“Hey,” Gershon said. “Here goes the probe. I’m passing through the ionosphere. Two hundred fifty miles above the ground. Progressing toward the main cloud layers, at hyperbolic speed… How about that.”

York unhooked herself from her stirrups and drifted over to Gershon. There was a TV monitor at the center of Gershon’s station; the screen showed nothing but a snowstorm of static.

The subprobe had been ejected twenty-three days ago, from a compartment at the base of the Mission Module, and had been pushed onto a slowly diverging orbit. Ares was missing Venus by a few thousand miles; the probe, pushed ahead of Ares, was supposed to impact the planet directly, a few minutes before the closest approach of the main craft. The probe would hit in the middle of the dayside, in an upland region called Ishtar Terra.

The probe was contained within its aeroshell deceleration module, a deep, streamlined pie dish. Its TV cameras couldn’t see out of the aeroshell, but there was a radio-transparent window at the top, so the probe could talk to Ares.

Gershon said, “I’m in the atmosphere now, but still above the main cloud banks. Fifty miles up. The temperature’s low here; under a hundred below, in fact. But this is the minimum; it should soon start to rise as I enter the main cloud banks. Here we come to breakout… Three, two, one. Mark. Watch the screen, Natalie.”

At just that moment, somewhere in those clouds, York knew, that fat pie dish was falling apart. A pilot chute would pull away the lid, and the main chute should open above the probe.

There was a break in the monitor’s snowstorm, a yellow, flickering blur.

Gershon whooped. “How about that. We can see out, at last.”

On the TV the pale, jaundiced wash brightened and darkened periodically: the probe was rotating, slowly, under its chute, and that cyclical brightening must be the sun, a glare behind the diffuse haze of sulfuric acid particles.

“Visibility’s dropping. Down to maybe four miles,” Gershon said. “I’ve got a pressure of three-quarters of Earth’s sea-level pressure, and the temperature is around fifty degrees. Yum. Balmy. And I’m still all of thirty-eight miles high.”

Thirty-eight miles Two hundred thousand feet On Earth, that would be the top of the stratosphere: pressure less than a hundredth of sea level.

The haze on the TV screen thinned out. “Whoa,” Gershon said. “Look at that. All of a sudden I can see for miles and miles.”

York found herself looking down on a layer of cloud, thick and unbroken, a pale, washed-out yellow. The clouds were fluffy, Earthlike. Almost friendly. Up above there was a featureless yellow sky; she could no longer tell where the sun was.

The probe dropped into the thick clouds.

“Coming up on twenty-eight miles. I’m through all that sulfuric acid shit. But temperature outside is all of four hundred degrees already. And pressure’s higher than an atmosphere already. Three, two, one. Mark. Chute sep.”

The picture seemed to shudder, then it stabilized again.

The pressure vessel — the heart of the probe — had hatched out of its aeroshell and cut itself loose from its parachute. The probe was still more than twenty-five miles high, but it had already cut away its last chute. The air of Venus was so thick that from where it was the probe could free-fall all the way to the surface.

The pressure vessel was a sphere of thick metal. There were vanes on the sphere to make it spin, so that it was stabilized during its fall, and there were tough little windows cut into the surface so that the probe’s instruments could see out.

“Hey,” Gershon said. “Look at these numbers from the mass spectrometer.” He tapped a screen. “I got me some heavy isotopes of hydrogen in the air.”

“So what?”

He narrowed his eyes. “Water, my dear. Oceans, maybe: once upon a time, anyhow. Long since boiled off by the greenhouse effect, caused by all this fucking CO2. But where there were oceans…”

Life, perhaps.

The probe was spinning slowly in the sluggish air. The light was dark, reddish, but the illumination was no worse than a cloudy day on Earth. She couldn’t see the sun at all; there was only an ill-defined glare, almost baleful, spread across half of the cloud bank that covered the sky.

And suddenly she could see the surface: the probe’s fish-eye camera returned panoramic views of a landscape, dimly visible through the murky air. York made out what looked like a cleft in the land, running from side to side of the picture — no, not a cleft, she realized; it was a ridge, hundreds of miles long, leading up to a plateau.

“Wind speed down to zip,” Gershon said. “Pressure and temperature still rising. Venus doesn’t have air; that stuff is more like my momma’s chicken soup.” He tapped the screen. “That’s Ishtar Terra,” he said. “Or the edge of it; right where we’re drifting. We’re slap on course. Look at it, Natalie. Seven miles above the mean surface, and—”

“ — and as big as the United States. I know.” Ishtar Terra was a high, exposed plateau, already mapped by radar from Earth: Ishtar was how a continent might look if someone drained away Earth’s oceans.

York felt excitement mount. At last, a chance to do some geology on this mission.

Venus and Earth were twins. So presumably Venus had a hot, radioactive core, just like Earth’s, whose heat must escape to space. On Earth, that happened in two ways: plate tectonics and vulcanism. But, in the radar mapping and the crude Russian probes’ results, nobody had observed any sign of plate tectonics on Venus: no rings of vulcanism, no rift valleys.

So York, along with every other geologist, believed that the dominant geological process for losing core heat had to be vulcanism: ongoing and continuing. There just had to be a whole bunch of live volcanic hot spots, all around the planet, feeding the heat to the atmosphere, and thence to the ultimate heat sink of space. Therefore, at Ishtar, she expected to see a young surface, heavily distorted by the upwelling of magma — liquid rock under the solid crust — and resurfaced by repeated lava flows. If there were any impact craters, they would be heavily distorted, maybe even buried, invisible under the fresh surface.

She pointed off to the right of the screen, to shadowy cones that loomed out of the murk. “Look at that. That must be the Maxwell Montes.” The tallest mountain range on Venus. The probe was drifting toward the Montes, she saw, floating like a fat metal balloon in some sluggish current. The Montes were steeper, in places, than anything on Earth. The mountains were folds in the surface, illuminated by the diffuse, ruddy light and wreathed by thick air; it was like swimming over some undersea ridge.

Something showed up on the edge of the screen: a circular feature, on the flank of the mountain range.

“Hey. What’s that?” The probe’s slow rotation took the feature out of shot, almost immediately. “Hot damn.”

Gershon grinned up at her. “Sorry,” he said. “No panning or zooming. This isn’t Wide World of Sports.”

A circle? Could it be a crater? What the hell was that doing there?

Something was wrong; York could smell it. She waited, excited, impatient, as the camera panned around, agonizingly slowly, the image wobbling as the probe hit turbulence pockets in the soupy air.

The circular feature came back again, drifting in from the right.

York shoved her face right up to the screen. Almost a perfect circle, surrounded by a dark blanket of material: it had to be an impact crater, surrounded by a layer of ejecta. Like a bullet hole centered in dried blood. And it was so large it was almost certainly several hundred million years old.

And it was pristine, no coverage by lava flows, no distortion by shifts in the landscape.

Which meant that Ishtar Terra had to have been geologically dead, too, for at least as long.