After decades of studying Venus, many questions remain about our planetary next-door neighbor. One question has particularly intrigued astronomers: which, if any, of Venus’s 1,600 volcanoes are still active?
Today’s article focuses on Imdr Regio, which is thought to be analogous to hotspots on Earth, where heat rises from below the surface and can cause volcanism as well as thermal features like the hot springs shown here. [National Parks Service/Damon Joyce]
Ancient History or Today’s News?
Venus’s surface is dotted with volcanoes and puddled with lava flows, but it’s challenging to discern which of these features are ancient and which are more recent. Using data from Venus-orbiting spacecraft, we can search for the subtle changes to Venus’s surface and atmosphere that signal the presence of erupting volcanoes.
Aside from the excitement of adding another item to the list of known active volcanoes in the solar system, figuring out which of Venus’s volcanoes are active is important because volcanoes are a potential source of phosphine, a compound that arises from biological processes on Earth and is thought to be an important biosignature on Venus. In order to interpret detections of phosphine, we need to know how many volcanoes are actively producing it.
Two radar views of Idunn Mons from the Magellan spacecraft. [Adapted from D’Incecco et al. 2021]
Evidence from Multiple Avenues
A team led by Piero D’Incecco (D’Annunzio University of Chieti–Pescara, Italy) rounded up spacecraft observations of Venus’s surface and atmosphere and combined them with findings from laboratory studies to build a compelling case for the active volcanism of Idunn Mons, a 2.5-km high, 200-km wide volcano in Imdr Regio. The team bolstered their case with three key pieces of evidence:
- Surface observations: The region surrounding Idunn Mons shows signs of overlapping lava flows, the uppermost of which is coincident with a region of unusually high thermal emission, which is thought to indicate a surface that hasn’t yet been corroded by Venus’s caustic atmosphere.
- Laboratory work: Recent laboratory studies, which recreate the hot, high-pressure environment of Venus’s surface to understand how it affects different minerals, have shown that chemical weathering — alteration of the surface material through chemical reactions with atmospheric gases — happens more quickly than previously thought. This means we’ve overestimated the ages of the lava flows surrounding Idunn Mons.
- Atmospheric observations: Venus’s surface also interacts with the atmosphere on a macroscopic scale; landforms like volcanoes generate standing waves in the atmosphere called gravity waves (not to be confused with gravitational waves!). These waves can cause Venus’s winds to slow down as they travel above a volcano. In the case of Idunn Mons, the winds slow down more than expected given the size of the volcano, which could be due to heat radiating from recent lava flows.
The European Space Agency’s upcoming EnVision mission, which is planned to launch in 2031, seeks to understand why Earth and Venus are so different. [NASA / JAXA / ISAS / DARTS / Damia Bouic / VR2Planets]
Venusian Explorations Ahead
Combining all the available evidence, D’Incecco and collaborators conclude that Idunn Mons has been active recently, perhaps within our lifetimes — anywhere from 10,000 years ago to just a few years ago. Recently selected spacecraft missions should soon allow us to study Idunn Mons further. In particular, NASA’s Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy (VERITAS) orbiter and the European Space Agency’s EnVision orbiter both plan to map Venus’s surface in extremely high resolution, which is key for detecting surface changes due to volcanic activity.
Citation
“Idunn Mons: Evidence for Ongoing Volcano-Tectonic Activity and Atmospheric Implications,” P. D’Incecco et al 2021 Planet. Sci. J. 2 215. doi:10.3847/PSJ/ac2258