Page 177 of Project Hail Mary

No immune system at all. Just heat. Well, why not? The hot circulatory system of an Eridian boils water to make the muscles move. Why not use it to cook and sterilize incoming food too? And with heavy oxides—basically rocks—as skin, they don’t get many cuts or abrasions. Even their lungs don’t exchange material with the outside. If any pathogens do get in, the body seals the area off and boils it. An Eridian body is a nearly impenetrable fortress.

But a human body is more like a borderless police state.

“Humans are very different,” I say. “We get diseases all the time. We have very powerful immune systems. Also, we find cures for diseases in nature. The word is ‘antibiotics.’ ”

“No understand,”he says.“Cures for diseases in nature, question? How, question?”

“Other life on Earth evolved defenses against the same diseases. They emit chemicals that kill the disease without harming other cells. Humans eat those chemicals and they kill disease but not our human cells.”

“Amaze. Erid no have this.”

“It’s not a perfect system, though,” I say. “Antibiotics work very well at first, but then over the years, they become less and less effective. Eventually they barely work at all.”

“Why, question?”

“Diseases change. Antibiotics kill almost all the disease in the body, but some survive. By using antibiotics, humans are accidentally teaching diseases how to survive those antibiotics.”

“Ah!”Rocky says. He raises his carapace a tad.“Disease evolves defense against chemical that kills it.”

“Yes,” I say. I point at the tank. “Now think of Taumoeba as disease. Think of nitrogen as antibiotic.”

He pauses, then raises his carapace back to its proper location.“Understand! Make environment barely deadly. Breed Taumoeba that survive. Make more deadly. Breed survivors. Repeat, repeat, repeat!”

“Yes,” I say. “We don’t need to understand why or how nitrogen kills Taumoeba. We just need to breed nitrogen-resistant Taumoeba.”

“Yes!”he says.

“Good!” I slap the top of the tank. “Make me ten of these, but smaller. Also provide a way for me to get Taumoeba samples withoutinterrupting the experiment. Make a very accurate gas injection system—I need exact control over the nitrogen quantity in the tank.”

“Yes! I make! I make now!”

He skitters down to the dormitory.

—

I check the results of the spectrograph and shake my head. “No good. Complete failure.”

“Sad,”Rocky says.

I put my chin in my hands. “Maybe I can filter out the toxins.”

“Maybe you can concentrate on Taumoeba.”There’s a special warble that Rocky does when he’s being snarky. That warble is especially present right now.

“They’re coming along fine.” I glance over to the Taumoeba processing tanks arrayed along one side of the lab. “Nothing to do but wait. We’ve had good results. They’re already up to 0.01 percent nitrogen and surviving. The next generation might be able to go as high as 0.015.”

“This is waste of time. Also waste of my food.”

“I need to know if I can eat your food.”

“Eat your own food.”

“I’ve only got a few months of real food left. You have enough aboard your ship to feed a crew of twenty-three Eridians for years. Erid life and Earth life use the same proteins. Maybe I can eat your food.”

“Why you say ‘real food,’ question? What is non-real food, question?”

I checked the readout again. Why does Eridian food have so many heavy metals in it? “Real food is food that tastes good. Food that’s fun to eat.”

“You have not-fun food, question?”