1 What Is Life?

       Starlight glistens on a spaceship’s silvery hull as it cruises, unseen and unmanned, amongst the planets of a distant solar system. Guided by the encoded instructions of an alien civilization it glides past dark, rocky planetary outposts and bloated gas giants until it reaches its goal, and swings into the orbit of an inner planet. A probe is released. Retrorockets fire that adjust the probe’s trajectory, easing it slightly from the mother-ship’s geostationary orbit and turning its heat-resistant nose towards the ground. The grip of the planet’s gravity drags the probe inwards, through ever-decreasing orbits. Faster and faster it spins until, plunging through clouds, it finally emerges under a leaden sky. A parachute is released to halt the headlong dive, and the craft slowly descends to land on a rock-strewn landscape.

       Minutes later, a metallic lid is drawn back, exposing a camera lens, and pictures are beamed back to the mother-ship. The camera pans across the rocky scene. The same rubble-strewn landscape is everywhere – rocks of all shapes and sizes lie sunken into fine grey sand. The air is still. Nothing moves. The camera scans the monotonous surface stretching in all directions towards the horizon – grey rocks, some precariously balanced atop others, others lie shattered, blasted by the forces of alien weather. The camera pans again, and then one rock, in shape and colour much like any other, spreads its