The Search for Extraterrestrial Life Is Picking Up Speed

Recently, the search for extraterrestrial life has started to gain significant momentum. NASA has just announced, for instance, that it is setting aside $25 million to develop the scientific instruments needed for a mission to Europa (Figure 1). This is the ice-covered moon of Jupiter that could harbor life in the ocean underneath its icy exterior. Finding any form of life on a solar system body other than Earth -- be it Mars, or one of the satellites Europa, Enceladus, or Titan -- would indeed be very exciting. The true revolution, however, will ensue once we find extrasolar life -- life on a planet orbiting another star. The main reason that makes extrasolar life the much bigger prize is very simple. If extraterrestrial life is found within the solar system, unless it is absolutely clear that it has arisen independent of our lineage, there will always be the possibility that life on Earth and this newly found life had the same origin. The discovery of life in a planetary system around another star, on the other hand, will immediately imply that life is not exceedingly rare, with all the extraordinary biological and cultural implications.