Watch a Giant, 4.6 Billion-Year-Old Comet Fly By Mars

Watch highlights of Comet Siding Spring zoom past Mars and get roughly within 87,000 miles of the red planet — the closest any comet has gotten to it in a long, long time.

The livestream from the Slooh Community Observatory was hosted by expert astrobiologist David Grinspoon and featured special guests.

“We’re going to observe an event that happens maybe once every million years,” Jim Green, planetary science division director at NASA, said this month at a press conference. “This is an absolutely spectacular event.”

Siding Spring is estimated to be 4.6 billion years old with a core somewhere between half a mile and 5 miles wide. Looking the comet’s close brush with Mars could teach scientists a lot about the planet’s atmosphere, writes Mike Wall at Space.com. Studying the comet could also provide insight into how planets are formed: Siding Spring is believed to have been created in an area of our solar system between Jupiter and Neptune, but unlike most objects in that part of space at the time, it never was incorporated into a planet.

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