Rocky waits for me on the other side. His clothes are a mess. Covered in the all-too-familiar gunky Taumoeba residue. And there are burns all along one side of his jumpsuit and two of his arms are in pretty bad shape. Looks like he had a pretty rough time. But his body language is sheer joy.

He bounces from handhold to handhold.

“I am very very very happy,” he says with a high pitch.

I point to his bad arms. “Are you hurt?!”

“I will heal. Attempted many things to stop Taumoeba infestation. All failed.”

“I succeeded,” I say. “My ship isn’t made of xenonite.”

“What happen, question?”

I sigh. “The Taumoeba evolved to resist nitrogen. But it also evolved to get into xenonite to hide from nitrogen. The side effect is Taumoeba-82.5 can work its way through xenonite over time.”

“Amaze. Now what, question?”

“I still have two million kilograms of Astrophage. Bring your stuff aboard. We’re going to Erid.”

“Happy! Happy happy happy!” He pauses. “Need to make nitrogen wash. Make sure no Taumoeba-82.5 get into Hail Mary.”

“Yes. I have full faith in your abilities. Make a sterilizer.”

He shifts from one set of bars to another. Those burned arms are hurting him, I can tell. “What about Earth, question?”

“I sent the beetles with the mini-farms. Taumoeba-82.5 can’t get through Eridian steel.”

“Good good,” he says. “I make sure my people take good care of you. They will make Astrophage maybe for you to go home!”

“Yeah…” I say. “About that… I’m not going home. The beetles will save Earth. But I won’t ever see it again.”

His joyous bouncing stops. “Why, question?”

“I don’t have enough food. After I take you to Erid, I will die.”

“You… you no can die.” His voice gets low. “I no let you die. We send you home. Erid will be grateful. You save everyone. We do everything to save you.”

“There’s nothing you can do,” I say. “There’s no food. I have enough to last until we get to Erid and then a few months more. Even if your government gave me the Astrophage to go home, I wouldn’t survive the trip.”

“Eat Erid food. We evolve from same life. We use same proteins. Same chemicals. Same sugars. Must work!”

“No, I can’t eat your food, remember?”

“You say is bad for you. We find out.”

I hold up my hands. “It’s not just bad for me. It will kill me. Your whole ecology uses heavy metals all over the place. Most of them are toxic to me. I’d die immediately.”

He trembles. “No. You no can die. You are friend.”

I float closer to the divider wall and talk softly. “It’s okay. I made my decision. This is the only way to save both of our worlds.”

He backs away. “Then you go home. Go home now. I wait here. Erid maybe send another ship someday.”

“That’s ridiculous. Do you really want to risk the survival of your entire species on that guess?”