Incandescence by Greg Egan

naked, he had nobody but himself to blame. He'd known from the moment Lahl had offered him the key exactly how vulnerable he'd be, and he'd poured scorn on his friends' concerns. These were the terms, this was the deal; it was too late to have second thoughts. In principle, the possibilities for abuse were endless: the Aloof could be systematically torturing a billion helpless Rakesh-clones at this very moment. When he'd mentioned this primal fear to Parantham back on Massa, she'd pointed out that, while she'd regret the Aloof making anyone suffer, they could easily construct
de novos
of their own from scratch in order to mistreat them; sufficiently deranged sadists could always manufacture someone to torture, removing any need to lure their victims into a trap. In any case, Rakesh decided, there was nothing to be gained now from such paranoid speculation. Having handed their minds and bodies to their hosts as open books, the only sensible strategy that remained was to take their pleasant surroundings at face value and assume that the Aloof's hospitality, however narrowly defined, was genuine.
    Back in the meteor room, they set to work. Rakesh had never had reason to be much of a materials scientist or ejecta expert before, and as he invoked the aid of the library the knowledge that flowed into him brought a thrill of discovery, a sense of new vistas opening up before him, that stretched far beyond his immediate needs. Imbibing a massive bolus of pre-digested information was not his usual means of educating himself — he much preferred the slow process of building incrementally on his own prior knowledge, testing and interpreting every assertion before accepting it — but there was no denying the rush of suddenly having thousands of new facts and insights jostling in his skull.
    The equipment the Aloof had given them could probe the meteor's surface down to an atomic level; elicit and analyze emissions across the spectrum from gamma rays to microwaves; tomograph it in a thousand different ways; strike it, tap it, pound it, tickle it, and listen to the harmonics as it rang like a bell. Its gross chemical composition and its rarest impurities, its crystalline microstructure and the subtlest deformations thereof, were there for the asking. This rock, Rakesh thought, was as naked to them as they were to the Aloof.
    He and Parantham collaborated efficiently, discussing the best strategies for the investigation, speaking a dense specialist lingo that would have been foreign to them both just minutes before. The primary interface to all of the instruments was a touch-screen console, but mercifully they weren't limited to reading the screen and tapping menus; the Aloof had tailored the interface to their detailed embodiments rather than a generic notion of the ancestral human phenotype, and the console could exchange data with the infrared ports in their fingertips.
    Tomography alone was enough to locate the dead microbes, but it was necessary to send nanomachines crawling through the crevices to extract reliable DNA sequences. A dose of paleogenetic expertise from the library left Rakesh with no doubt that Lahl had been correct: these were not the corpses of any micro-organism, from any epoch, from any of the known DNA worlds. Their ancestors had probably been blasted off one of those planets billions of years before, on an entirely different piece of rock; that earlier meteor must have fallen to the ground somewhere in the bulge, and seeded a whole new biosphere. A billion or so years later this lump of basalt had been flung into the sky; with better luck it might have contributed to the DNA panspermia itself, but it was a dead seed now. At least, no pristine world could have revived these desiccated, shocked, radiation-fried microbes, though perhaps if they'd achieved the unlikely fate of landing on a planet already awash with DNA-based life, the right species of distant cousin might have scavenged a few of these corpses' gene