Something extraordinary has happened over the past decade. Without any fanfare, scientists the world over have reached a consensus on one of the most profound questions ever to challenge the human mind: Are we alone? In all of this vast and ancient cosmos, is life confined to Earth?
No. Almost beyond doubt, life exists elsewhere. Probably, in microbial form at least, it is widespread. And more likely than not, we will find incontestable evidence of it quite soon—perhaps within the next ten to twenty years. These are the core elements of the remarkable new accord that is now routinely accepted by researchers across a spectrum of disciplines.
Behind this surge in scientific optimism about the prospects for alien life lies a rush of remarkable discoveries. A bewildering assortment of (mostly microscopic) life-forms has been found thriving in what were once thought to be uninhabitable regions of our planet. These hardy creatures have turned up in deep, hot underground rocks, around scalding volcanic vents at the bottom of the ocean, in the desiccated, super-cold Dry Valleys of Antarctica, in places of high acid, alkaline, and salt content, and below many meters of polar ice. The range of locales where organisms could be expected to survive in the universe is thus vastly expanded. Some deep-dwelling, heat-loving microbes, genetic studies suggest, are among the oldest species known, hinting that not only can life thrive indefinitely in what appear to us totally alien environments, it may actually originate in such places. If so—if the cradles of biogenesis tend to be hot, dark, subsurface hells rather than our familiar sun-drenched surface edens—then the widespread appearance of life throughout the cosmos is made much more likely.
Scientific opinion has also shifted dramatically toward the view that life may be "easy"—able to assemble itself from simpler components at the slightest opportunity. How else to account for the signs in ancient rocks that bacteria proliferated on Earth as long ago as 3.8 billion years, during the intense bombardment phase following the birth of our solar system? Terrestrial life appeared almost before it had a reasonable chance of long-term