Aeschliman was instructed in the planetary mappers’ technique by Bridges – ‘There were times when I thought I’d just never be able to do it’ – but his greatest respect was reserved for Inge. ‘He was very spontaneous. He worked very rapidly and his work sort of sparkles. It has a presence.’ Inge, now confined to a wheelchair by multiple sclerosis and myasthenia gravis, is flattered when I remind him that Aeschliman thinks of him as an artist. Though his living room walls are decorated with expressive abstracts he’s painted, Inge claims to set little store by them. ‘I’m a dabbler; I don’t think I qualify as anything better than a good motel artist.’ But then Inge didn’t set out to be an artist; he was always set on being part of the research programme itself. So while he plays down any pride that he takes in the obvious artistry of his maps, he is happy to boast about the projects they have made him part of. ‘Of the twenty-five mappable surfaces in the solar system – the solid planets and moons we’ve visited – I’ve worked on eighteen of them.’
Of all those surfaces, Mars had the most time and ink devoted to it. In 1971 Batson and Masursky decided that they would cover the whole planet at a scale of one to 5 million – fifty kilometres to the centimetre, a scale at which the smallest features identifiable in the Mariner 9 data would be just discernible. To make the work manageable, the surface was cut into thirty pieces, known as quadrangles. Pat Bridges mapped an astonishing eleven of them; Hall, Davis and Sanchez between them did another twelve; Inge did seven as well as maps and globes of the whole planet. He also oversaw the production process, imposing rigorous quality control, doing the half-tone separations personally, flying to the survey’s presses in Reston, Virginia to supervise the printing and making ‘an obnoxious little shit’ of himself. The series was not finished until 1979, eight years after Mariner 9 arrived at its destination. But the final result is magical. These are maps to lose yourself in, like windows in a spaceship’s floor. They seem at the same time transparent to the truth and dense in artistry. They combine the presence of that which is real with the power of that which is inscribed.
The 1960s and 1970s were a great time for mapping. The space age was coming home to roost: the earth, that always-inhabited, always-experienced world, was being made over into an objectivised planet just like its neighbours, a minutely measured ball of rock and water. In the 1960s Argon spy satellites, offshoots of the Corona programme with cameras optimised for map making, were used to produce vast mosaic maps of poorly surveyed Africa and Antarctica. Other satellites were busily tightening up a global control net far more sophisticated than the Martian one, refining humanity’s knowledge of the shape of its world so that missiles would more easily be able to find their targets. The needs of the nuclear submarines from which those missiles would be launched, along with the interests of a new generation of earth scientists, were driving new studies of the earth’s ocean floors; while detailed data on the ocean depths were highly classified, beautifully drawn maps based on those data allowed earth scientists to see the spreading ridges and transverse faults central to new ideas about plate tectonics.
But the earth, partly because of those submarine-hiding oceans, could never be mapped in its entirety in the way that Mars was. Nor could it be mapped with such supreme disinterest. Earthly maps are heavy with duties to property and strategy, duties which can warp and distort them. On Mars everywhere was alike; nowhere was rich, or strategic, or owned, and so a pure disinterest reigned. There was a political point in their publication – these were American products, based on American ingenuity, printed by the American government – but in the images themselves there was nothing but the data, the interpretation and the artist’s style.
Though they were in some sense less faithful to the truth of the planet than the television images they were based on, the maps were far more approachable, especially for the layperson.* They had a feeling of naturalism that the other forms the data were presented in lacked. Like most naturalism, this was highly contrived, depending on a number of strict conventions. Tricks of shading were used to make sure the users’ eyes saw craters as dimples, not domes (an inside-out illusion endemic in photographs of planetary surfaces). The regional differences in the surface’s albedo – the curves and blotches which are all that you can ever see of Mars through any earthly telescope – were suppressed. Mars’s albedo was controlled not by the nature of its surface features but by the way the wind blew dust around and over them (the dusty bits were bright – the bits swept clear were darker), and winds were not something the mapping project was interested in. Inge developed a clever way of making separate albedo plates so that the maps could be printed with regional patterns or without, but after a few quadrangles the effort was given up. Nor was the colour on the final prints – a soft, light-brownish pink – the real colour of Mars. It was a colour chosen by Inge just to give a feeling of Mars. And somehow it did. The maps are indeed, as Inge always insists, technical documents that happen to have been drawn up in pictures, not words. But they were something more, too. After the maps were made, the real Mars was not only a surface under the spacecraft’s circling cameras. It was also something directly available to, and through, human minds and eyes and hands.
Sadly, mapping Mars descended from being a delight to being a chore. Almost as soon as the first series of one to 5 million maps was finished, it was decided to revise them using new pictures taken by the Viking orbiters which had reached the planet in 1976. The original artwork was pulled out of storage and reworked on the basis of the new data. Because the control net had evolved, features had moved a bit and fudges had to be made. New detail was added, but in some cases the resulting maps looked cluttered and confusing. Inge was no longer checking the presses and the colours became less subtle. Frictions between Inge and Batson took their toll. Bridges retired in 1990; Inge left in 1994 and became embroiled in litigation with the Survey on the basis that his medical condition was unreasonably used to prevent his re-employment in 1997.
The airbrush artists were not replaced. Batson saw that new computer systems could make photomosaics ever more maplike – the Mars Digital Image Mosaic 1:2 million series he oversaw the creation of is now the basic reference for almost everyone who studies the Martian surface. The topographic mapping of the planets is now almost entirely a matter of image processing. This has not banished beauty. In the late 1980s a geologist named Alfred McEwen produced some magnificent views of large reaches of the planet on the computer while at Flagstaff. An image he made of the western hemisphere – the ridge of Tharsis volcanoes close to the limb, the gash of Valles Marineris across the centre, the thin trace of Echus Chasma running thousands of kilometres towards the north like a gold highlight – may be more widely circulated than any other picture of the planet. It is to Mars what Harrison Schmitt’s endlessly reproduced picture of east Africa, the Indian Ocean and Antarctica, taken during the Apollo 17 mission, is to the earth. But though they can be beautiful and highly accurate – on such work you can improve things pixel by pixel if need be – the computer images lack the intimacy of the airbrush. By 2000 the late-comer Aeschliman was the only old airbrush hand remaining at the Survey’s Flagstaff branch and he was doing his work entirely on screen. There is still an airbrush on the premises somewhere, but there is no longer any compressed nitrogen to bring it to life.
The maps themselves, scarred by revisions, sit in storage. All, that is, except one. Late in 1972, according to Jurrie van der Woude, who looked after some of the logistics of the Mariner 9 pictures and has been doing similar things at JPL ever since, Bruce Murray pleaded for a copy of the one-sheet shaded relief map of the whole planet that Batson’s team was making based on the Mariner data. Van der Woude called Batson in Flagstaff, who admitted that Inge and Bridges had finished the map. Plates of it were being made for reproduction. When it was released it would turn out to be big news – a page of its own in the New York Times, a British tabloid headline screaming ‘American Miracle – Map of Mars!’. But it was not yet released. Indeed, there were not yet any printed copies.