The definition of life and its role in astrobiology and the search for evidence of life in the universe

How may life be defined? This is a question that has growing importance as humanity develops the ability to explore beyond the Earth and searches for evidence of life being present on other astronomical bodies from the planets and moons in our own solar system to the thousands of exoplanets we are detecting around other stars. Such a definition is non-trivial and, as we discover life in ever more diverse and ‘extreme’ environments on Earth broadening the regions of ‘habitability’, increasingly complex. In this short article, we review the different definitions of ‘life’, the need for such a definition and the implications that such a definition may have on the future development of astrobiology and the search for evidence of life in the universe.