Biology
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p24b..01s&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P24B-01
Biology
[5200] Planetary Sciences: Astrobiology, [5400] Planetary Sciences: Solid Surface Planets, [6296] Planetary Sciences: Solar System Objects / Extra-Solar Planets, [6024] Planetary Sciences: Comets And Small Bodies / Interiors
Scientific paper
The habitability of planets has received increasing interest, in particular in view of the increasing number of detected extrasolar planets. Planetary habitability (for life as we know it) is thought to require water on (or near) the surface, a magnetic field to protect life against radiation, and transport mechanisms for nutrients. A chemoautotrophic biosphere would require volcanic activity and associated large thermal gradients. Volcanic activity is thought to have been instrumental for the formation of (initially chemoautotrophic) life on Earth. A magnetic field also protects an existing atmosphere against erosion by the solar wind and thus helps to stabilize the presence of surface water. Magnetic fields are generated in the cores of the terrestrial planets and thus habitability is linked to the evolution of the interior through magnetic field generation and volcanic activity. Moreover, the interior is a source and sink for water and may interact with the surface and atmosphere reservoirs through volcanism and recycling. The most efficient known mechanism for recycling is plate tectonics. Plate tectonics is known to operate only on the Earth, although Mars and Venus may have had phases of plate tectonics. Plate tectonics supports the generation of magnetic fields by effectively cooling the deep interior and rejuvenates near-surface nutrients. On the Earth, surface water is stabilized by complex interactions between the atmosphere, the biosphere, the oceans, the crust, and the deep interior in the carbon-silicate cycle. As plate tectonics is believed to require water in the mantle to operate, plate tectonics is another element linking the biosphere to the evolution of the planet's interior. Single-plate tectonics associated with stagnant lid convection would allow for transfer of water from the interior by volcanism but lacks a simple recycling mechanism. The question of whether or not extrasolar earthlike planets more massive than the Earth are likely to have plate tectonics or single-plate tectonics is hotly debated. We argue that the large interior pressure and its effect on the rheology of their mantles may frustrate plate tectonics and magnetic field generation altogether. We even argue that surface volcanic activity may become difficult with increasing mass of a rocky planet. On Earth, mantle melt is buoyant at depths smaller than a few 100km. Below this critical depth melt will be negatively buoyant because of its compressibility. The critical depth will decrease with increasing mass of the planet and may become shallower than the depth to the base of the stagnant lid on massive planets. We find the ratio between the stagnant lid thickness and the critical depth to increase approximately linearly with the planet radius. The great diversity of extrasolar planets may suggest a diversity of life forms and associated habitability parameters, however, and extrapolations from the Earth may be overly naive.
Breuer Doris
Höning D.
Noack Lena
Spohn Tilman
No associations
LandOfFree
Planetary Interior Evolution and Life does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Planetary Interior Evolution and Life, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Planetary Interior Evolution and Life will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-870145