Unmanned flights are the best way to discover the beauty of our cosmic neighbourhoodby Philip Ball / July 23, 2015 / Leave a comment
As David Cameron discovered on 8th May, success is all the more euphoric when your expectations start low. NASA’s New Horizons mission to Pluto and Charon (the largest of its five known moons) had been under the scientific radar for most of its nine-year journey to what used to be considered the edge of the solar system. Those who remembered the lonely spacecraft could have been forgiven for secretly thinking it wouldn’t find much of note when it arrived at the dwarf planet. A NASA mission to Pluto was proposed in the 1990s, but was dismissed as too unimportant. Then in 2006, only months after New Horizons set off, Pluto was demoted from planet status by the decision of the International Astronomical Union (IAU). New Horizons could have seemed like a voyage of obligation rather than necessity, filling in the gaps in our understanding of this obscure object, which is smaller than our own moon.
How wrong we were. New Horizon’s Pluto Flyby has easily been the most eye-opening scientific story of the year. The astonished expression of its leader, the planetary scientist Alan Stern, as the latest images hit the screens of mission control at Johns Hopkins University in Baltimore, summed up everyone’s fascination as Pluto’s surface came into focus during July. Some scientists had imagined it to be an inert ball of icy rock pocked with craters that, as on our Moon, testify to a steady, tedious rain of meteors over billions of years onto a static surface. But on the contrary, Pluto has a complex surface with smooth ice plains, some fractured like the intricate craquelure on an Old Master painting and, most extraordinarily, mountains the size of the Rockies, made of ice and weirdly out of scale on a body this small. The most striking implication is that Pluto has tectonic activity: its surface is moving and being renewed, rather like Earth’s. That’s the only explanation for why there aren’t impact craters all over it—they get swallowed back up into the crust, or buried by fresh material. But where, on a “planet” this tiny and this remote from the Sun, does the energy come from for that geological activity? One thing’s for sure: as Stern said, “It’s going to send a lot of geophysicists back to the drawing board.”