The massed ranks of the Marines confirmed what I had already strongly suspected: the asteroid was a dead hulk, with nothing living within in any state and just a few backup systems spluttering along on emergency power. The various units, large and small, investigated every volume inside the structure and every fragment of the outer surface, along with deep scans to ensure there were no hidden spaces concealed within.
We accumulated the intelligence gathered by the Marines and subjected it to a detailed analysis, but all of the data we acquired pointed to the same conclusion. There had been a major blow-out in a key reactor cell and the chain reaction had spread to the adjoining units. The resulting blast had caused that crater we had spotted earlier, being sufficiently powerful to punch its way through half a mile of high-nickel-content rock.
Although it was one of the largest and most well-equipped habitats we had encountered, it showed distinct signs of having been expanded at a frenetic pace. The manufacturing equipment had been run to the point of failure, and short-cuts and hacked overrides to the built-in safety systems was testimony to the urgency these people had felt.
The blast had probably killed most of the crew on board within minutes, from radiation burns and asphyxiation. A few appeared to have made it to emergency recompression chambers in time, there to wait until the worst of the blast had dissipated, then donned spacesuits and attempted to seal and repressurise the habitat. But to no avail: all had expired after further failures and consequent fatalities, the last few having died when the resources of their suit gave out.
There was precious little equipment showing any signs of life, too, with most of the batteries and backup power supplies having been exhausted a long time ago. A few independent systems sparked up when elements of the Marines drew near, and maybe a couple tried to interfere with the comms or even attack the devices, but to no significant effect. Although there were a couple of unexplained anomalies in the Marines' distributed databases, but after some discussion the Skipper and I put them down to mere glitches.
In truth, the whole place looked like a high-tech morgue, full of damaged and abandoned equipment, and dead and desiccated cadavers. There were perhaps fewer bodies than I might have expected, although many of them showed signs of having been overworked and under great stress in life, even before their untimely death. I found myself feeling a certain grudging respect for the fallen: they had struggled on through increasingly overwhelming odds of heroic proportions, although of course they were entirely misguided about the rightness of their cause.
Following standing orders, once there was nothing more to be gleamed from the scans and inspections, I instructed a couple of the larger elements of the Marines to implant thermonuclear devices at carefully selected intervals. A further command called for a withdrawal, the Marines pulling back and regrouping in an almost perfect reversal of the earlier deployment, refitting themselves into the bays in the ship's flanks in a ballet of coordinated movement.
At a word from the Skipper, once we had put a few thousand miles between us and the rock, I issued the final command, the one which reduced the Last Asteroid to scattered rubble. I watched the virtual screens as the silent yet potent detonations blew the last remnants of the Expansionists hideout into a haze of pulverized rock. Then I sent in our report, supported by all the raw data we had captured, and resumed our patrol following the courses previously given in our pre-mission briefing.