Courtesy of Norman Seeff/NASA/JPL
In January the Mars Exploration Rovers Spirit and Opportunity touched down, the first time since Pathfinder in 1997 that humans have had a mechanical representative on the surface of Mars. In short order the rovers found proof of past water on the planet, including minerals that can form only in the presence of water, and ripple patterns in fine-grained rocks shaped by sea currents. Steve Squyres oversees the science operations of both rovers and a team of 170 researchers at NASA’s Jet Propulsion Laboratory. He is a planetary scientist with special expertise in Mars, Venus, and the satellites of Jupiter. Squyres received his Ph.D. from Cornell University in 1981, then spent five years as a postdoctoral student at the NASA Ames Research Center before heading back to Cornell, where he is a professor of astronomy. As a graduate student, he was a member of the imaging team for Voyager’s encounter with Jupiter. Later he served as an investigator on the Magellan mission to Venus, the NEAR (Near Earth Asteroid Rendezvous) spacecraft encounter with the asteroid Eros, and the Mars Odyssey mission. He is the former chairman of NASA’s Space Science Advisory Committee.
What do you hope to accomplish with the current Mars exploration missions?
S: The objective is to learn whether Mars ever had conditions at its surface that would have been favorable to life. Mars is a cold, dry, miserable place now, but we have tantalizing clues, mostly from data taken from orbit, that suggest that in the past it may have been very different—warmer and wetter and more Earth-like. So we’ve landed in two places that might have been warmer and wetter in the past.
Have Spirit and Opportunity provided the kind of data you hoped to obtain?
S: Oh, yes, very much so.
Are you satisfied?
S: No. I’ll never be satisfied until we understand the whole planet. But it is very gratifying to have it work out this well. We went to Mars seeking evidence concerning whether or not it once had liquid water and a habitable environment, and I think we’ve found a definitive answer to that question.
What can’t the missions do that you wish they could?
S: Bring back samples. If we found some place that was really interesting and looked like it might have been favorable to life, we’d love to be able to gather up some samples and bring them back. That has to wait for a subsequent mission.
What is the most exciting result so far?
S: Opportunity’s findings at Meridiani Planum. We have compelling evidence that the rocks are made of sulfate salts, to the tune of 30 to 40 percent by weight—an enormous amount—including one mineral that requires water for its formation and actually contains water itself. What is even more intriguing about this stuff is that because the minerals precipitated from liquid water, they may preserve what was once in that water. If there was some biochemistry, if there were microorganisms present, those minerals could trap evidence of that for a long time. The best way to definitively detect that would be to bring the rocks back to a lab on Earth and take them apart.
What is the biggest surprise?
S: I’ll be honest with you: I almost feel that the biggest surprise is just how well everything is working.
You can say that after the Spirit scare?
S: That was pretty scary, but the spacecraft was in a lot less danger than it seemed it might have been at the time. It is an incredibly robust vehicle, and it really does a very good job of looking after itself. Saying I’m most surprised at how well everything is working is sort of a flip answer. Really, I think the biggest surprise has to be finding that bedrock outcrop at Meridiani Planum. It was an astonishing stroke of luck to have rolled into that crater. In my fondest dreams I sort of hoped that we might be able to find a good bedrock outcrop somewhere, but I thought we were going to have to work hard to find it.
So what else has been scary?
S: The landings, of course, were tense. I had a lot of confidence in the design, but the fact of the matter is that Mars can always get you. Our design could have functioned perfectly and still one inopportune gust of wind or one big sharp pointy rock in the wrong spot, and you’re done. I’ve got to tell you, to me the scariest parts came before we launched—when we were bursting air bags, when we were ripping parachutes, when we blew a fuse inside one of these vehicles and, as we analyzed what happened, realized that we might have a fatal flaw in the design of the pyrotechnic system. The thought that “My God, we might not even make it to the launch pad”—that was the worst.
At the beginning of the mission there appeared to be a giddy exuberance. Has the excitement worn off?
S: It has mounted. People are walking around two feet in the air. What you saw on television at touchdown was a combination of scientific excitement over what we were seeing and just pure excitement that we had landed successfully. Now it is just pure science, and if anything, the scientific excitement level is significantly higher than it was.
You seem to go out of your way to talk to the press and the public. Why?
S: This is something I feel passionate about. The American public has spent $800 million to enable this mission. I believe very firmly that those of us who have the enormous privilege to actually participate in this have an obligation to share this experience, to the greatest extent that we can, with the people who have made it possible—and to do so in a way that is not heavily laden with scientific jargon and not obscure and difficult to comprehend. We are not doing anything that is so esoteric and so complex that you can’t explain it to people in a very straightforward fashion. I think we are conducting a fantastic, fabulous, and exciting voyage of exploration and discovery, and we have all the tools that we need, via the Internet and via the media, to take the entire world along with us.
In your mind, when did the rover missions become successful?
S: I have always had two different measures of success. We have achieved one and not yet the other. This is not NASA’s definition of mission success; this is Steve’s definition of mission success. What we have not yet achieved is to work these vehicles and these payloads so successfully that we have learned everything we are capable of about the places where we touched down. The other measure of mission success was getting 12 wheels in the dirt with two healthy payloads. It was such a rough ride to get these missions built. Technically, these were incredibly challenging spacecrafts to build and deliver. What the team here at the Jet Propulsion Lab pulled off was astonishing and magical.
Can we answer all our questions about Mars with unmanned robotic missions, or do we need to send people?
S: We need to send people. There is nobody who is a bigger fan of sending robots to Mars than me. That is what I do. But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans. Maybe you can argue that if you spend enough time and effort and money on robotics, eventually they’ll be able to mimic human capability, but I think we are so far from that that ultimately sending humans would be the right thing. The sooner the better, as far as I’m concerned.
So why not skip all these incremental robotic missions and throw that money into a dedicated program to send humans to Mars?
S: There are two answers. One answer is that it makes sense, before you commit the enormous resources necessary to send humans, to learn enough about the planet so that when humans get there they can use their precious time and capabilities most effectively. Mars is an incredibly diverse and complicated place. If you have to pick one place to put humans down, where is the best place? If you pick wrong, you’ve wasted a lot of money. So it makes a lot of sense from a scientific standpoint to do precursor missions. Secondly, there is the simple reality that sending people to Mars will require an enormous amount of political will and commitment of national, and probably international, resources. If we’re not ready to do that yet, the way to make progress toward that goal is to explore the planet robotically.
