PASADENA, Calif. — Scientists at NASA believe that Venus may be a “squishy” planet that’s “repaving” its entire surface. Researchers are investigating whether volcanoes on the second planet from the Sun could be making it lose heat, essentially reforming its exterior layer.
The NASA team says archival data shows signs of geothermal activity, a discovery that provides a window into how planets like Earth may have had dynamic surfaces even before forming tectonic plates. The research shows that Venus may be losing heat from geologic activity in regions called coronae, possibly like the early tectonic activity on Earth.
NASA’s Jet Propulsion Laboratory (JPL) team explains that Earth and Venus are rocky planets which are about the same size and consist of the same rock chemistry. This means they should be losing their internal heat to space at about the same rate.
Scientists are well aware of how Earth loses its heat, but it’s still a mystery how Venus’ heat flow mechanism works. The team says that using three-decade-old data from NASA’s Magellan mission is helping them take a new look at how Venus cools. The new study finds that thin regions of the planet’s uppermost layer may provide an answer.
Earth has a hot core that heats the surrounding mantle, which carries that heat up to Earth’s rigid outer rocky layer, or 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.
How is Venus different from Earth?
Venus 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. The study looks at the mystery using observations the Magellan spacecraft made in the early 1990s of quasi-circular geological features on Venus called coronae. Making new measurements of coronae visible in the Magellan images, the researchers 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,” says Suzanne Smrekar, senior research scientist at NASA’s Jet Propulsion Laboratory in Southern California, in a media release.
The researchers focused on 65 previously unstudied coronae that are up to a few hundred miles 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, the lithosphere around each corona is about seven miles (11 kilometers) thick – much thinner than previous studies suggest. These regions have an estimated heat flow that is greater than Earth’s average, suggesting that coronae are geologically active.
“While Venus doesn’t have Earth-style tectonics, these regions of thin lithosphere appear to be allowing significant amounts of heat to escape, similar to areas where new tectonic plates form on Earth’s seafloor,” Smrekar explains.
“What’s interesting is that Venus provides a window into the past to help us better understand how Earth may have looked over 2.5 billion years ago. It’s in a state that is predicted to occur before a planet forms tectonic plates,” says Smrekar, who is also the principal investigator of NASA’s forthcoming Venus Emissivity, Radio science, InSAR, Topography, And Spectroscopy (VERITAS) mission.
A new Venus mission could launch within 10 years
VERITAS will pick up where Magellan left off, improving upon that mission’s data, which is low resolution and comes with large margins of error. Targeting launch within a decade, the mission will use a state-of-the-art synthetic aperture radar to create 3D global maps and a near-infrared spectrometer to figure out what the surface is made of.
VERITAS will also measure the planet’s gravitational field to determine the structure of Venus’ interior. The instruments will together fill in the story of the planet’s past and present geologic processes.
“VERITAS will be an orbiting geologist, able to pinpoint where these active areas are, and better resolve local variations in lithospheric thickness. We’ll be even be able to catch the lithosphere in the act of deforming,” Smrekar concludes. “We’ll determine if volcanism really is making the lithosphere ‘squishy’ enough to lose as much heat as Earth, or if Venus has more mysteries in store.”
The study is published in the journal Nature Geoscience.
South West News Service writer Dean Murray contributed to this report.
