"We found this inside a two-thousand-yard-deep core," Dixon said.

Larionova tried to imagine how this would have looked, intact and mobile. "This means nothing to me, Frank. I'm no biologist."

He grunted, self-deprecating. "Nor me. Nor any of us. Who expected to find life, on Mercury?" Dixon tapped at the data desk with gloved fingers. "We used our desks' medico-diagnostic facilities to come up with this reconstruction," he said. "We call it a mercuric, Irina."

A Virtual projected into space a foot above the desk's surface; the image rotated, sleek and menacing.

The body was a thin cone, tapering to a tail from a wide, flat head. Three parabolic cups -- eyes? -- were embedded in the smooth "face," symmetrically placed around a lipless mouth... No, not eyes, Larionova corrected herself. Maybe some kind of sonar sensor? That would explain the parabolic profile.

Mandibles, like pincers, protruded from the mouth. From the tail, three fins were splayed out around what looked like an anus. A transparent carapace surrounded the main body, like a cylindrical cloak; inside the carapace, rows of small, hairlike cilia lined the body, supple and vibratile.

There were regular markings, faintly visible, in the surface of the carapace.

"Is this accurate?"

"Who knows? It's the best we can do. When we have your clearance, we can transmit our data to Earth, and let the experts get at it."

"Lethe, Frank," Larionova said. "This looks like a fish. It looks like it could swim. The streamlining, the tail--"

Dixon scratched the short hairs at the back of his neck and said nothing.

"But we're on Mercury, damn it, not in Hawaii," Larionova said.

Dixon pointed down, past the dusty floor. "Irina. It's not all frozen. There are cavities down there, inside the Chao ice cap. According to our sonar probes--"

"Cavities?"

"Water. At the base of the crater, under a couple of miles of ice. Kept liquid by thermal vents, in crust-collapse scarps and ridges. Plenty of room for swimming... we speculate that our friend here swims on his back--" he tapped the desk surface, and the image swiveled " -- and the water passes down, between his body and this carapace, and he uses all those tiny hairs to filter out particles of food. The trunk seems to be lined with little mouths. See?" He flicked the image to another representation; the skin became transparent, and Larionova could see blocky reconstructions of internal organs. Dixon said, "There's no true stomach, but there is what looks like a continuous digestive tube passing down the axis of the body, to the anus at the tail."

Larionova noticed a threadlike structure wrapped around some of the organs, as well as around the axial digestive tract.

"Look," Dixon said, pointing to one area. "Look at the surface structure of these lengths of tubing, here near the digestive tract."

Larionova looked. The tubes, clustering around the digestive axis, had complex, rippled surfaces. "So?"

"You don't get it, do you? It's convoluted -- like the surface of a brain. Irina, we think that stuff must be some equivalent of nervous tissue."