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Super-Earths and Extraterrestrials

2009, December 16 - 11:14am — Greg Kontos
Features: Current EventsCritical Path Innovation: Space ExplorationPeople: Dimitar SasselovFree Tagging: super earths, Fermi ParadoxSites in Space: Gliese 581d, CoRoT 7b
Planet orbiting the star Gliese 667C, part of a triple system (ESO)

Super Earths are planets that range from 2-10 earth masses. Several of these planets have been in the news lately, a result of the several ongoing research projects dedicated to looking for new planets outside of our solar system.

In the attached article, Leslie Mullen talks with Harvard astronomy professor Dimitar Sasselov regarding the potential superiority of these super earths for harboring alien life. Sasselov makes the assertion that a low mass planet like Earth is probably not the ideal place for life to take root and grow.

The lower mass of Earth has several drawbacks compared to super-earths:

  • The lower mass makes it less likely for the planet to hold onto an atmosphere.
  • The planet's tectonics on earth are possibly slower acting that those of a more massive planet. The slow moving plate tectonics would have the net effect of trapping carbon needed for life within the planet, rather than releasing that carbon from volcanoes, etc.
  • The relatively small size of the earth means that the rotation about the axis is less stable than a larger planet. The moon helps to balance this lack of stability.
  • Larger mass planets have a deeper gravity well. If alien life were to develop to the point where they wanted to travel into space, they may need a technology superior to our chemical rockets. This may also mean that alien life is less likely to develop space travel in the first place.
  • The distance of the Earth from the sun as well as the internal core temperature of Earth, may not be the general ideal for the formation of life. These factors may contribute to the large fluctuation in temperature experienced by the earth between ice-ages and warming periods.

    • All these points together make Earth a marginal place for life to appear. This may be why we have not been contacted by alien life - the 'Fermi paradox'. If this planet is so unusual, perhaps nothing out there is looking in our direction.


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