Earth has a hot core that heats the surrounding mantle, which carries that heat up to the planet’s lithosphere. The heat is then lost to space, cooling the uppermost region of the mantle. This mantle convection drives tectonic processes on the surface, keeping a patchwork of mobile plates in motion. Venus, which is Earth’s twin in size, doesn’t have tectonic plates, so how the planet loses its heat and what processes shape its surface have been long-running questions in planetary science. In a new study, planetary scientists looked at the mystery using observations NASA’s Magellan mission made in the early 1990s of quasi-circular geological features on Venus called coronae. Making new measurements of coronae visible in the Magellan images, they concluded that coronae tend to be located where the planet’s lithosphere is at its thinnest and most active.
“For so long we’ve been locked into this idea that Venus’ lithosphere is stagnant and thick, but our view is now evolving,” said Dr. Suzanne Smrekar, a researcher at NASA’s Jet Propulsion Laboratory.
“Just as a thin bedsheet releases more body heat than a thick comforter, a thin lithosphere allows more heat to escape from the planet’s interior via buoyant plumes of molten rock rising to the outer layer.”
“Typically, where there’s enhanced heat flow, there’s increased volcanic activity below the surface.”
“So coronae likely reveal locations where active geology is shaping Venus’ surface today.”
In their study, Dr. Smrekar and colleagues focused on 65 previously unstudied coronae that are up to a few hundred km across.
To calculate the thickness of the lithosphere surrounding them, they measured the depth of the trenches and ridges around each corona.
What they found is that ridges are spaced more closely together in areas where the lithosphere is more flexible, or elastic.
By applying a computer model of how an elastic lithosphere bends, they determined that, on average,…
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