Destination Mars (20 page)

But, as always, there were issues. About two months after the science operations began, MRO experienced difficulty with the Mars Climate Sounder instrument. A so-called stepping mechanism malfunctioned, and the aim of the instrument became slightly off-axis. By December the problem had not corrected itself, and regular use of the device was abandoned. A partial work-around was later devised, and the MCS was pressed back into use, but not without compromises.

Additionally, the image-sensing electronics in the HIRISE camera, the CCDs (much like those in your home video camera) began to lose individual pixels and some electronic noise was found in the incoming images. While this was not a deal breaker, it didn't make anyone on Earth happy. Again, a work-around (utilizing a longer warm-up period for the electronics) minimized the problem, but it still remains as a weak point for the telescopic imager.

But perhaps the most alarming issue presented itself in mid-2009 when the onboard computer began resetting itself—shades of Pathfinder and Spirit. Perhaps the Great Galactic Ghoul has adapted itself to the modern era and figured out how to fool spacecraft computers into thinking that they are faulty, triggering a shutdown and restart. In any event, software changes seem to have alleviated the problem for the present. But the computer team remains vigilant. It took over two months to eventually solve the problem.

These issues did not stop the mission, however, and discovery after discovery continued to stream in. Wide measurements of the northern ice cap revealed more water than could have been hoped for, almost two hundred thousand cubic miles (not square miles, but cubic miles!) of water ice. This is equivalent to almost a third of Greenland's ice sheet and accounts for a lot of the “lost” water on Mars.

Some of the evidence of a wet past had come from the observation of phyllosilicates, heavily hydrated minerals formed in water.
But the lava flows in the north had covered any evidence of these. The researchers needed a hole punched in this lava layer, and through extensive observation with their new orbiting toy, they got one. Nine craters in the lava fields were investigated, and each of the craters revealed hydrated minerals in the older layers below.

More craters were targeted, and a number of them showed bright blue-white materials on the surrounding ground. A few passes of the orbiter later, the material was slowly disappearing. From the rate of evaporation and the colors seen, it was clear that, once again, water ice had been found (the color indicated that it was almost 100 percent pure water ice). Just to be sure, the spectrometer was pressed into service, and, sure enough, the spectral signature matched that of water. To make it even more dramatic, some of these were about forty-five degrees south of the pole. By now, spotting ice in the polar regions of Mars, and as far south as sixty degrees, which is roughly equivalent to Anchorage, was not a shock. But finding it at the latitudes equivalent to Paris or Seattle was. It just kept getting better and better.

All this talk of water may cause the untrained ear to become a bit jaded. So there is water on Mars…big deal. But it may be just that—a very big deal. How this ice is formed so close to the surface is still a bit of a mystery. Mars's atmosphere is far too thin to support liquid water on the surface, and the formation mechanism for these ice patches is still not well understood. One theory involves a process that on Earth is called
frost heave
, in which small amounts of water can remain liquid around a grain of solid ice, even at temperatures below which it should freeze. Pressure causes this liquid water to migrate upward, where it then freezes, forming a lens-shaped structure on top of the soil below. Why this is important (beyond the pure geological implications) is that this process, which keeps water temporarily liquid in certain places near the surface, could form environments where bacteriological organisms could thrive. And as biological studies on Earth continue to find basic life-forms colonizing areas as diverse as
undersea hot vents and the frozen dry valleys of Antarctica, the idea of water-bearing areas on Mars is tantalizing.

Continuing the search for water, in 2009 MRO used its camera cluster and spectrometer to image the vast reaches of Valles Marineris, the huge, hemisphere-girdling canyon that straddles Mars. In a region named Noctis Labyrinthus, scientists were looking for light-toned deposits (LTDs in the vernacular) indicative of water activity. They examined ten LTDs, which turned out to be troughs in the canyon, and found things they did not expect to see. The instruments on MRO, working in well-planned harmony, identified clays, hydrated silicas, and sulfates—all of which pointed to yet more watery activity sometime in the past. Some of the formations were dozens of miles across.

Small differences assumed large proportions. An example was one trough where most of the water-affected minerals were buried under later, wind-driven soil, but some was visible in the upper walls of the trough: a sure sign that the water-affected area was older than the trough itself. Another featured (water-derived) clays buried beneath newer plains. These and other findings, while seemingly innocuous, indicate a confused and jumbled timeline of multiple “wettings” of the area, multiple water-inundating events, which is in itself a major discovery. In short, Mars had not had just one watery time, but a number of them. This bodes well for a complex geological history, and again offers a possibility for the existence of past life.

Just how the water arrived in these troughs was not evident. It has been hypothesized that it may have been melted ice from the volcanoes nearby, or some subterranean hydrothermal event. Since then, clays (representing, again, water processes) have been identified throughout Martian bedrock, so it is not a unique occurrence.

These discoveries resulted from the elegant and coordinated use of the context camera and the higher-resolution HIRISE imager. First the low-magnification CTX would spot something
interesting, then the HIRISE imager would zero-in with its telescopic lenses and take a hi-res picture for detailed investigation. Finally, the spectrometer—the CRISM instrument—would take a careful look at the area and provide its chemical analysis. In this way, working in perfect three-part harmony, MRO was able to first identify, then analyze in detail, these kinds of soil deposits in high-resolution. The deposits dated back somewhere between 3.5 and 1.8 billion years ago—hardly recent, but important nonetheless. The troughs themselves seemed to have developed somewhere in the middle.

Glaciers were discovered in regions that first sparked interest among researchers in the days of the Viking orbiters; they surrounded the edges of cliffs in Martian valleys. They are lobe-shaped and gently sloping, and many are covered with debris and soil. Again, these are areas that apparently store huge volumes of water ice.

MRO also provided some of the first looks at earthly artifacts as well. When imaging Victoria Crater, the HIRISE camera captured an image of the plucky Opportunity as it went about its long traverse of the edge of the crater, making out the body of the rover and even the shadow of the camera mast. The HIRISE was also able to later photograph the Mars Phoenix Lander as it slowly descended toward the Martian north polar region in May 2008, dangling from its parachute. This was particularly exciting due to the fact that the landing event is short-lived and was snapped from an oblique angle—not the camera's strongest mode of operation. Both images were evocative and, besides being strong technological accomplishments, highlighted the infinitesimal human footprint on the Red Planet.

The images of Victoria Crater provided another benefit—to assist MER mission planners in their guidance of Opportunity into Victoria Crater. These were all examples of multiple Mars missions working together, something never before accomplished on such a scale. And not only did they provide data from different
perspectives; these multiple machines were actually able to help each other. Mars exploration was becoming a team sport.

There is one more area of discovery to be attributed to MRO: the observation of “real-time” or near-real-time events. One such occurrence was an avalanche seen by HIRISE in February 2008. A sloping hillside in Mars's northern regions had a huge dust cloud billowing from the base of the slope, clearly demonstrating a huge
movement of material to the base of the incline—an avalanche. The camera was actually targeting a dune field nearby as a part of its regular survey of carbon dioxide frost. The avalanche was a serendipitous capture, only noticed later when a mission scientist was reviewing the images. It may have been caused by water ice being exposed, suddenly sublimating, or evaporating, and undermining the soil.

Another new feature was spotted via a comparison of images taken by MRO and Mars Odyssey. Again, it was a team effort. MRO's wide-angle context camera had snapped an image in 2008 in which a small black dot was spotted. No big deal. But when compared to an image from Mars Odyssey from 2006, there was no such spot. Excited researchers aimed MRO's HIRISE camera at the same place and found a small, otherwise insignificant crater about eighteen feet across. The hole itself was not what was spotted by MRO—it was darker material exposed by the shock of the impact, which blew the overlying, lighter surface away. They had spotted a brand-new crater. While not hugely significant, it was a fun moment…and there is always room in science for some fun.

The Mars Reconnaissance Orbiter has, to date, returned more data than all the missions launched past the moon. It is a huge amount of scientific material, and it has been estimated that if just the HIRISE images were shown consecutively for ten seconds each, it would take over four years to view them. So make sure you are well-stocked for snacks.

And MRO isn't done yet. Stay tuned.

F
rom his home near the foothills of Southern California, Richard Zurek can look toward JPL and see the object of his study, some forty years since he began to study it: the air. When not enjoying the view, he hikes the local mountains. But his consuming interest is, of course, Mars. And he has been a part of seeing Mars as it has never been seen before, through the high-fidelity eyes of the Mars Reconnaissance Orbiter. His inspiration to study Mars would sound familiar to many of his compatriots at JPL…the flight of Mariner 4.

“I was in high school at the time, the Mariner 4 flyby. Now, as recently just a year or two before Mariner 4 was launched, you [could] still read papers on the dark areas, what did they represent, was it vegetation, what was this planet like? And at [that] time they overestimated the amount of atmosphere that it had…. [They estimated] the atmosphere to be ten times thicker than it really was.

“Mariner 4 was the first to see that this thing was about 1 percent of the Earth surface pressure…. [T]hen [there was] the challenge of orbiting a spacecraft around the planet; Mariner 9 succeeded in doing that, becoming the first earthly object to orbit a planet other than the Earth itself. So first we have Mariner 4 and say, ‘maybe there's nothing here,’ then the flybys for 6 and 7 and the controversy on whether or not they detected chlorophyll, and it turned out to be another weak indication of carbon dioxide, so arguments about Mars—what is it like, what it's not—continued.”
¹

Mars was proving to be more adept at hiding its secrets than anyone would have guessed, especially after the dramatic results of Mariner 4. Mars transformed from a planet populated (in the minds of some) by an advanced civilization of water-hoarding civil engineers to a dry desert wasteland overnight. But then the follow-up flights made it clear that things were not so simple. The highlight of this may have been when Mariner 9 arrived at Mars, only to see a huge planet-girdling dust storm. But sticking out of that storm were the peaks of three huge volcanoes on the Tharsis Bulge. Mars was revealing its past slowly, making us work for it.

“This happened to us a couple times, certainly with Mariners 4, 6, and 7, and then Mariner 9 changed the idea again, both in the sense of ‘yes, there were mountains, and there were vast channels on the planet,’ and ‘yes, the atmosphere was thin, but it was vigorous enough to be able to sustain regional dust storms into a global haze that could blanket the entire planet,’ and so Mars sort of came alive again.”

Inspired by JPL's missions of Mars exploration, Zurek decided to aim for the stars: “I went to the University of Washington, and mathematics graduate school, but I was pretty certain as I soon as I got there that I didn't want to be a theoretical mathematician. I chose the University of Washington because I knew they had a department of atmosphere and science that took people with math and physics backgrounds. I had that, [so I] transferred into that department, and it just happened that they had a new professor. This new professor had an interest similar to what I'd had as a kid, so I was fortunate. Not only was he a new professor at the school, he had an unfilled assistant role that he needed to fill, and so I walked in and I was a good match.

“When you get to a mission like MRO, which came along after the great discoveries of Mariner 9 and the Viking orbiters and landers, things kind of build up incrementally. But [the results were] profound, and I think a couple of the things really impressed me. The ground is so oddly patterned. There were polygons, and
fractures; it just looked like a surface that has had many places that were once wet and had since dried out. It's like looking at mudflats, only the scales are bigger than that, and I think that tells us two things. First, there's been these drying out episodes, that there's still ice in the surface of the planet, and the other one is of course the composition measurements that have indicated that you have these areas where these minerals are present. When you put that whole picture together, what you see is that what you're looking [at] is an ancient surface that's been covered up.

“With the ancient surface, we were looking at a lot of water interaction in it, because it altered the composition of the surface; actually changed the material into sulfates, and carbonates. Seeing [this] early history, and trying to figure out just how widespread it was is interesting. [However] the fact [that] there are different minerals indicating different kinds of watery environments, some of them more acidic than others, to me, once again increases the potential that Mars might have developed life somewhere.”

Every mission has its highs and lows. MRO was no exception, and coming on the heels of the twin failures of Mars Climate Orbiter and Mars Polar Lander, the stakes were still high, even years later: “Just getting into [Martian] orbit, getting safely into low-altitude orbit, was a high point. Scientifically, seeing these constant changes of Mars climate from an ancient period [when] water was active, there must have been water surging through the ground, and in salt lakes, to form these mineral deposits that we see today. And then you have the more recent climate change…in the polar caps, and the buried ice deposits. It's all very interesting. Of course, as an atmospheric scientist, dust storms are still a big question. Why do some storms get huge, [involving a] large fraction of the atmosphere, and at other times we only have [a small one] out of three Mars years?” These and other questions were nagging Zurek when the MRO entered its science orbit, bringing its revolutionary imaging capability to Mars.

“That's what resolution does for you. When you're looking at
a lower resolution, you don't see the variations that are there; they are fuzzed out by the inability to resolve. [At] the scale in which we're now seeing the planet, the colors [can be] stretched so we can see the variations. We do that because it tells us different things, the bluer materials are often the sand-covered things, the white-zoned areas are often things that get altered by being in contact with water.”

The resulting images are truly magical and have a beauty all their own. MRO brought a new dimension to the visuals coming back from the Red Planet: “The principal investigator of the high-res camera says that one of his prized moments was when he was here at JPL, and he was looking for an office. Someone told to him to go to the end of the hall where the abstract painting was, and to turn left. So he walked down the hall, and the abstract art turned out to be his camera's picture on the wall. The beauty of seeing these different elements at high resolutions and seeing that landscape…shows that they've done a great job.”

But MRO's job went beyond basic science. It was pressed into service as a relay for the Mars Exploration Rovers, and also to help identify landing areas for the upcoming Mars Science Laboratory (MSL).

“Today they announced the landing site for MSL, it's going to be Gale Crater, which was one of the four finalists. I took great pleasure in that, because our MRO team provided the basic data by which precise selections were made, both [in] terms of the engineering safety and also in terms what interesting things are in these places.

“So, we expect a lot more in MRO. It has enough fuel to go for another decade. [The spacecraft is] working so beautifully, sending so much data back, we're looking forward to continuing for hopefully nine more years. Things are looking pretty good at the moment.”

Here's to another decade of Mars Reconnaissance Orbiter, and the secrets that it will reveal.