title: Signatures of a shadow biosphere.
abstract: Astrobiologists are aware that extraterrestrial life might differ from known life, and considerable thought has been given to possible signatures associated with weird forms of life on other planets. So far, however, very little attention has been paid to the possibility that our own planet might also host communities of weird life. If life arises readily in Earth-like conditions, as many astrobiologists contend, then it may well have formed many times on Earth itself, which raises the question whether one or more shadow biospheres have existed in the past or still exist today. In this paper, we discuss possible signatures of weird life and outline some simple strategies for seeking evidence of a shadow biosphere.
authors.affiliation: BEYOND: Center for Fundamental Concepts in Science, Arizona State University, Tempe, Arizona 85287-1404, USA. paul.davies@asu.edu
authors.forename: Paul C W
authors.initials: PC
authors.lastname: Davies
authors.forename: Steven A
authors.initials: SA
authors.lastname: Benner
authors.forename: Carol E
authors.initials: CE
authors.lastname: Cleland
authors.forename: Charles H
authors.initials: CH
authors.lastname: Lineweaver
authors.forename: Christopher P
authors.initials: CP
authors.lastname: McKay
authors.forename: Felisa
authors.initials: F
authors.lastname: Wolfe-Simon
mesh_terms: D015415:Biomarkers / Q000737:chemistry / Q000378:metabolism; D018534:Earth, Planet; D055669:Ecological and Environmental Phenomena; D019143:Evolution, Molecular; D018559:Exobiology; D019369:Life; D008962:Models, Theoretical; D000069497:Origin of Life
chemical_list: D015415:Biomarkers