A Volcanic Hydrogen Habitable Zone

The Popocatépetl volcano in Mexico

This is an excerpt from my post on Astrobites:

Title: A Volcanic Hydrogen Habitable Zone
Authors:  Ramses Ramirez and Lisa Kaltenegger
First Author’s Institution: Cornell University
Status: Accepted in The Astrophysical Journal Letters, open access

The search for life beyond the solar system has long focused on the habitable zone (HZ).  This is the region around a star where a planet with the right properties could maintain liquid water on its surface for a substantial period of time. The classical inner edge of the HZ was set using the runaway greenhouse effect, in which a positive feedback loop causes oceans to evaporate creating an oven-like world similar to Venus.  The classical outer edge of the HZ was set using the maximum greenhouse effect from carbon dioxide, which is the distance at which adding carbon dioxide to a planet’s atmosphere starts cooling the planet (due to scattering the light or condensation).  There have been many other calculations of the HZ edges using different assumptions, such as a nearly desert planet and planets with different masses.  In this paper, the authors try to use volcanoes to expand edges of the HZ.  They calculate the HZ edges for atmospheres with significant amounts of hydrogen gas produced by volcanoes, another powerful greenhouse gas.