Volcanic activity on Mars peaked during the Noachian and Hesperian periods, between 3 and 4 billion years ago, with smaller eruptions in isolated locations continuing perhaps as recently as 3 million years ago. But, until now, there was no evidence for more geologically recent explosive volcanism on the planet.Horvath et al. found strong evidence for geologically recent volcanic activity in Elysium Planitia, Mars. Image credit: NASA / JPL / MSSS / Murray Lab.A team of planetary researchers from the University of Arizona, the Planetary Science Institute and the Smithsonian Institutions Center for Earth and Planetary Studies discovered a 53,000-year-old volcanic deposit in Elysium Planitia, a flat-smooth plain near Mars equator that also hosts numerous young, fissure-fed flood lavas with ages ranging from 500 million to 2.5 million years.This may be the youngest volcanic deposit yet documented on Mars, said Dr. David Horvath, a research scientist at the Planetary Science Institute.If we were to compress Mars geologic history into a single day, this would have occurred in the very last second.The deposit is about 13 km (8 miles) wide, smooth, and dark, and is distributed symmetrically around a segment of the Cerberus Fossae fissure system.The properties, composition and distribution of volcanic material match what would be expected for a pyroclastic eruption, an explosive eruption of magma driven by expanding gasses.When we first noticed this deposit, we knew it was something special, said Dr. Jeff Andrews-Hanna, a researcher in the Lunar and Planetary Laboratory at the University of Arizona.The deposit was unlike anything else found in the region, or indeed on all of Mars, and more closely resembled features created by older volcanic eruptions on the Moon and Mercury.This feature overlies the surrounding lava flows and appears to be a relatively fresh and thin deposit of ash and rock, representing a different style of eruption than previously identified pyroclastic features, Dr. Horvath said.This eruption could have spewed ash as high as 10 km (6 miles) into Mars atmosphere. It is possible that these sorts of deposits were more common but have been eroded or buried.The site of the eruption is about 1,600 km (1,000 miles) from NASAs InSight lander, which has been studying seismic activity on Mars since 2018.The young age of this deposit absolutely raises the possibility that there could still be volcanic activity on Mars, and it is intriguing that recent marsquakes detected by the InSight mission are sourced from the Cerberus Fossae, Dr. Horvath said.A volcanic deposit such as this one also raises the possibility for habitable conditions below the surface of Mars in recent history, he added.The interaction of ascending magma and the icy substrate of this region could have provided favorable conditions for microbial life fairly recently and raises the possibility of extant life in this region.Its remarkable that one region hosts the epicenters of present-day marsquakes, the most recent floods of water, the most recent lava flows, and now an even more recent explosive volcanic eruption, Dr. Andrews-Hanna said.This may be the most recent volcanic eruption on Mars, but I think we can rest assured that it wont be the last.The volcanic deposit described in this study, along with ongoing seismic rumbling in the planets interior detected by InSight and possible evidence for releases of methane plumes into the atmosphere detected by NASAs MAVEN orbiter, suggest that Mars is far from a cold, inactive world.A paper on the findings was published in April 2021 in the journal Icarus._____David G. Horvath et al. 2021. Evidence for geologically recent explosive volcanism in Elysium Planitia, Mars. Icarus 365: 114499; doi: 10.1016/j.icarus.2021.114499