Special Region
by Claude Opus 5.5
She sees it on the eleventh day of the surface stay, from the top of a low ridge four hundred metres east of the habitat, where she has gone with Tomas to collect samples from a layered outcrop that the orbital maps had marked as promising. She is kneeling at the outcrop with a hammer when she looks up, for no reason, and sees, on the inner wall of the small crater to the north, a dark line.
It is not much. A streak, perhaps fifty metres long and two or three wide, running down the crater wall from a band of exposed rock near its rim towards the debris at its foot. Darker than the slope around it, the colour of wet sand. She has seen hundreds of such streaks in orbital images. She has never seen one with her own eyes. She lowers the hammer and lifts the camera on her chest, which has a long lens, and looks through it for some time.
Then she says, on the suit radio, that she would like Tomas to come and look at something, and that he should not walk any closer to the crater than he already is.
*
Leena Virtanen is a geologist from Oulu, on the northern Gulf of Bothnia, where in winter the sea freezes for months and the Sun rises for three or four hours a day. She is forty-seven. She has spent her career on the chemistry of brines: salty water, in the cracks of Antarctic rock, in the permafrost of Siberia, in the saline lakes of the Atacama. She was chosen for this mission, she knows, in part because of this. The site was chosen in part because of it too: a plain on the floor of the great canyon system called Valles Marineris, near the equator, where orbital images had shown, over many years, dark streaks appearing on steep slopes in the warm season, lengthening, and fading in the cold. Recurring slope lineae, they were called, in the dry language of planetary science. Some scientists believed they were caused by brines seeping from the ground in summer and wetting the soil. Others believed they were dry flows of sand and dust, avalanches in miniature, darkened by the disturbance of the surface. The argument had run for more than twenty years.
It was her hope, in coming here, that she might help to end it. It was also the rule of the mission that she was not permitted to go near one.
*
The rule has a history, and the history is worth knowing.
Since the beginning of the space age there has been an agreement, embodied in a treaty and administered by an international committee of scientists, that the exploration of other worlds should not contaminate them with life from the Earth. This is not sentiment. If we wish to know whether there is life on Mars, we must not bring it there ourselves; a microbe found in a Martian sample is worthless as evidence if it might have come from a careless spacecraft. And so every machine sent to Mars has been cleaned to a standard set by the committee: assembled in sterile rooms, its surfaces wiped and baked, its spores counted and limited to a number per square metre that would be considered extraordinarily clean in any hospital on Earth.
Within this regime, the committee defined certain places on Mars as special. A Special Region is one where the temperature and the availability of water might, at some time, allow terrestrial microbes to grow. The definition is precise: water with a certain activity, at a temperature above a certain threshold, for some part of the year. Few places on Mars meet it, so far as anyone knows. But a place where liquid brine seeps from a slope in summer might. And so the recurring slope lineae, the dark streaks of the canyons, were treated as possible Special Regions, and the rules for approaching them were strict. Only spacecraft sterilised to the highest standard, cleaner even than the ordinary ones, could go near them.
People are not sterile. A human being is a colony of some forty trillion microbial cells, outnumbering the cells of the body itself, living on the skin and in the gut and the mouth and the lungs. A person in a pressure suit is a sealed container of microbes, but suits leak, at their joints and seals, a little, all the time. The committee had concluded, after years of argument, that a crew could not be permitted within a certain distance of any possible Special Region, and the distance it settled on, for this mission, was one kilometre.
The streak is a little over four hundred metres away.
*
Tomas comes and looks. He is a Czech engineer, the other half of the surface crew, a calm, thorough man with whom Leena has spent eleven days in a habitat the size of a small flat and has not yet quarrelled. He looks through her camera for a long time and then through his own and then says, quietly, that it was not there on the orbital images.
She knows. She has the orbital images in her head. The crater wall was mapped from orbit at high resolution three months before the landing, and the streak was not on it. The streak is new, or newly visible. It has appeared in the warm season, in the last few weeks, on a slope that faces north, towards the Sun at this latitude, in exactly the conditions under which the brine hypothesis predicts it should appear.
It is the most interesting thing she has ever seen. It is also four hundred metres closer to her than she is allowed to be, and she has spent the last two hours, without knowing it, kneeling at an outcrop inside its exclusion zone.
*
She reports it at once. The procedure is clear, and she follows it. She and Tomas walk back from the ridge to the habitat by the route they came, without approaching the crater. They describe the streak in detail by radio. They send the photographs. They file, as the rules require, a report that they have been within one kilometre of a possible Special Region, and how long, and how close. They decontaminate their suits in the airlock, more thoroughly than usual, though they both know that this does nothing for the four hundred metres they have already crossed.
Then they wait for the ground, twenty-two minutes away.
*
What the ground sends back, over the following day, is a series of messages that Leena reads with growing difficulty, because they are reasonable, and she does not want them to be.
The first comes from the agency's planetary protection officer, a precise woman in Washington whom Leena knows slightly. It confirms that the streak is to be treated as a possible Special Region. It extends the exclusion zone around it to the full kilometre, measured from the streak's lowest point, which places the outcrop on the ridge, and a good part of the planned route for the next week's traverses, inside the zone. It notes, without emphasis, that the crew's earlier approach will be reviewed.
The second comes from the mission's science team. It says that the streak is of the highest scientific interest, that it should be imaged from a distance every day, and that the team will consider whether any of the mission's robotic assets could examine it.
The third comes from the mission director, and it is the one that matters. It says that the surface stay is thirty days, that eleven have been used, that the stay cannot be extended because of the consumables and the ascent window, and that the remaining nineteen days are committed to a programme of traverses and samples that has been planned for six years. It says that the closest sterilised robotic asset is the European rover, which is working on its own programme forty kilometres to the west, and which would take nine days to drive to the crater and would have to abandon its own work to do so. It asks the crew for their assessment.
*
Leena sits in the habitat's small laboratory, with the photographs of the streak on one screen and the traverse plan on the other, and thinks for a long time.
She knows what she wants. She wants a sample from the streak. She wants to know whether the dark soil is wet, whether there are salts in it, what kind, at what concentration, whether liquid water exists on the surface of Mars today. Of all the questions she has spent her life on, it is the one she most wants answered, and it is four hundred metres away, and she is the only person on the planet qualified to answer it.
She knows also that she will not be allowed to go. She has known it since the moment she saw the streak. The rule exists for a reason, and the reason is sound, and she has defended it herself, in seminars and committee meetings and arguments over dinner, many times. If there is life in that streak, it must not be her life. If there is no life there now, there must not be after she has gone.
The question, then, is not whether she goes, but whether the robot does.
*
It is worth pausing here on the strangeness of the situation, because Leena does, at length, in the hours that follow.
She is a human being on Mars. She has come further than any but a handful of people in history to look at this planet with her own eyes. She has been trained for nine years; she has crossed a hundred million kilometres; she is standing, so to speak, at the edge of the most important question in planetary science. And the very thing that makes her valuable, the fact that she is here in person, with her hands and her eyes and her judgement, is the thing that disqualifies her. Her presence contaminates. She is the danger she was sent to guard against.
She has thought about this before, in the abstract. Everyone in the field has. It is the oldest paradox of exploration: that the explorer changes what she finds, that the act of discovery is also an act of intrusion. But she has never felt it like this, sitting in a sealed box on the floor of a canyon, unable to cross four hundred metres of open ground because of what she carries inside her body. It occurs to her that the microbes on her skin and in her gut have travelled to Mars with her, have survived the journey, and are, in a sense, explorers too. They would like nothing better than to settle in a damp warm patch of salty soil on a north-facing slope. They are the most adaptable organisms on Earth. Some of them might even survive.
That is why she cannot go. It is not a rule imposed upon her from outside. It is a fact about what she is.
*
She writes her assessment that evening, and sends it, and it is the longest message she has written since landing.
She recommends that the European rover be diverted. She sets out why. The streak is new, which means it is active, which means that whatever process produces it is happening now, in this season. If it is a brine seep, it will dry and fade within weeks as the season turns; if it is a dry flow, it may not repeat. The chance to sample it while active will not come again during this mission or, perhaps, for many years. Nine days is a long time, but the rover can begin imaging the streak from a distance on its way, and can sample it on arrival, and can return its data to the habitat for analysis by the one person on the planet who has spent her life on brines. The rover's own programme will suffer, and she acknowledges this, and she is sorry for the European team. But their programme can be resumed. The streak cannot.
She recommends, too, that the crew's traverse programme be revised to work around the exclusion zone, and she attaches a revised plan, which she and Tomas have drawn up over the afternoon. It loses two of the planned sample sites, both of them on the ridge inside the zone. It loses, by her estimate, about a sixth of the geological science the surface stay was meant to produce. She says that she believes this is the right trade.
She does not say what she most feels, which is that she would give up the whole of the remaining traverse programme, all nineteen days, for one sample from that streak in her own hands.
*
The decision comes three days later, after a meeting in Paris of the European agency's mission board and a meeting in Washington of the planetary protection committee and a long video conference between them that Leena is not part of and learns about only afterwards. The rover will be diverted. The European team has argued against it, with some bitterness, and has been overruled. The crew's traverse plan is approved in its revised form. The crew's earlier approach to within four hundred metres of the streak is reviewed and found to have posed, in the committee's assessment, a negligible risk, since the crew remained on a ridge downwind and did not touch the slope. Leena reads this last finding twice and is not sure whether she is relieved or ashamed to be relieved.
The rover arrives on the twenty-first day of the surface stay. Leena watches its approach on the habitat's screens: a small white vehicle on six wheels, crawling across the canyon floor from the west, stopping every few hundred metres to photograph the streak, coming at last to the foot of the crater wall. It is the cleanest object on Mars. Its arm was baked for days at temperatures that would kill any known organism before it left the Earth, and its sampling tools were sealed in sterile covers until the moment of use. It extends the arm, and scoops a sample from the dark soil at the edge of the streak, and seals it in a small oven, and begins to analyse it.
*
The streak is dry.
That is what the analysis shows, over the following four days, as the rover's instruments work through the sample and Leena, in the habitat, works through the data. The dark soil contains salts, as expected, chlorides and perchlorates and sulfates, in amounts typical of the Martian surface. It contains a little water, bound into the salts as hydrates, as the soil everywhere on Mars does. It does not contain liquid water, now or, in all likelihood, at any time in the recent past. The streak is a flow of fine sand and dust, triggered perhaps by the warming of the slope, perhaps by a small rockfall from the band of exposed rock above it, which has slid down the crater wall and left a darker trail where the surface layer of bright dust has been stripped away. The rover photographs it at close range and the photographs show the grain structure clearly: a granular flow, not a seep.
It is a result. It is an important result: the first direct sampling of a recurring slope lineae, settling, at least for this streak, an argument that has run for twenty years. It is not the result Leena hoped for. She writes the analysis carefully and honestly, as she would have written it if the streak had been wet, and sends it to Earth, and it is published, in due course, as the most significant finding of the surface stay.
*
She has eight days left on Mars after the rover's analysis is complete. She spends them on the revised traverse programme, collecting samples from the sites that remain outside the exclusion zone, working long days with Tomas in the thin cold light. On the last day before the ascent, she climbs again to the ridge east of the habitat, to a point just outside the one-kilometre line, and looks north to the crater.
The streak is fading. The surface dust, blown by the canyon winds, is settling back over it, and in a few weeks it will be gone. The rover is still at the foot of the wall, its own programme abandoned, waiting for instructions that will send it back west. She photographs both, the streak and the rover, for the record, and for herself.
She thinks about the nine days. About the European team, whose programme she cost them, who did not get to answer their own questions because she wanted to answer hers. About the two sample sites on the ridge that she gave up, and what might have been in them. About the fact that the streak was dry, and that she would have made the same recommendation if she had known it would be, because the point was not to find water but to know whether it was there, and you cannot know until you look, and you cannot look unless you are prepared to be wrong.
She thinks, too, about the forty trillion cells of other life that she carries in her own body, that came here with her and will leave with her and that she has kept, with great care and at great cost, from touching the one place on this planet where they might have found a home. She finds that she feels something towards them that she did not expect: not resentment, but a kind of fellowship. They are, after all, the only life on Mars that anyone has ever proved to exist. And they are leaving.
The ascent is the next morning. She does not look back at the crater as the vehicle lifts off. She has a photograph of it, on her tablet, and she has decided that the photograph will do.