Destination Mars (15 page)

M
ars and Earth both have elliptical orbits, one inside the other, so at varying times (about every two years), Mars and Earth are in “opposition,” when they make their closest approach to one another. Due to this, there are favorable launch opportunities every two years for Mars-bound spacecraft. This is a driving force behind scheduling for the Mars program at JPL, because a delay of even a few weeks in development, planning, building, or testing can cause a mission to be delayed for two more years. It is a headache common to all the “Martians” at the lab, as they often refer to themselves.

With the turn of the millennium, JPL and NASA were still recovering from two very embarrassing mission failures. Internal and external reviews had illuminated many failings within the development and the management structure of the program, and these revelations were hard to swallow. Heads rolled, teams were restructured, management methods were reevaluated, testing procedures were strengthened, hardware was reexamined, and perhaps most important, budgets were scrutinized. “Faster, better, cheaper” was deemed, arguably, to have been a fallacy and was quietly retired, though money was still a tremendous challenge.

And throughout, the Mars exploration program moved forward. Incredibly, even with all the shuffling and restructuring, a few missions stayed on track. And the next one to launch, the relatively inexpensive Mars Odyssey, was ready to go in 2001.

The spacecraft was built by Lockheed Martin. The aerospace contractor had proved to be a capable and willing partner, unusually cooperative in unmanned space efforts, an arena where government/contractor relations can get sticky. Previous partnerships with NASA and JPL had gone well.

The primary goal of Mars Odyssey would be to search for water from orbit. To do this, the spacecraft would carry two principal instruments: one, called THEMIS (Thermal Emission Imaging System), would image the planet in infrared, allowing scientists to map Mars in temperatures instead of traditional visual wavelengths. The infrared images could then be aligned with images taken in visible light, and the correlation of visible landforms with areas that radiated stored heat at night would provide a better understanding of the mineralogical makeup of much of the planet. Toward this end, Mars Odyssey also was capable of taking traditional images as well.

The other was called HEND (High Energy Neutron Detector), which would identify elements in the Martian environment, specifically in the first few inches of soil. Here, planetary scientists would be looking for hydrogen, an indicator of water and water ice. Between the two instruments, it was hoped to clarify where the moisture might be on Mars and in what concentrations, among other things.

A third instrument was called MARIE (Mars Radiation Environment Experiment), which would measure radiation in the Martian orbital path. This was not only of interest in strict science terms, but would also assist in the planning of eventual crewed missions to the planet.

The overall spacecraft was about the size of an upright refrigerator, with a boom extended out one end (which held the gamma-ray spectrometer sensor) and solar panels out to two sides.

Mars Odyssey left Earth on April 7, 2001, aboard a Delta II rocket and successfully headed off toward the Red Planet. As the rocket sped toward Earth orbit, the distance from Earth to Mars
was about seventy-eight million miles, but due to the course the spacecraft would follow to reach the its goal, Mars Odyssey would travel over 285 million miles.

Once within Mars's wispy embrace, aerobraking was again used to circularize the lopsided orbit inherent in missions utilizing a smaller rocket (the technique saved almost 450 pounds of fuel, which is a huge amount in Mars-bound launches). After the braking rocket fired, dropping Mars Odyssey into that lopsided orbit, aerobraking continued for almost three months until the ellipse became a circle that was proper for surface mapping to begin. This required not only circularizing the orbit but also adjusting it to an almost north-south orientation, also known as a
polar orbit
, which has been used for most post-Viking orbital missions. With this, the planet rotated perpendicular to the orbit of the spacecraft, allowing it to repeatedly photograph almost every part of the surface as the planet slowly turned below.

And then, in late February 1992, Mars Odyssey got to work. The major risk milestones had been passed, and things seemed to be going well. The folks at JPL breathed a bit easier. Mars Odyssey, it seemed, would not disappoint.

You see, lessons had been learned since the multiple failures of the 1990s. Most of the flight systems (i.e., most things likely to fail or malfunction) were now redundant and had backup units. It was almost as if JPL had taken a page from the manned spaceflight playbook, in which as many systems were doubly and triply redundant as possible.
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This was, in some ways, now applied to Mars Odyssey.

The brain of the spacecraft was a radiation-hardened version of Apple's Macintosh
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processor of the time, the Motorola Power PC
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chip. With 128 megabytes of RAM and three megabytes of other storage, it was hardly a powerhouse but would do the job.

As data moved from here out to the rest of the spacecraft (and back), an ingenious parallel design was used. Computer cards enabled specific tasks, and were placed in double rows
downstream from the processor, allowing for 100 percent backup capability. The only parts of the computer not backed-up were the main processor and a (then staggering) one gigabyte storage card for imaging.

Finally, the flight software, which was carried onboard as opposed to the commands later sent up from Earth, had more sophisticated “fail-safe” routines written in and had frequent self-checks. If something went wrong, the craft would immediately enter a “safe” mode and begin troubleshooting the situation. This had always been a part of deep-space software, but had been beefed up following the reviews of recent losses.

By late March 2002, Mars Odyssey was sending back images that were then posted online almost immediately by the JPL team. It was the second Mars mission to offer the public such immediate feedback, and it had been pioneered by the impressive online presence of the Mars Pathfinder mission. The images were spectacular even in their raw state, and doubly so once enhanced.

And in an ongoing quest, Mars Odyssey was looking for life on Mars.

Of course, as an orbiter, it did not have the luxury of a dirt scoop and an analytical lab like Viking did, nor the ground-based mobile capabilities of Pathfinder. But with the growing understanding of the nature of Mars, the Odyssey team had been able to focus its instruments on the investigation of water present on Mars. Where water was found, past or present, there could be life, past or present.

The strategy was to look at the surface, and shallow subsurface, environment of Mars for both hydrogen, indicative of water, and various mineral types, indicative of past water. The probe would also be able to spot hot springs now suspected to possibly be on Mars. With patience, a holistic picture of the planet would eventually come to light. The machine simply had to function long enough to allow these results to emerge…and in this, Mars Odyssey would shine like none before or since.

By April 2002, Mars Odyssey had already allowed planners to select landing sites (from many dozens of candidates) for the upcoming Mars Exploration Rovers, which would leave Earth in just a few months. The images being studied were critical to making an informed choice, and the results had been immediate and gratifying. There was a high level of confidence in the selected sites.

Concurrently, visible light images had been combined with earlier shots from Mars Global Surveyor to examine some gullies that appeared suspiciously like drainage channels. It was soon realized that a few had been caused by
recent
melting of water snow. This was a breakthrough, as it provided proof that water was still “running” on Mars, something long suspected but until now unproved. The key idea was that ice was melting underneath snow packs, and the mass of ice above prevented the water from flash-evaporating in the thin atmosphere as it flowed out to create the gullies.

On Earth, a few little erosion channels might not cause even a moment of excitement, as we are used to seeing such things constantly and easily in our own dynamic ecosystem. But these gullies had first been observed on Mars in 2000 from Mars Global Surveyor images, after countless hours of painstaking investigation of thousands of pictures. They seemed to occur only on the colder, pole-facing “shadow” side of some craters, and as such, indicated that a special set of circumstances was contributing to their formation. This colder, shaded location allowed snow to accumulate and remain across an entire Martian season, so that melting could occur gradually, allowing the water to seep out and create the features observed. Here was the explanation, the “smoking gun,” that so many had been waiting for. For a Mars scientist, it was nirvana.

Soon another result came in, supplying a broadly opposite picture of another part of Mars. When the region called Ganges Chasm was investigated, a huge deposit of the mineral olivine was discovered. Olivine is soluble in water over time, so this large an
area of the mineral indicated a long dry period in the region. The infrared imaging was also allowing planetary scientists to develop a far better idea of mineralogical distribution, lava flows, and soil types. All this was derived from observing thermal or temperature differences between one area and another, as seen in daytime and then at night when the more slowly cooling areas (indicative of differing soil and rock types) were clearly visible in this invisible spectrum. Not only do different kinds of rocks cool at different rates, but sand and sedimentation (dirt, pebbles, boulders) of a given type of rock cool faster than a solid mass of the same material. So the temperature measurements showed broad swaths of geological and erosional formations, allowing the paint-by-numbers map of Mars to be filled in, for the first time, with some authority.

These results did much to redeem JPL in the public eye, as well lift the spirits of those who labored there and at affiliated institutions. But there was more to come. The gamma-ray spectrometer was showing the planetwide distribution of ice under the surface, demonstrating far more water than even optimistic projections had predicted. This helped to answer the question of where all the water had come from to form the many huge, water-created features seen across the surface, and ruled out some of the more farfetched hypotheses. Mars was now confirmed as having a
currently
living (if less so than Earth's) environment, and the Red Planet was far from the dead place it had appeared to be so long ago in the fuzzy Mariner 4 pictures. There was clearly water—if not gold—in those hills out yonder.

Look at it this way: not all the visual images coming back were of much higher quality, and in some cases less so, than the previous Mars Global Surveyor. But the thermal information was almost three hundred times better. So until now, scientists had been forced to deduce geological and environmental conditions from images that could see nothing smaller than a schoolbus—not as useful as they desired. But the new and highly detailed thermal
information from Mars Odyssey showed what was below the sand, what existed in large areas invisible to the naked eye, painting a larger and better-defined map of the surface composition.

But wait, as the Ginsu
^®
salesman said, there is more.

The instruments also showed large areas of bare rock where the excessive dust and sand found all over Mars had been scoured away, as well as large deposits of rubble at the base of hillsides and mountains. This was a dead giveaway that weather was hard at work on Mars, reinforcing the notion that, while dry and dusty, there was a vibrant meteorological system at work on Mars.

As the days grew colder in the Martian winter of the northern hemisphere, the expected dry ice layer appeared. But when it retreated, a dense layer of permafrost—water ice in the soil—was quickly apparent below. Again, water, water, everywhere, even if it was frozen. This was good news for those seeking possible habitats for some form of life on Mars.

This was remote science at its best. In many cases, incomplete answers from Mars Odyssey were fleshed out by data from Mars Global Surveyor and vice versa. The two spacecraft were working in tandem—each according to its strengths—to develop a clearer, planetwide picture of Mars. And this gave scientists something else they had been lacking heretofore: context.

The picture of Mars that was emerging was an intriguing one. Water ice was found widely distributed across the planet. The concentrations lean out nearer the equator; in the polar regions, one might find a half pound of water per pound of soil, or 50 percent water by weight. Closer to the equator, this falls to 2–10 percent. There were exceptions though. Arabia Terra, an almost 2,000-mile-wide equatorial desert, and other equatorial exceptions showed indications of large masses of water. Mars was much more complicated than most had thought.