Greg Egan - The Arrows of Time

It was a nice idea in principle; maybe she really could live up to it. But whether or not her competitors had already had the last word, she was hungry to return to her calculations, reinvigorated by this proof that her efforts so far had not been wasted.

Tarquinia said, ‘Make sure everything’s secure in your cabins. I’ll need to run the engines hard for a while; we still have a lot of velocity to shed before we can go into orbit around the planet.’

Agata said, ‘Right.’ The shape of the cosmos would have to wait; there was still the small matter of Esilio.

While Azelio and Tarquinia debated the merits of different landing sites, Ramiro clung to a rope beside the window and gazed down at the starlit world below. How could he understand Esilio? Of all the sciences he’d studied as a child, geology had been the least developed – and at the time, he’d imagined, the least likely ever to be of use to him. Of the little that he remembered, he remained unsure what he should trust. The ancestors had had no idea what a rock was actually made of, while their successors, with all their superior knowledge, had never set eyes on a planet.

‘We need to be within walking distance of four or five different kinds of soil, or what will the crop tests be worth?’ Azelio said heatedly.

‘I appreciate that,’ Tarquinia replied. ‘But if we don’t come down on flat, stable ground, we could damage the Surveyor irreparably.’

Over the eons, Ramiro had been taught, every kind of rock exuded traces of gas, and for a body with sufficient gravity this gas would accumulate into an atmosphere. If the body also happened to orbit a star, winds driven by the temperature difference between day and night eroded the rock, and once there was airborne dust and sand that accelerated the process. The routes of the dust-flows carved out valleys and mountains, shaped as well by the differing durability of the underlying rock. But where had those various minerals come from? As far as he recalled, no one even knew for sure whether they dated all the way back to the entropy minimum, had formed over cosmic time from the sedate decay of some primordial substance, or had been forged in the core of a giant ur-world where liquid fires – contained for a while by its unimaginable gravity – thrashed and churned until the whole thing finally split apart and scattered.

Tarquinia brought an image of the next candidate onto her console, taken in full sunlight with the time-reversed camera. Ramiro struggled to interpret it, but the combination of near-smoothness and suspiciously delicate ridges suggested a plain of wind-ruffled dust into which the Surveyor might sink and vanish.

‘Can’t we just settle for the safest-looking ground?’ he proposed. ‘If it turns out that there’s a problem with the soil, we can always ascend and come down somewhere else.’

Azelio turned to stare at him angrily. ‘I’m not spending years hopping from site to site! That’s not what we agreed to!’

‘All right. Forget it.’ Ramiro regretted speaking so carelessly; Azelio had his niece and nephew to think of.

Tarquinia summoned another image. ‘Why do we only have two probes?’ she fretted. They could send one down in advance of the Surveyor , and the second if their first choice proved unsuitable, but that was the limit: the probes weren’t sophisticated enough to explore more than one location each.

‘Perhaps we could extend the survey for a few more days,’ Ramiro suggested. The planet was turning beneath them as they circled from pole to pole; each successive orbit carried them over a different meridian, and though they’d sampled a wide variety of terrain they were still far short of seeing everything. ‘There has to be a perfect site down there.’

‘Exactly!’ Azelio replied. He gestured at the console. ‘None of these are acceptable.’

‘We can keep looking,’ Tarquinia agreed. ‘A few more days is nothing.’

Azelio excused himself to check on the plants. Weightlessness wasn’t good for them, but it wasn’t worth setting up the tether again – not unless the selection process was going to stretch out into stints, rather than days.

Tarquinia switched to the live feed from the time-reversed camera: dawn was breaking over a red plain criss-crossed by brown fissures.

‘Look at all that land!’ Ramiro marvelled. If every field of wheat in the Peerless were laid out here side by side, they would pass by in a flicker, lost in the vastness. The sagas were full of journeys on foot that had crossed ancient empires and lasted for years, but nothing he’d read or imagined had prepared him for the scale of the world below. ‘How could the first travellers ever give up so much freedom?’

‘I think the Hurtlers might have helped,’ Tarquinia suggested.

‘Yes, but I still wouldn’t have been able to do it. We never belonged cooped up in a mountain; it’s a wonder we didn’t all lose our minds generations ago.’

‘So you’re set on making this your home?’ Tarquinia asked. ‘Esilio’s won you over already?’

Ramiro buzzed softly. ‘Esilio’s one thing, but twelve more years of travelling will probably finish me off.’ He would have relished defying Greta and staying behind when the Surveyor departed – and it would not have undermined the purpose of the mission if the rest of the crew returned to the Peerless with the news that a colony had already been established. But he couldn’t do it alone.

Tarquinia said, ‘And wide-open spaces are one thing, but you can’t eat dirt. Before you start picturing the flowers on your grave, let’s see if anything can take root here at all.’

The probe parted from the Surveyor , separated by a burst of air before it fired its engines to start the descent from orbit. Ramiro peered over Tarquinia’s shoulder to watch the instrumentation feed. Azelio looked on from Tarquinia’s right, and even Agata had left her calculations for a while to cling to the rope beside him.

As the probe slowed to let gravity bring it down, it didn’t take long to fall back behind the Surveyor ’s horizon, cutting the link. ‘Do you want to sleep for the next few chimes?’ Agata teased Ramiro. ‘I promise to wake you when all the results are in.’

‘No thanks.’ Ramiro asked Tarquinia to replay the recorded data; something unsettling had caught his eye. ‘Look at how hot it was, just before we lost contact!’

Azelio said, ‘We were expecting some frictional heating, weren’t we?’

‘Not so soon. Not at that altitude.’

Tarquinia frowned. ‘We’re not suffering any unexplained drag ourselves, so I don’t see how we could have the density profile that wrong.’

Ramiro didn’t want to argue about the cause; the fact remained that the heating was unexpected. ‘If this thing burns up out of sight, we’re never going to know what happened – or what we need to change when we try again. If we make the wrong guess we could lose the second probe the same way.’

Tarquinia contemplated this gloomy scenario. ‘Then we’d better move quickly,’ she said.

Ramiro was already strapped to his couch, but Agata and Azelio had to clamber into place as the Surveyor tilted then ascended rapidly. The cabin window faced the stars, but on the navigation console the land could be seen falling away as Tarquinia widened their horizon to reestablish a line of sight to the probe.

When the link was restored she cut the engines, letting them continue the upwards arc from momentum alone. Ramiro was dizzy after the unaccustomed weight, but when his head cleared he focused on the data feed. The probe’s temperature was still high, but it was less than before.