He clicks across the tunnel to the far side of the lab. He paces when he thinks. Interesting that humans and Eridians would both have that behavior. “Predators is only explanation. Maybe predators no live in Petrova line. Maybe predators live further down in atmosphere.”

I perk up. “Maybe.”

I look over to the lab monitor. I have it showing the external camera view of Adrian. Not for any scientific reason—just because it looks cool. Right this moment we’re about to cross the terminator into the day side of the planet. The light of orbital dawn glows along an arc.

“Okay, let’s say the predator lives in the atmosphere. What altitude?”

“What altitude is best, question? If you predator, where you go, question? You go to Astrophage.”

“Okay, so what altitude are the Astrophage at?” The question answers itself. “Ah! There’s a breeding altitude. Where air has enough carbon dioxide for Astrophage to breed.”

“Yes!” He clatters back up his tunnel and stands above me. “We can find. Easy. Use Petrovascope.”

I slam my fist into my palm. “Yes! Of course!”

Astrophage have to breed somewhere. Some partial pressure of carbon dioxide will be key. But we don’t have to work that out or take any guesses. When an Astrophage divides, it and its offspring head back to Tau Ceti. And they use IR-light emission to make it happen. That means there will be a glow of Petrova-frequency light coming from all over the planet at that specific altitude.

“To the control room!” I say.

“Control room!” He scampers across the lab ceiling tunnel and disappears through his personal control-room entrance. I follow along beside but I’m not quite as fast.

I climb up the ladder, take the pilot’s seat, and flip on the Petrovascope. Rocky has already taken up position in his bulb and points his camera at my main screen.

The entire screen glows red.

“What is this, question? No data.”

“Wait,” I say. I bring up the controls and options and start moving sliders. “We’re inside the Petrova line. There’s Astrophage all around us. Let me just change the setting to only show the brightest sources….”

It takes a lot of manipulation, but I finally manage to get the brightness range set. What I’m left with are irregular blotchy areas of IR light coming from Adrian.

“I think this is our answer,” I say.

Rocky gets closer to his textured screen to “see” what I’m lookingat.

“Not what I expected,” I say.

I thought it would just be a general layer of IR glow at a given altitude. But it’s nothing like that. The clumps are basically clouds. And they don’t match up with the wispy white clouds I can see with visible light. These are, for lack of a better term, IR clouds.