Mystery Marstronaut

Comet ‘Siding Spring’ headed for close encounter with Mars

Mars is about to dodge a cosmic snowball on this Sunday. On October 19, Comet Siding Spring will pass within 88,000 miles of Mars – just one third of the distance from the Earth to the Moon! Traveling at 33 miles per second and weighing as much as a small mountain, the comet hails from the outer fringes of our solar system, originating in a region of icy debris known as 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.

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The Colliding of Cosmic Winds

This is a beautiful and ethereal display of a “bow shock” about a half a light year across in the Orion Nebula. A bow shock is created in space when two streams of gas collide. In this image, the young star L.L. Orionis emits a solar wind ­– a stream of charged particles moving rapidly outward from the star. As the fast stellar wind runs into slow moving gas from the surrounding Orion Nebula a shock front is formed, similar to the bow wave of a boat moving through water or a plane traveling at supersonic speed.

"To fly in space is to see the reality of Earth, alone. The experience changed my life and my attitude toward life itself. I am one of the lucky ones." — Astronaut Roberta Bondar