(ORDO NEWS) — The study uses archived NASA data showing that Venus may be losing heat due to geological activity in regions called coronas, much like during early tectonic activity on Earth.
Earth and Venus are rocky planets of roughly the same size and rock chemistry, so they should release their internal heat into space at roughly the same rate.
How the Earth loses heat is well known, but the mechanism of Venus’s heat flow remains a mystery.
The authors of the study, which uses thirty-year-old data from NASA’s Magellan mission, have taken a fresh look at how Venus cools and found that thin regions of the planet’s uppermost layer could provide the answer.
Our planet has a hot core that heats the surrounding mantle, which in turn transports that heat to the Earth’s solid outer rocky layer, or lithosphere.
The heat then escapes into space, cooling the top of the mantle. This mantle convection drives tectonic processes on the surface, keeping a patchwork of moving plates moving.
Venus has no tectonic plates, so the question of how the planet loses heat and what processes form its surface has long been a serious question in planetary science.
The study explores this mystery using observations made by the Magellan spacecraft in the early 1990s of Venus’s quasi-circular geological features called coronas.
By making new measurements of the coronas seen in the Magellan images, the researchers concluded that coronas tend to be located where the planet’s lithosphere is thinnest and most active.
“We’ve been fixated on the idea that Venus’s lithosphere is stagnant and thick for so long, but our view is now changing,” said Suzanne Smrekar, senior scientist at NASA’s Jet Propulsion Laboratory in Southern California, who led the published study in the field of geological and geophysical research.
Just as a thin sheet releases more body heat than a thick blanket, a thin lithosphere allows more heat to escape from the planet’s interior through floating streams of molten rock that rise to the outer layer.
Generally, where there is increased heat flow, there is increased volcanic activity below the surface. Thus, the crowns likely represent locations where active geology is shaping the surface of Venus today.
The researchers focused on 65 previously unexplored coronas up to several hundred miles in diameter.
To calculate the thickness of the lithosphere surrounding them, they measured the depth of the trenches and ridges around each crown.
They found that the ridges are closer together in areas where the lithosphere is more flexible or elastic.
Using a computer model of how the elastic lithosphere flexes, they determined that, on average, the lithosphere around each crown is about 7 miles (11 kilometers) thick much thinner than previous studies suggest.
The estimated heat flux in these regions is higher than the Earth average, suggesting that the coronas are geologically active.
“While Venus does not have Earth-like tectonics, these regions of thin lithosphere appear to allow a significant amount of heat to escape, similar to regions where new tectonic plates form on the Earth’s seafloor,” Smrekar said.
A window into the Earth’s past
To calculate the age of material on the surface of a celestial body, planetary scientists count the number of visible impact craters.
For a tectonically active planet like Earth, impact craters are obliterated by subduction of continental plates and covered by molten rock from volcanoes.
If there is no tectonic activity and regular mixing of terrestrial geology on Venus, it must be covered with old craters.
But, by counting the number of Venusian craters, scientists came to the conclusion that the surface is relatively young.
Recent studies suggest that the youthful appearance of Venus’s surface is likely due to volcanic activity that is causing regional surface renewal today.
This conclusion is supported by a new study pointing to higher heat flow in coronal regions – a state that may have resembled Earth’s lithosphere in the past.
“The interesting thing is that Venus opens a window into the past, helping us better understand what the Earth might have looked like more than 2.5 billion years ago.
It is in a state that is predicted to occur before the planet forms tectonic plates,” said Smrekar, who is also the principal investigator for NASA’s upcoming Venus Exploration, Radio Science, InSAR, Topography and Spectroscopy (VERITAS) mission.
VERITAS picks up where Magellan left off by improving the data from this mission, which have low resolution and high errors.
Scheduled to launch within the next decade, the mission will use state-of-the-art synthetic aperture radar to create 3D global maps and a near-infrared spectrometer to find out what the surface is made of.
VERITAS will also measure the planet’s gravitational field to determine the internal structure of Venus. Together, these tools will complete the story of the planet’s past and present geological processes.
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