NASA Releases New Image of Comet Set for Close Approach to Mars

Thursday NASA released an image of a comet that will pass within 84,000 miles of Mars later this year - nearly grazing the planet's surface in astronomical terms.

The comet will get so close to the Martian surface that it represents a unique opportunity for scientists to calculate how spacecraft stationed around Mars and equipment on the Martian surface may be impacted by the comet.

On Oct. 19 comet C/2013 A1, also called Siding Spring, will pass by Mars at a distance less than half of that between Earth and the Moon.

The new image of the comet reveals it has two streaming jets of dust coming off opposite ends of its nucleus. Astronomers report these jet streams will enable them to calculate the comet's axis of rotation, measure the direction of the nucleus's pole, and determine the speed of dust jettisoning from the nucleus.

"This is critical information that we need to determine whether, and to what degree, dust grains in the coma of the comet will impact Mars and spacecraft in the vicinity of Mars," Jian-Yang Li of the Planetary Science Institute in Tucson, Ariz., said in a NASA statement.

The image of Sliding Spring was was taken as it was crossing the orbital plane, which is the path the comet takes as it orbits the Sun. It was photographed by NASA's Hubble Space Telescope at a distance of 353 million miles from Earth.

The comet's nucleus is obscured by a glowing dust cloud that measures 12,000 miles across.

Sliding Spring was discovered in January 2013 by Robert H. McNaught at Siding Spring Observatory. McNaught and his colleagues determined that the comet is on a 1 million-year orbit around the Sun. The closest it is expected to get to the Sun is 130 million miles, well outside of Earth's orbit. The comet is not expected to become bright enough to be seen with the naked eye.