The Surface of Venus Is Active, Recording a Thin Lithosphere and High Heat Flow

Credit: SSV, MIPL, Magellan Team, NASA.

Venus is an enigma. It is similar in size to Earth and likely has a similar heat budget; therefore, it might be assumed that Venus cools through similar mechanisms. Earth cools predominantly due to a thin, recycled lithosphere, which is associated with plate tectonics. The processes that govern heat loss on Venus, which currently lacks plate tectonics, remain a mystery. Does the lithosphere of Venus behave as a single plate like the much thicker lithospheres of Mars and Mercury, resulting in low rates of heat loss? Or does it behave more like the lithosphere of Earth? Heat loss from the interior of a planet is the driver of geologic activity, and understanding it is critical to addressing fundamental questions regarding Venus.

Suzanne Smrekar from NASA Jet Propulsion Laboratory (JPL) and colleagues believe they have found regions of enhanced heat loss relative to the venusian average. Using analyses of 65 quasi-circular surface features called coronae, which are associated with tectonic and volcanic activity, and potentially isolated subduction-like behaviors, the team used topographic flexure models to calculate elastic lithosphere thicknesses, from which heat flows were inferred. They found that the average thickness at the coronae is 11±7 km, which implies an average heat flow through the coronae of 101±88 mWm-2. In contrast, Earth’s average elastic lithosphere is a few to 30 km thick for younger to older ocean lithosphere, respectively. The range of heat flow varies from >500 mWm-2 in mid-ocean ridges and volcanic centers (e.g., Yellowstone) to <25 mWm-2 for old oceanic lithosphere. The high heat flows on Venus likely reflect areas of active extension and faulting. These results suggest that the behavior of Venus may be intermediate between that of single plate-planets, such as Mars and Mercury, and plate-tectonic planets, such as Earth, indicating that tectonic states operate as a continuum on planetary bodies. While tantalizing, these few areas of thin lithosphere and higher heat flow do not necessarily reflect global behavior or heat loss mechanisms. Future missions may be able to shed additional light on this enigma about Venus. READ MORE