I sometimes think that humans will never rest until they have succeeded in contaminating every corner of the available universe with their germs. We had to drill in Lake Vostok, a pristine environment cut off from the rest of the world for thousands, if not millions of years. Life will find a way into any environment, however hostile and barren it may seem to be. Chemolithotrophic bacteria can be at the center of an ecosystem that never sees sunlight. We know this to be true of deep sea ocean vents. Why not on Europa, in her salty seas? And what will happen when we contaminate them irrevocably? Humans are very destructive.

If you don't care for reality, just wait a while; another will be along shortly. --A Rose