Is the power working? Do we have communication? Is the rover on stable ground?
A successful landing of Curiosity will set off jubilation at Mission Control at JPL and in observatories and labs, government and industry offices, and homes around the globe. But then the small army of scientists and engineers tasked with operating the rover will quickly move on to the actual work at hand: Determining if the vehicle landed with its essential systems intact. If they are working, then comes a gradual unfolding, deploying, and revving up of the ten science instruments and cameras that are Curiosity’s reason for being.
It’s a process that will take days, and in some cases weeks or months. But the MSL team will know soon whether the key power and communication systems have sustained any damage during the 352-million-mile journey or during the high-wire landing.
Communication is largely accomplished through relays to three satellites orbiting Mars or through the Deep Space Network, a system of giant interconnected antenna dishes in Madrid, Spain; Canberra, Australia; and the Mojave Desert. Assuming that communications are established, the first order of business will be to verify the health of the small nuclear battery that will provide power for the rover. Curiosity carries ten pounds of plutonium-238 dioxide as a heat source, which is then used to produce the onboard electricity needed to move the rover, operate the instruments, and keep the frigid nighttime cold at bay.
If all is well, what follows will be a highly choreographed unpacking of the rover. First the mast goes up, with its suite of cameras. Weather and radiation monitoring instruments are turned on, as well as the laser-camera combination that can zap rocks up to 23 feet away and take readings of the “excited” gases released in the process.
By “sol 10” (“day 10”—each Martian solar day, known as a sol, is 24.66 hours long), all ten instruments should have been started up to see if they’re working, and Curiosity is scheduled to take its first tentative steps—kind of like shaking one’s legs to get rid of the pins and needles after a long journey. Only around sol 30 will the seven-foot robotic arm be tested, grabbing Martian soil for the first time to crush and deliver to the two rover mini-laboratories—Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin).
All the while, scientists will be determining exactly where Curiosity is in relation to both the walls of the 80-mile-diameter Gale Crater and the three-mile-high Mount Sharp in the middle of its huge depression. Gradually, the science team will take more control of the mission and address the first big questions: Where should Curiosity be headed? And then, which rocks should be sampled? Where does the soil look especially interesting and worthy of a full and time-consuming examination?
“We’ll have about two hundred to three hundred scientists on site at JPL, and I can assure you it will be both fascinating and grueling,” says Joy Crisp, deputy project scientist for the MSL project. “We’ll be working 16-hour days for those first months, and we’ll be entirely on Mars time.” That means the data and instructions coming and going to Curiosity are pushed 40 minutes later each day to compensate for the extra length of the Mars sol. Eventually, the JPL team will be having science meetings and making decisions about the next day’s instructions and activities at 3:00 in the morning.
But seldom in human history has science had an opportunity this grand. Curiosity will be looking for the carbon-based building blocks of life, using instruments that have a good chance of finding them if they’re present; it will be searching for habitats that could have once supported life; and just possibly it will find some biosignatures that show, or at least strongly suggest, that Mars was indeed once home to living things.
It’s interplanetary forensics at its most complex and exciting, a kind of CSI: Mars. While it’s conceivable that Curiosity will actually come across the signature of a long deceased life-form, that is considered highly unlikely given the cold, dry, and highly irradiated surface of the planet and the choice of a now-parched crater as a landing site. So the goal of Curiosity is to collect clues about what has happened over the eons at Gale Crater—its history as recorded in the layering of rocks, the presence of telltale minerals, and the chemicals that fill the atmosphere and rock faces.
For instance, scientists know from satellite imaging that substantial amounts of water were once present in the desiccated crater. But how much? Was there a lake, a river, a set of mud or clay flats—or possibly all of the above at different times? And during which Martian eras was the water present, and what might have been dissolved in it? Curiosity has the instruments to potentially answer these questions.
With liquid water broadly confirmed as having once existed on Mars, NASA is ready to move beyond its “follow the water” game plan to a new one: “Follow the carbon.” That element in its myriad forms and combinations is essential and central to life as we know it—serving as the organizing substance to all organic compounds, including amino acids, proteins, nucleobases, and other building blocks of life.
Ancient organics in rock are famously hard to find even on Earth, where samples can be studied extensively in labs. So, when explaining Curiosity’s search for organics on the way back from our Death Valley field trip, MSL science leader John Grotzinger was eager to downplay expectations. “We do have a chance of finding organics, but it’s very, very hard to do. We’ll need both extremely savvy work, and some good luck.”
The likelihood that Curiosity will succeed in its organics quest remains something of a long shot. Much of the rock on Mars is not known for preserving organics, and the surface is bombarded daily by cosmic radiation (which on Earth is deflected by our atmosphere) that may destroy Martian organics.
That said, organics certainly fall on the Martian surface, because they are everywhere in space and fall on Earth in large amounts in the form of meteorites and cosmic dust. Previous Mars exploration came up short in terms of finding organics, leading some to conclude that the planet could never have supported life.
But what if the instruments used in the past were just not up to the task of finding the elusive organics? And what if something in the Martian atmosphere or on the surface destroys organics, or modifies them in unexpected ways? Curiosity can provide some answers.
Scientists are also eager to know the kinds of minerals formed in the Gale Crater water and when that mineralization took place. Knowing both will help them understand the nature of the quite possibly deep waters that once filled the crater, and how likely it is that the crater’s rocks have preserved any organic (carbon-based) material.
The scientists are hopeful because sulfur-based, or “sulfate,” minerals such as jarosite and gypsum are present on Mars and are well known for preserving organics. The same is true of silicon-based phyllosilicates and clays, which have also been identified on Mars. If present at Gale Crater, Curiosity has the wherewithal to find them. (Sulfates, phyllosilicates, and clays are also known to generally form only in liquid water that is not too acidic and not too alkaline—the same kinds of conditions that support life.)
The question of Martian organics has gotten even more interesting within just a few months of the landing. Researcher Andrew Steele of the Carnegie Institution of Washington (and member of the MSL science team) and colleagues published a paper that identified carbon-based organics in a number of Martian meteorites that had been collected on Earth. His team concluded that the organics were not created through biological processes but rather through volcanic activity. Nonetheless, Steele said the presence of organics—firmly established for the first time—increases the possibility of Mars once being habitable and even inhabited.
The heart of the rover is probably SAM, the Sample Analysis on Mars. With more than a third of a mile of wiring crammed into a gold-covered box the size of a microwave oven, SAM holds miniaturized equipment that would normally take up most of a laboratory room on Earth. Nonetheless, it can heat pulverized and powdered samples up to 1800°F on just 40 watts of power, and in the process it can detect a fainter trace of organics than any instrument sent previously to Mars. Together, Curiosity’s ability to sample a wide range of rocks and soils as it moves around the crater and the sophistication of the SAM detection abilities are a major step in the follow-the-carbon game plan.
CheMin, the Chemistry and Mineralogy experiment, also examines rock samples, but it is looking for minerals rather than organics. Minerals all form under particular environmental conditions, and so identifying a phosphate or carbonate or sulfate tells scientists about the chemistry, temperatures, atmospheric pressure, and presence of water on Mars at the time the mineral was formed. The experiment shoots x-ray beams at crushed rock samples and can tell if a particular mineral is present if it makes up at least 3 percent of the original rock. Like SAM, CheMin requires substantial amounts of power—up to ten hours of x-ray bombardment for one sample analysis.
The hunt for the building blocks and conditions needed for life on Mars is at the heart of Curiosity’s science mission, but there are many more paths for discovery. Other instruments will sniff the atmosphere, drill into rocks, magnify rock outcrops, and bounce particles off Mars—getting newly sophisticated information about its weather, the radiation hitting the surface, the size of grains in the rock, and the prevalence of frozen water and water in minerals underground.
Often lost in the drama and science of the mission is another Curiosity surprise: It is a remarkably international effort. Although it is a NASA mission, Canada, Russia, and Spain were largely responsible for three instruments, while Germany and France supplied sophisticated (and costly) components and direction. Curiosity’s laser, for instance, was made in France. The radiation detection system was designed and built in collaboration with German engineers and scientists. A highly sophisticated spectrometer, which will identify elements in rocks, was made in Canada. MLS may well be the most international Mars mission ever.
The landing is expected to be on what is believed to be ancient Martian rock—not covered by lava or weathered by other conditions that can change it—but the real prize is Mount Sharp. Named after former NASA planetary scientist Robert Sharp, it is known to have lots of minerals at its base and many layers of rock to study. Scientists want to understand how towering Mount Sharp came to be in the middle of a crater. The mountain doesn’t seem to have a volcanic history, leading some to theorize it was carved out of the crater by powerful, circular winds.
However it came to be, the mountain offers the best look ever at the geology of Mars. Gale Crater is known to be more than three billion years old, and so Mount Sharp is expected to have a geological history—present in the layering and composition of different kinds of rock—going back that far. If all goes well, the rover will intensely examine the mountain base and then continue to climb up its sloping valleys during its functional life. Curiosity will examine exposed geological layers never seen before and analyze their contents. It will be quite literally a field day for geologists, though at a many-million-mile remove.
The mission calls for Curiosity to be roving, sampling, analyzing, and sending back images for two years. With a power source that can supply electricity far longer than two years, though—as well as a history of Mars rovers lasting years longer than their expected life span—there’s a good chance that a healthy Curiosity could make it far higher, even to the top of Mount Sharp. The limiting factor would be NASA funding, which is in increasingly short supply.
The journey of Curiosity will unquestionably be an odyssey of surprises, discoveries, and difficulties. The limitless promise is what excites scientists like John Grotzinger, Joy Crisp, and the hundreds of others who will gather at JPL and then gradually trickle back to their homes and labs to work their Curiosity data from tied-in computers around the world. And those difficulties are accepted as inevitable by the engineers. The distinction became apparent in a conversation at JPL with John Wright, one of the team that will “drive” Curiosity.
Wright, who helped remotely drive the Mars rover Spirit, said that directing Curiosity “is at least ten times more complicated.” This is a function of its size, its science payload, the terrain it will travel, and the fact that it can make more than 4,000 unique maneuvers.
Its path and the timing of its moves will be largely written in code sent to the rover from Earth at the beginning of each Mars day, but Curiosity presents another unique challenge: The rover can make many more decisions on its own than past models and so requires a different and far more intense kind of oversight. In this sense, Curiosity is more of a self-controlling robot than past rovers, although the MSL team is clear in saying it does not have artificial intelligence per se.
While Spirit and Opportunity could also make some limited decisions on their own about which path to take to avoid an obstacle, that information was lost to the rovers as soon as they made their moves. Curiosity will be more capable of guiding itself and will also keep track of everything it has done and where it has gone. As Wright explained it, this new capability for storing Curiosity’s decision-making onboard requires his team not only to know where the robot-rover has been but also to understand where “the rover thinks it drove.”
“The people who designed and built the software tried to make it easy to use,” he said. “The way they did that was to make the rover smarter and more aware, to remember more things so it could respond on its own. We wouldn’t have to specify everything.
“But for us, that means we have to know everything that the rover knows. It’s possible that Curiosity could think it is in a different place than we know it to be, and that could cause some problems. So we have to know, in a sense, what it’s thinking.
“This is a brand-new world for all of us. We have to know what it knows. And when it gets really, really smart, we need to know what it will do.”
This is where the R2-D2, C-3PO, and WALL-E qualities of the Curiosity persona begin coming into focus. Nobody at JPL has any illusions that Curiosity is anything but a roving robot, but it’s nonetheless not unusual to hear scientists and engineers talk about what “he” will do in particular circumstances.
There’s a certain pride (along with wariness) about Curiosity’s increased knowledge, and there’s an unspoken but undeniable sense of the rover as brave and heroic. This is really not unexpected: The previous, surprisingly long-lived Mars rovers Spirit and Opportunity became famous worldwide as the “little rovers that could”—plucky fellows that far exceeded human expectations.
As Curiosity makes its Martian trek—and especially when it starts climbing Mount Sharp—it would be surprising if a similar kind of emotional attachment didn’t develop with the NASA team and the public at large. The rover is a machine, but that doesn’t mean it can’t have personality, too.