As I get closer, I see how terrible he looks. He’s got blisters all over his skin, his lips are cracked and bloody, his hair matted and singed. He must not have had water for days, and this heat—barely tolerable for me in the space suit—is baking him alive.

“Save yourself. Take the gestation device. Now,” Yarrow croaks. “And Owl, there’s a sea. You need to know. It’s to the south. There are giant rusty aliens in it.”

I have no idea what he’s talking about, and don’t have time to ask. “Yarrow,” I say, fighting to keep words coming out of me instead of raw shrieks, “Father and I found the beacon. It’s not your fault. We can help you.”

He blinks. He looks to the gestation device, flat on the tarp a hundred yards away.

“Can you walk?” I ask.

Yarrow nods, stunned, his mouth agape. He’s somehow managed to bind his own hands behind him, but his legs are free. He lurches to his feet.

I step toward theAurora, scanning the countdown as I do. Five minutes.

My brother pitches forward beside me. He cries out, in pain or shock or frustration, I don’t know. His tunic has ridden up, and I see his legs are flayed by the heat and light. They twitch. There’s no way he can walk. He probably can’t even get up to his feet again. Five minutes.

I get my hands under Yarrow’s shoulders, clenching my teeth against the feeling of my brother’s soft damaged flesh bursting wetly under my fingers. I try to lift him. I can’t. He’s always been a good ten kilos heavier than I am. “I’m sorry, I can’t lift you,” I say.

“Leave me,” he cries. “Owl,leave me! I just came to tell you about the sea creatures.”

I look between him and the gestation device. The wounded brother beside me and the small unaware body, a shadow behind the translucent wall.

The heat bores into the top of my helmet.

Four minutes and four seconds.

I give up on the shoulders and grasp my brother’s ankles instead, one in each hand. He yells in pain as I haul him over the soil.

He screams louder whenever his tender skin drags on any bump on the surface. “I’m sorry!” I cry over the hot wind. To him, mainly, but also to the embryo in the gestation device, left in the increasing distance behind me, on the pounded soil where we used to live.

We pass through the fence, the unpowered guns limpatop it, guarding an open clearing. The home that was.

The comet fills the sky before me, beautiful and horrible, with its hot rocky core, its plumes of radiation. The secondary ion tail flares out to one side, slightly bluish. I scream at it between my own labored breaths. Even with the weight he’s lost, my brother isheavy.

One minute remains. I won’t be going back for the gestation unit. It’s just not possible. OS won’t let me risk the lives of the group for an unaware embryo that has only a small chance of surviving anyway.

As I kneel by the hatch, I get one last look at the fence surrounding a jagged pit and the slowing gestation device. After the comet strikes, all surface evidence of us will be gone. If the integrity of theAurorafails, there will be no sign that humans ever lived on Minerva at all, except for some skeletons entombed below the surface. Even if what Yarrow is saying is true, and those alien life-forms out there wind up being intelligent, if they survive the comet they’ll probably have no idea that we were ever here until one of them happens to dig above theAuroraand receives the shock of their little alien life.

I get one last look at the impending comet as I push my brother toward the open hatchway. It’s turned the horizon purple. I can see some detail of the giant hurtling mountain—the electromagnetic field it sends cascading around it, the blues and blacks of ice and heat and rock.My skin breaks out in sweat, the cold kind that comes with fainting.

But I will not let myself faint. Twenty-seven seconds remain. I lower my brother into the tunnel to safety, as far as I can, then drop his limp body the rest of the way before barreling in after him and slamming the hatch shut.

Cool darkness.

There at the bottom of the shaft, crumpled against an orange portal that once would have connected theAurorato Dad’s ship, is the body of a person. Yarrow.

He doesn’t move the whole time that I climb down the rungs of the shaft. My heart seizes as I step off at the bottom. “Yarrow? Are you...?”

He stays in his fetal position, but raises his head enough to look at me with haunted eyes. “You dropped me.”

I stop. “I did. I had to.”

There’s the hint of a smile on his cracked and bleeding lips. My brother might still be inside this shell. “I deserved it.”

I take another step in his direction. His hands are out of view. I know I saw them bound, but my paranoid brain tells me he could have freed them, could now be holding anything: a gun, a blade, some other weapon I don’t expect. Maybe I saved him only for him to murder all of us. “I know you’re joking,” I say, “but no, you didn’t. You didn’t deserve any of this.”

I hear Father’s thudding footfalls elsewhere in theAurora, his yelled commands and Rover’s calm responses. He’s finalizing the sealing of the ship. Already the comet has struck our planet; the shock waves will come anytime. I can’t risk interrupting or distracting him now. Dad is still out of commission. Yarrow is mine to deal with alone. I take a slow step toward him.

“Stop,” he says, pain in his voice. “Don’t come anywhere near me.”