“If we saw something anything like this on Mars, we’d stop right away. We’d spend a lot of time with it and check it out with everything we’ve got.”
So said John Grotzinger, top scientist for NASA’s Mars Science Laboratory (MSL) mission—probably the most ambitious and important planetary mission ever flown. As the science lead for the mission, he coordinates the team that decides where the roverrobot Curiosity will go on Mars and what it will investigate.
A group of us were with Grotzinger on a mountainside in the barren Nopah Range of southeastern California, not far from Death Valley. The view to all sides was entirely Mars-like, except for the occasional barrel cactus or lonely browned grass. With the wind blowing, the dust kicking up, and the land parched and hot in the extreme, it wasn’t hard to imagine we might actually be on Mars—a place equally parched and often as cold as Death Valley is hot. That’s why the Curiosity team brings the rover’s test twin to the area for simulated runs.
What Grotzinger wanted to show us was an unusual presence in the rock—the remains of a cylinder formation embedded in a bedrock with the kind of wavy lines that suggest the ancient presence of life. To the unschooled eye, it’s just another jumble of rocks on the undistinguished side of what is known as Ash Hill. But to Grotzinger, it was a sign that the craggy hills of the area had once been flat—indeed, the bottom of an ocean. And more than a billion years ago, mats of single-cell microbes grew across that ocean floor. The California Institute of Technology geologist had studied the rocks intensively in the past and had written an important journal article about them, concluding that the “tubes” were most likely the remains of an unusual columnar form of ancient life. Though in the American desert, Grotzinger was identifying the kind of features Curiosity would be looking for on Mars and explaining some of the ways scientists hoped the rover would locate and examine its targets.
It has been a long time since NASA has sent a mission to Mars that was explicitly involved in astrobiology—the search for life beyond Earth. The last astrobiology mission was in the 1970s, when the two Viking landers initiated human exploration of the Martian surface and sent back negative, though equivocal and even conflicting, results.
While MSL/Curiosity is not a “life detection” mission per se, it is definitely searching for the presence of the possible building blocks of life on Mars. It carries extremely powerful cameras, a robotic arm that can grab and drill, a laser, and two mini-laboratories with capabilities unlike anything sent beyond Earth before. One formal goal is to look for organics—the complex carbon compounds that are essential for life on Earth and presumed to be similarly essential on Mars. In addition, Curiosity will be assessing whether its destination—Gale Crater—ever had the characteristics that make a place “habitable” or was potentially once even inhabited. So while Curiosity might not exactly be looking for signs of life, it is definitely on the trail of extraterrestrial life present and past.
Both of its primary searches involve painstaking and highly complex gathering and testing of crushed bits of rock at the superhigh temperatures that can be generated within Curiosity’s portable chemistry labs. But they also involve geology—the kind of forensic investigation that practitioners use on Earth to tell the history of a place through its rock formations. Gale Crater was selected as Curiosity’s landing site precisely because it has a huge mountain at its center—18,000-foot Mount Sharp—on which many layers of rock are clearly exposed, allowing for an entirely unprecedented examination and reading of the planet’s past.
Grotzinger wanted some of us who will be writing about the journey of Curiosity across the surface of Mars to be introduced to one of the important tools that scientists will be using, and to learn about it in a setting that feels positively Martian. The layering of rocks can tell geologists stories about whether and when water was present, whether the planet experienced long-ago quakes and faulting, whether the very weak Martian atmospheric magnetic field used to be much stronger, and what compounds (including those organic compounds) were on the surface and how they interacted to form minerals. All this just by reading and analyzing the rocks.
And then there’s the distant chance of finding something like the tubes in the rock with biologically formed wavy lines on the surface that Grotzinger wanted us to understand. It won’t take the discovery of a deposit like that to make the Curiosity mission a success, but if it happened, it would be among the most important scientific discoveries in human history.
To bring the point home again, Grotzinger took us several miles away to an area of abandoned talc mines. We didn’t have to hike up a mountain to learn the next lesson; it was in an outcrop we could practically drive to because of those earlier mining operations that pulled the soft, white mineral from the earth. We trooped only down a ravine and back up before coming to a rock face that told a most intriguing tale.
Near the bottom of the rock face was a collection of light silver, oblong shapes two to four inches long. Scanning upward, these stopped abruptly and were bordered by a foot of rock with the straight lines of building sediment. Then came a larger area with fanlike patterns, once again the wavy variety generally associated with life. Then another line of sediment. And so it continued up the rock face.
Grotzinger explained what we were seeing: The beautiful, curvy shapes were fossils of stromatolites, most likely the first life-forms on Earth that could leave behind an actual fossil. Stromatolites were (and still are in some locales) colonies of single-cell microbes that form structures large and small by collecting passing sand and other sediment. Those thumb-shaped outlines on the bottom were a particular kind of stromatolite and the fan shapes were another. The sediment lines represented a time when the stromatolites were gone, and then they appeared again at later times in different forms. If Curiosity came across any Martian shapes like these, Grotzinger said, scientists in the NASA control center on Earth would direct it to begin an intensive examination.
But the chances of coming across this kind of undeniably biological formation at Gale Crater are not great. That’s why Grotzinger had us hike the next day up to the ridge of Ash Hill to do some classic geology. We all examined the rocks—as scores of geology classes had done before us on this somewhat iconic ridge—for unusual shapes, grain sizes, interactions between rocks, or faults and maybe even for a long-ago deposit of oolites, a form of sedimentary rock we had seen on the side of the hill the day before. As their name suggests, oolites are tiny white spheres that look, through a field magnifying glass, a lot like eggs. They’re beautiful and suggestive of biology, but are entirely the result of inorganic activity. (They’re also similar to pearls that were once created outside of oysters and without the help of biology at all.) If the origins of rocks and the deposits in them can be so complex on Earth—where you can actually pick up a specimen—imagine what challenges might lie ahead on distant Mars.
A morning of geology on the ridge introduced us to the pleasures and complexities of rock layering—the stories it can tell, and those it can hide. The outsides of rocks change as they weather, so it’s important to break them open and see the original material inside. Curiosity has the ability to brush Martian rocks and drill a few inches into them, as well as to zap them with lasers and release original fragments and gases. But there won’t be any actual breaking apart of Martian rocks until an astronaut-geologist arrives sometime in the future. As NASA and Mars scientists see it, that’s the ultimate goal of their efforts, and Curiosity is a most important explorer and fact finder on the way to that distant but much hoped-for day.
We left Ash Hill hot and sunburned but enthused about what Curiosity might find. The combination of its landing site with all that exposed rock nearby, its ability to rove for miles, and its extremely high-tech portable chemistry labs seemed destined to write a new chapter in our understanding of the planet in our solar system most like Earth.
And then a different reality intruded. As we headed to a final teaching site, one of the three large SUVs in which our party was riding suddenly pulled off the road. A tire had blown out. We were still very much in the desert and it was blazing hot, but a tire change didn’t seem like such a big obstacle. At first, that is. But in the new Chevy Suburban, finding the equipment to remove a tire and then retrieving the spare is no simple matter. Indeed, for a half hour or more it seemed that it would be impossible and we’d have to call for help—if only we could get a phone signal in the desert. Our journey to Mars-on-Earth came to a disquieting halt.
The obvious question that arose as we considered our situation was this: What happens if Curiosity blows a tire, or something similar? Here we were—17 very bright and resourceful people—marooned (temporarily) in the California desert and struggling to return to normal. What can be done when something similar happens to Curiosity, which will be at least 127 million miles away and can only repair itself via computer commands? It will be traveling on terrain studied by satellites from above, but still unpredictable. Its goal is to climb partway up Mount Sharp, and that will mean some awkward maneuvering for a vehicle the size of an SUV.
As the NASA team on the trip knew well, the most recent American rover on Mars did, in effect, blow a tire—or the rover equivalent of that. The wheels are actually wide rings of fine, lightweight aluminum designed to keep the rover from sinking in sand, but they are subject to failure, too, and one wheel motor on the precursor, and far smaller, rover Spirit did wear out in 2006. That led to much consternation at the time until a work-around was conceived and the Spirit team determined that the vehicle would now move better backward.
Limping in reverse around an area known as the Columbia Hills, the rover with its dangling wheel ended up getting stuck in the sand. Trying to pull Spirit free, the team was forced to spin its wheels aggressively, in a way that initially proved useless logistically but became invaluable scientifically. In fact, the stuck rover eventually made what may well be the most important scientific discovery of the mission: Digging through the crust, it exposed a rock deposit that turned out to be a sulfate mineral, jarosite. It was the first of its kind ever found on Mars and highly significant since that kind of mineral is formed only in the presence of water and often nearby a steam vent—the kind of hydrothermal activity that comes with volcanoes. Sulfate minerals are an important clue about the Martian past and also happen to be associated with both habitable environments and life itself. And now we know about Martian sulfate minerals—simply because one of Spirit’s wheels broke.
That was a reassuring thought as we sought to change the Suburban’s tire, and ultimately we succeeded. Working through adversity is part of life on Earth—and definitely on Mars, too. But while adversity can set a mission back on Mars, it can also create an opportunity.
Of course, that will become true for Curiosity only after it safely lands on Mars, and the blown tire got me thinking about the fact that most missions to the planet have actually failed. The United States, the former Soviet Union, Russia, Japan, and the European Space Agency have sent 43 missions to orbit, fly by, or land on Mars, and more than two-thirds have failed. Only six of the descents to the Martian surface have succeeded (landed and completed their missions) and they’ve all been flown by NASA—an accomplishment often lost in the public assessment of the agency.
So, landing on Mars is very hard under the best conditions. And the MSL/Curiosity spacecraft will require no simple landing—not that any Martian landing is really simple. It will involve technology and procedures never before used on Mars, and the margin of error is slim. NASA officials are confident of their plan, but that doesn’t mean it will work. What happens if the equivalent of a blown tire occurs during entry, descent, or landing?
Since the spacecraft will enter the Martian atmosphere at 13,000 miles an hour and has just six or seven minutes to slow down to the speed where it can touch down gently and safely, the answer is pretty obvious. Any equipment failure on entry means one thing only: The dreams of the thousands of scientists and engineers working with Curiosity crash with the rover and $2.5 billion in taxpayer funds are lost.
Clearly, when those seven high-anxiety minutes of spaceship reckoning arrive on August 6, many people—indeed, a nation—will be holding their breath.