Life shows up where you least expect it — both in the future, and the present. For instance, in the Star Trek: The Next Generation episode "A Matter of Honor," during interactions between the U.S.S. Enterprise-D and a Klingon ship, an unanticipated infection of the outer hull of both ships by a rather hardy strain of space bacteria leads to a lot of finger-pointing as to who infected whom.

In the Star Trek: Voyager episode "Demon," Captain Janeway and her crew encounter a so-called "Demon-class" planet — one covered with toxic gases and liquid metal. Seemingly inhospitable, life abounds. In another Voyager episode, "Thirty Days," the Delta Flyer travels to the center of a water planet and encounters life at incredibly remote depths.

Then of course, there is the classic encounter between Kirk, Spock and McCoy and the silicon-based Horta deep within a planet in "The Devil in the Dark."

And this is just a short list of the exotic places Starfleet crews have discovered unique lifeforms.

Not too many years ago, some of the lifeforms seen in Star Trek would have been dismissed as impossible. Throughout most of the 20th century, life was thought to exist within a narrow range of environmental conditions — the warm and friendly climate we're familiar with — and that energy from the sun, directly or indirectly, was required for all forms of life.

In 1976, a discovery in the deep ocean depths changed all that. In the years that followed, rich ecosystems of bacteria, invertebrates and fish were found in many locations miles below the sea at truly crushing pressures. These locations feature thermal vents on the ocean floor that spew ultra-hot water laden with various metals and compounds — what we'd call "poison," the locals call "food." (Photo courtesy NOAA.)

Once scientists started to look in unexpected places, they began to see that life had managed to stake claim to so-called "extreme environments" that would have been inhabited only in the minds of science fiction writers a few years earlier. Indeed, it is now thought that these bizarre places may well be where life first arose on Earth.

One of the questions that often arises when life is found in a new bizarre location is how it got there in the first place. And since these strange environments are similar to those that may exist on (or within) other worlds, there are broad implications for just how habitable the universe may actually be.

Research announced this week shows that seemingly common bacteria that we encounter every day can thrive in conditions once thought to be impossible. Researchers at the Carnegie Institution, working with the NASA Astrobiology Institute, have shown that common bacteria can thrive under high-pressure conditions 16,000 times the pressure found at sea level — pressures equivalent to about 50 kilometers beneath the Earth's crust (where we might find Horta eating rock) or 160 kilometers in a hypothetical sea (where Tom Paris took the Delta Flyer). Since these conditions are likely to be found within many worlds in our solar system, the number of potentially habitable zones increases dramatically.

If this wasn't bizarre enough, another research team at Texas A&M announced this week that rock-eating bacteria exist deep in the ocean off the coast of Peru. They don't need sunlight, carbon dioxide or oxygen. They get their nutrition by eating the rocks within which they live.

We have now found life that lives in nuclear reactors, infects aircraft fuel tanks, thrives in boiling hot springs, eats methane ice under the sea, and chews rock many kilometers below the Earth's surface. There are even bacteria that "breathe" metal and others that can easily survive radiation doses that literally blow their genomes apart. This certainly starts to sound like "Demon-class" conditions — and it happens here on Earth. (Photo courtesy U.S. Department of Defense.)

So... the next time you see some lifeform on Star Trek do something utterly improbable, just stop and think: Today's known lifeforms were yesterday's science fiction.

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