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Early Earth

Research on the coevolution of life and the environment 

Information on the early Earth and its evolution can be found on the links below.

External links:

The Early Earth: Life and atmospheric change

Planetary Origin of Life

Research interests


Earth is currently our only example of a habitable planet. Consequently, studying its long-term evolution is essential for understanding why the Earth became habitable and why terrestrial life has persisted for billions of years.

Earth's  climate has been influenced by the Sun, which has gradually brightened by 25-30% in the last 4 billion years, and by the presence of three major greenhouse gases, carbon dioxide (CO2), water vapour (H2O),  and methane (CH4) [1]. Methane was probably an important greenhouse gas during the first half of Earth's history. The rise of atmospheric oxygen (O2) around 2.4 billion years ago may have caused the collapse of the methane greenhouse that  triggered worldwide glaciation at that time. In addition to altering the climate, the rise of O2 permitted the evolution of complex life and created a stratospheric ozone layer that blocks out solar ultraviolet radiation [2,3].

Understanding the influence of biology on the evolution of Earth's atmosphere could help us find life on planets around other stars. Oxygen, ozone, and methane are only produced in simultaneous abundance by life. These gases create absorption lines in the spectra of light from planets around other stars that may allow us to identify the presence of life.


References:
[1] J. F. Kasting and D. C. Catling, Evolution of a habitable planet, Annual Reviews of Astronomy and Astrophysics, 41, 429-463, 2003.
[2] D. C. Catling and M. Claire, How Earth's atmosphere evolved to an oxic state: A status report, Earth Planet. Sci. Lett., 237, 1-20, 2005.
[3] D. C. Catling, C.R. Glein, K.J. Zahnle, and C. P. McKay. Why O2 is required by complex life on habitable planets and the concept of planetary "oxygenation time",  Astrobiology, 5, 415-438, 2005.

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