Pluto's Heart, 2015
Pluto's heart, seen by the first spacecraft to reach it, and the nitrogen ice cycle in it that drives the dwarf planet's winds.
On 14 July 2015 New Horizons became the first spacecraft to reach Pluto, ending a voyage of more than three billion miles begun in January 2006. Clyde Tombaugh had found it in 1930 as a moving dot on photographic plates at Lowell Observatory. Pluto is 2,377 kilometres across, about a fifth the width of Earth. It sits in the Kuiper Belt. The heart now carries his name.
Colour is enhanced from blue, red and infrared frames, because many landforms carry their own distinct colour. The pale heart is not centred: its ragged left border runs roughly down the disc's own midline, and it fades into grey cratered ground short of the right-hand limb. Nitrogen ice there sublimes each day and condenses back each night, and that cycle drives winds that circulate around Pluto at up to 20 miles an hour.
