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Summary: ASTROBIOLOGY
Volume 3, Number 3, 2003
© Mary Ann Liebert, Inc.
Methodologies and Techniques for Detecting
Extraterrestrial (Microbial) Life
Terahertz Circular Dichroism Spectroscopy: A Potential
Approach to the In Situ Detection of Life's Metabolic
and Genetic Machinery
JING XU,1 GERALD J. RAMIAN,1 JHENNY F. GALAN,2 PAVLOS G. SAVVIDIS,1
ANTHONY MICHAEL SCOPATZ,1 ROBERT R. BIRGE,2 S. JAMES ALLEN,1
and KEVIN W. PLAXCO3
ABSTRACT
We propose a terahertz (far-infrared) circular dichroism-based life-detection technology that
may provide a universal and unequivocal spectroscopic signature of living systems regard-
less of their genesis. We argue that, irrespective of the specifics of their chemistry, all life
forms will employ well-structured, chiral, stereochemically pure macromolecules ( 500
atoms) as the catalysts with which they perform their metabolic and replicative functions. We
also argue that nearly all such macromolecules will absorb strongly at terahertz frequencies
and exhibit significant circular dichroism, and that this circular dichroism unambiguously
distinguishes biological from abiological materials. Lastly, we describe several approaches to
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