Space enthusiasts are given a once-in-a-million-years encounter as a comet the size of a small mountain whizzed past Mars on Sunday. The comet, known as Siding Spring (C/2013 A1), made its closest encounter with Mars on Sunday at 2:27 p.m. E.D.T., racing past the Red Planet at a breakneck 126,000 miles per hour.
The comet came so close that Mars Odyssey, Mars Reconnaissance Orbiter and the Mars Atmosphere and Volatile Evolution (MAVEN) had to duck and cover on the other side of the planet. Otherwise, Siding Spring’s debris of dust and gas flying at 126,000 miles per hour just 87,000 miles above Mars’ surface could have blasted them like a shotgun.
But fortunately they’re all right, NASA said in a statement. It will take a few days for them to transfer pictures and data to Earth.
Astronomers are champing at the bit, too, because they believe this to be a long-period comet that originates from the Oort cloud, a giant frozen reservoir of billions of comets that envelope the solar system far beyond Pluto.
Every once in while one of these ice balls receives a gravitational tug out of its slumber, which sends it dive-bombing the sun, only to head back out again to the Oort cloud.
Comets from the Oort cloud are both ancient and rare. Since this is Comet Siding Spring‘s first trip through the inner solar system, scientists are excited to learn more about its composition and the effects of its gas and dust on the Mars upper atmosphere. NASA will be watching closely before, during, and after the flyby with its entire fleet of Mars orbiters and rovers, along with the Hubble Space Telescope and dozens of instruments on Earth. The encounter is certain to teach us more about Oort cloud comets, the Martian atmosphere, and the solar system’s earliest ingredients.
“What could be more exciting than to have a whopper of an external influence like a comet, just so we can see how atmospheres do respond?” said Nick Schneider, the remote sensing team leader from NASA’s Maven mission to Mars. “It’s a great learning opportunity.”
Discovered by Australian comet hunter Robert McNaught early last year, the comet has been tracked by NASA as it falls in toward the inner solar system, allowing scientists to refine the comet’s exact trajectory.