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

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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.

PHOTOS: 20 Breathtaking Images of Earth From Space

Aleppo, Syria
Aleppo, Syria, May 26, 2013 – The Citadel of Aleppo – medieval fortified palaceDigitalGlobe—Getty Images
Belfast, Northern Ireland
Belfast, Northern Ireland, Nov. 3, 2013 – “Wish,” a large-scale art workDigitalGlobe—Getty Images
Colorado River
Utah, USA, April 22, 2013 – Colorado RiverDigitalGlobe—Getty Images
Cuanza River, Angola
Cuanza River, Angola, April 28, 2013 – Cambambe DamDigitalGlobe—Getty Images
Doha, Qatar
Doha, Qatar, March 4, 2013 – Artificial island spanning nearly four million sq meters.DigitalGlobe—Getty Images
Dunalley, Australia
Dunalley, Australia, Jan. 6, 2013 – fires, false color image (red = healthy vegetation)DigitalGlobe—Getty Images
Great Barrier Reef
Australia, April 22, 2013 – Great Barrier ReefDigitalGlobe—Getty Images
Gwadar coast, Pakistan
Gwadar coast, Pakistan Sept. 29, 2013 – new island created by earthquake in PakistanDigitalGlobe—Getty Images
Croatia
Croatia, Feb. 16, 2013 – Galešnjak (Island of Love)DigitalGlobe—Getty Images
Hong Kong, China
Hong Kong, China May 9, 2013 – giant rubber duckDigitalGlobe—Getty Images
Manam Volcano
Madang Province, Papua New Guinea, March 22, 2013 – Manam VolcanoDigitalGlobe—Getty Images
Namib Desert, Namibia
Namib Desert, Namibia, May 13, 2013 – Sossusvlie areaDigitalGlobe—Getty Images
Mount Vesuvius
Naples, Italy, Feb. 19 2013 – Mount VesuviusDigitalGlobe—Getty Images
Niger
Niger, Feb. 13, 2013 – Arlit Uranium MineDigitalGlobe—Getty Images
Schooner Cays, Bahamas
Schooner Cays, Bahamas, May 26, 2013DigitalGlobe—Getty Images
Sochi, Russia
Sochi, Russia, March 17, 2013 – Site of 2014 winter OlympicsDigitalGlobe—Getty Images
Near the city of Sur, Oman
Near the city of Sur, Oman, Feb. 13, 2013 – massive “green tide”DigitalGlobe—Getty Images
Valencia, Spain
Valencia, Spain, July 19, 2013 – Palau de les Arts Reina Sofia and Gulliver Park with an enormous fiberglass model of Lemuel Gulliver trappedDigitalGlobe—Getty Images
Versailles, France
Versailles, France, Aug. 20, 2013 – Palace of VersaillesDigitalGlobe—Getty Images
Xi'an, China
Xi'an, China, Sept. 24, 2013 – Shiyuan Park DigitalGlobe—Getty Images

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Write to Nolan Feeney at nolan.feeney@time.com