New Horizons images of Arrokoth show building blocks for planets

NASA’s New Horizons spacecraft zoomed past a city-sized object just over a year ago. The most distant object ever explored, since named Arrokoth, was a “planetesimal” lurking quietly in the outer solar system a billion miles past Pluto. The spacecraft beamed back images of what looked like two lumpy, reddish snowballs, one larger than the […]