Paper: astro-ph/0510224
Date: Fri, 7 Oct 2005 15:22:56 GMT (806kb)

Title: Biosignatures from Earth-Like Planets Around M Dwarfs

Authors: Antigona Segura (1), James F. Kasting (1), Victoria Meadows (2),
Martin Cohen (3), John Scalo (4), David Crisp (5), Rebecca A.H. Butler (5)
and Giovana Tinetti (6) ((1) Penn State, (2) Caltech, (3) UC Berkeley, (4) UT
Austin, (5) JPL/Caltech, (6) Caltech/NRC. Members, Virtual Planetary
Laboratory, NASA Astrobiology Institute)

Comments: 34 pages, 10 figures, Astrobiology, in press
\\
Coupled one-dimensional photochemical-climate calculations have been
performed for hypothetical Earth-like planets around M dwarfs. Visible,
near-infrared and thermal-infrared synthetic spectra of these planets were
generated to determine which biosignature gases might be observed by a future,
space-based telescope. Our star sample included two observed active M dwarfs,
AD Leo and GJ 643, and three quiescent model stars. The spectral distribution
of these stars in the ultraviolet generates a different photochemistry on these
planets. As a result, the biogenic gases CH4, N2O, and CH3Cl have substantially
longer lifetimes and higher mixing ratios than on Earth, making them
potentially observable by space-based telescopes. On the active M-star planets,
an ozone layer similar to Earth's was developed that resulted in a
spectroscopic signature comparable to the terrestrial one. The simultaneous
detection of O2 (or O3) and a reduced gas in a planet's atmosphere has been
suggested as strong evidence for life. Planets circling M stars may be good
locations to search for such evidence.

\\ ( http://arXiv.org/abs/astro-ph/0510224 , 806kb)