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 other, gently pressed together to form an extraterrestrial snowperson.
On Thursday the New Horizons scientists published their full analysis and high-resolution images of Arrokoth in three voluminous reports in the journal Science. They contend this quirky object provides compelling evidence for how planets in our solar system, including Earth, formed four and a half billion years ago from a primordial cloud of dust. The reports suggest planet formation is not as violent and chaotic a process as once assumed.