The LIFE initiative - establishing a space mission to search for biosignatures in exoplanet atmsopheres in the mid-infrared

One of the major goals - and possibly the most challenging one in 21st century exoplanet research - is the investigation of the atmospheric properties for a large number of terrestrial exoplanets. On the one hand, a statistically significant dataset is invaluable for understanding the diversity of planetary bodies, but on the other hand, this is driven the motivation to search for habitable conditions and identify potential biosignatures, i.e., indications of biological activtity, outside our Solar System. First steps in this direction will be taken in the coming 10-15 years with funded or selected ground- and space-based projects and missions. In addition, the US astrophysics decadal recommended a UV-optical-NIR space telescope (the Habitable Worlds Observatory) with an aperture diameter of at least 6 meters as next flagship mission for the 2040s. This telescope shall be sensitive enough to survey dozens of Earth-sized exoplanets. A highly synergistic approach to this mission, which focuses on the reflected light of the exoplanets, is to directly detect the exoplanets’ thermal emission in the mid-infrared by means of a space-based nulling interferometer. In this contribution, we summarize the current status of the European-led LIFE initiative, which has the goal to develop the science, the technology and a roadmap for such an ambitious space mission that will allow humankind to detect and characterize the atmospheres of hundreds of nearby extrasolar planets including dozens that are similar to Earth. Given the outcome of ESA’s "Voyage 2050" process and the corresponding recommendations from the ESA Senior Committee, the direct detection of the thermal emission of temperate terrestrial exoplanets is given very high scientific priority in ESA future science program and is considered as a candidate theme for a future L-class mission. The unique discovery space for a mid-infrared mission, in particular for the detection of atmospheric biosignatures in exoplanets, will be discussed, the international scope of the inititiative (including contributions from the US, Japan and Australia) will be highlighted, and synergies between LIFE and the NASA's future Habitable Worlds Observatory mission will be emphasized.