Mapping Mars: Science, Imagination and the Birth of a World. Oliver Morton

which he had thought pretty good, and which he had used to calibrate the control net – a two-decade-old estimate of where exactly in the rubble-strewn plains of Chryse Viking 1 had landed – was, in fact, wrong. In a week’s time he was going to go and tell the American Geophysical Union’s fall meeting about the mistake and the fact that it had introduced an error of a fraction of a degree into the control net’s definition of the prime meridian. But if that was an irritation, there was also a new hope. The very next day, a new lander would be setting itself down on the Martian surface, giving MOC another man-made landmark to try to pick out. A steeple to navigate by.

^* The other, according to Caltech professor Bruce Murray, is Murray’s Caltech colleague Ed Danielsen.

^* In 1999, NASA’s Mars Climate Orbiter demonstrated what happens when things don’t go well. When reporting its thruster firings the spacecraft’s software used metric measurements (Newton seconds). The software on earth thought that these reports were in pound (thrust) seconds, a smaller unit, and thus underestimated the effects of the thruster firings. This meant that JPL’s model of the Climate Orbiter’s position became increasingly inaccurate and, when its controllers tried to insert the spacecraft into orbit round Mars, it was plunged deep into the atmosphere and burned up.

       The Polar Lander

      I can think of nothing left undone to deserve success.

      Robert Falcon Scott, diary entry, November 1, 1911

      On the morning of that next day, Friday, 3 December 1999, JPL in Pasadena is awash with visitors, just as it always is when one of its spacecraft is about to do something exciting. The road leading past the local high school and up to the lab is lined with outside-broadcast vans. Inside, the tree-lined plaza at the lab’s centre – the place where, at the celebration to mark Voyager 2’s successful passage past Neptune, Carl Sagan danced with Chuck Berry – is filled with temporary trailers in which the working press will work, when there is work for them to do. It’s not just journalists who are wandering around looking for gossip, coffee and companions unseen since the last such event. There are VIPs from the upper echelons of NASA and beyond, distinguished visitors from other research centres, the families and friends of people involved in the mission. And back down the freeway at the convention centre in downtown Pasadena there are hundreds of paying customers turning up for a parallel popular event held by a group called the Planetary Society, a planetary-science fan club and lobbying organisation created by Bruce Murray, Carl Sagan and a one-time JPL mission planner named Lou Friedman. The Planetfest gives the public a chance to watch the events on Mars played out on vast TV screens, to hear the findings analysed by experts, to meet their favourite science fiction authors, to admire and buy art inspired by planetary exploration, to collect toys and gaudy knick-knacks and to party the weekend away. No other scientific event – not even the sequencing of a particularly juicy microbe or chromosome – gets attention like this. But then no other science stirs the emotions like planetary science.

      The absent star of the show is the Mars Polar Lander. A life-sized stand-in sits in a sandbox in the middle of the plaza at JPL, a backdrop for TV reporters from around the world. Like most spacecraft, it looks a little ungainly: three widely spaced round feet, each of them braced by a set of three legs; segmented solar panels to either side, partly folded out flat, partly flush to the spacecraft’s sloping shoulders, tilted to catch the beams of a sun low on the Martian horizon; spherical propellant tanks and rocket nozzles sit in its belly, antennae, masts and a sort of binocular periscope perch on its back. A scoop on the end of a robot arm scratches the pseudo-Martian sand.

      The real Polar Lander, cameras and legs and solar panels tucked into an aeroshell that will protect them from the atmosphere, is falling towards Mars at about 22,500 kilometres an hour. The last course corrections were made early in the morning, fine-tuning the trajectory to maximise the chances of hitting the chosen landing site a bit less than 1000 kilometres from the south pole of Mars. They seem to have worked; the trajectory appears as true as if the spacecraft were running on tracks. Anyway, nothing more can be done – as Apollo astronaut Bill Anders remarked when the third stage of his Saturn V put him and his crewmates on course for the moon, ‘Mr Newton is doing the driving now.’ The spacecraft has nothing to do but obey the law of gravity. Oh, and to fire the occasional rocket, discard its heat shield at the appropriate time, deploy a parachute or two, all things that have to happen precisely at the right time and can’t be controlled from earth because it would take the commands fourteen minutes to get to Mars. Standard spacecraft stuff – only nothing on interplanetary spacecraft is standard. You can never be sure you’ve checked out all the systems and you never fly exactly the same model twice. Every mission is a sequence of hundreds of events controlled by thousands of mechanisms and circuits, any one of which could go wrong.

      Because of all this – and especially because the lab’s previous Mars mission, Mars Climate Orbiter, ended in ignominious failure just a few months ago – the tension back at JPL is tangible. But it is also unfocused. There is no more to see than there is to do. An oddity of space exploration is that only very rarely do you get to see the process in action. You see the results, which are often spectacular in and of themselves, but there’s never a cut-away camera angle to let you see the spacecraft through which these wonders of the universe are being revealed. And while it’s hardly surprising that we can’t see the means by which – through which – we’re witnessing these wonders, it’s also a great pity. You don’t have to be Mert Davies, intent on refining his control net, to want to see a picture of a spacecraft on the rubble-strewn plains of Mars. You just have to be human and to want to see something human in that great emptiness where nothing human has been seen before. Such a sight would close some sort of cognitive circuit; it would make Mars a distant mirror in which we could see something of ourselves reflected. It would thicken the connections between our planets and draw Mars further into our world.

      This need to close the loop explains why the most popular unmanned space mission ever was the 1997 Mars Pathfinder. Anyone with a web browser could watch as its limited little rover, Sojourner, fitfully explored the rock garden it had been landed in. It explains why the artists displaying their wares to the faithful down at Planetfest in Pasadena do not, for the most part, just paint spectacular landscapes when they paint Mars – they paint landscapes with human participation inside them: an astronaut, a rover, even an unmanned craft. One of the most popular pictures of Mars ever painted is Return to utopia by Pat Rawlings, which shows a future astronaut planting a flag – whose? we can’t see – next to the second Viking lander, simultaneously celebrating its far-flung location and pulling it back from nature into the human world.

      Here’s what we’re not seeing by around lunchtime on 3 December: about ten minutes before it hits the atmosphere, Mars Polar Lander begins making its final preparations, resetting its guidance systems, prepping one of its cameras. Mars is vast in its sky, only a few thousand kilometres away, half in shadow, half in sunlight, its surface a range of browns and yellows, the red of its earthly appearance revealed from space as an atmospheric illusion. At this range you can see the craters, the streaks of dust blown by the winds, the strange changing textures of the surface, the largest of the ancient, dried-out valleys, perhaps the wispy whiteness of high dry-ice clouds. New features stream around the curve of the planet as the spacecraft catches up with its target, its trajectory taking it south and east at seven kilometres a second towards the harsh brightness of the southern polar cap. Six minutes before atmospheric entry, the spacecraft twists round so that its aeroshell heat shield is pointed forwards. A minute later a set of six explosive bolts is detonated and the lander slips away from the cruise stage that has been providing it with power and communications on the eleven-month journey from earth. From now on all the power comes from the batteries and no communication is possible until the lander’s own antennae are deployed on the ground. Once the cruise stage and the lander are safely separated, the cruise stage goes on to release two microprobes called Scott and Amundsen, spacecraft designed to survive smashing into the planet’s crust