A study discovered that Venus' 'squishy' outer shell may be resurfacing the planet.

The study employs archival NASA data to demonstrate that Venus may be losing heat due to geologic activity in locations known as coronae, similar to early tectonic activity on Earth.

This depiction of Venus's enormous Quetzalpetlatl Corona exhibits active volcanism and a subduction zone, where the foreground crust plunges into the planet's interior. According to a new study, coronae identify regions where active geology is altering Venus' surface.
Credits: NASA/JPL-Caltech/Peter Rubin

Because Earth and Venus are rocky planets with similar sizes and rock compositions, they should lose interior heat to space at roughly the same rate. The process by which Earth loses heat is generally understood, while Venus' heat flow mechanism has remained a mystery. A new study using three-decade-old data from NASA's Magellan mission has examined how Venus cools and discovered that thin portions of the planet's uppermost layer may hold the solution.

Our planet has a hot core that heats the surrounding mantle, which then transports that heat up to Earth's stiff outer rocky layer, known as the lithosphere. The heat is then lost to space, cooling the mantle's highest area. This mantle convection drives surface tectonic processes, keeping a patchwork of mobile plates in motion. Because Venus lacks tectonic plates, planetary scientists have long wondered how the planet loses heat and what mechanisms form its surface.

The investigation is based on observations of quasi-circular geological landforms on Venus known as coronae made by the Magellan probe in the early 1990s. The researchers found that coronae tend to be located where the planet's lithosphere is thinnest and most active by taking fresh measurements of coronae visible in Magellan photos.

This composite radar image of Quetzalpetlatl Corona was made by superimposing data from about 70 orbits of NASA's Magellan mission onto an image collected by Puerto Rico's Arecibo Observatory radio telescope. The corona's rim implies likely tectonic activity.
Credits: NASA/JPL-Caltech

"We've been locked into this assumption for so long that Venus' lithosphere is static and thick, but our view is suddenly altering," said Suzanne Smrekar, a senior research scientist at NASA's Jet Propulsion Laboratory in Southern California and lead author of the study published in Nature Geoscience.

A thin lithosphere, like a thin bedsheet, permits more heat to escape from the planet's interior via buoyant plumes of molten rock rising to the outer layer, just as a thin bedsheet releases more body heat than a heavy comforter. If there is higher heat movement, there is usually more volcanic activity beneath the surface. Coronae are expected to disclose sites where active geology is now sculpting Venus' surface.

The researchers concentrated on 65 previously unstudied coronae that can span hundreds of kilometers. They measured the depth of the trenches and ridges around each corona to compute the thickness of the lithosphere surrounding them. They discovered that ridges are more closely spaced together in locations where the lithosphere is more flexible, or elastic. Using a computer model of how an elastic lithosphere bends, scientists discovered that the lithosphere around each corona is roughly 7 miles (11 kilometers) thick on average - significantly thinner than earlier research suggested. These locations have a higher estimated heat flux than the Earth's average, indicating that coronae are geologically active.

Planetary scientists count the number of visible impact craters to determine the age of a celestial body's surface material. Impact craters on a tectonically active planet like Earth are erased by continental plate subduction and covered by molten rock from volcanoes. Venus should be covered in old craters if it lacks tectonic activity and the regular churn of Earth-like geology. Scientists assume that the surface of Venus is relatively new by calculating the number of Venusian craters.

The circular fracture patterns surrounding Venus's "Aine" corona are visible in this radar image from NASA's Magellan mission. The corona is approximately 124 miles (200 kilometers) broad and contains a variety of phenomena that may be related to volcanic activity.
Credits: NASA/JPL-Caltech

Current research indicates that the young aspect of Venus's surface is most likely due to volcanic activity, which is responsible for regional resurfacing today. This discovery is reinforced by fresh studies revealing increased heat movement in coronae zones - a state that Earth's lithosphere may have resembled in the past.

The upcoming Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy project from NASA will follow up where Magellan left off, improving on the data from that mission, which was low resolution and had huge margins of error. The mission, which is expected to launch within a decade, will utilize a cutting-edge synthetic aperture radar to build 3D global maps and a near-infrared spectrometer to determine what the surface is comprised of. VERITAS will also measure Venus' gravitational field in order to discover the structure of the planet's innards. The instruments will help to fill in the gaps in the story of the planet's geologic processes, both past and current.