Free Blonde Bombshell by Tom Holt

alarming level of pollution, particularly combustion-formed hydrocarbons. Population density was all wrong; most of the inhabitants of Dirt were crowded into a pawful of major cities, while most of the surfaces of the main land masses were barely inhabited at all. These, his historical, ecological and cyological databases told him, were classic signs, all pointing in the same direction. There must have been a war.
    Or something of the sort, anyway; some catastrophe that had led to potentially lethal overheating, wrecking of the ozone layer, disruption of normal society, poisoning of the atmosphere. He considered alternative explanations, but dismissed them as wildly improbable. Disasters on this scale weren’t the sort of thing that a species, even a primitive one like the Dirters, did to themselves if they could possibly help it. The obvious conclusion was that they’d had to fight for their survival as a species, most likely against an alien invader, and the horrendous collateral damage to their environment was the price they’d had to pay. That too would explain why the Dirters were huddled together in overcrowded slums — for safety, in the event of invasion — and why the planet bristled with military installations. Further sensor readings showed that the warming and the pollution had stopped (just in time) not more than five or so years ago, presumably after the enemy had been defeated, but not before they’d done something dreadful that had nearly wiped out the indigenous species and turned Dirt into a barren rock incapable of supporting life.
    Twain considered a number of further hypotheses — asteroid strike (no sign of that); a shift in the planet’s orbit (no, not so you’d notice); massive volcanic or magma-core activity (none of that, either) — and dismissed them. Which left only one possibility: the Mark One. When the planetary defences had taken it out, it had exploded somewhere in the upper atmosphere. The resulting heat had partially melted the polar ice-caps, while the fallout had filled the air with noxious garbage. A plausible theory, and one that (for obvious reasons) he needed to verify before he went much further. Silently he uploaded a command to the Mark Two in planetary orbit, ordering it to construct and send down a basic Dirtershaped level-2 probe, to collate data on the flooding and report back before self-destructing. A few seconds later he received the confirmation, probe launched. Meanwhile, the door connecting the bleak room to the conference room where the interviews were being held had opened, a Dirter had come out and the female had gone in. The young religious had stopped praying and was sending text messages through his handheld communications device. The music fan had his eyes closed, and his left foot was tapping the carpet softly.
    So, new hypothesis. The Mark One had hit the defence grid and exploded, causing widespread devastation, but failing to achieve its objective. The planet and its dominant species were still very much here — over six billion of them, according to preliminary scans, considerably more than there’d been when the Mark Two had been launched, but living on a planet that was now only just habitable.
    It stood to reason, then, that Dirt civilisation was still vigorous, in spite of the damage done by the Mark One; also that in the intervening time, made aware that they faced a serious threat from an unidentified but savagely hostile neighbour, they’d devoted a significant proportion of their species’ mental and material resources in improving the defence grid. That was what any sane species would do. In which case, the grid must be even more effective than it had been when it stopped the Mark One, and the task facing the Mark Two must, accordingly, be that much harder.
    So where was this confounded grid? Sensors had so far failed to find any traces of any form of technology that could conceivably be connected with such an elaborate and efficient