“Understand. Good observation.” But it nags at me. “Still unusual. Humans and Eridians are close in space. Earth and Erid are only sixteen light-years apart. The galaxy is one hundred thousand light-years wide! Life must be rare. But we are so close together.”

“Possible we are family.”

We’re related? How could—

“Oh! You mean…whoa!” I have to wrap my head around this one.

“I not certain. Theory.”

“It’s a darn good theory!” I say.

The panspermia theory. I argued with Lokken about it all the time.

Earth life and Astrophage are way too similar for it to be coincidence. I suspected Earth was “seeded” by some ancestor of Astrophage. Some interstellar progenitor species that infected my planet. But it never occurred to me until now that the same thing might have happened to Erid.

There could be life all over the place! Anywhere it can possibly evolve from an Astrophage-like ancestor into the cells I have today. I don’t know what this “pre-Astrophage” organism would be like, but Astrophage is pretty darn tough. So any planet that can possibly support life of any kind would be likely to get it.

Rocky might be a long-lost relative. Very long. The trees outside my house back home are closer relatives to me than Rocky. But still.

Wow.

“Very good theory!” I say again.

“Thank,” Rocky says. I guess he’d worked that all out a while ago. But I still had to let it sink in.

* * *

—

For once, an aircraft carrier was the perfect place to be.

The Chinese Navy didn’t even question Stratt’s orders anymore. The higher-ups got sick of approving every action and finally just issued a general order to do whatever she said as long as it didn’t involve firing weapons.

We anchored off the coast of western Antarctica in the dead of night. The coastline sat in the extreme distance, visible only by moonlight. The entire continent had been evacuated of humans. Probably an overreaction—the Amundsen–Scott South Pole Station was 1,500 kilometers away. The people there would have been just fine. Still, no reason to take chances.

It was the largest naval exclusion zone in history. So big, even the U.S. Navy had to stretch itself thin to make sure no commercial ships entered the area.

Stratt spoke into a walkie-talkie. “Destroyer One, confirm observation status.”

“Ready,” came an American accent.

“Destroyer Two, confirm observation status.”

“Ready,” came a different American’s voice.

The scientific team stood together on the carrier’s flight deck, staring toward land. Dimitri and Lokken hung back away from the edge. Redell was off in Africa running the blackpanel farm.

And of course Stratt stood slightly ahead of everyone else.

Leclerc looked for all the world like a man being led to the gallows. “We’re almost ready,” he said with a sigh.

Stratt clicked on her walkie-talkie again. “Submarine One, confirm observation status.”

“Ready,” came the response.

Leclerc checked his tablet. “Three minutes…mark.”

“All ships: We are at Condition Yellow,” Stratt said into her radio. “Repeat: Condition Yellow. Submarine Two, confirm observation status.”

“Ready.”

I stood next to Leclerc. “This is unbelievable,” I said.

He shook his head. “I wish to God this wasn’t on my shoulders.” He fiddled with his tablet. “You know, Dr. Grace, I have spent my entire life as an unapologetic hippie. From my childhood in Lyon to my university days in Paris. I am a tree-hugging antiwar throwback to a bygone era of protest politics.”

I didn’t say anything. He was having the worst day of his life. If I could help by just listening, I’d do it.

“I became a climatologist to help save the world. To stop the nightmarish environmental catastrophe we were sinking ourselves into. And now…this. It’s necessary, but horrible. As a scientist yourself, I’m sure you understand.”

“Not really,” I said. “I spent my whole scientific career looking away from Earth, not toward it. I’m embarrassingly weak on climate science.”

“Mm,” he said. “Western Antarctica is a roiling mass of ice and snow. This whole region is a giant glacier, slowly marching to the sea. There are hundreds of thousands of square kilometers of ice here.”

“And we’re going to melt it?”

“The sea will melt it for us, but yes. Thing is, Antarctica used to be a jungle. For millions of years it was as lush as Africa. But continental drift and natural climate change froze it over. All those plants died and decomposed. The gases from that decomposition—most notably methane—got trapped in the ice.”

“And methane’s a pretty powerful greenhouse gas,” I said.

He nodded. “Far more powerful than carbon dioxide.”

He checked his tablet again. “Two minutes!” he called out.

“All ships: Condition Red,” Stratt radioed. “Repeat: Condition Red.”

He turned back to me. “So here I am. Environmental activist. Climatologist. Antiwar crusader.” He looked out to sea. “And I’m ordering a nuclear strike on Antarctica. Two hundred and forty-one nuclear weapons, courtesy of the United States, buried fifty meters deep along a fissure at three-kilometer intervals. All going off at the same time.”

I nodded slowly.

“They tell me the radiation will be minimal,” he said.

“Yeah. If it’s any consolation, they’re fusion bombs.” I pulled my jacket tighter. “There’s a small fission reaction with uranium and stuff that sets off the much larger fusion reaction. And the big explosion is just hydrogen and helium. No radiation from that.”

“Well, that’s something.”

“And this was the only option?” I asked. “Why can’t we have factories mass-produce sulfur hexafluoride, or some other greenhouse gas?”

He shook his head. “We’d need thousands of times the production that we could possibly do. Remember, it took us a century of burning coal and oil on a global scale to even notice it was affecting the climate at all.”

He checked his tablet. “The shelf will cleave at the line of explosions and slowly work its way into the sea and melt. Sea levels will rise about a centimeter over the next month, the ocean temperature will drop a degree—which is a disaster of its own but never mind that for now. Enormous quantities of methane will be released into the atmosphere. And now, methane is our friend. Methane is our best friend. And not just because it’ll keep us warm for a while.”