NINE years ago, as part of its New Frontiers Programme, the National Aeronautics and Space Administration launched the New Horizons spacecraft. Icy mountains on Pluto and a new, crisp view of its largest moon, Charon, are among the multiple discoveries that NASA announced on July 15, a day after the spectacular success of New Horizons’ first-ever Pluto fly-by. “The mission has had nine years to build expectations about what we would see during the closest approach to Pluto and Charon… and I can tell you it dramatically surpasses those high expectations,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington.
A new close-up image of an equatorial region near the base of Pluto’s bright heart-shaped feature shows a mountain range with peaks as high as 3,500 metres. The mountains are likely to have formed no more than 100 million years ago, according to planetary scientists. For a 4.56-billion-year-old solar system, such recent activity suggests that the region, which covers about 1 per cent of Pluto’s surface, may still be geologically active. According to Jeff Moore of the New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA, this is one of the youngest surfaces ever seen in the solar system. Unlike the icy moons of the giant planets, this could not have been driven by gravitational interactions with a much larger planetary body. Some other process must be generating the mountainous landscape, according to NASA. “This may cause us to rethink what powers geological activity on many other icy worlds,” said the GGI deputy team leader John Spencer of the Southwest Research Institute (SwRI) in San Antonio.
Scientists are surprised by the apparent lack of craters in the young and varied terrain of Charon. A swathe of cliffs and troughs stretching about 1,000 km suggests widespread fracturing of Charon’s crust, probably the result of internal geological processes, a NASA release said. A canyon estimated to be 7-9 km deep has also been seen.
New Horizons also observed the smaller members of the Pluto system, which includes four other moons: Nix, Hydra, Styx and Kerberos. The new image of Hydra has revealed for the first time its apparent irregular shape and its size, which is estimated to be about 43 km × 33 km. The observations also indicate that Hydra’s surface is probably coated with water ice. Future images will reveal more clues about the formation of this and the other moons billions of years ago. Spectroscopic data from New Horizons’ Ralph instruments reveal an abundance of methane ice, but with striking differences among regions across the frozen surface of Pluto, according to the release.
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