Curiosity: One Year Later
- Created: Sunday, 01 September 2013
On August 5, 2012, the Mars Science Laboratory (MSL) rover, Curiosity, landed in Gale Crater in a perfectly executed procedure originally referred to as “7 Minutes of Terror.” A year into its two-year exploration of the Red Planet, Curiosity has already achieved the major goal of its mission.
Last year, NASA Tech Briefs spoke with members of the MSL team just two weeks before the historic landing about what NASA hoped to find, the technologies used onboard Curiosity, and how the mission was expected to progress. Here, we revisit MSL team members and program executives to get updates on the current state of the mission.
Our MSL “all-star” roundtable includes Dr. Jim Green, Planetary Science Division Director; Dr. Michael Meyer, Lead Scientist of the Mars Exploration Program and Program Scientist for the Mars Science Laboratory; and Adam Steltzner, Entry, Descent, and Landing Phase Lead.
NASA Tech Briefs: Let’s start at the beginning, before Curiosity landed last August. Adam, as an engineer, how do you begin the process of designing the components necessary to complete entry, descent, and landing (EDL)?
Adam Steltzner: The process was trial-and-error. It had a lot of dead-ends. We started out trying to use techniques we had used in the past, and we were not successful with that, which forced us into more innovative directions.
We couldn’t put it on airbags, because airbags scale poorly. They are very massive and there is no fabric known to humans that is strong enough to make airbags that would survive a rover that size. We thought about legged landers like Viking, and just putting it on top. But the loss of the Mars Polar Lander in 1999 and the subsequent failure analysis underscored some of the sensitivities of legged landers to slopes. When you put a big, heavy rover on top of it, it becomes even more unstable, so we took that out of consideration.
So we came back to the problem in the fall of 2003, and we had a brainstorming session, and we looked at a lot of ideas, including those we had rejected previously. And out of that came the sky crane. It’s the first time that was used.
The sky crane was only one piece of the puzzle. We had aeroshells, an entry vehicle, parachutes, and at the very end, we have touchdown. And how you assemble that into a whole system architecture is also something that evolved. We try to keep it as evolutionary as possible, because you’re trying to minimize risk. Operationally, a failure in one system, and we’re dead. So what you want to do, from a development perspective, is to compartmentalize everything so that if there is a problem in the development of one of the subsystems, it doesn’t upset the boundary conditions of all the other subsystems so the entire system design falls apart.
NTB: We all remember the “7 Minutes of Terror” video (www. techbriefs.com/tv/7minutes) describing the EDL phase. Was it possible to test, on Earth, all of the tightly choreographed steps of EDL?
Steltzner: We could not test on Earth the entry, descent, and landing. So that again focused our attention on the architectural choices we make and how we do each of the pieces so that they are as independent from one another as possible. So we break the system up into pieces, and we string together this collection of testable, analyzable elements into a system simulation that we do on a computer.
NTB: Was MSL the first planetary mission to use guided entry?
Steltzner: We used guided entry in the Apollo era for Earth return, but it’s certainly the first autonomous, robotic-only application, and the first application outside of Earth.
NTB: Was that used because you had a much smaller targeted landing ellipse?
Steltzner: That’s kind of a chicken-and-egg question because we actually picked that landing location because we had guided entry. We employed guided entry because we were trying to advance the technology of landing on Mars to allow us to land in places like Gale Crater.
NTB: Adam, you said “the biggest surprise about EDL is that there were no surprises.” I’m sure your team went through every scenario and how to correct or avoid them, but were you still expecting something to go wrong?
Steltzner: I couldn’t emotionally believe that it would work. It was our duty to figure out how it would break, and fix that. If you relax and actually imagine that it will work, you’re letting down your guard. I can remember the feeling of disbelief – “it’s really going to be this easy?”
After the fact, we discovered a surprise. There was a gravity anomaly at Gale Crater, and because of that, we landed slower than we had thought, but only three one-hundredths of a meter per second slower. So it wasn’t that big of a surprise.
NTB: What did MSL’s instruments tell you about the trip to Mars that you didn’t know from other missions?
Dr. Jim Green: It told us a lot about the trip there and what its like on the surface. The RAD detector saw several solar proton events and measured them from inside the capsule that housed the rover, just as if a human would be in an Apollo-like capsule on their way to Mars. In studying those data, it appears to be a very survivable trip. The surface of Mars also receives high-energy particles, but its flux is only half as much as found in space because the planet obscures half the sky. Unfortunately, the atmosphere is not much help in retarding the radiation. But building and using a shelter underground on Mars will provide substantial protection from harmful high-energy radiation. All that’s very important information that we didn’t have before.
Steltzner: We learned that the heating was not as bad as we feared it might be. We had margined our heating predictions to account for things we didn’t know or understand. And we found through those measurements that we didn’t need to margin them as heavily as we did.
We also found that, largely, the aerodynamics of the vehicle were as we anticipated. We found thermodynamics that we were less accurate in predicting. The instrument suite we took to Mars previously was focused on the hypersonic and high supersonic flight regimes, and because of that, it was not designed to get good data in the low supersonic and subsonic flight regimes. So when we go next time, we’ll want to have low supersonic and subsonic flight focus on that instrumentation package.
NTB: So let’s fast-forward. Michael, two weeks before Curiosity landed, we talked about what NASA hoped to find with this mission, and how you expected the mission to progress. Can you update us on both of these things after a year on Mars?
Dr. Michael Meyer: It’s one of those things where when the mission is getting ready to land, all you care about is that it lands safely. There is a real conservatism in making sure you don’t overpromise or dare to hope that you’ll realize all your expectations. And in Curiosity’s case, it’s just been fantastic in terms of landing within 500 meters of what looks like a triple junction of three different geological units — the blast from the retrorockets actually exposing some bedrock — to having the purpose of the mission to determine whether or not the region of Gale Crater has ever been habitable. And to have that decided within the first half-year of the mission is fantastic.
Looking at rounded pebbles that form what we call conglomerates is visual proof that there was water flowing on the surface of Mars near the base of Mount Sharp. That’s like, wow. Already, it’s turned out very well. The fact that we landed and headed almost in the opposite direction to the entrance to Mount Sharp, going to Glenelg, and finding that low-lying area has been scientifically very promising and very challenging, too.
In terms of the science, and our expectations of the region and what we hope to find, it’s been really panning out. We’re just now headed back to sort of the prime target: the layers at the base of Mount Sharp.
Green: Curiosity is all about going to a place on Mars that hasn’t changed in several billion years. Curiosity landed in an ancient lake bed where flowing water perhaps for millions or hundreds of millions of years rounded pebbles, created conglomerates, just like we see in stream beds here on Earth. When we bored into the rock in that region, the material that came out of the hole is not red, it’s gray. Where is red Mars? It’s on the surface. But inside the rock, it’s gray and it’s full of the materials necessary to support life. We could drink the water if we were there at the time it flowed on the surface. In other words, Curiosity found an environment on Mars that was potentially habitable in its past.
That is an absolutely sensational set of observations, and we’ve done those already. Now we’re heading to Mount Sharp and we’ll stop along the way and find interesting things. But what’s critical about going to Mount Sharp is that it has an extensive layered geology. We can see this stratigraphy from orbit. By making measurements in each layer we will uncover how Mars has evolved over time.
The number-one science question for MSL was to assess and determine if Mars had a potentially habitable environment in its past, and it’s already answered that question. The answer is yes.
Meyer: The other thing is that the instruments are doing great — just fantastic. They are all working; they’re all getting data. Some of the instrumentation is kind of new in terms of how you go about using it to explore, and it’s been working very well. That’s been fantastic also. It’s interesting that in theory, we kind of understood this, but in practice it’s much harder than we expected. That is, how do you use all these instruments while you’re roving around on the surface and trying to get samples to feed into the analytical laboratory?
One of the challenges and the thing we didn’t expect to be this difficult is coordinating all the instruments so each Sol you’re getting lots of things accomplished. Of course, in the beginning you want to be extremely conservative, so most of the measurements we’ve done, we’ve done sequentially. We’re now getting used to the idea of doing measurements simultaneously because we’re confident in the instruments and how they work, how much the power draw is, what the timing is for different aspects of it. So one of the things that will be fun as we go forward is looking at improvements in the efficiency of all the things we measure in any one science spot.
NTB: How far has Curiosity traveled to date?
Meyer: As of tosol(330), 906 meters were on Curiosity’s odometer.
NTB: Is that a reasonable distance almost a year into the mission?
Meyer: In one aspect it seems painfully slow. Another part is that we’ve gone through all the instruments, we’ve done measurements, we’ve already accomplished the primary goal of the mission, and we’ve explored a place we didn’t expect to explore when we were planning the mission — and that is the area around Yellowknife Bay. Right now, what’s nice is that the science team is busy writing their science papers about that area and what they’ve learned, and all the things this tremendous rover has put together in terms of data sets and how they’re related. We sent an instrument that’s new to planetary science, ChemCam, which is a laser-induced breakdown spectrometer, so matching that up with what other measurements have been made that are more traditional, such as the Alpha Particle X-Ray Spectrometer, gives us a great match across the board as to what we are seeing remotely and what we end up actually sampling.
So thinking about all that’s been accomplished, the rover has actually been busy doing samples and running the analytical lab. The distance traveled is not really that important.
NTB: Any surprises from the samples obtained so far?
Meyer: Probably the biggest surprise is the one that was most obvious. That is, as soon as they drilled a sample, you went from red Mars to gray Mars within the first several millimeters. The importance of that is that you’re sampling in a neutral area of Mars in its ancient environment, not the acidic Mars that we see today, but it also is encouraging in that one of the big concerns of exploring Mars is the fact that it’s a different planet today than it was early in its lifetime. Whatever’s going on and oxidizing everything on the planet and turning it acidic may permeate through the rock record. Even in an environment that was neutral deposited rocks and they were left in a pristine state, as Mars changed, maybe that oxidizing capability that was happening at the surface may permeate down and alter the rocks and potentially destroy any reduced compounds that might be there, including organics.
Mars has a “good news, bad news” kind of thing, and that is since early on in the planet, it seems to have stopped plate tectonics if it had any. Approximately 50% of the planet has ancient rocks on the surface — the same rocks laid down 3 to 4 billion years ago. Because of that, you have lots of rocks to choose from to sample that give you a window into what the environment was like early in the evolution of Mars. So Mars has the best sedimentary record of what was going on in our solar system in the first billion years, and that includes the period when life started on Earth.
NTB: What did Spirit and Opportunity teach you that helped make Curiosity better?
Green: When I look back and see what Spirit and Opportunity did, I believe they provided one essential element immediately. That was ground truth. Even here, when you have Earth science missions that fly over regions and take images in different colors, and they have certain signatures, they need someone to go out in the field and say “I’m standing in a field of corn.” Those signatures that say this is corn, they can look anywhere else, getting the same signatures, and make the assumption it’s corn. That’s called ground truth. Spirit and Opportunity gave us a great set of ground truth. It then enabled us to interpret observations from our orbiters about where the next best landing place would be, and that pointed to several places.
Combining our ground truth data with our orbiter images we could see at the base of Mount Sharp what we thought was clay. That’s important because clay gets laid down in water. It’s also important because some theories on the formation of life within water start out by first attaching to a surface, and clay is a perfect surface to use.
NTB: We’ve seen the high-resolution color images that are just incredible. Have the images obtained so far by Curiosity’s cameras exceeded your expectations?
Meyer: The images have been fantastic and there are some practical reasons. One is that we landed in a pretty cool spot, so you have topography to look at, and that’s extremely interesting. But more importantly, the cameras are amazingly capable. They are such a high resolution that it’s spectacular.
The other aspect of the cameras that I did not fully appreciate until we got into operations is that it’s designed to take a spectacular panorama and store it and then send back thumbnails of the images you took. That has been a real boon in terms of science discussion, understanding where you are and what things may be more or less important in terms of targeting.
I want to complement the imaging team for putting the images out there. It is their data, but I think it’s been tremendous in helping to bring the public along with our thrill of exploration. They can see where we are and what we’re looking at and almost at the same time, the public and the scientists see something in an image and wonder what it is.
It’s a tremendous effort in coordinating the whole thing. It really is pretty amazing to think of it. The science team is over 400 people. Just getting everybody to participate in the science team discussions and remain on target as far as what our plan is and how do we move forward. That’s been exhilarating and a challenge. I think we’re really lucky to have everything working, and now we have this tremendous asset on the surface that now can just rove and do the science. It’s wonderful to be in that mode.
Steltzner: There is one point that is very important, that I think people sometimes miss. A job this size and this complicated is fundamentally bigger than one person, two people, or ten people. The fact that it worked is a triumph of teamwork. It really is all about the team, and the capacity of a very talented group of people to work together under very stressful conditions, and keep their heads screwed on straight. I think that’s something that frequently gets under-appreciated. People focus on the design itself, but the human aspect of it and the absolute rigorous requirements on high-performance teaming cannot be undervalued. That’s perhaps what I’m most proud of — the way the team performed.
Green: This project is so uniquely NASA. This is so uniquely the can-do spirit that this country has. It points to us as examples of what we can do, what we aspire to do, and the accomplishments are unbelievable.
Watch a video of the rover’s eye view of driving, scooping, and drilling during Curiosity’s first year on Mars, August 2012 through July 2013, on Tech Briefs TV at www.techbriefs.com/tv/curiosity-firstyear. Keep up with Curiosity as it continues its journey, and learn more about the next Mars mission, at http://mars.jpl.nasa.gov.