Curiosity

by Rod Pyle

  Then, after a few more stops, Curiosity will enter the foothills of Mount Sharp. As of now we can only look at orbital imagery and telescopic pictures from Curiosity to try to get a sense of what kind of terrain the rover will encounter, but if what we see is any indication, it will be a grand adventure.

  Fig. 32.2. PENULTIMATE DESTINATION? Curiosity's destination is these rugged foothills at the base of Mount Sharp. The sedimentary layering should keep the rover busy for a year or more. I did not say “final destination” because if all goes well with Curiosity and its nuclear power supply, it should live long enough to cross through the foothills and continue its adventures beyond, perhaps for many years. Image from NASA/JPL-Caltech/MSSS.

  The many stops between Bradbury Landing and Mount Sharp, including Yellowknife Bay and now Kimberley, have pleased Grotzinger. They have also served to validate the contentious debate about landing sites for the mission. He can remember when, during that process, “There were a lot of people that didn't want Gale Crater, that took the rather-pejorative view that [Mount Sharp] is just a pile of windblown dust. ‘You guys are going to go in there and not find anything!’ Now, that could still be the case. But the point is, that pile of windblown dust must have been altered with water because we see clays and we see the hydrating sulfates.” And that alteration is, after all, a driving force of the mission.

  Grotzinger continues: “The question is, are all these layers [in Mount Sharp] a result of wind blowing material around? Or are they a result of water transporting sediments and building layers? Are they a combination of both? What we got in Yellowknife Bay was five meters of stuff that looks like it was pretty much just transported by water, including the possibility of a standing body of water on the lake. But we don't know how the age of those rocks at Yellowknife Bay relate to the strata that make up Mount Sharp. One version is that maybe we have already been at the base of Mount Sharp.” By this he means that what was found at Yellowknife might be very similar to what they will find at Mount Sharp. “Maybe if we could scrape all the dust and the stuff away, we would go look and see the layers at Yellowknife Bay, they just go right down and beneath Mount Sharp, that was the very oldest stuff. There's another version, that there's a big unconformity where layers were deposited, layers were eroded to leave the mound and then the crater rim had its evolution with the flowing water. Then we had the alluvial fan come down and [provide] the sediment that [filled the interior] of the crater. So it could be that the Yellowknife Bay is actually the youngest stuff we'll see there.” So Mount Sharp might be a repeat, in geological terms, of what has already been seen, or it may represent material far, far older than they have examined. We will have to wait until Curiosity gets there to find out.

  And how will the drive into the foothills be planned and accomplished? “I'm setting up a group right now called Mount Sharp Ascent Team,” Grotzinger says. “As much as possible, I will coach some of them myself because it's so important. But the goal of this is to actually quantitatively figure out how the hell we are going to go way up in there.” But they are well prepared. “We did enough work on it to know qualitatively that it is doable. We know the slopes well enough. We know from the surface process materials that even though there is windblown sand there, that if I take the scarecrow [Curiosity's earthbound double] out to the Mohave Desert that we can handle going up slopes of at least twenty degrees. We know that from the HIRISE images that we can work our way up without worrying about any slopes where we get too deep to drive.” It looks like the coast is clear to continue into the foothills once the rover has completed its work at Kimberley and a few successive stops.

  He concluded: “We have a lot to do [to understand] how to use the instruments on the way up there, the materials that we are going to get and how are we going to understand the ancient history of water. Are we going to be able to measure the isotopic composition not just of the water in the modern-day Martian atmosphere, but [of the] rocks and minerals that we are able to place in SAM and so forth? We are still figuring out how to do that.” Then, with a tired smile, he added, “It is never boring. Absolutely never boring. There are times when you can catch me on a bad day, when I have [had] it up to here with MSL…but you will never hear me say it's boring.” He goes on to remind me, and not for the first time, that while he is nominally the leader for Curiosity's study of Mars, the team makes the choices, writes the papers, and takes the hard knocks together…nearly five hundred of them. The message is clear: he is not an emperor, he is not out to seek the limelight. He is here merely to lead the team to consensus and to inspire their best work.

  I asked him to contextualize the foothills of Mount Sharp in a way most of us could relate to. “Well, when we start driving into Mount Sharp we will return to our mission objective, which is to explore these foothills that are about the size of one- to three- [to] five-story-tall buildings with narrow canyons between them. That will be what's it like as we get to that terrain. It's going to be, we think, visually quite beautiful. But those layers that you see there…well, we know from orbital data that they have clays and sulfates. So we hope to be able to able sample a number of what could be different habitable environments.” He sighed. “We have a long drive. We think that it would take…if we stop to smell the roses a little bit, it could take until the end of the operable mission. I know that NASA is going to back us and so we have confidence that we'll continue on with this great exploration mission.”

  Amen to that.

  DAYBREAK AT GALE CRATER: This NASA-created image shows the terminator just crossing Gale Crater (center top), with the mountain in the middle. With vast geological diversity, Gale Crater provided a worthy target for Curiosity. However, reaching it—with a narrow landing zone between the crater wall and Mount Sharp—would be a huge challenge. Image from NASA/JPL-Caltech.

  TUCKED IN: Curiosity as seen at JPL. The rover and descent stage are folded together and tucked into the aeroshell. The bottom will be covered by the heat shield, and the assembly will then be mounted atop an Atlas V rocket for launch. Image from NASA/JPL-Caltech.

  LANDING, REVISED: As the mission specifications changed, so did the landing ellipse, or acceptable range of error. The fainter line represents the old landing ellipse; the dark oval, the newer, far smaller one. Constant improvements in software and engineering meant a more accurate landing. Image from NASA/JPL-Caltech.

  GALE CRATER: A wide overview of Gale Crater. This is a composite image created from data supplied by the orbiters. Clearly visible are the sharply defined edge of the crater rim and the smoother central mountain, Mount Sharp, rising about eighteen thousand feet into the Martian sky. Image from NASA/JPL-Caltech.

  THE FOOTHILLS: Curiosity's ultimate target: the foothills of Mount Sharp. The sedimentary layering can be clearly seen. The rover will have to negotiate the winding pathways between the hills; it will be treacherous driving and slow going. With luck, Curiosity will last long enough to move beyond the mountain when its work there is done, which may take a matter of years. Image from NASA/JPL-Caltech.

  DRILL SITES: The two locations where Curiosity was sent to drill are seen in this image of Yellowknife Bay. John Klein is marked with the green dot, Cumberland with the yellow. The “50 cm” scale bar near Cumberland equates to about twenty inches. The foothills of Mount Sharp are seen in the distance to the upper left. Image from NASA/JPL-Caltech/MSSS.

  GRAY MARS: Finding that the soil on Mars is not an oxidized, rusty red just below the surface was a welcome development. It means that there is a better chance for life to have existed in the past on Mars. This image shows the John Klein test drill hole (upper center), the main sample drill hole (bottom center), and two small mounds of material dropped by CHIMRA after it separated the fine particles it needed for the instruments aboard Curiosity. Image from NASA/JPL-Caltech/MSSS.

  OPEN WIDE: This is the sample funnel for CheMin with the door flap open. The mouth to the funnel, covered with a screen mesh, is about 1.5 inches across. Image from NASA/
JPL-Caltech/MSSS.

  HOW LONG? Robots work more slowly than people do. How long, then, does it take to sample one area? In this case, which was the first set of soil scoops taken by Curiosity and also allowing for a learning curve and system cleaning, it took just over a month. Image from NASA/JPL-Caltech/MSSS.

  OVER THE SHOULDER: Mount Sharp is seen behind the rover as the Mastcam looks over Curiosity's “shoulder.” The nuclear power source, or RTG, is seen looking like a thorax with fins, angled up off the back end of the rover to the right. Image from NASA/JPL-Caltech/MSSS.

  PORTABLE LAB: This is the SAM, or Sample Analysis on Mars instrument. About the size of a small oven, SAM comprises what would have been a medium-sized university lab just a few years ago. Image from NASA/JPL-Caltech.

  CHEMIN AT WORK: These images are the result of x-ray diffraction tests within CheMin. The image to the left is generated from the windblown sand from Ripple at Rocknest, and the image to the right is generated by the drill sample from John Klein. The differences are subtle, but to the experienced eye, it is clear that the John Klein sample contains a lot more clay, which is water-formed. Image from NASA/JPL-Caltech/Ames.

  HARD AT WORK: The drill is seen here working at John Klein. The bit is just above the small gray patch, and the locating/stabilizing posts are to the left and right of the bit. The DRT metal rock brush is visible to the far right, and MAHLI is the gold-colored circular object in the upper right corner. Image from NASA/JPL-Caltech/MSSS.

  FIRST TARGET: The rock Jake, named after deceased JPL engineer Jake Matijevic, was the first rock targeted for examination by the ChemCam (the red dots), as well as “contact science” with the MAHLI instrument and the APXS probe (the lightened circles). Jake turned out to be of a rock type previously not seen on Mars, known on Earth as a mugearite. Image from NASA/JPL-Caltech/MSSS.

  TOUCHDOWN: This artist's rendering shows the moment of contact between Curiosity's wheels and Mars. Within seconds, the rover will send the “fly away” command to the descent stage hovering above and will release the cords, as well as the wired umbilical, allowing the rocket pack to fly off and impact elsewhere. Image from NASA/JPL-Caltech.

  LIKE A JACKHAMMERED SIDEWALK: When Curiosity reached Hottah, it was a revelation. “Hottah looks like someone jackhammered up a slab of city sidewalk, but it's really a tilted block of an ancient streambed,” said John Grotzinger. It was the first conclusive proof of flowing, hip-deep water on an arid planet. Image from NASA/JPL-Caltech/MSSS.

  TEST, TEST, TEST: Curiosity's parachute was a big challenge, as it kept ripping during development. Seen here is a test in Moffett Field's huge wind tunnel, the largest in the world, in Northern California. Image from NASA/Ames.

  SPOTTED: Aiming purely by calculations, controllers of the Mars Reconnaissance Orbiter caught this image of MSL descending to the Martian surface. The rover has not yet been released from the aeroshell. Image from NASA/JPL-Caltech/University of Arizona.

  HOT STUFF: The plutonium fuel source is seen being placed inside Curiosity's RTG power source. It has a half-life of fourteen years and should last longer than that, if the Voyager spacecraft, still operational after thirty-seven years, are any indication. Image from NASA/JPL-Caltech.

  JOY: Mission control erupts into jubilation as word comes back of Curiosity's successful landing. Rob Manning, MSL's chief engineer, is seen to the center left. At the top, turned away from camera, John Groztinger high-fives Pete Theisinger, MSL project manager. Image from NASA/JPL-Caltech.

  IT SAYS “JPL”: A technician inspects one of Curiosity's six wheels. When the scientists wanted a way to count wheel revolutions, someone suggested embossing “JPL” onto the wheels. This idea was reportedly shot down by NASA, so instead the designers cut Morse code into the wheels…code for “J…P…L.” Image from NASA/JPL-Caltech.

  THREE FACES OF MARS: This image of Mount Sharp shows three ways in which images of Mars are viewed and interpreted. On the left, a raw, uncorrected version as it comes from the cameras. At the center, the image has been color corrected to what it would look like if you were standing on Mars. On the right, the image has been “white balanced” in order to see what the formations would look like if seen on Earth. This last technique is particularly useful when comparing Martian geology to formations found on Earth. Image from NASA/JPL-Caltech/MSSS.

  WHERE THEY WENT: This topographical map shows the landing sites of all US missions to land (or attempt to land) on Mars. It also shows topography: blue = lower, red = higher. Curiosity's landing area is circled to the right. Image from NASA/JPL-Caltech.

  MARTIAN SELFIE: Curiosity shot this self-portrait over the course of many hours. The MAHLI camera on the arm had to be maneuvered into dozens of positions, then the images were stitched together to eliminate duplicate parts of the image. The final result is a flawless portrait of the rover after it had taken soil samples at Rocknest. The scoop trenches can be seen to the lower left. Mount Sharp is to the upper right. Image from NASA/JPL-Caltech/MSSS.

  HOW HARD CAN IT BE? To get a rock or soil sample on Mars, that is. Pretty hard, as it turns out. This schematic shows the CHIMRA, the part of the turret that separates and processes the sample before it is deposited into the instruments inside the rover. CHIMRA sits beside the drill, collecting rock powder from the bit or soil from the scoop and then running it through a system of sieves to get ever-finer grains. The arm must be moved into a whole series of positions to process the sample. Image from NASA/JPL-Caltech.

  THE GRAIL: In the distance, Mount Sharp looms over the floor of Gale Crater, which Curiosity is slowly crossing. This image shows little of the dramatic terrain in the foothills (it's too far away), but the dark bands near the center indicate sand dunes that must be crossed en route—always a nerve-racking time for Mars rovers. Curiosity should begin working its way through the foothills by the end of 2014. Image from NASA/JPL-Caltech/MSSS.

  So what revs up the people involved on this mission about the future? What do they dream about at night when they dream of Mars? Or, as Grotzinger puts it, what is their “dinosaur-bone moment” (imagine finding that on Mars…yeah!)? Here is what many of the lead scientists had to say.

  John Grotzinger, Project Scientist: “In Yellowknife Bay where we drilled, we realized that the scent was getting warmer and warmer. We looked at Mars as it changed from red to gray. What we got was an understanding of a habitable environment which is not just another discovery of water…. [It characterizes the] water and rocks that were there to tell us that the simple microorganisms, so simple that they don't need sunlight, they need only chemical energy, could live there.”

  He continued, “This was a truly integrated set of observations—every instrument was involved in this. It all added up to understanding this environment as being chemically one that was favorable for life, [and] not in a harsh way but actually quite a benign environment that was very much like Earth.”

  Scott McLennon, Participating Scientist: “For me the next really big thing is getting on to Mount Sharp, especially now that we have the results from Yellowknife Bay. We found a habitable environment, but the age of it is younger than a lot of us thought it would be—it could be quite a bit younger. As we go into Mount Sharp, the whole paradigm for Mars-system evolution is this idea of a transformation from a relatively wet, benign setting to a much more arid, dry, and acidic environment. That transformation is supposed to be recorded in the layered rocks in Mount Sharp…to those of us who work in terrestrial geology, there's [a] sort of symmetry in the history of the two planets, and that's very exciting.”

  John Grotzinger again: “The story of MSL is that the increase in capability [of the rover and its instrumentation] leads to a scale of complexity that takes a toll on humans…it's tiring, it's exhausting. But we are all committed to it because, thank God, the rocks delivered…. There's a ton of cool stuff that we can learn about the atmosphere of Mars, but at the end of the day, if it would have [gotten] down into Yellowknife Bay and found a bunch of unaltered bas
alts [vanilla Mars rocks] there, it would have been a tough moment for the mission. Because then what do we have to show for the first year of operations? As it turned out, we got really lucky and it all worked out. In fact, I wouldn't say it was pure luck, I would call it…serendipity.”

  Ken Edgett, Principal Investigator for MAHLI: “Think of the Martian [history] as a twenty-four-hour clock and right now, this moment, is just some tiny fraction microsecond before midnight of the next day. The rocks that we were looking at and exploring in Gale are back somewhere around in the 3 a.m. to 6 a.m. time frame of Mars history. It was a very long time ago, so Mars was a different place. At that time there were large craters forming more frequently than [there are] now. And there were volcanoes erupting, and all of those things produce sediments. The atmosphere was thicker, and wind transports sediment. We now think, and know, from all the missions over the last fifteen years that there was [also] water.”

  Edgett sees Mount Sharp as I described it—like a sort of time machine to go back to that ancient, earthlike Mars. “We can go there and see not only that there are habitable environments recorded there, but we can witness how these environments changed over time. As we go up the mountain we will see the time get closer and closer to now; what we see will be younger and younger.”

  David Blake, Principal Investigator of CheMin: “The next big thing that the community wants to see is the return of the Mars sample to be analyzed on Earth. That is a tremendous added value in itself, it is a tremendous undertaking. The Mars 2020 mission would take a Curiosity-class rover and land it on the surface and find habitable zones as Curiosity did, then collect drill cores that would then be placed in a returnable cache that would be collected by a second flight that would land and take that second cache of material and bring it back to Earth.”