Mars used to be a lot more interesting. It once had an Earth-like atmosphere, as well as active volcanoes and even liquid oceans. Now, it’s a red, dead planet that might possibly have some life still hiding beneath its surface and tooting out methane.

As revealed in a new study, its past was even more exhilarating than anyone realized. Through a combination of satellite analyses and mathematical modeling, a team led by the University of South Paris has concluded that a gigantic set of tsunamis swept from Mars’ northern hemisphere across to its southern hemisphere about 3 billion years ago.

Mars never had effective plate tectonics, which means that huge, subduction zone earthquakes were unlikely to have caused this megatsunami. Instead, a handful of major asteroid impacts almost certainly generated the continental-sized splashes – and the team thinks they’ve found the impact craters responsible.

The researchers, writing in the Journal of Geophysical Research: Planets, note that their “modeling suggests several potential impact craters 30-50 kilometers [19-31 miles] in diameter as the source of the tsunami events.”

However, based on the spread of the tsunami deposits around the planet, the Lomonosov crater, based in the northern plains, is the likely culprit of what is sure to be the largest tsunami Mars has ever experienced. This crater is so large that it could fit Hawaii inside it.

The thickness and type of deposits around this crater indicate that the average wave height was around 150 meters (492 feet), although it initially peaked at around 300 meters (984 feet) upon its fiery creation.

The megatsunami swept across the planet, traveling up to 150 kilometers (95 miles) inland at a breakneck speed of 216 kilometers (134 miles) per hour. The event was so powerful that it would have rebounded off the coastline and generated a second tsunami all by itself.

^{Several asteroid strikes were responsible for generating these megatsunamis. Vadim Sadovski/Shutterstock}

This paper is actually one of several recent studies that have claimed to have identified tsunami deposits in the region. Although it’s long been acknowledged that Mars was a lot wetter in the distant past, this new piece of research once again adds credence to the hypothesis that Mars was once home to large bodies of water.

Based on this body of work, the planet’s northern basin, the Vastitas Borealis, would have almost certainly contained a colossal ocean.

Long before the formation of the basin’s so-called Oceanus Borealis, it’s thought that the northern hemisphere of Mars contained plenty of ice that couldn’t melt due to Mars’ distance from the Sun. It’s suspected that volcanic activity then melted this ice, which caused the ice to drain via channels into the Vastitas Borealis, which formed the gigantic, ancient ocean.

Sadly, Mars’ inability to hold onto its atmosphere meant that it lost its ocean too, several million years later.