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. Learn more: <a href="https://www.youtube.com/watch?v=FG4KsatjFeI" rel="nofollow">www.youtube.com/watch?v=FG4KsatjFeI</a> Credit: NASA’s Goddard Space Flight Center <b><a href="http://www.nasa.gov/audience/formedia/features/MP_Photo_Guidelines.html" rel="nofollow">NASA image use policy.</a></b> <b><a href="http://www.nasa.gov/centers/goddard/home/index.html" rel="nofollow">NASA Goddard Space Flight Center</a></b> enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. <b>Follow us on <a href="http://twitter.com/NASAGoddardPix" rel="nofollow">Twitter</a></b> <b>Like us on <a href="http://www.facebook.com/pages/Greenbelt-MD/NASA-Goddard/395013845897?ref=tsd" rel="nofollow">Facebook</a></b> <b>Find us on <a href="http://instagram.com/nasagoddard?vm=grid" rel="nofollow">Instagram</a></b>

This artist concept shows NASA Mars orbiters lining up behind the Red Planet for their duck and cover maneuver to shield them from comet dust that may result from the close flyby of comet Siding Spring C/2013 A1 on Oct. 19, 2014.

These images were taken of comet C/2013 A1 Siding Spring by NASA Mars Reconnaissance Orbiter on Oct. 19, 2014, during the comet close flyby of Mars and the spacecraft.

NASA NEOWISE mission detected comet C/2013 A1 Siding Spring on July 28, 2014, less than three months before this comet close flyby of Mars on Oct. 19.

Dwayne Brown, NASA public affairs officer, moderates a media briefing where panelists outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. Photo Credit: (NASA/Joel Kowsky)

Carey Lisse, senior astrophysicist, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland gives remarks during a media briefing where he and other panelists outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. Photo Credit: (NASA/Joel Kowsky)

Jim Green, director, Planetary Science Division, NASA Headquarters, Washington gives remarks during a media briefing where he and other panelists outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. Photo Credit: (NASA/Joel Kowsky)

Padma Yanamandra-Fisher, senior research scientist, Space Science Institute, Rancho Cucamonga Branch, California, right, gives remarks during a media briefing where she and other panelists outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. Photo Credit: (NASA/Joel Kowsky)

Panelists, from left, Jim Green, director, Planetary Science Division, NASA Headquarters, Washington, Carey Lisse, senior astrophysicist, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, Kelly Fast, program scientist, Planetary Science Division, NASA Headquarters, Washington, and Padma Yanamandra-Fisher, senior research scientist, Space Science Institute, Rancho Cucamonga Branch, California, are seen during a media briefing where they outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. (Photo credit: NASA/Joel Kowsky)

Panelists, from left, Jim Green, director, Planetary Science Division, NASA Headquarters, Washington, Carey Lisse, senior astrophysicist, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, Kelly Fast, program scientist, Planetary Science Division, NASA Headquarters, Washington, and Padma Yanamandra-Fisher, senior research scientist, Space Science Institute, Rancho Cucamonga Branch, California, are seen during a media briefing where they outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. (Photo credit: NASA/Joel Kowsky)

Jim Green, director, Planetary Science Division, NASA Headquarters, Washington, left, is seen with fellow panelists Carey Lisse, senior astrophysicist, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, Kelly Fast, program scientist, Planetary Science Division, NASA Headquarters, Washington, and Padma Yanamandra-Fisher, senior research scientist, Space Science Institute, Rancho Cucamonga Branch, California during a media briefing where they outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. Photo Credit: (NASA/Joel Kowsky)

Panelists, from left, Jim Green, director, Planetary Science Division, NASA Headquarters, Washington, Carey Lisse, senior astrophysicist, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, Kelly Fast, program scientist, Planetary Science Division, NASA Headquarters, Washington, and Padma Yanamandra-Fisher, senior research scientist, Space Science Institute, Rancho Cucamonga Branch, California, are seen during a media briefing where they outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. (Photo credit: NASA/Joel Kowsky)

Dwayne Brown, NASA public affairs officer, left, moderates a media briefing where panelist, seated from left, Jim Green, director, Planetary Science Division, NASA Headquarters, Washington, Carey Lisse, senior astrophysicist, Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, Kelly Fast, program scientist, Planetary Science Division, NASA Headquarters, Washington, and Padma Yanamandra-Fisher, senior research scientist, Space Science Institute, Rancho Cucamonga Branch, California, outlined how space and Earth-based assets will be used to image and study comet Siding Spring during its Sunday, Oct. 19 flyby of Mars, Thursday, Oct. 9, 2014 at NASA Headquarters in Washington. (Photo credit: NASA/Joel Kowsky)