  The discovery of extra-solar planets is one of the greatest achievements of
modern astronomy. There are now more than 200 such objects known, and the
recent detection of planets with masses approximately 5 times that of Earth
demonstrates that extra-solar planets of low mass exist. In addition to
providing a wealth of scientific information on the formation and structure of
planetary systems, these discoveries capture the interest of both scientists
and the wider public with the profound prospect of the search for life in the
Universe. We propose an L-type mission, called Darwin, whose primary goal is
the study of terrestrial extrasolar planets and the search for life on them. By
its very nature, Darwin advances the first Grand Theme of ESA Cosmic Vision.
Accomplishing the mission objectives will require collaborative science across
disciplines ranging from planet formation and atmospheres to chemistry and
biology, and these disciplines will reap profound rewards from their
contributions to the Darwin mission.
