Something had gone wrong when they'd loaded the ship, and the rations hadn't quite lasted long enough to make the outbound end of the uranium prospecting trip. Then they found an abandoned world, and landed the ship on an old warehouse facility . . . and tried to found somehting to eat.
Not an easy thing to do, going through an alien warehouse when they could barely read the manuals, and had not much cluse as to the nature of the local biology.
They would have eaten a horse, if there'd been one. But there wasn't. And that was probably for the best -- it might have eaten them first!