Hal Clement falls into the same category as folks like Fletcher Pratt and James Blish for me -- giants of the field whom I haven't quuiiiite gotten around to yet. Meant to. They've each contributed a major classic or two to the genre, including Pratt's The Well of the Unicorn and The Incomplete Enchanter series (written with L. Sprague de Camp), and A Case of Conscience and Cities in Flight from Blish. Clement hasn't been as prolific as some, but 1953's Mission of Gravity is reputed to be one of the great early works of hard SF, and he's also produced such well-respected novels as Close to Critical (1964), and The Nitrogen Fix (1980). They all sit in tidy rows in my library, unread. Just something about classics, I guess.

The arrival of Half Life provided a convenient opportunity to break with tradition and sample some Hal Clement and I seized it with gusto. It's his first SF novel since 1993's Isaac's Universe: Fossil. An earlier version of Half Life was originally published in four installments in the fine SF magazine Harsh Mistress/Absolute Magnitude in 1994 and 1995, though the finished product shows no readily apparent seams.

The premise for Half Life is pretty bleak. The time is roughly two centuries from now, when the population of Earth has been devastated by a series of unremitting plagues. For each one conquered, several more pop up. Millions are dead, billions are dying, and the human race may be on the way to extinction.

There's no explanation for the sudden eruption of new diseases, and it's clear that humanity's understanding of the way life is created -- especially microscopic life -- is broken. In desperation, a small crew of men and women undertake a journey to the moons of Saturn, specifically to Titan, in the hopes that an investigation of the bio-chemistry of pre-life conditions will yield some clue. En route nearly half of the crew members die, and by the time the ship arrives only 21 crew members remain -- and all but two are gradually succumbing to some form of fatal illness. As the book opens, in orbit around Titan, total quarantine is in effect on board and the crew communicates exclusively through shared intercom. No one sees another human face, and in many cases most of the major characters are not even aware what their co-workers look like.

It's an unusual set-up, to say the least, and one that somewhat blunts the dramatic potential of the opener. It doesn't help that the isolated crew of dying scientists never seems to express an emotion stronger than mild annoyance, either. Clement's prose also seems distanced from the action at times, which compounds the sterile nature of the narrative even further. But as the mysteries of Titan begin to surface, unexpected fatalities arise, and the crew begins to face potentially critical shortages, the silent halls of the orbiting station prove to be a surprisingly tense backdrop for a well-plotted novel of scientific investigation and discovery.

I should emphasize that last point. This is a hard science fiction novel, and an unapologetic one at that. Fairly advanced knowledge of bio-chemistry and engineering are required to completely follow much of the casual dialogue -- at least, more advanced than I've got, anyway. [Editor's Note: This could be somewhat worrisome, since I know this reviewer has a Ph.D. in chemical engineering!] This is a book that had me bouncing out of my chair to look up unexplained references (things like thermotropic reactions, Cepheid stars, and Mollweide projections) a lot more often than I'm used to. There's even a critical plot point that requires the reader to know what nitrogen triiodide monoammate is (it's a type of explosive). I know that's a plus to the tried-and-true hard SF fans in the audience, but in general I prefer to use less energy in my quiet reading hours.

Clement's references aren't all scientific, and some of them will be quite amusing to Golden Age SF fans. A lot of space is given over to General Order 6 -- an attempt to avoid hastily jumping to conclusions by requiring anyone with a hypothesis to present at least one viable alternative. This is also referred to as the "Aaron Munro instant-certainty syndrome," in reference to John W. Campbell's famous character of the same name. Also, Clement's characters have clearly read more Heinlein than I have, if the number of quotes tossed about is any indication.

I haven't read a true hard SF novel in a long time, and at times reading Half Life felt like exercising long-unused muscles. But the end result is worth it, and a fine reminder of why hard SF resides at the very core of our genre -- that part of our diet that really forces us to think, and think hard, about the big questions -- such as life, death, and the fragile chemical barriers between the two.

Half Life is an eye-opener in more ways than one. Keep an eye out for it yourself.

John O'Neill is the founder of the SF Site.