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.

long-term

methane

evolution

habitable zones

ozone

Exoplanets

halogen occultation experiment

Climate

Early Earth

Biomarker

hydrogen

Atmospheres

middle-atmosphere

earth-like planets

2-dimensional model

Författare

J. L. Grenfell

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

H. Rauer

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

Technische Universität Berlin

F. Selsis

Universite de Bordeaux

L. Kaltenegger

Harvard-Smithsonian Center for Astrophysics

C. Beichman

Jet Propulsion Laboratory, California Institute of Technology

W. Danchi

NASA Goddard Space Flight Center

C. Eiroa

Universidad Autonoma de Madrid (UAM)

M. Fridlund

ESTEC

T. Henning

Max Planck-institutet

T. Herbst

Max Planck-institutet

H. Lammer

Institut fur Weltraumforschung

A. Leger

Universite Paris-Sud XI

René Liseau

Chalmers, Institutionen för radio- och rymdvetenskap, Radioastronomi och astrofysik

J. Lunine

University of Arizona

F. Paresce

Istituto Nazionale Di Astrofisica, Rome

A. Penny

Rutherford Appleton Laboratory

A. Quirrenbach

Landessternwarte Heidelberg

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

Open University

Rutherford Appleton Laboratory

Astrobiology

1531-1074 (ISSN)

Vol. 10 77-88

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

10.1089/ast.2009.0375