New Study Finds Venus’ Atmosphere is a Consequence of Ancient “Earth-Like” Plate Tectonics
October 26, 2023
The mountainous Ishtar Terra region of Venus formed during a time when Venus had a mobile surface geology similar to present-day plate tectonics on Earth. The Maxwell Montes mountains (white region at lower right) are the highest area on Venus and taller than Mount Everest on Earth. Image based on NASA Magellan mission data. Credit: NASA.
A paper published today in Nature Astronomy indicates that Venus-type atmospheres are potentially a consequence of early phases of plate tectonics.
Of all the first-order questions about the evolution of Venus, perhaps the most significant centers on the apparent divergence between the sibling terrestrial planets of Venus and Earth. Despite broad similarities in mass and size to Earth, Venus shows no clear evidence of plate tectonics recorded on its young surface, and Venus’ atmosphere is strikingly different.
Venus is shrouded by a thick carbon dioxide-dominated atmosphere resulting in an extreme greenhouse climate with surface temperatures exceeding 800 degrees Fahrenheit. A planet’s atmosphere is fundamentally linked to its interior through melting and outgassing. As a result, Venus’ atmosphere offers important constraints on the planet’s tectonic evolution.
Researchers at the Lunar and Planetary Institute (LPI), Brown University, and Purdue University compared the current venusian atmosphere with atmospheres generated by numerical experiments of long-term thermal-chemical-tectonic evolution. The study finds that a continuous single-plate stagnant lid regime operating since antiquity cannot explain present-day observed atmospheric abundances of nitrogen (roughly 3.5 times greater than Earth’s atmospheric nitrogen) nor can it explain carbon dioxide (roughly 230,000 times greater than Earth’s atmospheric carbon dioxide). Instead, the venusian atmosphere requires volcanic outgassing in an early phase of plate tectonic-like activity. Venus’ atmosphere then is the result of a great tectonic-climatic transition, from an early phase of plate-tectonic-like activity that lasted for at least one billion years followed by the current period of reduced outgassing rates, called a “stagnant lid” mode.
“One of the big-picture takeaways is that we very likely had two planets at the same time in the same solar system operating in a plate tectonic regime — the same mode of tectonics that allowed for the life that we see on Earth today,” says Dr. Matthew Weller, lead author of the study and Urey Fellow at the LPI. Eventually, however, plate tectonics ended on Venus, possibly due to both the loss of water and the planet’s atmosphere becoming too hot and thick from the outgassing, drying up the necessary ingredients that make tectonic movements possible.
The study authors suggest that the details of how this happened may hold important implications for Earth’s future.
“That’s going to be the next critical step in understanding Venus, its evolution, and ultimately the fate of the Earth,” Weller said. “What conditions will force us to move in a Venus-like trajectory and what conditions could allow Earth to remain habitable?”
For more information, visit https://www.nature.com/articles/s41550-023-02102-w.
