In May 1989, NASA launched its Magellan mission to Venus with the goal of mapping the entire surface of the planet using synthetic aperture radar (SAR) and measuring the planet’s magnetic field. Magellan would prove to be a very successful mission that met many of its scientific goals, including producing the most detailed map of Venus’ surface to date. The mission would ultimately end when the spacecraft performed a controlled entry into Venus’ atmosphere in October 1994.
Magellan was so successful, in fact, that its data is still being used to make new discoveries on Venus’ surface. In 2023, Magellan data revealed what appeared to be an active volcano on the Venusian surface, and, now, new data analysis has revealed two more volcanoes that were actively erupting on the surface in the 1990s when Magellan was active around Venus. This is only the second time that direct geological evidence for ongoing volcanic activity on Venus’ surface has been discovered, with scientists confirming the volcanic activity from the presence of new rock created from lava spewed by the volcanoes in the 90s.
“Using these maps as a guide, our results show that Venus may be far more volcanically active than previously thought. By analyzing the lava flows we observed in two locations on the planet, we have discovered that the volcanic activity on Venus could be comparable to that on Earth,” said lead author Davide Sulcanese of d’Annunzio University in Pescara, Italy.
While the new results aren’t the first direct evidence of volcanic activity, they do solidify and almost prove scientists’ predictions that Venus is currently volcanically active. As mentioned, the first evidence of volcanic activity on Venus was discovered in 2023, when a vent near the volcano Maat Mons near the Venusian equator was seen to change its appearance over time as molten rock from the planet’s interior filled the vent and spilled out onto its slopes.
Magellan being deployed to Venus from the payload bay of Space Shuttle Atlantis on the STS-30 mission. (Credit: NASA)
Earth and Venus have long been considered “sibling” planets by scientists due to their similarities in size, atmospheric characteristics, and surface composition. However, the planets are radically different in many ways, and scientists have been trying to determine how the two planets could have evolved differently to result in their current states. Volcanic activity, which can alter a planet’s surface, composition, evolution, and habitability, is driven by the changing interior of a planet, and understanding the interior of Venus is paramount to understanding how it evolved and how it differs from Earth.
Magellan used SAR to map 98% of Venus’ surface, which works by the radar sending radio waves through the thick cloud layer in Venus’ extremely dense atmosphere. After passing through the clouds, the radio waves hit the surface and bounce back up through the atmosphere, where they ultimately hit the spacecraft again. These reflected radio waves are called backscatter and they carry important information about the surface material and composition of the planet’s rocky surface.
The new study studied two volcanoes: Sif Mons, located in the Eistla Regio region, and a volcano located in the western part of the Niobe Planitia region. Both regions exhibit numerous volcanic features, and backscatter data collected by Magellan in 1990 and 1992 showed an increase in signal strength along certain paths in later orbits. The changes in signal strength suggest the formation of new rock on the surface, and scientists believe the new rock was most likely formed from volcanic activity between 1990 and 1992.
However, scientists also believe that there’s a chance that volcanic activity is not responsible for the formation of the new rock. For example, the presence of microdunes, which are formed from windblown sand, or atmospheric effects could have altered the backscatter data.
Computer-generated 3D model of Venus’ surface, specifically of the Sif Mons volcano. (Credit: NASA/JPL)
To confirm that the new rock is indeed rock, Sulcanese et al. analyzed altimetry — surface height — data from Magellan to determine the slope of the topography of the new rock and locate surface features that lava would need to flow around.
“We interpret these signals as flows along slopes or volcanic plains that can deviate around obstacles such as shield volcanoes like a fluid. After ruling out other possibilities, we confirmed our best interpretation is that these are new lava flows,” said co-author Marco Mastrogiuseppe of Sapienza University of Rome.
To better understand the flow of lava on Venus and the formation of the new rock, the scientists compared the Venusian lava flows to those on Earth. The scientists estimate that the new rock on Venus is between three and 20 meters deep. Additionally, the team estimates that the eruption of the Sif Mons volcano created around 30 square km of rock, and the eruption of the Niobe Planitia volcano created around 45 square km. In contrast, the 2022 eruption of the Mauna Loa volcano in Hawaii on Earth produced enough lava flow to fill 100,000 Olympic swimming pools, whereas the Sif Mons and Niobe Planitia volcanoes could only fill 36,000 and 54,000 pools.
“This exciting work provides another example of volcanic change on Venus from new lava flows that augments the vent change Dr. Robert Herrick and I reported last year. This result, in tandem with the earlier discovery of present-day geologic activity, increases the excitement in the planetary science community for future missions to Venus,” said co-author Scott Hensley, senior research scientist at NASA’s Jet Propulsion Laboratory (JPL) in California.
In recent years, the amount of planetary science research missions sent to Venus has decreased as NASA and its partners looked to other places in the solar system. However, two new missions to Venus, named VERITAS and DAVINCI, were selected by NASA in 2021 and are set to launch to the planet in the next decade. VERITAS specifically will use a state-of-the-art SAR to re-map Venus’ surface and 3D global maps, as well as a near-infrared spectrometer to discern Venus’ surface composition and volcanic activity. Also similar to Magellan, VERITAS will measure Venus’ gravitational field to determine its internal structure.
“These new discoveries of recent volcanic activity on Venus by our international colleagues provide compelling evidence of the kinds of regions we should target with VERITAS when it arrives at Venus. Our spacecraft will have a suite of approaches for identifying surface changes that are far more comprehensive and higher resolution than Magellan images. Evidence for activity, even in the lower-resolution Magellan data, supercharges the potential to revolutionize our understanding of this enigmatic world,” said JPL’s Suzanne Smrekar, VERITAS’s principal investigator.
Sulcanese et al.’s results were published in the journal Nature Astronomy in May.
(Lead image: Artist’s impression of Magellan at Venus. Credit: NASA/JPL)