Destination Mars (17 page)

The FIDO rover covered only about 450 feet during the ten
days of the simulation, and the longest single traverse was about ninety feet. But it was enough: great pains had been taken to include problems and obstacles that would test the controllers' abilities and nerves. When asked, most of them felt as if they had already survived a compressed version of the mission.

As Spirit prepared to begin its historic travels, one programming team was sweating out the upcoming events more than the others. These were the authors of the autonomous hazard-avoidance software, essentially an advanced cruise control with the ability to avoid ramming into things or getting stuck, or so they hoped.

Beyond the driving-and-navigation software, programming was also used to make sure that the mechanical arm housing much of the instrumentation on the rover would not bang up against rocks and dunes. This required the rover to load 3-D images from its mast-mounted cameras into the computer, where it would build a 3-D map of the area being examined. This would then be compared to the projected path of the mechanical arm. If there was a conflict, changes to the arm's path (or suggestions to change the position of the rover) would be enacted to prevent damage to the sensitive electronics.

Overall, important lessons were learned, implemented in updates to software or procedures, then tried again. It's hard to say how many mishaps were avoided by the use of these simulations, but most would agree that they were worth many, many times their cost.

Back on Mars, it was January 15, 2004, and Spirit rolled onto Martian soil for the first time. Like a timid child heading off for a first day at school, the first image Spirit sent down was a (nervous?) look back at the now-empty landing stage. Its own tracks in the ruddy soil led to the bottom of the frame. Mission control erupted in cheers. In just over a minute, Spirit had moved ten feet, much faster than Sojourner. As a sign of how long things take when dealing with the lag time between Earth and Mars,
including relay time from the assisting orbiter, the elapsed time between the sent command and reception of the confirmation from MER was over ninety minutes. You wouldn't want to drive in rush-hour traffic this way, autonomous software or not.

The first target, to be reached in about four days, was a rock called Adirondack. It was a low-lying football-sized chunk with flat sides that were fairly smooth. This made it a fine test candidate for the RAT, which could clean and, if needed, grind down the surface of the rock for closer examination. The rock and nearby dirt were examined, and almost immediately the surprises began. The first and most profound was the discovery of a mineral called
olivine.
This is a mineral that is easily altered by water, and the fact that it was here in relatively unaltered form meant that there had perhaps not been as much water in this area over the millennia as had been thought (and hoped for).

Then, just as things were getting interesting, Spirit went quiet. On January 21, eighteen days after its arrival, Spirit lapsed into silence. After a long and knuckle-biting day back home, the robot sent a message to its masters on Earth. It said, in effect, “I AM HERE. I RECEIVED YOUR LAST MESSAGE. I AM IN FAULT MODE—STANDBY.” For the next few days, technicians at JPL worked overtime trying to determine if this was a software or a hardware problem (one was probably recoverable, the other probably not, respectively). Then a few more short and cryptic messages came in from Spirit. Frustrated, JPL ordered the spacecraft to downlink an engineering data dump. It eventually did so, and it the problem revealed itself: the rover was having insomnia; it was dropping out of “sleep mode” and using excess battery power in the dark of the Martian night. This was also causing excess heating, which could be a danger to the craft.

Various theories were forwarded by increasingly desperate programmers and engineers. A leading candidate was that the machine was stuck in a “reboot loop,” an endless condition that occurs when the computer onboard the rover thinks there is a
problem, restarts the computer, only to run across the problem when the computer is booting. It senses the fault and restarts again. The cycle can run forever, or at least until the rover's power supply or circuitry fails. It is a sort of cybernetic Möbius strip of the mind. Spirit had acquired a case of digital obsessive-compulsive disorder.

Programmers came up with a solution and it was sent up. The trick was to avoid a certain part of Spirit's cybernetic mind: the flash memory. It was not unlike a built-in version of the flash sticks we all use today. There was simply too much of the wrong kind of data in this area, and it was causing the faulty reboot sequence.

It took until the thirty-third day since landing, February 6, to resolve the issue, but resolve it they did, and Spirit regained consciousness. The historic mission of exploration was on once again.

Spirit was still parked near Adirondack; it was a bit like someone falling asleep in his soup and waking up, unfazed, to continue eating. Unsurprisingly, little had changed since it went comatose two weeks previous, and the rover resumed its chores as if nothing had happened. The RAT was brought to bear and began grinding away at the surface of the small rock. Controllers were careful—this was the first use of the tool on a Martian rock, and nobody wanted to be the person responsible for breaking it—but despite their caution, a nicely ground disk soon appeared on Adirondack, and the microscopic imager and spectroscopes on the robotic arm were brought into play. While the hole produced was only about one-tenth of an inch deep across an area just under two inches wide, it was enough. The results of this first-ever in-depth investigation of a Martian rock was like the first performance of a well-rehearsed ballet, and with the software issue resolved, things appeared to be back on track, and handsomely so.

The next challenge for the recently reawakened rover was to think on its own. A rock named White Boat was selected as its next target, and this time Spirit was told where to drive, but not
specifically how to get there. It would have to use its hazard-avoidance cameras and software to plot a course and execute it. To do this, the stereo camera atop the mast on the rover provided images that the onboard computer used to build a 3-D map of the area ahead. Based on this, the rover would select the safest path, then continually update it with information gleaned from this and the hazard-avoidance cameras. It was a bit like handing your teen the keys to the car for the first time, with the attendant parental nervousness.

Meanwhile, there was more excitement afoot. On the other side of Mars, in a scene not witnessed since the twin Viking landings of 1976, another fireball appeared in the skies above a region called Meridiani Planum. The area had been selected, like Spirit's landing area, from a carefully parsed list of candidates. Of particular interest here was the presence of the mineral hematite, also known in some variations as magnetite, a form of iron that normally occurs in the presence of water. And since possible life, past or present, is the holy grail of Mars exploration, Opportunity, like its twin, would follow the water.

About six minutes after entering the thin Martian atmosphere, Opportunity had bounced to a halt, safe and sound, on Mars. But this rover, Opportunity, had been a bit luckier in its somewhat random final destination. JPL could pick the region, but the final resting place was at the whim of its Superball
^®
-like arrival. For while mission planners had aimed for Meridiani, they had not known Opportunity would end up almost fourteen miles from the anticipated landing zone in an area soon known as Eagle Crater. While the rover could have later driven to such a crater, landing in one was a lucky stroke, and JPL considered the shot a “hole in one.”

You see, craters are like holes punched into the crust of a planet to reveal the materials inside. Eagle Crater was no exception, and in addition to what the scientists might have expected to see, they also spotted layers of rock outcrops not far from the
rover, about twenty-five feet away. Closer examination revealed apparent sedimentation…a possible sign of water-created processes. The layers, ranging from thick to thin (perhaps half an inch to paper thin), were presumed to be either a result of waterborne sediments or deposits of falling volcanic ash. Either pointed to a living, geologically active planet. And one possibility—water—was yet another indicator of the possibility of life. Meridiani was going to be an interesting place.

In early March there was another ripple of excitement through the MER team. Spirit had stopped at another rock, this one affectionately named Humphrey. It was about two feet tall and wide and appeared to be worth a closer examination. Spirit closed with Humphrey and got to grinding with the RAT. Once scientists got a look at the freshly revealed surface, there was a surprise in store. What they found literally sparkled in the sunlight: crystals. If found on Earth, this would assuredly indicate that water had moved through this volcanically formed rock at one time. The same could be true on Mars.

For anyone left from the Mariner 4 years, the scene would be somewhat surreal: a wheeled, mobile, drivable machine with semiautonomous computers onboard was parked next to a Martian rock, grinding away with a rock drill. It then employed devices of which folks from the 1960s could only have dreamed, at close range. The future had arrived.

Opportunity then moved toward its most attractive immediate target: the freshly named Opportunity Ledge. In an area dubbed El Capitan, an outcrop that displayed what were apparently different kinds of layering and weathering from top to bottom. This is the kind of thing that sets a planetary scientist's blood aboil, a four-inch molehill named after a mountain in Texas. After much visual examination, the RAT set to work grinding away. Once this was complete, besides showing the expected profile of a layered rock, two round shapes were visible. Known as “spherules” in the trade, they excited the researchers to even greater heights. About the size
of BBs, averaging about one-sixteenth of an inch, these were later named “blueberries.” They can be formed by different geological processes, and, as is so often the case in geology, the context in which they are found can have a lot to do with how they are interpreted. But finding them here, inside a rock on Mars, was downright dreamy. More were found nearby, both inside the outcrop and on the ground.

But there was more. Empty areas, called
vugs
, were laced throughout the ground area. These hollows were consistent with comparable terrestrial rocks where something had been dissolved—by water—after the rock formed. To add to the mounting evidence, the spherules were found to be composed of waterspawned hematite. Further work with the spectrometer revealed another mineral, jarosite, which is also formed in water—more evidence of a watery past. This is the kind of evidence planetary geologists love—three distinct sources of aquatic evidence had emerged in one location, and things were looking good.

On March 2, JPL announced that water had at one time flowed through the rocks, changing their texture and chemistry. While these words may not sound profound to a layman's ears, from ever-cautious planetary scientists, they are almost ironclad. There had been water, and probably a lot of it, in Meridiani Planum.

It was the first victory dance, albeit a low-key one. Time to move on.

Spirit meanwhile reached a crater called Bonneville. It peered cautiously over the edge, looking for points of interest. Across the crater, about five hundred feet away, the rover spied its own heat shield, which came to rest there after being discarded during the craft's descent. While the crater looked inviting, and while the end of Spirit's primary mission was drawing near, it was elected not to risk descending into the crater, and Spirit, prompted by its earthly controllers, moved on. Far off, across the floor of Gusev, the Columbia Hills beckoned. Soon the rover was over one
thousand feet away from its lander; a pittance by human exploration standards but a vast distance for a Martian rover.

Back at Meridiani, Opportunity had left the rocky outcrop that had consumed so much of its short life. Greater adventures lay ahead, as it spent some time evaluating the skies above—including observation of a somewhat rare transit of the Martian moon Deimos across the face of the small and distant sun. At only nine miles across, Deimos would not block the sun; it was merely a speck on the face of our star. The rover next began a long look at a rock euphemistically named Last Chance, which it had come upon as it neared the end of its primary mission. Then there was a bit of a showstopper.

In a wide-angle picture of the area, a bizarre-looking object appeared. It was the wrong color to be here; it was also the wrong shape. It looked like…the head of a rabbit. Now, planetary researchers are not the type of folk given to flights of fancy, and most anything other than a beer can or an abandoned Chevy Corvette
^®
found on Mars is going to find a bunch of men and women huddled around monitors, seeking a logical explanation for what they are seeing. But when something appears that triggers the human impulse to make a familiar shape out of the unfamiliar, especially in a place where it is so unexpected, let's just say that it is a reason to pause and reflect.

And then, just as they were taking a better look…the two-inch yellow oddity vanished.

The first assumption was that it must be man-made, something that came from Opportunity as it was landing. Lots of events occur during a landing cycle, and some are somewhat violent. Little bits can fall off a lander as it plummets to Mars, especially when it lands the way the MER spacecraft did, bouncing to a final stop. But the color didn't quite match anything they could think of on the lander, though it had a general resemblance to the material from which the landing bags were made.

A painstaking examination of other images taken earlier
revealed the bunny closer to the lander. Aha. Then one bright soul performed a spectrographic analysis of the object and compared it to the stuff from which the airbags were made—and it was a match. Later the object was spotted hiding underneath one of the petals of the lander. The final conclusion reached was that it was a piece of torn airbag material after all, that had been blown around by light local breezes. Mystery solved, and not too soon, for on a mission of this magnitude, one can't have researchers spending too much time on any one problem unless it is promising of a relevant discovery…and while the bunny did appear to be shy in its choice of a final hiding place, it was pretty clear that it was not a living thing nor an ancient Martian artifact. In the end, one of the more arcane mysteries since the Face on Mars had, again, been solved via patient thought and analysis. But it had been fun.