Pluto a world of 'spectacular' colours and dynamic geology
Pluto is a world of "spectacular" colours, dramatic surface features and dynamic geology, the first published results from a fly-by of the dwarf planet have shown.
The American space agency Nasa's New Horizons spacecraft discovered towering ice mountains and ridges, rolling plains, and icebergs floating in lakes of frozen nitrogen.
Enhanced colour pictures from the probe's multi-spectral visible imaging camera (MVIC) also revealed a striking assortment of colours, ranging from dark red regions at the equator to brighter, bluer regions at higher latitudes.
Another surprise was Pluto's blue hazy atmosphere, which like Earth's is chiefly composed of nitrogen.
New Horizons grabbed the snapshot of data as it sped past Pluto and its five moons in July to complete the first robotic mission to the dwarf planet.
What has been seen so far is just the first glimpse of a treasure trove of information from the spacecraft's suite of seven instruments that will take scientists until late next year to download.
An overview of an initial analysis of New Horizons data appears in the journal Science.
Astronomer Dr Silvia Protopapa, from the University of Maryland, US, said: "We knew Pluto's surface was heterogeneous based on ground-based data. However, I was astonished to see such spectacular surface colour and geological diversity."
Pluto's colours are thought to be due to different mixtures of organic compounds, nitrogen, carbon monoxide and water.
The red regions indicate the presence of organic chemicals called tholins, which are created by the irradiation of surface material containing methane.
Images from New Horizons also revealed smooth regions, unmarked by impact craters, which appear to be relatively young.
This and other evidence suggests that geological processes are still shaping the surface of the world.
One of Pluto's most dramatic features are blade-like ridges standing hundreds of metres tall that form rippled, scaly patterns.
Another are clusters of mountains that are thought to be icebergs - chunks of water ice floating on a deep pool of frozen nitrogen.
New Horizons chief investigator Dr Alan Stern said in a Science journal podcast: "We were very surprised by the level of complexity and very surprised by the fact that Pluto is currently geologically active - something that almost no-one expected and which is revolutionising our understanding of planetary physics."
Pluto is the largest of the many objects that form the Kuiper Belt, a collection of planetary bodies girdling the solar system beyond the orbit of Neptune.
In 2006 international astronomers re-classified Pluto as a "dwarf planet". Previously it was known as the ninth and most distant planet from the sun.