The latest pictures to be beamed back from the far reaches of the solar system show a newly discovered mountain range on Pluto and the first close-up images of two of the dwarf planet's smaller moons.
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The Norgay Mountains discovered by New Horizons on July 15 are much taller, about 3350 metres.
The new range is just west of the region within Pluto's heart called Sputnik Plain and about 100 kilometres north-west of the Norgay Mountains.
"There is a pronounced difference in texture between the younger, frozen plains to the east and the dark, heavily-cratered terrain to the west," said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA's Ames Research Centre in Moffett Field, California.
"There's a complex interaction going on between the bright and the dark materials that we're still trying to understand."
While Sputnik Plain is believed to be relatively young in geological terms - perhaps less than 100 million years old - the darker region probably dates back billions of years.
Moore said that the bright, sediment-like material appeared to be filling in old craters.
This image was acquired by New Horizons' Long Range Reconnaissance Imager (LORRI) on July 14 from a distance of 77,000 kilometres and sent back to Earth on July 20.
Features as small as a kilometre across are visible. The names of features on Pluto have all been given on an informal basis by the New Horizons team.
New Horizons has also picked up the first images of two of Pluto's smaller moons.
Nix and Hydra – the second and third moons to be discovered – are approximately the same size, but their similarity ends there.
Pluto has five known moons: Charon, Styx, Nix, Kerberos, and Hydra.
New Horizons' first colour image of Nix shows a jelly-bean shaped satellite, which is 42 kilometres long and 35 kilometres wide.
Although the overall surface colour of Nix is neutral grey in the image, a newfound region has a distinct red tint. Hints of a bull's-eye pattern lead scientists to speculate that the reddish region is a crater.
"Additional compositional data has already been taken of Nix, but is not yet downlinked. It will tell us why this region is redder than its surroundings," said mission scientist Carly Howett, of the Southwest Research Institute, Boulder, Colorado.
She added: "This observation is so tantalising, I'm finding it hard to be patient for more Nix data to be downlinked."
Meanwhile, the sharpest image yet received from New Horizons of Pluto's satellite Hydra shows that its irregular shape resembles the state of Michigan.
There appear to be at least two large craters, one of which is mostly in shadow.
The upper portion looks darker than the rest of Hydra, suggesting a possible difference in surface composition.
From this image, mission scientists have estimated that Hydra is 55 kilometres long and 40 kilometres wide.
"Before last week, Hydra was just a faint point of light, so it's a surreal experience to see it become an actual place, as we see its shape and spot recognisable features on its surface for the first time," said mission science collaborator Ted Stryk, of Roane State Community College in Tennessee.
Images of Pluto's most recently discovered moons, Styx and Kerberos, are expected to be transmitted to Earth no later than mid-October.
Nix and Hydra were both discovered in 2005 using Hubble Space Telescope data by a research team led by New Horizons project scientist Hal Weaver, of the Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland.
New Horizons' findings on the surface characteristics and other properties of Nix and Hydra will help scientists understand the origins and subsequent history of Pluto and its moons.
Telegraph, London
