Biosignatures from Earth-Like Planets Around M Dwarfs

Details Biosignatures from Earth-Like Planets Around M Dwarfs Biosignatures from Earth-Like Planets Around M Dwarfs

2005-10-07

arxiv.org/abs/astro-ph/0510224v1

Astronomy and Astrophysics

Astrophysics

34 pages, 10 figures, Astrobiology, in press

Scientific paper

10.1089/ast.2005.5.706

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.

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