Stalwart Life

Over the last few decades scientists have discovered life thriving in environments that were once considered to be too hostile and barren. For example, dozens of miles under the sea surface, where it's inky black and noxious fumes vent from smoky fumeroles, organisms thrive in water as hot as 200^oF. Deep in underground mines (some 2 ½ miles down), far from the sun and its life-giving rays, microorganisms feed on minerals and soak up heat from radioactivity, in lieu of any photosynthetic processes. In extremely acidic water, near its boiling point (such as in Yellowstone National Park), other organisms prosper. Only a few decades ago scientists would have been convinced that life (as they then knew it) could not survive in such harsh environments.

These discoveries of life's robustness have forced biologists to revise the conditions under which they believe life could survive. The very definitions of what constitutes life and what life requires to take root and thrive have been dramatically amended.

A recent example of another unlikely site for life has been the discovery of robust creatures deep under the Antarctic ice shelves, far from sunlight, in a location that was expected to be dark, cold, and lifeless. After having drilled a half-mile deep hole through the ice shelf, 500 miles inland from the open ocean and that far from any sunlight, researchers found microbes and small fish—in a completely dark location. How did these critters get there? How do they survive? I won't go into the details here, but the scientists were dumbfounded, when they lowered an underwater robot and photographed creatures. It blew their minds.

These recent discoveries have caused scientists to revise their theories about what life requires to survive, as well as to recognize the new kinds of life they've found in these hostile environments. The requirements for life on Earth have been significantly broadened. Maybe life doesn't require water—once thought to be absolutely necessary. Maybe it doesn't require photosynthesis of the sun's energy—which most every life form must have. Maybe it can use the energy and heat emitted by radioactive decay deep underground. Indeed, these are all true.

We are thus expanding our understanding of the extremes under which life can survive. We are getting past our myopic view that life must be very much like us, in order to exist. Microbes have been proven to be incredibly robust. Some have even been attached to the exterior of the International Space Station, where they have been exposed to high radiation, extreme temperature changes, and a total lack of atmosphere for over a year... and they survived!

What fascinates me is the implications that these discoveries have had on our guesses about the existence of extraterrestrial life. Earth offers very cordial conditions for life, compared to the harsh environments found elsewhere. Life thrives on our planet, in countless forms and in many pleasant ecosystems. Until these recent discoveries of life existing in harsh locations, scientists were inclined to discount the possibility of life other than on Earth. Many people thought that our little planet could be the only place in the universe where life arose. This is turning out to be a narrow-minded viewpoint.

Now we are thinking differently. In fact, right here in our solar system life may have gained a toehold in places other than Earth. Mars is looking more and more likely that it may have had life, a few billion years ago. Europa—an ice-covered moon of Jupiter—is thought to harbor an internal ocean of water; in conditions not that much different from Antarctica. Researchers are making plans to visit Europa and run experiments to see if life may be found there. Other moons in our solar system may have conditions where life may be able to survive. Farther out in space, thousands of planets have been discovered orbiting their stars. Preliminary findings suggest that some of them may be conducive to life. Life almost seems simply to be waiting for us to find it.

The existence of extraterrestrial life has, until the last couple of decades, either seemed doubtful or was confined to the realm of science fiction. Humanity is beginning to realize that life just may be abundant in our universe. Stay tuned... the answer may come in another decade or two.