Scientists study active volcanoes to comprehend how a planet’s interior can form its crust, drive its evolution, and alter its habitability.
Venus has a geologically young surface, but whether it has ongoing active volcanism is unknown. From 1990 to 1992, the Magellan spacecraft imaged the planet’s surface using synthetic aperture radar.
After poring over archival radar images of Venus taken more than 30 years ago, in the 1990s, by NASA’s Magellan mission, scientists now have direct geological evidence of recent volcanic activity on the surface of Venus for the first time.
Images showed a volcanic vent that had grown greatly in size and changed shape in less than a year.
Scientists examined dull-resolution Magellan images of each area of interest. They were looking for changes in geologic features between cycles. Whenever they observed a feature as having changed, they used stereo radargrammetry to produce a topographic model for the area surrounding the feature and to orthorectify the images.
They then used the stereo-derived topography and the orthorectified images to interpret the nature and potential cause of the observed change in appearance.
Next, scientists evaluated the viability of each interpretation using a simple geometric model of the feature. The model simulated the appearance of the feature under different viewing geometries.
The Atla Regio, a massive highland region near Venus’ equator, home to two of the planet’s greatest volcanoes, Ozza Mons and Maat Mons, is where scientists discovered the geological changes. Although there was no concrete evidence of recent activity, the area has long been considered volcanically active. While examining Magellan radar photos, scientists discovered a volcanic vent connected to Maat Mons that underwent a significant alteration between February and October 1991.
The vent was virtually round and less than one square mile in size in the February image (2.2 square kilometers). It had lava draining down its external slopes and steep internal sides, which suggested activity. Eight months later, the same vent was seen in radar photographs with a doubled size and became misshapen. It also appeared to be filled to the rim with a lava lake.
Yet, because the two observations were made from different vantage points, they had distinct viewpoints and were difficult to compare. The three decades’ worth of low data resolution made the work more difficult.
Scientists collaborated with Scott Hensley from JPL, who is an expert in processing radar data like Magellan’s and is the project scientist for VERITAS. To test various geological event scenarios, including landslides, the two researchers built computer models of the vent in various configurations. They deduced from those models that an eruption could have only brought about the alteration.
Hensley said, “Only a couple of the simulations matched the imagery, and the most likely scenario is that volcanic activity occurred on Venus‘ surface during Magellan’s mission. While this is just one data point for an entire planet, it confirms modern geological activity.”
One of NASA’s new missions to Venus will do just that. Led by the agency’s Jet Propulsion Laboratory in Southern California, VERITAS – short for Venus Emissivity, Radio Science, InSAR, Topography, And Spectroscopy – will launch within a decade. The orbiter will study Venus from surface to core to understand how a rocky planet about the same size as Earth took a very different path, developing into a world covered in volcanic plains and deformed terrain hidden beneath a thick, hot, toxic atmosphere.
Scientists are eager to see how the mission’s suite of advanced science instruments and high-resolution data will complement Magellan’s remarkable trove of radar imagery, which transformed humanity’s knowledge of Venus.
Jennifer Whitten, associate deputy principal investigator of VERITAS at Tulane University in New Orleans, said, “Venus is an enigmatic world, and Magellan teased so many possibilities. Now that we’re very sure the planet experienced a volcanic eruption only 30 years ago, this is a small preview for the incredible discoveries VERITAS will make.”
- Robert Herrick and Scott Hensley. Surface changes observed on a Venusian volcano during the Magellan mission. Science. DOI: 10.1126/science.abm7735