| Terrestrial studies of life in extreme environments now show that Earth is teeming with microorganisms. Nearly every locale that contains two ingredients, liquid water and some form of energy, appears to host a variety of microbes living happily under conditions that just a few years ago would have seemed impossibly inhospitable. There is also increasing evidence that life emerged very early on Earth, almost as soon as the planet stopped being punished by the deadly rain of debris coursing through the young solar system.
These findings have greatly expanded the horizons of potential habitats for life in the solar system and beyond. Whereas the prior assumption of life as a fragile and extremely rare occurrence put the focus on Mars, the only other planet that might once have had earthlike conditions, the new view of life as relatively robust, if not unstoppable, brings several other bodies into contention.
Jupiter’s moon Europa is foremost among the new candidates for harboring past or present life forms. Europa’s smooth crust of fractured water ice suggests a subsurface ocean that might provide just the conditions that can host life on Earth. Discovered by Galileo and studied for the past few years by the spacecraft that bears his name, Europa is now considered “one of the places in our solar system with the greatest potential for the existence of life” (see p. 3 in the Executive Summary).
This study assesses our current knowledge of Europa and outlines a strategy for multiyear investigations that would lead to definitive understanding of this moon and its possible biota. COMPLEX concludes that Europa should have a priority for future investigation equal to that accorded to Mars. And as has already been stressed in the strategy for martian investigations, the report underlines the need for a systematic approach to obtaining a global view of Euorpa science, rather than attempting a rapid and possibly poorly conceived rush to detect life. Such a course will not be easy—the intense radiation environment around Jupiter’s moon is just one of the many technical challenges. But the reward in understanding this remarkable object and in pursuing the possibility for discovery of extraterrestrial life will be substantial. |
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