Photograph by Gregg Segal
Growing up in rural Tennessee, I was always fascinated by space. It probably had to do with watching the Apollos as a boy and dreaming of being an astronaut. When I was in high school, I started to realize that I was more interested in building the machines—in being an engineer—than in being a real scientist. Almost all of the people who the public calls “rocket scientists” actually consider themselves to be engineers. If you study rockets, you’re an engineer, and if you’re a real scientist, you don’t study rockets. So when you use that phrase, both the scientists and the engineers kind of cringe. People who consider themselves scientists tend to see the world as a question to be answered. Engineers tend to see the world as a problem to be solved.
My job involves working a lot with scientists. Scientists tend to be unfettered by the practicalities of how anyone’s going to build the system to make the measurements that they want. They don’t shy away from telling you, “This is what I need the mission to do. You guys go figure out how to make that happen.” At the Jet Propulsion Lab, I lead the advanced studies for all of the robotic missions NASA is considering sending to Mars in the latter half of this decade and beyond.
I’ve worked at JPL since I graduated from college in the early 1990s. JPL is where to go if you want to explore planets beyond the moon. It’s pretty much the only place outside the former Soviet Union that’s got a track record of doing those kinds of missions. I’ve been involved in half a dozen or so missions in my career, and each one of them has been akin to Admiral Byrd’s or Ernest Shackleton’s, someone setting off on a mission of exploration.
The first project I worked on was called Mars Observer. It was very expensive. Things went more or less as we intended for the better part of ten months—from the launch all the way out to Mars, when the Observer was less than a week away from going into orbit. The spacecraft had been in hibernation mode, and there was a guy responsible for controlling it as we were bringing the propulsion system back up. I had the shift after him. I showed up early and was on console—you know, the guy talking with the headset on. We were waiting to bring the vehicle out of hibernation and put it into orbit. The last commands to make it all happen were sent, and the radio signal winked out. We never established contact with it again. And so, there it was.
You don’t ever think that you could come into work one day and the thing you worked on yesterday isn’t there anymore. There was a huge failure investigation. I was answering all these questions—a lot of “What were you guys thinking?” “How did you test this?” Bottom line, there’s never a definitive way of determining “This is what did it in,” but the odds are that a leakage between two parts of the propulsion system caused it to explode just prior to going into orbit around Mars.
When your first project is a total loss—I had three years invested in it, and there were people who had much more than that—it colors your perspective. You get a proper paranoia. You send people out—“OK, go study this area and come back with three different designs about how you might solve that problem”—and then the people at the level I worked at look at the pros and cons of each design and say, “This one’s probably the best, but have you thought of a different way of doing this?” You want as many people as possible checking the work and testing the hell out of it. You realize how many other people’s work you are dependent on to make the whole a success. It can be a humbling experience.
Systems engineering, my specialty, focuses on how you subdivide the space vehicle’s job—what the thermal system has to do, what the computers have to do, what the radios have to do—and decide on the different ways of solving a problem. Does it make sense to create the vehicle so that it can land on top of a rock and deal with leveling itself once it’s on a rock? Or does it make more sense to make the vehicle so that it sees the rock and avoids landing on it? You take a problem that looks intractable and break it into pieces that are a little bit more tractable, and then you do that again and again until you get to the point where somebody can look at the problem and say, “Yeah, I know how to build that piece.” The thing about engineering—particularly space engineering, particularly Mars space engineering—is there’s a right answer and there’s a wrong answer, and at the end of the day it either works or it doesn’t work. One way or the other it will be on the front page of the paper, so you have to be prepared to deal with that, to learn from your mistakes, and to come back and try it again.
Going into deep space, the time it takes for radio signals traveling at the speed of light to get from here to there means that at some point you have to trust the vehicle to make decisions for itself. If you send a spacecraft a set of commands, you have to wait for it to acknowledge them and send back the results. It’s like playing chess by mail. If you send the wrong command, by the time you realize what you did, it’s all over. That’s driven the people around here to invest the machines with a certain level of intelligence and sophistication that makes them more self-aware and truly robotic than a lot of the other systems we work with—ships that make their own decisions and deal with contingencies and anomalies that happen on board. When you talk about flying these spacecraft, it’s months of boredom punctuated by minutes of terror. When a rover crashes through the atmosphere of Mars to land on the surface, it’s all under the vehicle’s control. You’ll hear at the other end whether it worked or didn’t work.
A surface mission in the 1990s called the Mars Pathfinder was the first to use air bags to absorb the shock of landing on Mars. The vehicle was encased in them so that when it hit the surface of Mars, it bounced around until it came to rest. We used the same technology for the Spirit and Opportunity rovers, which were launched in 2003. I was in a position similar to the one I am in now. But the rovers were a lot heavier than the Pathfinder, and there were challenges in making the bags big enough to protect the rovers when they smashed into the surface of Mars. So there was some sleeplessness associated with the landing.
Once they’re on the surface, rovers rove. They lift themselves up out of the air bags and head across the plains to do their science mission, driving from one set of rocks to the next. When the rover gets to a pile of rocks, the scientists come in and specify what measurements to take and what rocks are the most interesting to study. After they’ve exhausted a certain rock pile or geological feature, they’ll say, “OK, now let’s spend a couple of weeks or a couple of months going to the next rock pile over here,” based on the pictures we send back from the orbiters that are flying over the planet.
We had expected the rovers to operate for about 90 days before the day-night, cold-to-not-so-cold would cause chips to start popping off the computer electronics board. But we didn’t take into account that there’s a windy season several times a year that cleared all the dust off the vehicles’ solar panels. As a result, we had a lot more electricity to work with on the rovers than we thought we were going to have, and we were able to put more of the electricity into the vehicle’s thermal control. So chips never ended up popping off the board as expected, and the pair operated for six Earth years. Opportunity is still going.
The Curiosity is our new rover. It has been in the works since 2002. I was the chief engineer for this development until Christmas 2008. One of the most exciting features of the Curiosity is it will be able to send out a laser beam to zap a piece of rock and vaporize it. The color of the light coming back from the vaporized rock (it’s kind of a fingerprint—each mineral has a different fingerprint that you see in the spectrometer) connects to a chemical analysis of what the rock is made of without ever getting near the rock. It’s a way to quickly analyze a lot of different rocks at the same location before deciding which are the most interesting to drive to for more detailed measurements.
The heart of the science on this mission is a couple of instruments in the rover that are each the size of a large microwave. They take rock that’s been finely ground and sieved, then they do measurements that answer questions about what Mars was like 3 billion, 4 billion years ago. Because of those two instruments, this rover can’t land with air bags. It will sit inside the rocket’s nose cone when it launches, and the air bags that would be required to support a rover this heavy would be too big to fit in such a space. So we concluded that it would be more cost effective to invent a rocket-powered helicopter—a sky crane—than to build a new rocket that has a bigger nose cone.
The rover sort of flies itself across the solar system. When it reaches Mars, a kind of sacrificial “life-support” system gets jettisoned and burned up in the atmosphere, and everything inside the heat shield of the entry capsule goes through the atmosphere. As the entry capsule slows, getting close to the speed of sound, a parachute comes out the back. The heat shield pops off. The rover sends the commands up to the sky crane, which will lower the rover to the planet’s surface using cables. When the rover is on the surface, it tells the sky crane, “OK, I’m done with your services. You can fly off and crash.”
At some point we’d love to see a human mission to Mars, but it’s getting harder for me to imagine one happening during the course of my career. Going to Mars, collecting samples, and bringing them back is about as complex a mission you would try with robots. It’s one of the concepts I’m working on, and it’s how we’d lay the groundwork to enable humans to sail to the other side of the solar system, land on another planet, and provide a way for them to get safely back.
There’s a line of questioning that goes, If humans ever needed to go to Mars, if we needed to leave this planet and learn how to live somewhere else, what would we need to know in order to make that possible? It’s a problem to be solved, and that’s what engineers do. We solve problems. How would you design a vehicle to keep humans alive as they cross deep space from Earth to Mars and make sure that they stay healthy, that the effects of low gravity don’t cause their bones to deteriorate, that the radiation they’re going to be exposed to in deep space doesn’t cause them genetic damage, and then put them on the Mars surface and return them to Earth? Those are challenges; those are feats to be accomplished on the same scale or much greater than the scale the nation committed to in the 1960s.
The main emphasis of the Mars program is understanding how the planet has changed over time, what it was like in the distant past. Plenty of data suggests that Mars was a lot more like Earth than it is now, that the atmosphere was thicker and there was running water—and standing water. Scientists have been able to analyze some of the minerals on the surface of Mars and show that these minerals don’t only form underground; they have to form in standing water that has been present for some time. If Mars had enough of an atmosphere and was warm enough to keep water standing, well, was there life? If not, why? And if there was, what happened to it? How did the climate of Mars evolve over time, and what caused it to take the path that it has taken?
When you get into issues like global change and what are we doing to this planet, a really important question is, How can things like most of the atmosphere and whole oceans run away and escape into space? That’s what looks like happened to Mars. There’s plenty of data about climate change, if you’re inclined to believe data and work with facts and scientific measurements. Pretty much everyone who’s coming from that kind of quantitative background doesn’t engage in the debate about whether or not it’s happening but rather what to do about it and how bad it will get before we can do something to stop it. Whatever occurred on Mars didn’t happen because factories were overpolluting. There’s a second level of discussion about how either to halt what’s happening or to slow it down—and how to do that through policies, dealing with human beings and the way they make decisions.
If it turned out Earth was a fluke, that life only exists here, then we have a very different set of responsibilities and we should have a different attitude toward the rest of the universe. But I have a hard time believing there’s anything that special about this planet that would make it the only place with life. I have enough of a grasp of the number of stars in this galaxy, the number of those stars that have planets in this galaxy, the number of those planets in this galaxy, the number of those planets likely to have atmosphere and terrestrial surface in this galaxy, and the number of galaxies, that I can’t imagine it could only happen once. For me it’s a no-brainer. I don’t want to taunt anybody into a debate, but a preponderance of evidence suggests there should be life somewhere else in the universe.
We see a wide variety within life that exists on this planet. There are a bunch of things that are different. At each level you step back and ask, What do they have in common? Forget the difference. What is it that makes all living things the same? What is it that makes all animals the same? What is it that makes all plants the same? Whether it’s animals and plants, which are made out of cells that have a nucleus, or bacteria that don’t have a nucleus, they all use DNA to make amino acids. And as far as this planet is concerned, everything that moves and replicates does so based upon DNA.
This concept of life on Mars speaks to the human being in me, and I would hope that it speaks to the engineer in a lot of people. If we find life on Mars, I think the next question is whether or not that life is based specifically on DNA and RNA—the exact same chemistry that Earth life is based on. If it is the same, how did that happen? Did it spontaneously occur exactly the same way? And if we went to another planet after Mars and found life there, would it be the same, too? And is that the only way life can get started? Does it have to combine in the specific chemical way that it happened here, or are there other ways to imagine it?
If we find existence of variations, that will raise questions at a fundamental level about what life is. What is it that we mean when we say “life”? What is it that we mean when we say something is alive? Or if you find it on Mars and it’s based on something totally different from DNA—my God!—then you have to say life could happen anywhere. That to me is just fascinating. I can’t do that science, but I can help build machines that will help the people who can do that science get the data they need to answer those questions. If that’s what I was put on this planet to do, I’m OK with that.
Looking For Signs Of Life
Seeing Red: JPL created the image with a model of Spirit and footage of Mars’s “Husband Hill”
In 1964, the Mariner 4 launch marked the first successful attempt to send a ship to Mars. Images from its flyby offered an unprecedented glimpse into deep space. With 1969’s successful Mariner 7, it was official: The Mars program was on its way.
1971: The same year Mariner 8 plunges into the sea on takeoff, Mariner 9 soars. It provides more than 7,000 images, showing signs that water once flowed on the planet’s surface.
1975: Viking 1 lands successfully on Mars, four years after a short-lived Soviet craft did. Viking 2 launches in 1975 as well. It operates for more than four years; the Viking 1, for more than six.
1992: After a 17-year hiatus and talk in the ’80s of closing JPL to cut costs, the $813 million Mars Observer launches. It vanishes near Mars. NASA adopts “faster, better, cheaper” as its m.o.
1996: Mars Global Surveyor begins its mission. It will return masses of data, including images of gullies and remnants of debris flows. The ship goes silent in 2006, years beyond expectations.
1997: Pathfinder lands using a new technique: airbags to reduce impact. The vessel carries with it Sojourner, the first robotic rover to explore the planet.
1998: Mars Climate Orbiter burns in the Martian atmosphere due to a basic mathematical error. Polar Lander fails the next year. NASA soon jettisons “faster, better, cheaper."
2001: Mars Odyssey locks into orbit. Its images provide the most detailed global map of the planet, revealing swaths of frozen subsurface water in the northern arctic plain.
2004: Rovers Spirit and Opportunity land on Mars using airbags. They were intended to last three months. Spirit went into hibernation mode only last spring; Opportunity rolls on.
2006: Mars Reconnaissance Orbiter becomes NASA’s sixth spacecraft in orbit around the planet and has sent back more information than all other Mars missions combined.
2008: Phoenix Mars Lander descends to the Red Planet—the sixth craft to do so successfully—and discovers ice while digging with its robotic arm. It is declared dead in May 2010.
Photograph courtesy (Seeing Red) nasa/jpl—caltech/cornell, (below) nasa/jpl/caltech; nasa/jpl (2); nasa/jpl/malin space science systems; nasa /jpl (2); nasa/jpl/arizona state university; courtesy nasa/jpl/caltech (3)