Sputnik Planitia

physical feature of Pluto

Written by

The Information Architects of Encyclopaedia Britannica

Last updated

July 21, 2026

Quick Summary

Sputnik Planitia is a prominent physical feature on the dwarf planet Pluto. It is the western half of the large, white, heart-shaped plain known as Tombaugh Regio. This smooth plain is composed of nitrogen ice and is notable for its lack of impact craters, suggesting it is a geologically young feature, indicating that Pluto likely experiences some form of geologic activity.1

The composition of Sputnik Planitia includes nitrogen ice, with potential underlying water ice mountains. Its location on Pluto's tidal axis, opposite its moon Charon, suggests the presence of a subsurface ocean above the rocky core and below the water ice mantle. Pluto's atmosphere, primarily nitrogen with traces of methane and carbon monoxide, can vary significantly with temperature.12

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

2 Britannica Sources

Ask Britannica AI about this topic

Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.

Pluto
The surface and interior
…half of Tombaugh Regio is Sputnik Planitia, a smooth plain of nitrogen ice without impact craters. The lack of craters shows that Sputnik Planitia is a very young feature and thus that Pluto likely has some geologic activity. Tombaugh Regio is surrounded by less smooth regions that contain some mountain…
Read More
…half of Tombaugh Regio is Sputnik Planitia, a smooth plain of nitrogen ice without impact craters. The lack of craters shows that Sputnik Planitia is a very young feature and thus that Pluto likely has some geologic activity. Tombaugh Regio is surrounded by less smooth regions that contain some mountain…
Read More