The cosmic impact that formed Pluto's moon Charon several billion years ago may also have created the dark regions seen at Pluto's equator (pictured).

Credit: NASA/Johns Hopkins Univ. Appl. Phys. Lab./Southwest Research Institute

Scientists led by Yasuhito Sekine at the University of Tokyo ran laboratory experiments to see what might happen if a comet rich in organic compounds slammed into the proto-Pluto. Heat from the impact would have warmed liquid water, possibly allowing organic materials in pools of this water to transform into chemically more complex, darker substances.

Simulations of the Charon-forming impact suggest that it could have heated vast areas in similar locations to those where the dark materials lie today. The work contradicts earlier studies that suggested that the dark material was delivered by comets, or formed over billions of years as solar radiation bombarded Pluto's surface.

Nature Astron. 1, 0031 (2017)