A Possible Mechanism for Methane Outgassing in Water Planets


Thursday, May 2, 2013, 9:00am


Biological Laboratories, 16 Divinity Ave., BL Room #1075, Cambridge, MA

Amit Levi (Harvard-Smithsonian Center for Astrophysics)

Planets with a substantial ice mass fraction, covering their entire surface, and lacking an H/He atmosphere are commonly referred to as water planets. These planets, first suggested as a Gedanken experiment by Kuchner (2003) and Leger et.al. (2004) based on the large variety among discovered extra-solar systems, have become an astronomical fact with the large number of low planetary mean densities as measured by the Kepler mission. Water planets appear to be relatively common, and being a novel type of planet, the like of which is absent from our own solar neighborhood, raises new questions regarding their geophysical nature, possible exobiology and more. In my talk I will concentrate on describing the internal structure, the possibility for plate tectonics and present a mechanism for methane outgassing in water planets. I will briefly describe the theory of clathrates and filled ice (Levi et al. 2013) and show that these structures are natural transport mechanisms for methane in the icy mantle, while also leading to a hindrance in the formation of subterranean oceans and resulting in higher expected mantle temperatures. I will further discuss the possibility of plate tectonics in icy worlds and show that for the geophysical parameter space probably occupied by water planets a sluggish lithospheric plate is a probable outcome, having implications on the rate of methane outgassing. 1) Kuchner, M. 2003, ApJ, 596, L105 2) Leger, A. et al. 2004 , Icarus, 169, 499 3) Levi A., Sasselov D. and Podolak M., 2013 http://arxiv.org/abs/1304.4215

See also: Chalk Talks