The Zeus Orbital Weapons Platform was the pride of the EXN defense fleet. Orbiting within sight of the tiny asteroid moon, Metis, it sat in the perfect place to dominate all Jovian airspace. It was fitted with five massive railguns, each capable of executing strikes on any target in the solar system, accurate to within a few centimeters, and with enough force to make such precision redundant. Motors peeked out of the superstructure on all sides, balancing it when one of the guns was fired, and preventing the considerable recoil from pushing the station off course. Radio telescopes attached to the platform supplied the constant stream of data the artillery computers needed to thread their cataclysmic needles.
These telescopes immediately noticed something very unusual near the orbit of Europa. One moment there was nothing, the next a distinct and clear heat signature. Central command was immediately notified and human eyes first looked upon the hole in the sky.
There was some confusion, at first. The object was almost perfectly spherical, and exuding a microwave frequency not seen in most planetary objects. Contact was established with naval forces operating nearby, and it was ascertained that the object could not be related to any official flights nearby. It was eventually decided that the best course of action was to fire a test round at it.
The slug soundlessly exploded from the muzzle of one of the hulking railguns and soared toward the hole in the sky. As it approached the object, there was a flash of light and an army appeared.
To the radio telescopes on Zeus, it looked like a warm cloud of hydrogen that spontaneously materialized all around the puncture. When it started moving, it did so in a predictable fashion, falling toward Jupiter. Things became interesting when the tendrils of gas began curving to intercept the slug.
The impact was unremarkable. The artillery shell simply disappeared into the cloud and radio contact with it ceased. Its cameras showed nothing but stars, then static. Again, confusion rippled through the command room of the weapons platform. A volley of fire was ordered at the object and its shroud of gas.
There were ten sharp booms as the railguns spun up and released. Ten identical explosive rounds soared in a graceful arc toward the expanding cloud of material. Almost immediately, the cloud reacted. It glowed faintly and rushed to meet the ten artillery shells. They disappeared as the first had, and the cloud continued to charge forward, directly toward the station.
Now there was some measure of terror in the eyes of the personnel manning the station. The only sound in the command room was the loud hum of the life support. The cloud continued to accelerate, now visible as a dim blue veil slung over the portholes. No one would take any action; all were frozen with doubt.
When the cloud struck, it did so with a quiet hissing, as if sand were being poured down a metal pipe. Suddenly, reports came in that fuel lines and antennae on the fringes of the weapons platform were failing all at once. The cameras showed them floating away and rapidly disintegrating, momentarily glowing orange and white before puffing away into the blue haze.
Panic overtook the command personnel. There was short burst of frenzied activity before the oxygen lines burst and the walls began to wear away. Like rats, they suffocated, catching blurred glimpses at the terrifying expanse of nothing that found its way into their tiny bubble of safety. Now the emptiness was not quite so empty as it usually was.
The Zeus Orbital Weapons Platform was the first dot on the monitor to blink off. Several other military installations in the Jovian system ceased to exist an hour later. Then the civilian reports began to roll in.