Space
Pluto: What New Horizons Found in 2015 and What We Still Don't Know
New Horizons flew within 12,550 km of Pluto on July 14, 2015 — the only spacecraft ever to do so — and transmitted data for 16 months afterward. What it found was not a dead, cratered iceball at the edge of the solar system but an active world with mountains of water ice, a heart-shaped nitrogen glacier the size of Texas, and possibly a liquid ocean beneath the ice.