Abstract
Is it possible for a rocky planet to have too much internal heating to
maintain a habitable surface environment? In the Solar System, the best
example of a world with high internal heating is Jupiter’s moon Io,
which has a heat flux of approximately 2 W m-2 compared to the Earth’s
90 mW m-2. The ultimate upper limit to internal heating rates is the
Tidal Venus Limit, where the geothermal heat flux exceeds the Runaway
Greenhouse Limit of 300 W m-2 for an Earth-mass planet. Between Io and a
Tidal Venus there is a wide range of internal heating rates whose
effects on planetary habitability remain unexplored. We investigate the
habitability of these worlds, referred to as Ignan Earth’s. We
demonstrate how the mantle will remain largely solid despite high
internal heating, allowing for the formation of a convectively buoyant
and stable crust. In addition, we model the long-term climate of Ignan
Earth’s by simulating the carbonate-silicate cycle in a vertical
tectonic regime (known as heat-pipe tectonics, expected to dominate on
such worlds) at varying amounts of internal heating. We find that
Earth-mass planets with internal heating fluxes below 30 W m-2 produce
average surface temperatures that Earth has experienced in its past
(below 30 oC), and worlds with higher heat fluxes still result in
surface temperatures far below that of 100 oC, indicating a wide range
of internal heating rates may be conducive with habitability.