  The search for life beyond the Earth is the overarching goal of the NASA
Astrobiology Program, and it underpins the science of missions that explore the
environments of Solar System planets and exoplanets. However, the detection of
extraterrestrial life, in our Solar System and beyond, is sufficiently
challenging that it is likely that multiple measurements and approaches,
spanning disciplines and missions, will be needed to make a convincing claim.
Life detection will therefore not be an instantaneous process, and it is
unlikely to be unambiguous-yet it is a high-stakes scientific achievement that
will garner an enormous amount of public interest. Current and upcoming
research efforts and missions aimed at detecting past and extant life could be
supported by a consensus framework to plan for, assess and discuss life
detection claims (c.f. Green et al., 2021). Such a framework could help
increase the robustness of biosignature detection and interpretation, and
improve communication with the scientific community and the public. In response
to this need, and the call to the community to develop a confidence scale for
standards of evidence for biosignature detection (Green et al., 2021), a
community-organized workshop was held on July 19-22, 2021. The meeting was
designed in a fully virtual (flipped) format. Preparatory materials including
readings, instructional videos and activities were made available prior to the
workshop, allowing the workshop schedule to be fully dedicated to active
community discussion and prompted writing sessions. To maximize global
interaction, the discussion components of the workshop were held during
business hours in three different time zones, Asia/Pacific, European and US,
with daily information hand-off between group organizers.
