Bobbie’s armor had been designed to let a soldier walk through a nuclear bomb crater minutes after the blast. It also worked well at keeping Jupiter from frying Martian Marines.

Behind the Earth soldiers on patrol, their dome glowed in a shaft of weak sunlight captured by enormous orbital mirrors. Even with the mirrors, most terrestrial plants would have died, starved of sunlight. Only the heavily modified versions the Ganymede scientists cranked out could hope to survive in the trickle of light the mirrors fed them.

“Be sunset soon,” Bobbie said, still watching the Earth Marines outside their little guard hut, knowing they were watching her too. In addition to Snoopy, she spotted the one they called Stumpy because he or she couldn’t be much over a meter and a quarter tall. She wondered what their nickname for her was. Maybe Big Red. Her armor still had the Martian surface camouflage on it. She hadn’t been on Ganymede long enough to get it resurfaced with mottled gray and white.

One by one over the course of five minutes, the orbital mirrors winked out as Ganymede passed behind Jupiter for a few hours. The glow from the greenhouse behind her changed to actinic blue as the artificial lights came on. While the overall light level didn’t go down much, the shadows shifted in strange and subtle ways. Above, the sun-not even a disk from here as much as the brightest star-flashed as it passed behind Jupiter’s limb, and for a moment the planet’s faint ring system was visible.

“They’re going back in,” Corporal Travis said. “Snoop’s bringing up the rear. Poor guy. Can we bail too?”

Bobbie looked around at the featureless dirty ice of Ganymede. Even in her high-tech armor she could feel the moon’s chill.

“Nope.”

Her squad grumbled but fell in line as she led them on a slow low-gravity shuffle around the dome. In addition to Hillman and Travis, she had a green private named Gourab on this particular patrol. And even though he’d been in the Marines all of about a minute and a half, he grumbled just as loud as the other two in his Mariner Valley drawl.