Polar Orbiter Shows Evidence of Minicomet Bombardment

This multiple‐exposure ultraviolet image, taken last September by the Visible Imaging System (VIS) aboard NASA's Polar orbiter, shows a 500‐km‐long trail of something roughly 10 000 km above the Atlantic, coming in toward Europe and shining brightly at 130.4 nm, a prominent UV emission line of atomic oxygen. The VIS has also recorded many such trails at 308.5 nm, a characteristic wavelength of hydroxyl‐radical fluorescence.