question:  What is ironic about Ledman's quick departure to Mars?
context: The planet itself was tough enough—barren, desolate, forbidding; enough to stop the most adventurous and dedicated. "The surest way to die out here on Mars is to give up." Nothing but what had stopped us could stop a sandcat: sand in the delicate mechanism of the atomic engine. But no; she blamed it all on me somehow: So we were out walking on the spongy sand of the Martian desert. She had been just as much inflamed by the idea of coming to Mars to help in the search for uranium as I was. We knew the pay was poor, but we had felt it a sort of obligation, something we could do as individuals to keep the industries of radioactives-starved Earth going. No, we had decided together to come to Mars—the way we decided together on everything. I longed to lie down on the soft, spongy Martian sand and bury myself. I stopped, slipped out of the geiger harness, and lowered myself ponderously to the ground. She slid down beside me, curled up, and in a moment she was fast asleep, sprawled out on the sands. Maybe we shouldn't have come to Mars after all. I watched her, sleeping peacefully, a wayward lock of her soft blonde hair trailing down over one eyebrow, and it seemed hard to believe that we'd exchanged Earth and all it held for us for the raw, untamed struggle that was Mars. It had been spun on us only a short time ago, I realized. He wore an outmoded, bulky spacesuit and a fishbowl helmet, all but the face area opaque. I thought I knew everyone on sparsely-settled Mars. Earth needed radioactives, and the only way to get them was to get out and look. The great atomic wars of the late 20th Century had used up much of the supply, but the amount used to blow up half the great cities of the world hardly compared with the amount we needed to put them back together again.
output:  Inventors discovered a way to create prosthetics using atomic power
options:  Victims of the Sadlerville blast received a large settlement and were culturally recognized as heroes  Inventors discovered a way to create prosthetics using atomic power  In hunting Geigs, Ledman is killing the only people with the power to help him walk again  He needs uranium in order to survive and went to a place where there is scant uranium