TY - GEN
T1 - Searching for an alternative form of life on Earth
AU - Davies, Paul
PY - 2007
Y1 - 2007
N2 - Biologists tacitly assume that all life on Earth descended from a common origin. This assumption is based on biochemical similarities and gene sequencing, which enables organisms to be positioned on a common tree of life. However, most terrestrial organisms are microbes, and it is impossible to deduce their biochemical nature from morphology alone. The vast majority of microbes remain unclassified, leaving open the possibility that some of them might be an alternative form of life, arising either from an independent origin, or representing a hitherto overlooked very ancient branch of the known tree. Thus there may exist an extinct, or even extant, shadow biosphere. I discuss various research proposals for locating and identifying "alien" organisms on Earth, both ecologically separate and ecologically integrated.
AB - Biologists tacitly assume that all life on Earth descended from a common origin. This assumption is based on biochemical similarities and gene sequencing, which enables organisms to be positioned on a common tree of life. However, most terrestrial organisms are microbes, and it is impossible to deduce their biochemical nature from morphology alone. The vast majority of microbes remain unclassified, leaving open the possibility that some of them might be an alternative form of life, arising either from an independent origin, or representing a hitherto overlooked very ancient branch of the known tree. Thus there may exist an extinct, or even extant, shadow biosphere. I discuss various research proposals for locating and identifying "alien" organisms on Earth, both ecologically separate and ecologically integrated.
KW - Arsenate
KW - Biogenesis
KW - Impact reseeding
KW - Shadow biosphere
UR - http://www.scopus.com/inward/record.url?scp=42149114136&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=42149114136&partnerID=8YFLogxK
U2 - 10.1117/12.742355
DO - 10.1117/12.742355
M3 - Conference contribution
AN - SCOPUS:42149114136
SN - 9780819468420
T3 - Proceedings of SPIE - The International Society for Optical Engineering
BT - Instruments, Methods, and Missions for Astrobiology X
T2 - Instruments, Methods, and Missions for Astrobiology X
Y2 - 28 August 2007 through 30 August 2007
ER -