Comet Siding Spring sailed past Mars on Sunday, coming 10 times closer to the Red Planet than any comet on record has come to Earth.

At the time of the comet’s closest approach at 2:27 p.m., it was just 87,000 miles from Mars. That’s less than half the distance between Earth and the moon.

Jim Green, director of planetary science for NASA, said the close encounter between planet and comet was a once-in-a-million-year event.

Comet Siding Spring traveled a long way to make its rendezvous with Mars. Its journey began a million years ago and billions of miles away in the Oort cloud.