Venus may have been Earth-like until recently, new ASU study suggests
Artist concept of carbonatite lava erupting and eroding canali on Venus. Image by by Hernán Cañellas
Though Venus is often called Earth’s twin due to its similar size and composition, the planet today is an uninhabitable inferno, with surface temperatures around 880 F (740 K) and atmospheric pressures 90 times higher than Earth’s.
Now, a research team led by Allyson Trussell, a PhD candidate at Arizona State University’s School of Earth and Space Exploration, has uncovered new evidence that Venus may have sustained a temperate, Earth-like climate until just a few hundred million years ago.
The study, published in Science Advances, points to a surprising culprit behind the planet’s transformation: a rare, water-like lava known as carbonatite.
Scientists have long puzzled over Venus’s vast river-like channels, or canali, which stretch thousands of kilometers across the planet. The longest of these, Baltis Vallis, extends over 6,800 kilometers, making it the longest channel in the solar system. These sinuous structures resemble Earth’s river systems, complete with deltas and cutoff meanders. But with no water on Venus today, what could have carved them?
Using a combination of planetary mapping and lava flow modeling, Trussell’s team proposes that carbonatite lava, which is low in viscosity and unusually cool compared to typical lava, could have eroded the surface mechanically to create the canali.
“Carbonatite lavas have viscosities closer to water than to typical lava, and they solidify at temperatures just above the current surface temperature of Venus,” Trussell said. “That makes them capable of flowing great distances under Venus-like conditions, much farther than we’d expect from basalts or even high-temperature komatiites.”
On Earth, carbonatite eruptions are infrequent and are currently observed only at Ol Doinyo Lengai in Tanzania. There, the lava is black and fluid when erupted, but weathers to a white crust. On Venus, where weathering is minimal and surface pressures are immense, such lava could repeatedly melt and flow with shallow burial in the crust, potentially resurfacing large areas of the planet.
Using a 1D lava erosion model, the researchers calculated the volumes and flow rates necessary to carve the canali.
They found that lavas that are relatively common on Earth, such as basalt or komatiite, would require extreme conditions that exceed those known for even the largest eruptions on Earth. In contrast, carbonatite lavas could have plausibly formed the channels under more realistic eruption scenarios.
Crucially, carbonatite eruptions release carbon dioxide, or CO2. Past studies explained how a runaway greenhouse could have boiled Venus’s oceans into steam but had difficulty explaining the massive amount of CO2 in the atmosphere today. The team’s analysis suggests that these carbonatite eruptions may have outgassed enough CO2 to transform Venus’s atmosphere within the last billion years.
“If the canali formed through carbonatite flows, then Venus might have remained temperate and potentially even habitable for most of its history,” Trussell said. “A global volcanic shift could have tipped the climate into the hothouse state we see today.”
"There have been many theories, but until now, there has been limited analysis of the available data. These findings represent a big step forward for our understanding of the evolution of Venus’ atmosphere and volcanism,” said co-author Ian Flynn, research professor at the University of Pittsburgh.
The findings have broader implications for exoplanet science. Many planets identified around other stars are roughly the size of Venus and may undergo similar climate evolution.
“In an era when we are discovering many Venus-sized planets orbiting distant stars, we need to understand when and why Earth and Venus took different paths,” said co-author Joseph O’Rourke, assistant professor at ASU. “That’s why I was so excited when in 2021, NASA announced the VERITAS and DAVINCI missions to Venus, plus a contribution to ESA’s EnVision mission.”
It’s been over 30 years since NASA’s Magellan mission last mapped the planet, yet researchers are still finding new insights in its data. Future missions could provide higher-resolution scans of the canali and surface composition to determine if carbonatites shaped Venus’ fate.
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