Searching for biological activity on exoplanets via atmospheric biosignatures, assessing the habitability of terrestrial exoplanets, and investigating the diversity of planetary bodies.

Exoplanet science is omnipresent on the roadmaps of all major space agencies and ground-based observatories, and continues to drive the research activities of an increasing number of scientists worldwide. One of the long-term objectives is the investigation of the atmospheric properties of a statistically significant number (>100) of terrestrial exoplanets. The key motivations are to:

1. Search for and identify potential biosignatures (such as oxygen, ozone, methane and phosphine) in the exoplanet atmospheres
2. Assess the habitability of terrestrial exoplanets
3. Understand the diversity of planetary bodies and how our Solar System fits into the larger context of (exo)planetary systems)

Key steps towards achieving these objectives will be possible in the coming 10-15 years with ongoing and upcoming missions such as JWST, PLATO, the Roman Space Telescope or ARIEL. Also, the ground-based Extremely Large Telescope will contributed. However, no mission or instrument will provide a large statistical dataset of terrestrial exoplanets that is ultimately needed. Given the precision and sensitivity requirements, a space mission seems inevitable for achieving the science goals. NASA is pursuing the Habitable Worlds Observatory (HWO), a large infrared/optical/ultraviolet space telescope recommended by the National Academies’ Pathways to Discovery in Astronomy and Astrophysics for the 2020s. HWO will detect and characterize the reflected light of terrestrial exoplanets orbiting Sun-like stars. As a nulling interferometer working at mid-infrared wavelength, LIFE follows a complementary and more versatile approach that probes the intrinsic thermal emission of exoplanets. LIFE can probe for a wider range of atmospheric biosignatures in exoplanets orbiting a wider range of host stars and will also have access to atmospheric technosignatures.