Researchers analyzing images from NASA’s New Horizons mission have discovered six massive landslides on Pluto, some large enough to bury a small city, according to a study published in the journal Icarus.
The landslides were found along the inner walls of three craters on the western edge of Sputnik Planitia, the vast heart-shaped nitrogen ice plain that dominates Pluto’s surface. The features were identified in images captured by the Long-Range Reconnaissance Imager (LORRI) instrument during New Horizons’ flyby of the dwarf planet on July 14, 2015, which remains the only close encounter with Pluto in the history of space exploration.
The largest of the debris aprons covers approximately 130 square kilometers (50 square miles), enough to bury a large town or small city. The landslides traveled between 10.1 and 14.5 kilometers (6.3 to 9 miles) from their source, dropping as much as 2.2 kilometers (1.4 miles) in the case of the slide within Coughlin crater.
The landslides are among the most mobile in the solar system, a consequence of Pluto’s low gravity and the low-friction properties of its icy rubble. The debris consists largely of solid ice boulders that rolled great distances rather than stopping close to their source cliffs.
The six landslides are distributed across three craters. Coughlin crater contains one landslide. Giclas crater hosts two. An unnamed crater near the region contains the remaining three. Each slide originates from a well-defined concave cliff face, with debris aprons spreading at the base in bumpy deposits characteristic of large ice boulders.
Researchers identified two likely trigger mechanisms. The Coughlin crater landslide was probably caused by a secondary impact on the crater’s rim, where debris from another impact event struck the area. The other five slides may be driven by thermal stresses in Pluto’s surface ice. As Pluto travels through its elliptical orbit, which periodically brings it closer to the Sun than Neptune, slight temperature changes cause volatile ices such as molecular nitrogen, carbon monoxide, and methane to sublimate and then re-condense. This repeated cycle stresses the icy surface, eventually triggering collapses along crater walls.
The discovery carries broader significance for understanding Pluto’s geological activity. The presence of relatively recent landslides indicates that the dwarf planet remains geologically active on timescales that are geologically recent, even if the activity unfolds over thousands or millions of years rather than human timescales.
New Horizons captured only a fraction of Pluto’s surface during its brief flyby. The spacecraft photographed the hemisphere that faced the Sun at the moment of closest approach, leaving the far side unexplored. Scientists suspect additional landslide evidence exists in other craters, but confirmation would require a follow-up mission with better imaging coverage.
The study adds to a growing body of evidence that Pluto, far from being a frozen inert world, hosts dynamic geological processes including glacial flow, cryovolcanism, and now large-scale mass wasting. The findings were published in Icarus by researchers analyzing the highest-resolution LORRI images, which can resolve features as small as 300 meters (984 feet) across.