Photo of Pluto silhouetted against the Sun, surrounded by a blue atmosphere

Factfile: Pluto

4 January 2016

A blue atmosphere, smooth areas, and youthful mountain ranges - this dwarf planet is full of surprises. 

When NASA's New Horizons probe flew past Pluto in July 2015, the images it returned astonished scientists. Not only was the surface more varied than anyone had predicted, but the photographs also showed a tenuous atmosphere that was visually similar to our own.

This image of Pluto, one of 77 composite photographs appearing in Otherworlds: Visions of our Solar System, shows the dwarf planet lit from behind by the Sun, surrounded by a tenuous, hazy blue atmosphere.

Scientists believe that the atmosphere is caused by clouds of soot-like 'haze particles' scattering sunlight as it passes through.

Young mountains

Images from New Horizons revealed another unexpected feature: an area of the planet featuring a range of mountains rising to 3,500 metres from the surface, surrounded by smooth terrain with few signs of craters.

Pluto's surface has been bombarded by space debris for billions of years, so the absence of craters suggests the area and its mountains are relatively young - 'one of the youngest surfaces we've ever seen in the solar system', according to NASA researcher Jeff Moore.

Black and white photo of the surface of photo, with patches of mountains and smoothness

New Horizons image showing Pluto's smooth surface and mountains. Courtesy NASA


A young surface suggests that the planet may still be geologically active, but scientists are uncertain about what form that activity may take. It was thought that other icy worlds were shaped by the gravity of larger objects nearby, but Pluto's young mountains might cause us to rethink that theory.

Pluto is a less special object than we once thought - scientists predict that there are hundreds of objects like Pluto in our solar system. But if an unremarkable icy world can hold so many surprises for scientists, just how many other secrets are out there waiting to be discovered?

Audio commentary extract

In such an exciting and fast-paced time for science, what are the next big questions and what's the next frontier? The Museum's Director of Science, Ian Owens, gives his thoughts.

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