The light came from peaks projecting into the sunlight, from scattered skylight which was growing rapidly fainter and from the brighter celestial objects such as Earth. Even with the tractor’s lights it was getting harder to spot crevasses and seismometer markers. Zaino quickly found the fun wearing off. . though his pride made him cover the fact as best he could.

If Hargedon saw this, he said nothing. He set Zaino to picking up every other instrument, as any partner would have, making no allowance for the work the youngster was doing for Schlossberg. This might, of course, have had the purpose of keeping the radioman too busy to think about discomfort. Or it might merely have been Hargedon’s idea of normal procedure.

Whatever the cause, Zaino got little chance to use the radio once they had driven into the darkness. He managed only one or two brief talks with those left at the ship.

The talks might have helped his morale, since they certainly must have given the impression that nothing was going on in the ship while at least he had something to do in the tractor. However, this state of affairs did not last. Before the vehicle was four hours out of sight of the Albireo, a broadcast by Camille Burkett reached them.

The mineralogist’s voice contained at least as much professional enthusiasm as alarm, but everyone listening must have thought promptly of the dubious stability of Mercury’s crust. The call was intended for her fellow geologists Mardikian and Harmon. But it interested Zaino at least as much.

“Joe! Eileen! There’s a column of what looks like black smoke rising over Northeast Spur. It can’t be a real fire, of course; I can’t see its point of origin, but if it’s the convection current it seems to me the source must be pretty hot. It’s the closest thing to a genuine volcano I’ve seen since we arrived; it’s certainly not another of those ash mounds. I should think you’d still be close enough to make it out, Joe. Can you see anything?”