What did New Horizons discover about Pluto’s surface?

The New Horizons mission, which performed the first flyby of Pluto in 2015, provided detailed observations of one hemisphere of the dwarf planet, revealing a geologically active and diverse surface.12

Key findings regarding Pluto's surface include:

• Tombaugh Regio: This prominent, heart-shaped region is a vast plain of nitrogen ice. Its western half, known as Sputnik Planitia, is remarkably smooth and lacks impact craters, indicating that it is a very young geological feature.12
• Mountain Ranges: Surrounding the smoother plains are mountain ranges composed of water ice. These mountains are thought to float within the surrounding nitrogen ice.12
• Cthulhu Regio: Located to the west of Tombaugh Regio, this dark area—nicknamed "the whale"—features varied topography, including plains, scarps, mountains, and craters. Its dark coloration is attributed to organic compounds known as tholins.1
• Surface Composition: The surface is characterized by a thin layer of frozen nitrogen, carbon monoxide, and methane. The presence of these ices, combined with the lack of craters in certain regions, suggests that Pluto possesses internal geologic activity.1