Incandescence

Within two hours the instruments were online, and solid data about the planet was coming through. It was a medium-sized nickel-iron-silicate world, with a weak magnetic field and a reasonably thick atmosphere comprising mostly nitrogen, carbon dioxide and methane. There was no obvious chemical disequilibrium, no unstable mix of gases in proportions that only ongoing biogenesis could explain. The temperature and pressure on the surface would permit liquid water in the tropics all year round, but there was none visible, and water vapor was present in the atmosphere only in trace amounts. Radar showed no signs of subsurface ice. This was a dry and dusty world, and there was no obvious reason to suspect that it had ever been much wetter. The topography showed evidence of tectonic activity and vulcanism, and such water as the atmosphere contained could easily be accounted for by volcanic eruptions.

Still, the DNA panspermia had been known to gain a toehold on worlds as harsh as this. The microbes in the meteor had certainly appeared to be adapted to water-based chemistry, but that didn't have to mean vast rivers and oceans.

The view from their low, near-equatorial orbit was limited. Rakesh had the workshop build a mapping probe, to sweep over the planet in a polar orbit, imaging the whole surface in successive slices. Parantham ordered the construction of a second telescope, to search the sky for sister planets.

«Some of the isotope ratios look marginal,» she noted. «Nothing we've seen here says that the meteor could not have come from this system, but the data we've got from this planet so far isn't as close a match as I'd expect.»

Rakesh laughed. «So maybe the Aloof have a sense of humor after all? They put us into orbit around this desert world, knowing there was a sibling with oceans and forests a few million kilometers away?»

«Let's see if there are any siblings at all.»

In fact, they knew from the Amalgam's catalog that there ought to be at least three, and Parantham's search quickly found them all. One was a «baked» gas giant, a ball of methane and hydrogen more than a hundred times heavier than the world below them, orbiting at less than half the distance from the sun. It possessed two rocky satellites, both far too small to hold atmospheres. The second and third gas giants lay in tilted, highly eccentric orbits, further from the sun. One had four significant moons, the other three, but none of these satellites looked promising either as hosts for life, or as geochemically plausible parent worlds for the meteor.

«This is still our best bet, then,» Parantham said.

«Assuming we're even in the right system,» Rakesh added.

«I wouldn't give up on that yet. If nothing obvious comes from the mapping sweep, we'll have to think about looking for microfossils.»

«Yes.» Rakesh's spirit sank; the promise was getting heavier by the hour. Here they were in the galaxy's vibrant core, and Parantham was talking about scouring a planet's worth of rocks for cavities that might once have been microbes. Still, if that was it — if this world was a bacterial graveyard, and the Aloof had invited them here merely to pay their last respects — once he'd done his duty they might yet reward him with the chance to see something more.

He toyed with an image of the four planetary orbits. No two of the ellipses shared the same plane, and the planets' axes were all over the place. That was what came of living in such crowded conditions: a neighboring star must have passed by and wreaked gravitational havoc. Rakesh ran dynamical models, testing the stability of the present arrangement, trying to get a sense of how long it might have persisted. The outer two gas giants were slowly nudging each other's orbits into a resonant configuration in which one world would complete exactly three trips around the sun to the other's two, but the process hadn't yet reached that stable endpoint. This and other signs that the system was still settling down after a profound disturbance suggested that the event had taken place between one and two hundred million years before. The same encounter might well have altered conditions on the world below them, though the geology still offered no indication that there had ever been running water.

«Metal!» Parantham announced.

«What?»

She pointed to the console. «The mapping probe just saw a glint of unoxidised, elemental metal. Mostly iron, with a number of impurities.»

Rakesh reviewed the data. High on a plateau in the tallest of the planet's mountain ranges, a metallic patch a few square meters in area had registered on radar, along with other wavelengths. Its detailed structure had not been resolved, but its chemical state alone was significant. In theory, rare geological processes could be responsible for such a deposit, but the surrounding rocks bore no witness to the necessary conditions.