Co-Evolution of Atmospheres, Life, and Climate
Artikel i vetenskaplig tidskrift, 2010
After Earth's origin, our host star, the Sun, was shining 20-25% less brightly than today. Without greenhouse-like conditions to warm the atmosphere, our early planet would have been an ice ball, and life may never have evolved. But life did evolve, which indicates that greenhouse gases must have been present on early Earth to warm the planet. Evidence from the geological record indicates an abundance of the greenhouse gas CO2. CH4 was probably present as well; and, in this regard, methanogenic bacteria, which belong to a diverse group of anaerobic prokaryotes that ferment CO2 plus H-2 to CH4, may have contributed to modification of the early atmosphere. Molecular oxygen was not present, as is indicated by the study of rocks from that era, which contain iron carbonate rather than iron oxide. Multicellular organisms originated as cells within colonies that became increasingly specialized. The development of photosynthesis allowed the Sun's energy to be harvested directly by life-forms. The resultant oxygen accumulated in the atmosphere and formed the ozone layer in the upper atmosphere. Aided by the absorption of harmful UV radiation in the ozone layer, life colonized Earth's surface. Our own planet is a very good example of how life-forms modified the atmosphere over the planets' lifetime. We show that these facts have to be taken into account when we discover and characterize atmospheres of Earth-like exoplanets. If life has originated and evolved on a planet, then it should be expected that a strong co-evolution occurred between life and the atmosphere, the result of which is the planet's climate.
habitable zones
ozone
methane
hydrogen
evolution
earth-like planets
2-dimensional model
Biomarker
halogen occultation experiment
Atmospheres
long-term
middle-atmosphere
Early Earth
Climate
Exoplanets
Författare
J. L. Grenfell
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
H. Rauer
Technische Universität Berlin
Deutsches Zentrums für Luft- und Raumfahrt (DLR)
F. Selsis
Université de Bordeaux
L. Kaltenegger
Harvard-Smithsonian Center for Astrophysics
C. Beichman
California Institute of Technology (Caltech)
W. Danchi
National Aeronautics and Space Administration (NASA)
C. Eiroa
Universidad Autonoma de Madrid (UAM)
M. Fridlund
Europeiska rymdorganisationen (ESA)
T. Henning
Max-Planck-Gesellschaft
T. Herbst
Max-Planck-Gesellschaft
H. Lammer
Institut fur Weltraumforschung
A. Leger
Université Paris-Sud
René Liseau
Chalmers, Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik
J. Lunine
University of Arizona
F. Paresce
Istituto nazionale di astrofisica (INAF)
A. Penny
STFC Rutherford Appleton Laboratory
A. Quirrenbach
Landessternwarte Heidelberg-Königstuhl
H. Rottgering
Universiteit Leiden
J. Schneider
Observatoire de Paris-Meudon
D. Stam
Netherlands Institute for Space Research (SRON)
G. Tinetti
University College London (UCL)
G. J. White
STFC Rutherford Appleton Laboratory
Open University
Astrobiology
1531-1074 (ISSN)
Vol. 10 1 77-88Ämneskategorier (SSIF 2011)
Astronomi, astrofysik och kosmologi
Fundament
Grundläggande vetenskaper
DOI
10.1089/ast.2009.0375