The Mariana Trench is the deepest part of the ocean, and its center, Challenger Deep, is the lowest point on the Earth. Yet, more than 11 kilometers below the surface, life teems. Research published this week suggests that there may be twice as much life living in the Earth's harshest environment as previously thought. If that's the case, it lends support to the notion of life existing kilometers below the icy surface of moons such as Europa or Enceladus.
We've been to the Moon more times (six) than we've been to Challenger Deep (two), so it is little surprise that there's much we don't yet understand about the remotest parts of our own oceans. What's clear, however, is that conditions in the Mariana Trench probably resemble those on other worlds more closely than any other terrestrial environment. Virtually no light penetrates the incredible mass of water above the site, meaning plant life is non-existent. Only a tiny fraction of one percent of the organic material generated at the surface trickles down this far, so food is extremely rare. With a pressure more than a thousand times greater than on the surface, and at a temperature only a degree above freezing, even the water in this strange world behaves differently.
If life can survive and thrive in these conditions, it doesn't seem so unlikely that it could flourish similarly in the sub-surface oceans of some of the outer moons. The water there is likely more chemically harsh and interaction with the surface even more limited, but these are conditions to which extra-terrestrial life could adapt. And why not? Many of these moons are chemically active, providing a source of energy not tied to the Sun and similar to the method these Earth creatures use to survive.
The problem, of course, is that life almost certainly didn't arise in the Mariana Trench. A warmer, more energetic environment probably spawned the first life, because chemical reactions are greatly enhanced with additional energy. On the Earth, such conditions existed on the surface for much of our planet's early life, but these conditions probably never happened on the frigid, airless surfaces of these icy moons.
So, if life could arise, it seems as if it could thrive in the barren conditions of a sub-surface ocean. But is it possible to create life in such harsh environments? That's the real question, and one that research on the Earth may never be able to answer.
Source: Live Science