A towering plume from the 2022 Hunga Tonga-Hunga Ha’apai eruption did more than blast ash, seawater and gases deep into the atmosphere. It also appears to have triggered an unexpected burst of methane destruction. This offers scientists a rare look at how one of the planet’s most powerful greenhouse gases can be broken down in open air. That surprise emerged from satellite observations of formaldehyde, a short-lived chemical that forms as methane oxidizes. In the days after the South Pacific volcano erupted on Jan. 15, 2022, researchers spotted unusually high formaldehyde levels inside the plume. They tracked the cloud for 10 days as it drifted toward South America. “When we analysed the satellite images, we were surprised to see a cloud with a record-high concentration of formaldehyde. We were able to track the cloud for 10 days, all the way to South America. Because formaldehyde only exists for a few hours, this showed that the cloud must have been destroying methane continuously for more than a week,” said Dr. Maarten van Herpen of Acacia Impact …