Scientists study active volcanoes to understand how a planet’s interior can form its crust, drive its evolution and change its habitability.
Venus has a geologically young surface, but whether there is ongoing active volcanism is unknown. From 1990 to 1992, the Magellan spacecraft imaged the planet’s surface using synthetic aperture radar.
After studying 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 enormously in size and shape in less than a year.
Scientists examined Magellan images with dull resolution of every region of interest. They were looking for changes in geological features between cycles. Whenever they saw that a feature had changed, they used stereo radargrammetry to create a topographical model for the area around the feature and orthorectify the images.
They then used the stereo-derived topography and the ortho-rectified images to interpret the nature and possible cause of the observed change in appearance.
Scientists then evaluated the viability of each interpretation using a simple geometric model of the feature. The model simulated the element’s appearance under different viewing geometries.
The Atla Regio, a huge highland region near the equator of Venus, home to two of the planet’s largest volcanoes, Ozza Mons and Maat Mons, is where scientists discovered the geological changes. While there was no concrete evidence of recent activity, the area has long been considered volcanically active. Examining Magellan radar photos, scientists discovered a volcanic vent connected to Maat Mons that underwent major alteration between February and October 1991.
The vent was nearly circular and less than a square mile in the February image (2.2 square kilometers). Lava flowed down the outer slopes and steep inner walls, indicating activity. Eight months later, the same vent was seen on radar images with its size doubled and became misshapen. It also turned out to be filled to the brim with a lava lake.
But because the two observations were made from different vantage points, they had different points of view and were difficult to compare. The three decades of low data resolution made the job more difficult.
Scientists teamed up with JPL’s Scott Hensley, who is an expert at processing radar data like Magellan’s and is the project scientist for VERITAS. To test different geological event scenarios, including landslides, the two researchers built computer models of the vent in different configurations. They deduced from those models that an eruption could only have caused the change.
Hensley said: “Only a few simulations matched the images, and the most likely scenario is that volcanic activity occurred on the surface of Venus during Magellan’s mission. While this is just one data point for an entire planet, it confirms modern geologic 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 be up and running within a decade. The orbiter will study Venus from the surface to its core to understand how a rocky planet about the same size as Earth took a very different path and evolved into a world covered with volcanic plains and deformed terrain hidden under a thick, hot, poisonous atmosphere.
Scientists are excited to see how the mission’s array of advanced science instruments and high-resolution data will complement Magellan’s remarkable trove of radar images that have transformed humanity’s knowledge of Venus.
Jennifer Whitten, VERITAS deputy principal investigator at Tulane University in New Orleans, said: “Venus is an enigmatic world and Magellan teased so many possibilities. Now that we are very sure that the planet experienced a volcanic eruption only 30 years ago, this is a small preview of the incredible discoveries that 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