  The discovery of extra-solar planets is one of the greatest achievements of
modern astronomy. The detection of planets with a wide range of masses
demonstrates that extra-solar planets of low mass exist. In this paper we
describe a mission, called Darwin, whose primary goal is the search for, and
characterization of, terrestrial extrasolar planets and the search for life.
Accomplishing the mission objectives will require collaborative science across
disciplines including astrophysics, planetary sciences, chemistry and
microbiology. Darwin is designed to detect and perform spectroscopic analysis
of rocky planets similar to the Earth at mid-infrared wavelengths (6 - 20
micron), where an advantageous contrast ratio between star and planet occurs.
The baseline mission lasts 5 years and consists of approximately 200 individual
target stars. Among these, 25 to 50 planetary systems can be studied
spectroscopically, searching for gases such as CO2, H2O, CH4 and O3. Many of
the key technologies required for the construction of Darwin have already been
demonstrated and the remainder are estimated to be mature in the near future.
Darwin is a mission that will ignite intense interest in both the research
community and the wider public.
