Origin. Stephen Baxter

diameter, as large in area as five old Moons put together – and a lot more than five times as bright, because of its reflective cloud and water.

      And this morning, the Red Moon was blue. The hemisphere facing him showed a vast, island-strewn ocean, blue-black and cloud-littered, with the shining white of ice caps at the northern and southern extremes. The Red Moon’s north pole was tilted towards Earth by ten degrees or so, and Malenfant could see a huge high-pressure system sitting over the pole, a creamy swirl of cloud. But dark bands streaked around the equator, clouds of soot and smoke.

      Malenfant, for all his personal animosity, admitted that the new Moon was hauntingly lovely. It even looked like a world: obviously three-dimensional, with that shading of atmosphere at the sunlit limb, and sun casting a big fat highlight on its wrinkled ocean skin, as if it were some immense bowling ball. Poor Luna had been so dust-choked that its scattered light had made it look no more spherical than a painted dinner plate.

      Malenfant, understandably obsessive, had kept up with the evolving science of the Red Moon.

      The new Moon turned on its axis relative to Earth – unlike departed, lamented Luna with – a ‘day’ of about thirty hours, so that Earthbound watchers were treated to views of both sides. The other hemisphere was dominated by the worldlet’s main landmass: a supercontinent, some called it, a roughly circular island-continent with a centre red as baked clay, and fringed by grey-green smears that might be forests. The Red Moon was hemispherically asymmetric, then: like Mars and Luna, unlike Earth and Venus.

      That great continent was pitted by huge, heavily eroded impact craters: to Malenfant they were an oddly pleasing reminder of true, vanished Luna. And the centre of the supercontinent was marked by a single vast volcano that thrust much of the way out of the atmosphere. Its immense, shallow flanks, as seen in the telescope, were marked at successively higher altitudes by (apparent) rings of vegetation types, what appeared to be glaciers, and then by bare rock, giving it to terrestrial observers something of the look of a shooting target. (And so the commentators had called it Bullseye.)

      The Red Moon’s mightiest river rose on the flanks of the Bullseye. Perhaps that great magma upwelling had lifted and broken ancient aquifers. Or perhaps air uplifted by the great mountain was squeezed dry of its water by altitude. Anyhow the river snaked languidly across a thousand miles to the eastern coast, where it cut through a mountain chain there to reach the sea at a broad delta.

      There were mountains on both east and west coasts of the supercontinent. They were presumably volcanoes. Those on the east coast appeared to be dormant; they were heavily eroded, and they seemed to cast a rain shadow over the desiccated interior of the continent. There was, however, a comparatively lush belt of vegetation between the mountains and the coast. The commentators had called it the Beltway. The greenery pushed its way into the interior of the continent in a narrow strip along the valley of that great river, which was a Nile for this small world.

      But the mountains on the west coast were definitely not dormant. Presumably prompted by rock tides induced by Earth’s gravity field, they had been observed to begin erupting a few days after the Red Moon’s arrival in orbit around Earth.

      They must have been spectacular eruptions. Thick, dense rock near the surface appeared to have blocked the magma flows, bottling up increasing pressure before yielding explosively like a champagne cork flying out of a bottle. On Earth, such stratovolcanoes – like Mount Fuji, Mount Rainier – could eject debris miles into the air. On the Moon the volcanoes had blown debris clear of the planet altogether. Meanwhile vast quantities of dust and gases had been pumped into the atmosphere, to spread in thick bands around much of the Moon’s middle latitudes.

      There was a great deal you could tell about the Red Moon, even from a quarter-million miles, with telescopes and spectrometers and radar, as the two hemispheres conveniently turned themselves up for inspection. For instance, those oceans really were water. The temperature range was right – as you’d expect since the Moon shared Earth’s orbit around the sun – and examination of the visible and infra-red spectra showed that the clouds’ caps were made of water vapour, just the right amount to have evaporated off the oceans.

      The Red Moon’s surface gravity was some two-thirds Earth’s – a lot more than Luna’s, and, crucially, enough for this miniature planet to have retained all the essential ingredients of an Earthlike atmosphere: oxygen, nitrogen, carbon, water vapour, carbon dioxide – unlike poor barren Luna. So the Red Moon had water oceans and a nitrogen-oxygen atmosphere.

      Already the study of the Red Moon had revolutionized the young science of planetology. With a quarter of Earth’s mass – but four times the mass of Mars, some twenty times the mass of Luna – the Red Moon was a planet in its own right, intermediate in size between the Solar System’s small and large denizens, and so a good test-bed for various theories of planetary formation and evolution.

      It differed in key ways from Earth. Because it was so much smaller, it must have started its formation (wherever that had occurred) with a much smaller supply of heat energy than Earth. And that inner heat had been rapidly dissipated through its surface.

      Like a shrivelled orange, the Red Moon’s rind was thick. Probably aeons ago, the tectonic plates fused, and continents no longer slid over its face. There was no continental drift, no tectonic cycling, no oceanic ridges. Unlike Earth, the Moon’s uncycled surface was very ancient; and that was why the interior of the continent bore those huge eroded craters, the scars left by immense impacts long ago.

      And that was why the Bullseye was so vast. The huge shield mountain had probably formed over a fountain of magma erupting through a flaw in the crust layers. The crust beneath it must have been held in place over the flaw for hundreds of millions of years – so it more resembled Mars’s Olympus Mons than, say, Earth’s Hawaiian islands.

      But there was more than geology up there. On the Red Moon, it appeared, there was life.

      The air was Earthlike, containing around a sixth oxygen – a smaller proportion than Earth’s atmosphere, but difficult to explain away by non-living processes. It hadn’t taken long to establish that the green-grey pigment that stained the fringes of the supercontinent and its wider river valleys, as well as the shallower sections of the world ocean, was chlorophyll, the green of plants. There were other fingerprints of a living world: an excess of methane in the air, for example, put there perhaps by bacteria in bogs, or burning vegetation, or even the farts of Moon-calves. Though some scientists remained sceptical – and though nobody could say for sure if the Red Moon harboured anything like bogs or bacteria or cows – most people seemed to concur that there was indeed life on the Red Moon, life of some sort.

      But was there intelligence?

      Nobody had detected any structured radio signals. There had been no response to various efforts to signal to the Red Moon using radio and TV and laser, not to mention a few wacko methods, like the cutting of a huge right-angled triangle of ditches into the Saharan desert filled with burning oil.

      But what were the mysterious lights that flickered over the night lands? Most observers claimed they were forest fires caused by lightning or drought. Perhaps, perhaps not. Could the streaming ‘wakes’ sometimes visible on the great oceans be the wakes of ships, or were they simply peculiar meteorological features? And what about the geometrical traces – circles, rectangles, straight lines – that some observers claimed to have made out in clearings along the coasts and river valleys of the Red Moon’s single huge continent? What were they but evidence of intelligence?

      And if any of these signs were artificial, what kind of being might live up there to make them?

      Malenfant was willing to admit that one manned expedition could do little to probe the mysteries of a world with fully half the surface area of Earth. But there were mysteries that no amount of remote viewing could unravel. The fact was, the most powerful telescope could not resolve an individual human being up there.

      Malenfant was never going to find Emma by staring up from Earth.

      But at this time of crisis, nobody wanted to see Malenfant’s drawings of rocket boosters and gliding spaceships.