Pluto’s icy mountains

“WE ARE outbound from Pluto.” So said Alice Bowman, mission operations manager for New Horizons, an American space probe, when her charge resumed contact with Earth following its passage by the place on July 14th. After nine and a half years of its being inbound to Pluto, her announcement was met with jubilation. On July 15th the craft sent back the first hints of what it had seen as it whizzed by at 14km a second. Even these preliminary data are filled with mysteries that will take years to unravel.

Pluto is, on first blush, unlike any single world yet seen in the solar system. Instead, it is a composite of many of them—with mountain ranges more than 3km high. These are altitudes that suggest the crust of frozen nitrogen and methane on Pluto’s surface must be supported by ice, which is much stronger.