of the image has been stretched to emphasize contrasts among different-colored parts of the rock.

We're looking at an outcrop of very thinly bedded rock. There is a fracture in the rock, and discoloration and bright veins along the fracture. One might hypothesize that fluids once flowed along this fracture, and altered the surrounding rocks. Or it could be something else. In any case, Curiosity drove away after taking this photo. I don't see any ChemCam shots of this feature. There were a couple of other nearby Mastcam targets, including what looks like an incredibly thinly eroded layer of rock. The cohesion of these thin rock layers is really surprising to me, even in Mars' relatively low gravity (38% of Earth's).

So Curiosity drove on, pausing briefly to take in this view of the tracks she left after she crossed Jubilee Pass.  At the end of the sol 747 drive, which was a relatively long one at 95 meters, she took the unusual post-drive step of capturing a full 360-degree view of her surroundings with the left Mastcam. The view contains tons of delicious outcrop making up the western end of Panamint Butte, as well as another nice perspective on her tracks. On sol 748, she re-imaged much of the Panamint Butte outcrop with her Mastcams, capturing views of some of the clearest-cut examples of crossbeds I've seen from Curiosity. Crossbeds form wherever sand-sized particles are being transported, either by wind or by water. Geologists will be able to read these rocks to say whether it was wind or water, and which direction the flow was happening.

Cross-bedded rock within Panamint Butte, Curiosity sol 748

NASA / JPL / MSSS / Emily Lakdawalla

Cross-bedded rock within Panamint Butte, Curiosity sol 748
Before driving on sol 748, Curiosity took in a panoramic view of rock layers displaying crossbeds. This image contains two sections of the same panorama. Crossbeds form where sand is being transported in a current of wind or water, making sand ripples. Sand cascades down the slip faces of the ripples, building out a series of inclined rock layers. Later erosion may plane off the tops of the originally inclined beds before another set of cross beds is deposited on top.

After taking these photos, Curiosity drove a short distance to the east end of another outcrop named Upheaval Dome, presumably of the same material that Panamint Butte was made of. The rock at the rover's feet had a decidedly strange erosional expression. After taking the weekend off, they shot the target, named Shinarump, with ChemCam and Mastcam to take a closer look. But much of the pre-drive science time on sol 751 was devoted to a huge stereo Mastcam panorama of Upheaval Dome. Everywhere I look in this panorama, there are fascinating rock formations. There are crossbeds, and the crossbeds have been planed in different directions and then wind-eroded to make fantastic series of paper-thin layers. The thinly bedded rock is peppered with large round nodules -- from their look, I'd hazard a guess that they're concretions, but that's not the only possible interpretation, and I couldn't begin to tell you what mineral they're made of. Here is just one small piece of the panorama; please click through twice to enlarge it to its full majesty to appreciate all of the fine geomorphological detail.

Fascinating geomorphology at Upheaval Dome, Curiosity sol 751

NASA / JPL / MSSS / Emily Lakdawalla

Fascinating geomorphology at Upheaval Dome, Curiosity sol 751
A tall outcrop of rock contains crossbeds, fine- and coarse-grained sedimentary rocks, and unusual small structures.

After taking this fine panorama, they drove a total of 117.56 meters, the longest single drive since sol 665. And this was a sweet, sweet drive. The terrain is benign for the wheels, so the drivers didn't need to sweat every little detail; they could let some of the rover's own intelligence take over. As a rule of thumb, whenever you can clearly see the impressions of the wheel tracks in the soil, it's great driving terrain. That means it's soft and fine-grained enough for the rover's grousers to sink in and make good contact with the soil, allowing the webbing between the grousers to spread out the rover's weight across a wide area of wheel surface, but it's firm enough for the wheels not to slip. It also means that the next time HiRISE gets a picture of this area from orbit, the wheel tracks will show up as a clear dark double line on the ground.

Curiosity's sol 751 drive (animation)

To begin the drive, they neatly straddled a small pile of rocks. They drove about 40 meters and then hung a hard left turn in order to run the rover along what looks like a narrow bridge between two ripple fields; you can see the rover making little turns to adjust its position to follow that bridge and not stray into the ripples. Finally, a slight right turn took them up a slope to its peak. Nailing the center of that bridge between the ripple fields after driving 40 meters was pretty great. In order to do that, the rover really has to know exactly where it is, relative to where the drivers expected it to be. The rover does that with visual odometry, using stereo pairs of the images in the animation above to track the distance it's traversed from one image to the next. You can see in this map from curiosityrover.com just how well the rover threaded the needle between those two ripple fields.

Curiosity's sol 751 drive

NASA / JPL / UA / curiosityrover.com (Joe Knapp)

Curiosity's sol 751 drive

Once Curiosity reached the top of that rise, she had a great view down onto Pahrump Hills, with two buttes on either side, and Mount Sharp behind it. This is it, what Curiosity has been aiming for. Pahrump Hills is an outcrop of relatively light-colored rock that the Curiosity science team thinks might represent the lowest-elevation rock unit they can reach at Mount Sharp. As such, it represents the beginning of the story they can tell about Mount Sharp. It's the first drilling target of their extended mission, and they expect to spend several weeks studying the outcrop, though not likely all from the same position.

The Base of Mount Sharp, Curiosity sol 752

NASA / JPL / MSSS / Emily Lakdawalla

The Base of Mount Sharp, Curiosity sol 752
Curiosity paused on a rise in order to look ahead at Pahrump Hills, the rock unit interpreted to be the lowest accessible layer of Mount Sharp. Mount Sharp looms beyond the black sand dune field in the distance.

Curiosity bumped forward to the outcrop on sol 753, putting a nice flat area of outcrop within reach. Here's a top-down view of the rover in her fourth drilling location.

Curiosity at Pahrump Hills, sol 753

NASA / JPL / Elisabetta Bonora & Marco Faccin

Curiosity at Pahrump Hills, sol 753
Navcam panorama of Curiosity's position at the bright-colored outcrop called Pahrump Hills on sol 753 (September 18, 2014).

Work proceeded very rapidly from there. On sol 753, just after arriving, they captured Mastcam panoramas of the area within reach of the arm. On sol 755, they picked a target, brushed it, then stuck the APXS on it to determine its elemental composition. That was Saturday. Sol 756 was Sunday, and the rover went right on to perform the mini-drill test, without having had any Earth command in the loop. That's awesome for two reasons: one, that brush-APXS-minidrill all happened autonomously; and two, that the rover drivers managed to get all that work sequenced in a single Earth planning day.

Unlike the previous attempt at a mini-drill at Bonanza King, this drill went great; it reached its full depth, even though the rock cracked as Curiosity drilled it. On sol 758, they imaged and lasered some cool-looking little rosettes named Mammoth and Morrison on the otherwise flat plates of the outcrop before brushing and APXSing again in order to prepare to drill. And on sol 759, they drilled again, at a target named Confidence Hills. Just one week between their arrival at the outcrop and the full drill. If they can achieve this kind of speed on a regular basis, the extended mission is going to see a lot more rock samples than the prime mission did! Here is a nice three-image sequence of the drilling work.

Drilling at Confidence Hills, Curiosity sols 755-759

NASA / JPL / MSSS / Chris Simundson

Drilling at Confidence Hills, Curiosity sols 755-759
These three images were taken on sols 755, 756, and 759, as Curiosity performed a mini-drill and full drill activity on a rock target called Confidence Hills within the Pahrump Hills outcrop.

What's odd about this drill hole is that the tailings from the full drill hole look quite different from the tailings that came out of the firt drill hole. They are lighter, pinker, and clumpier. I'm not sure what that means! Hopefully CheMin will tell us.

After sol 759, things slowed down a bit. According to Ken Herkenhoff at the USGS blog, "there was a problem with one of the rover's gyroscopes that halted the transfer of drill sample to the scoop." The rover was preoccupied, anyway, with a software patch followed by preparing a SAM oven for ingesting a sample from the Confidence Hills drill hole. And the weekend intervened. But by sol 762 they were back to work and had sieved the drill tailings. With the weekend over, they're now ready to deliver the sample to CheMin.

What happens after that? The site where they drilled is at the base level of the Pahrump Hills outcrop. They will probably not stay exactly where they are. But now that they are at the base of Mount Sharp, it's time for them to start reading these rocks like the pages of a book. They could drive a short distance away to access a different part of the outcrop; the whole outcrop represents several vertical meters of rock section, so there could be a long of Mars history recorded in it. Or they may decide one sample was enough, and drive off to new rocks. We'll have to wait and see!

 
See other posts from September 2014

 

Read more blog entries about: pretty pictures, mission status, Mars, Curiosity (Mars Science Laboratory)

Comments:

Spock: 09/29/2014 08:16 CDT

Emily: Aeolis Mons is a mud volcano formed by geothermal activities long after Gale crater was formed. The material at Pahrump Hills is from Aeolis Mons, However, it is not the base of the mountain but material that has cascaded from the slopes either from mud slides or from avalanches caused by Mars quakes or tremors resulting from meteoric impacts in the past. The stratification at Pahrump can not be considered reliable because the top layers may well be the oldest and the lower layers the youngest. The same goes for boulders resting on Aeolis Palus. They do not necessarily lie where they were formed but could have have been brought to the crater from miles away via impactors or vulcanism outside Gale Crater. Analysis of the drill material will show that it is from Aeolis Mons.

Ricky Egeland: 09/29/2014 09:50 CDT

How big across are those boulders on the top of the Upheaval Dome photo? How can boulders like that form on Mars? Rocks like that make me think of big-time weathering – rain, glaciers, etc..., but I'm no geologist.

DavidPalmer: 10/01/2014 04:36 CDT

There is no evidence of volcanism in the Gale Crater complex, not within hundreds of miles. However, there is strong evidence of fluvial activity sourced from springs, even in geologically recent times, which I elaborate on in my essay "An Interpretation of the Geology of Gale Crater & Mt. Sharp, with Implications for the History and Habitability of Mars" (see web address below). I would interpret the Pahrump material as the lowest (and oldest)in a sequence of lacustrine deposits making up the lower section of Mt. Sharp, probably formed in the hydrothermal stage just after the impact. http://galecratergeology1.tumblr.com/post/85407991682/an-interpretation-of-the-geology-of-gale-crater-mount

Spock: 10/01/2014 10:44 CDT

Yes David, I read your analyis when you posted it and found it rather interesting. Since most reports in the past about Aeolis Mons stated that it was a very large mound of dust I was happy to see that someone else knew better. Using satellite and Curiosity imagery, I wrote and submitted a report to JPL and NASA in May of this year. It is entitled "Analysis of Gale Crater, Aeolis Palus, Lake Aeolin and Aeolis Mons". You and I have interpreted the data contained within the imagery in a slightly different way. You see Aeolis Mons as a mud volcano formed by an artesian well bringing material to the surface at or about the time Gale Crater was formed. I see evidence that it is a mud volcano formed as the result of a secondary impact within Gale after millions of years of sedimentary accumulations within the rim. Heat from this object or from deep within Mars itself, brought warm mineral rich water to the surface through fissures which eventually produced the 3 mile high mountain. The foot hills at the base of the mountain is material from higher up the slopes that has cascaded down into what I call Black Sand Gorge. this Gorge once contained a body of fresh water which I call Lake Aeolin. If the team climbs the slopes of Aeolis Mons we may be able to see which scenario is correct but it looks as though they will go no higher than these foothills.

DavidPalmer: 10/02/2014 02:28 CDT

Interesting. Do you have your essay published online, such that I could take a look at it? There are specific tests of my hypotheses which the Curiosity team may or may not carry out. I doubt that I have gotten their attention sufficiently for them to change course on my account, but the relevant data may be something they will acquire anyway. I am predicting that 1) the sediments of the Lower Formation will be shown to be lacustrine in nature, 2) turbidite deposits in the Lower Formation should be in evidence, 3) the cosmic-ray exposure age of the channel fill of what I am calling the "Northern Channel" will be shockingly young, probably only several million years, 3) the chemistry of the channel fill will have earmarks of a mineral-rich groundwater origin for the depositing and lithifying water, rather than that water being from atmospheric precipitation, 4) there will likely be materials in the channel fill (clays and sulfates) that are at too high a concentration to be detrital material eroded from further upslope, and 5) the hydrogen/deuterium ratio of mineral-bound water in the channel fill will be markedly different from atmospheric and surface values, again indicating a groundwater origin. The proposed path of Curiosity will take it right next to the channel fill, and it would be a horrible shame if it were not sampled, as I believe it is the key to understanding the entire complex. It is also vitally important that Curiosity samples a clay-and-sulfate-rich trough that lies parallel to the channel, just below the contact with the "Light-Toned Yardang Unit," as its chemistry indicates enrichment that is not in keeping with any upslope source of sediment (possibly a still-active spring is located there?). I would be interested in hearing the specific, testable predictions of your model. I'm not proposing that Mt. Sharp is a mud volcano, that would imply that the sediments constituting its flank have flowed down from a higher point of discharge. It is more correct to say I am proposing that Mt. Sharp is a huge concretion: the water seeping from the artesian hydrant, once it was buried by sediments (sediments which completely filled the bowl of the crater), resulted in the lithification of the aeolian sediments above the Lower Formation, transforming them into a protective cap that didn't extend much beyond the central area of Gale. I am also proposing that the artesian hydrant was not only active in the early history of Gale, but is still occasionally active (hence my predicted young cosmic-ray exposure age for the channel fill). Since the Gale/Mt. Sharp complex is not a one-off, but rather is one of a class of craters with central mounds (Nicholson is another example, and Asimov is apparently on the road to forming such a complex), I would assume that the explanation for its structure is to be found in processes that are intrinsic to any crater of similar size and age and geophysical context, rather than be the result of a highly improbable event (a large meteor impact in the center of a pre-existing crater, which is not something that would be expected to happen many times in the history of Mars).

phenporter: 10/02/2014 08:56 CDT

Quick comment on the drill tailings.... Looks as if there are two types of material coming from both holes. At the end of the first drilling there is a light cone of material - likely from deeper down, and the dark material has been spread out - likely from the upper layer and has subsequently been moved around by the drilling vibrations. Assuming the same is true for the second hole one would expect to see more material from deeper down. All the material from the first hole has been scattered by vibration and it appears the two types respond to vibration differently and are further separated.

TimR: 10/03/2014 09:21 CDT

Stop the presses. Stop the music! Second Curiosity photo of this article - there is a cargo ship grounded in the foreground. The hull is completely blackened, probably the iron is in a reduced state.Definitely send this image to the Mars websites of interest. :) Its remarkable to me how much similarity there is between the rock strata at MSL's and MER Opp's. Each have flat tiled plated areas such as Pahrump Hills or areas traversed by Oppy some exposed by impact craters or local winds. Then also both have the wafer thin sedimentary layers & outcrops such as shown at Upheaval Dome. Why? Same epochs? Long epochs of consistent conditions? For as much indicators of standing and flowing water that there are in Gale, it seems that flowing water and standing water had a lot of time to hand around - to deposit sedimentation consistently over and over again. Also, conglomerate doesn't come cheaply, time wise. To have long periods of standing and lowing water, you need a thick atmosphere. I do not think that flash floods would create what we are seeing. Certainly, there were flash floods that surely rivaled the floods that crossed Washington state to the Pacific from Lake Missoula during the last Glacial. Hmmm, one thing you do not see at Gale that the Lake Missoula floods did have - huge or large boulders carried by flood waters and ice-pack. Palmer. I took a look at your web site. A lot of work, interesting Mars images. I'll read through it.

DavidPalmer: 10/03/2014 09:04 CDT

To TimR: There are 10-meter-wide boulders in the channels on Mt. Sharp, but I wouldn't expect flows large enough to transport boulders out onto the crater floor of Gale.....I am hypothesizing that lakes in Gale filled through the outflow of springs during "thermal excursions," so the flow rate would be limited and it could take centuries to fill Gale to the level that is indicated by terraces and deltas....we're definitely NOT talking about the Lake Missoula type of floods! And yes, my essay took a LOT of work! I have been very interested in Mars since I encountered "The Exploration of Mars" (featuring the artwork of Chesley Bonestell) when I was a young boy in the 1960s, but didn't have much to contribute until, about a year and a half ago, I was looking at photos of Mt. Sharp and trying to understand its strange geology, and it was like a light coming on when I saw the parallels to the geology I was familiar with in California and Oregon, and so I set to work writing, and researching hundreds of articles, and my essay is a result of that effort. And I also have tried to capture the beauty of Mars in my photographic selections....I originally wanted to be a space artist, but that didn't work out, so I had to wait till there was a large enough catalogue of photos available. And like Emily does in her blogs, I'm trying to convey ideas in a way that professional scientists can respect and that educated laypeople can understand (which is where I'm at, an amateur scientist).....while at the same time doing the "pretty picture" thing!

Handee: 10/04/2014 06:43 CDT

With so much riding on the shoulders of the groucers, I have not been sleeping well. Mount Sharp looked a long way away, a few blogs ago, amongst those sharp, pionted, cemented in, stones. Then, Mars lays out it's magic carpet. To my mind, you are telling the best stories in the world. I am completely hooked on the drama, and excitement. Thank you Emily. Thank you Planetary Society. I read all the blogs, and also appreciate fellow comments, content fillers. I imagine there might be the odd retired proffesor adding anonymously, though I suspect Arbitary is not Freeman Dyson. I am a bum. I predict I will sleep well tonight.

Handee: 10/07/2014 04:40 CDT

"Woohoo!" for regolith

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