A landmark on Pluto that was previously designated as an impact crater may actually be the caldera of a supervolcano that has exploded in the past few million years, new research suggests.
When NASA’s New Horizons mission flew by Pluto in 2015, it revealed a geologically rich world, rather than the cold, dark landscape many had anticipated. Almost immediately, researchers identified two features, called Wright Mons and Piccard Mons, that were strongly suspected to be icy volcanoes, and further study confirmed their identity.
But not every cryovolcano was easy to spot. The suspected supervolcano, Kiladze, was initially classified as an impact crater. However, now scientists suspect it’s something else.
“We evaluated the possibility of the depression as a cryovolcanic caldera versus having an impact crater origin,” said Al Emran, a planetary scientist at the Jet Propulsion Laboratory in California. Emran presented his team’s results in July at the Progress in Understanding the Pluto System: 10 Years After Flyby conference in Laurel, Maryland.
“We think it’s more like Yellowstone Caldera in Wyoming,” Emran said. At least two of Yellowstone’s eruptions, millions of years ago, reached supervolcano status.
Impact crater or caldera?
Kiladze remains listed as a crater. But the rich supply of water ice surrounding the bowl-shaped feature sparked Emran’s curiosity, and he wondered if it might be a cryovolcano instead.
At first glance, the elongated oval bears a strong similarity to an impact crater. It’s large, with an average diameter of 2.5 miles (4 kilometers). Its walls are irregularly shaped, and the complex features it would require could easily have been eroded by Pluto’s active surface processes.
The landscape itself is marked by pits and other geological features, many of which have collapsed. If an incoming impactor broke through the surface and exposed veins of frozen lava beneath, it could have created the explosive distribution of water ice seen on the surface.
But when Emran dug into the topography maps of Pluto created by the New Horizons team, he realized there was a problem: The crater was too deep. Across the solar system, crater depth scales with crater diameter in a predictable way, and the same law appeared to hold true for other craters on Pluto — but for not Kiladze.
At best, estimates put an impact crater of its size at 1.7 miles (2.74 km)…
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