About eight months ago, just a few days after Thanksgiving, a NASA Atlas V rocket launched the Mars Science Laboratory rover Curiosity from the tropical coast of Cape Canaveral toward its August 5 encounter with the Red Planet. Now, just a few weeks before the rover is set to land, Mars is getting bigger in the proverbial windshield, and people are starting to get nervous and excited.
Landing a robot on Mars is no trivial thing. The Russians have tried it six times and have never succeeded. NASA, in contrast, is six for seven, with just one landing failure: Mars Polar Lander in 1999. Curiosity will be NASA's eighth and by far most ambitious attempt at revealing, up close, the secrets of our most Earth-like of planetary neighbors.
Space missions, whether robotically tended or human-crewed, have to deal with a number of critical mission events as they unfold. One of the most violent, and risky, is the launch -- when million-pound rockets push their payloads with tens of thousands of pounds of thrust beyond the escape velocity of our home world and out to destinations beyond. Shock waves, vibrations, and crazy accelerations, not to mention the risk of a catastrophic explosion, could all end a space mission in seconds. But, luckily, this is rocket science, and the men and women who study this craft usually get it right. Accidents happen, but on November 26 of last year, everything worked perfectly for Curiosity.
The rover's 350-million-mile, gently curving cruise to Mars over the past eight months, tucked away inside a warm, protective cocoon called the aeroshell, has been relatively uneventful. There have been a few minor scares: concern about the effects of large solar flares on the spacecraft, or the occasional but quickly corrected "upset" of the rover's computer by stray high-energy cosmic rays.
By contrast, the team of engineers and scientists back on Earth has been getting more and more stressed-out, running test after test on a practice backup rover at NASA's Jet Propulsion Laboratory and other venues to prepare for the rover's landing and then mission operations on Mars. The tests that I've been involved with, as a science team member, have been called Operational Readiness Tests, or ORTs. We've had five of them since the beginning of 2012, and as is typical of these kinds of mission practice tests, none of them has been particularly successful. It's a humbling but important experience to realize how much we don't yet know about how to operate a complex vehicle like Curiosity on Mars. How do you get to Mars safely? Practice, practice, practice...
Some ORTs are designed to be problematic on purpose, with colleagues called "test gremlins" intentionally injecting problems and failures into the system to see how and if the team can react and recover the mission. These are sometimes frustrating experiences, because the rover and its systems and scientific payload are so complex that there are almost an infinite number of ways that things can go wrong. Diagnosing and sleuthing why something went wrong, and how it can best be fixed (often with the clock ticking and the test rover's systems failing), is truly an art in the space business. Experiencing this kind of detective work in earlier missions is where I'd first heard of the concept of a "fault tree" -- a complex, branching series of pathways like the limbs and branches of a tree that has to be followed, out to the very smallest, least likely limb, to try to solve a problem. I have immense respect for my engineering colleagues who have mastered this art. They literally saved the Mars rover Spirit when it had a computer anomaly shortly after landing in 2004, and other teams of space experts have performed similarly heroic (but usually unsung) hardware and software forensic work for many other missions over the past four decades.
Curiosity's next violent and risky critical mission event will, of course, be the landing on Mars, late night (Pacific time) on Sunday, August 5. A Rube Goldberg series of hundreds of individual events involving a heat shield, parachute, retrorockets, and a so-called "sky crane" that will gently (we hope) lower the rover to the ground during the last seconds of a 7-minute terror ride through the Martian atmosphere all have to occur without a hitch for the landing to be successful. If you haven't seen and been terrified (or entertained) yourself by the NASA animation of the rover's landing sequence, check it out online here and here.
Yes, it seems like a crazy way to land a car on another planet. And it is, but I'm told by my engineering colleagues that it's the best way to do it, given the resources available -- mass, volume, power, and money. So I trust them, and I believe in them. In fact, I've actually developed a newfound respect for the concept of faith by going through three past Mars landings, and now this one. I could not design a landing system on my own, and in fact I don't really understand the technical or engineering details of how Curiosity's landing system works. But, regardless, I have faith and blind trust in the men and women who built the systems. They will get us to the surface safely. How do I know it? I just do. How can I be sure? I just am. Faith.
And when we do open our silicon-based rover eyes in those first few minutes after touchdown, what a glorious sight it will be. Curiosity is being sent to a place called Gale crater, a hundred-mile-wide and 3-mile-deep hole in the ground formed by a 3- to 4-billion-year-old asteroid impact. I believe that Gale was chosen from more than two dozen other great potential landing sites for Curiosity for one main reason: There's a story there. After the crater formed, a bunch of sediments, some carried by flowing water, others carried by the wind, piled up inside and filled in the hole. Over the past few billion years those sediments have been eroding away, leaving behind an enormous isolated mountain of layered rocks in the crater's center. River channels and giant canyons have been carved into this mountain, exposing layered rocks that date back to the earliest epochs of Martian time. Driving up into these layered rocks will be like walking up through the Grand Canyon, studying the history of the planet layer by layer, era by era, like turning the pages of a glorious book called The History of the Red Planet.
The scenery will be spectacular, to be sure (in some ways with mesas and canyons evocative of the American desert Southwest), but depending on how things work out, the adventure could be more than just picturesque; it could be historic. That's because Curiosity carries the most sophisticated set of chemical, mineral, and biologic experiments yet sent to Mars. While it will likely be slow going initially to get all these instruments (and their scientists!) to work efficiently together, once we get cranking and start exploring those layered rocks, especially the water-lain ones, the payoff could be enormous. Most specifically, one of the instruments, called SAM, is a very sensitive mass spectrometer that will conduct a detailed search for organic molecules -- chains of carbons, hydrogens, oxygen, and other atoms -- that could have been potentially formed by early Martian biologic processes. To be sure, there are plenty of ways to form organic molecules in nature without invoking biology, and the team will be extremely careful and skeptical in interpreting the rover's measurements. But still, just the fact that there could potentially be a biologic signature revealed in the data - -especially if the environment of Gale is discovered to have indeed been potentially habitable to life as we know it -- is incredibly exciting.
Such a discovery is regarded as an unlikely gamble by many scientists. Maybe. But I'm proud of NASA and the other space agencies collaborating on Curiosity's mission for taking that gamble. I'm proud of our country and our species for taking that gamble, for about the cost of a cup of coffee per U.S. taxpayer over each of the last eight years. There's a place right next door (only about nine months' travel away) where we can try to answer the question, "Are we alone?" Let's go find out.
Come celebrate with us in person at Planetfest in Pasadena, or follow along online with Curiosity and our team, and wish us a safe landing on the night of August 5!
Jim Bell is an astronomer and planetary scientist, a professor in the School of Earth and Space Exploration at Arizona State University in Tempe, and the president of the Planetary Society, the world's largest public space advocacy organization. He is the lead scientist for the Pancam color stereo cameras on the NASA Mars rovers Spirit and Opportunity, is a member of the science camera team on NASA's Curiosity rover, and has authored several space photography books, including Postcards from Mars, Mars 3-D, and Moon 3-D.
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