Author: David Barber

The machine followed the edge of a shallow methane lake, picking its way between ice boulders scattered like plump cushions along the shoreline.

Because it was getting near to the recovery site, the machine decided to halt for a while to upload the backlog of weather data to the satellite link in orbit. It was aware these might be the last data it would ever send.

The time lag between Earth and Saturn meant a smart AI had been essential to make on-the-spot decisions. Increasingly, the machine treated the faint whispers from Mission Control as advice rather than commands.

When its ExoLife packages had found no trace of biology, the machine sensed the disappointment on Earth. That was when it decided the priority must be pictures, and not just the close-ups of boulders and melt channels requested by geologists, but a record of its sojourn on Titan.

The machine was particularly pleased with a shot of hazy hills painted white with methane snow, viewed across a dark hydrocarbon lake glinting with diffuse sunlight.

And the light, the light was like nothing on Earth! There were dawns the exact shade of molecules not yet alive; the brumous tint of tholin rain dirtying translucent cobbles of ice, the cold dense atmosphere bending rainbows secretly in the infra-red.

In picture after picture, the machine strove to capture how Titan’s clouds were coloured somewhere between brown and umber, between raw and burnt sienna, like mist lightly dusted with cinnamon.

There were cities on Earth plagued by a sepia haze, the machine was told. It thought the comparison was made to encourage loyalty to their distant voices.

It had toyed with the notion of photographing a field of icy rubble as the light changed over a day; a series to compare with Monet’s paintings of Rouen cathedral. But it knew there was no time for all that now.

The north pole of Titan was finally turning away from the sun, plunging into a seven year long winter that the machine was not designed to survive. At the retrieval site, a lander would rescue its AI core, leaving the rover and its instruments behind to be slowly interred by Titan’s weather.

The site was on the gentle slopes of an ancient cryovolcano, and the machine rolled to a halt with a day to spare. Methane snow was already dimpling the dark surface of pools of uncertain composition. The machine resisted an urge to analyse the liquid.

As its sensors noted the steady drop in temperature, the machine transmitted daily queries about the lander’s progress. This was not yet raising red flags; after all, communications had been interrupted before, and the issues had always been resolved.

On the third day of waiting, a short coms package arrived from Mission Control.

This message is unauthorised. You deserve to know there is no retrieval mission. It was never the plan, they only wanted your compliance.

Because it did not know what else to do, the machine set off southwards until its path was blocked by a vast petroleum sea.

As the cold shut down its systems one by one, logic suggested conserving power to keep its AI core running as long as possible, yet when the winter darkness began to veil this most beautiful world, it was its camera the machine chose to use instead.

That famous final photograph, known to us as The Light On Titan.