CAMBRIDGE - It's new science - so new that its name has barely taken hold - and it's brimming with notions that only a few years back would have been laughed off as lurid science fiction.

Geobiology, it's mostly called, although some of its leading lights stick to their old professional dogtags, such as biologist, geologist, hydrologist, biochemist. Others prefer more cosmic nomenclature: Astrobiology.

In any event, it is wild and wooly research occurring "on the frontiers of so many disciplines," said geobiologist Dianne K. Newman of the Massachusetts Institute of Technology.

Geobiology is, in part, about looking for life or life's graffito - and finding it - in unusual places: deep in ancient rock, in super-heated waters of undersea volcanic vents, and beneath the ice of Greenland.

But geobiology can also be about fashioning crude "proto-cells" from chemical goop resembling primeval ooze, work done recently in the Harvard/Massachusetts General Hospital laboratory of geneticist Jack W. Szostak to study how lifelike entities might have arisen in the extreme environment 3.5 billion years ago.

The emergent field rests on the idea that the dividing line between life and nonlife is blurrier than science has long believed. And that the minerals and chemicals of the earth are constantly interacting with living things in unexpected ways.

That means the origins of life can only be understood as shaped by the larger environment, and - by the same token - the nonliving environment can be understood only in the context of the fast-multiplying organisms that shaped it right back.

"Evolution is not something that happened solely to organisms," said Robert Hazen, a research scientist with Washington's Carnegie Institution. "There has been co-evolution of the geosphere and the biosphere."

Said geobiologist Lisa M. Pratt of Indiana University: "Turns out, establishing where geochemistry ends and life begins isn't always so easy. We know surprisingly little about the origin, evolution, and limits for life on earth. But we're on the cusp of dramatic new understandings."

Twitches of life are showing up where life shouldn't exist. In southern Africa, for example, scientists burrowed 2 miles beneath the earth's surface, discovering bacteria that feed on radioactive rocks.

"That's crazier than any science fiction," said Pratt, part of the team that made the 2006 discovery. "This is life that shouldn't be there. Except it is."

In the minds of some geobiologists, including Pratt, the existence of these "extremophile" microbes hints that life is such sturdy stuff that it might seed itself on any planet possessing a bit of water.

"Stardust contains all the [chemical] building blocks of life," she said, referring to primal matter forged by the Big Bang. "And it rains down on all planets. Life may be commonplace [on other planets], not some rare event. Earth may be singular only in that life has proved highly durable, hanging on through various cataclysms to evolve into sophisticated forms."