Scientists have discovered ancient supervolcanoes on Mars similar to the caldera that sits under Yellowstone National Park.

Volcanoes previously have been spotted on Mars, which is known to have been volcanically active billions of years ago. What’s different about this supervolcano network is that it was found in the northern highlands, a place not known to be active in the past. Studying images from several spacecraft orbiting Mars, researchers at London’s Natural History Museum and NASA found at least one massive volcano and evidence for several others that spewed huge clouds of lava and ash. The finding described the journal Nature suggests that early Mars was more active than previously realized, and that such eruptions could have affected the red planet’s climate and atmosphere.

Knowing the nature of early, widespread volcanic activity will also aid researchers in determining if Mars was once habitable, the scientists wrote. Using the size of the craters’ depressions as a guide to how much rock was expelled, the average minimum eruptions spewed 4,600 to 7,200 cubic kilometers of debris. Yellowstone’s most-recent eruption, 640,000 years ago, was a thousand times the size of the 1980 Mount St. Helens eruption in Washington state, spreading ash from California to Iowa, and from Canada to the Gulf of Mexico.