OXON HILL, Md. — Pluto’s got a roughly 4-billion-year-old case of heartbreak. The left side of the dwarf planet’s infamous heart-shaped feature might owe its existence to a run-in with a big space rock, planetary scientist Paul Schenk reported November 10 at the 47th meeting of the American Astronomical Society’s Division for Planetary Sciences.
The area, informally called Sputnik Planum, is an 825-kilometer-wide, 4-kilometer deep basin, said Schenk, of the Lunar and Planetary Institute in Houston. And except for some erosion to the south, the basin is roughly circular, which is typical for other impact craters in the solar system. If an interplanetary interloper is at fault, it would have smashed into Pluto at least 4 billion years ago. “It’s difficult to explain by other mechanisms,” he said.
Editor’s note: This story was updated November 23, 2015, to specify throughout that the possible impact would have been in the left half of Pluto’s heart-shaped region.