In his newly released book, Roving Mars Steve Squyres the Principal Investigator for the Mars Exploration Rovers, tells a tight and candid tale of his numerous attempts to get a string of mission concepts approved by NASA for Mars missions, then having to race to build MER A and MER B for an opportune launch window in June and July of 2003.

The aim of Squyres' mission - once he can get a rover to Mars - would be to search for past or present evidence of water and life. Sustained geologic activity on Earth over the last four billion years has made it impossible to obtain fossilized evidence showing how the miracle of life began, but on geologically quiescent Mars, nearly half the Martian surface is covered with rocks that are close to four billion years old.

'Mars is a world that can help us learn our place in the cosmos', says Squyres. 'If we go to Mars and find that it developed life, we've learned something fundamental about how common a phenomenon life may be. And if we go there and find that the conditions were once warm, wet and habitable, yet that somehow life didn't emerge, then we have learned something profound about the conditions that are required for life to develop'.

It was not enough for Squyres, he writes, to merely put an orbiter in place, around Mars, and take pictures. Rather, the only way to find out what secrets lay inside its rocks was to get down on the ground, and bang them open, like a geologist does with their hammer on Earth.

Once on the surface, a mobile vehicle could be the hands and eyes of geologists back on Earth, able to carry out detective work to piece together clues to learn in detail what this ancient world was like:

'Every rock preserves evidence of what conditions were like when it was formed. When sediments are deposited, the coarse grains settle close to shore and the fine ones in deeper water. Look at the grain size in a sedimentary rock, then, and you learn something about where it was laid down. Ripples preserved in rocks can tell you what was dissolved in the water.

Squyres' rover conception began, he says, soon after NASA's Mars Observer spacecraft went missing in the fall of 1993. JPL responded to the crisis by organizing some advisory committee meetings to try to help them decide what to do next. Mars Pathfinder would fly as planned in 1996, as well as a new orbiter called Mars Global Surveyor.

NASA had also decided they wanted to fly two missions in 1998- one an orbiter, the other a lander. A new concept that arose out of all those committee meetings was to have the Announcement of Opportunity seek an integrated suite of instruments for the lander: the whole scientific payload together in one proposal, instead of a bunch of separate proposals for separate instruments.

'What NASA was soliciting for the first time, was every tool that would be needed to go after some big scientific problem on another planet, all in one package. The idea was to give the scientists who wrote the proposal the ability to create a payload that could work as a carefully crafted ensemble of instruments maximizing the overall science return of the mission'.

Squyres introduces the reader to a collection of individuals � engineers who have designed instruments (Mini-TES, the Mossbauer spectrometer, the Alpha Proton X-ray Spectrometer, the Raman spectrometer, RAT and Pancam) for taking photographs and conducting science on Mars- whom he approaches to have their technologies incorporated into his competing rover concepts.

At every Announcement of Opportunity, Squyres' rover concepts fall short of being chosen by NASA headquarters, who tell him his payloads are not fully appropriate for the goals of the mission.

The disappearance, though, of Mars Polar Lander and Mars Climate Orbiter, open new opportunities, short-listing his Athena rover in 2003, that is then abandoned for cost and schedule reasons.

Squyres' hopes are lifted again when his Mars Geological Rover is just one of two (the other being the Mars Science Orbiter) missions short-listed by NASA to go to Mars in 2003.

New photos of gullies on Mars, taken by Mars Global Surveyor, become the next scientific 'puzzle of the moment'; Squyres frets the next mission will tip in favor of MSO, as the gullies are in the polar regions, where sunlight is faint - where only an orbiter could scrutinize them; a job not possible for a solar-powered rover.

A 'head-to-head shootout' gets underway on July 13 and 14, 2000, with both project teams summoned before a 'group of 12 wise men' at NASA headquarters to pitch for their missions.

'The card that we played aggressively came from simple celestial mechanics. The year 2003, it turned out, would provide the best opportunity to send a solar-powered rover to Mars for the next eighteen years. The trip required less rocket fuel than it would in most years, and once the rover arrived, Mars would be comparatively close to the sun, which was good for solar power, and also close to Earth, which was good for communications'.

A phone call from Scott Hubbard at NASA HQ a few days later not only confirms that Squyres' team had won, but that Dan Goldin wanted two rovers going to Mars!

Squyres then describes the race to get the rovers built in time for the 2003 launch window. The instruments must be calibrated and integrated; propulsion, motors, and telecom systems tested; painful choices will have to be made (i.e. some instruments removed) to reduce mass, and a new parachute and inflatable bag system developed to safely get the rovers onto the Martian surface.

In an ATLO (Assembly, Test, and Launch Operations) Readiness Review, the team's preparation for building flight hardware is seriously questioned by the Independent Review Team, who also deem Squyres' project to be too risky and over budget. Their recommendation is to "Focus ATLO on single flight vehicle to assure a fully flight qualified and characterized system".

The thought of their mission being reduced to just one rover horrifies Squyres. But with two rovers to test with, the team manage to meet ATLO deadlines and keep the two:

'With identical spacecraft, you can run two different tests at the same time, one with each vehicle, picking up time in your schedule. Or if something breaks before some critical test, you can pull a part off the other spacecraft and swap it in, rather than waiting for the broken part to be fixed'.

Unexpected technical problems arise with some instruments - speckled Pancam images, a broken APXS sensor head, a blown fuse and damaged ballast resistor- that threaten to derail launch readiness, but impressive trouble shooting by the team keeps them on track.

When launch day comes for Spirit and Opportunity, Squyres' sadness for them is almost akin to the death of a loved one:

'Spirit was leaving forever, and the best we could wish for her was a one-way trip with certain death at the end. We had done our best to prepare her for the dangers she would face, but had we done enough? We would hear from her, in the months ahead, reading her temperatures and her voltages, and viewing her pictures and spectra if she made it safely to Mars. But none of us would ever see her again with our own eyes, and that made me surprisingly sad'.

In preparation for a successful landing, the team use the ORT (Operational Readiness Test) facilities at JPL for full dress rehearsals for navigating MER A and MER B on the Martian surface. Training results turn out to be farcical, with bad commands repeatedly triggering the fault protection software, and lost data being accidentally deleted; Squyres recounts the test rovers often sat motionless sol after sol, and he estimates they did less than ten meters driving all up in the ORT's. 'At $4 million a sol, its not a very satisfying prospect', Squyres laments.

Squyres consoles himself by putting some of the errors down to JPL trying to trick the earth bound rovers into believing they were on Mars. In an ORT, there's no Sun. The rover gyros expect to have to compensate for the rotation of Mars. In an ORT, they have to compensate for the rotation of Earth:

'We're pretending to communicate with the rovers through the Deep Space Network, with radio signals traveling hundreds of millions of kilometers at the speed of light. In an ORT, all the communication takes place through network cables strung under the sidewalks at JPL, and we fake the light-time delays'.

The final, third section of Roving Mars gives a thrilling second-by-second description of Spirit and Opportunity's successful landings (as witnessed from within JPL's Cruise Mission Support Area), followed by diary-like entries of what the rovers discover each sol. The logs stop with Opportunity still inside Endurance Crater on sol 227, and Spirit climbing the West Spur of Columbia Hills on sol 248.

The rovers, by now, have found evidence that the rocks in the Columbia Hills and Meridiani had once been laid down in liquid water, being rich in minerals, like hematite, jarosite, and goethite (that precipitated from water). These areas must have been suitable for some primitive forms of life, says Squyres, but there is no way of knowing, from the data, whether life ever took hold here.

Only by picking apart the rocks, molecule-by- molecule, in a laboratory back on Earth, could scientists reveal what secrets hid in these rocks. Squyres says conditions at Meridiani are more suitable for life than anywhere else scientists can point to, on Mars, making it a great target for future exploration.

Squyres concludes his book by pondering the rovers' fate, marvelling at their longevity, and wondering when, and how, they'll inevitably die. He pays tribute to 'the skills and guile' of the engineers who built enough 'margin' into them, along with good fortune, for keeping the rovers alive, still, after 600 sols (for Spirit, that is, and slightly less for Opportunity). Squyres hopes someday, someone will see them again, when humans are ready to go to Mars.

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