As Stephen Baxter’s Moonseed opens, Venus is inexplicably exploding, visible in earth’s daytime sky as a smudged, brilliant disc of light. Startling as the sight is, geologist Henry Meacham has other problems foremost in his mind. His marriage is breaking up, his longtime hope of probing the moon for its frozen subsurface water has been quashed, and only one laboratory—in Edinburgh—offers to support his boring second choice project, studying a sample brought back many years ago from the moon’s bedrock.

This choice is fateful, however, as the seemingly inert rock contains a wholly new form of matter. Or is it even matter? It could be an alien entity, or the information code for a galactic remodeling plan. In any event, when Henry’s assistant “loses” some dust grains from the rock, it burrows into the ground and eats away at the basalt. Before anyone can learn why bubbling silver pools are appearing, the undermined city collapses.

The moonseed spreads, consuming the earth’s mantle. Tsunamis, earthquakes, volcanic explosions, and nuclear power plant disasters roll across the planet. Countermeasures are only fitfully effective; the earth is doomed. To save something from the catastrophe, Henry persuades NASA to bootstrap a new moon mission. There he finally gets his wish, to release water from under the moon’s polar caps. The resultant “instant terraforming” makes the satellite livable, so at least part of the earth’s population and resources can survive.

Moonseed is a giant scale disaster novel. Like most such works, it gives readers glimpses of people’s lives, only to kill off most characters when they have come to care about them. The scenes of imploding cities are dramatic, scary—and relentless. There is also a 200-page account of the space flight and lunar landing.

If the book has a cautionary message, it is the foolishness of letting manned spaceflight programs languish for so long. Hard-science types may ponder the book’s rationale for the cataclysm, but everyone can shiver at its picture of a planetary meltdown.