Comet Siding Spring Will Graze Mars This October in Rare Fly-by

Mars is going to get a spectacular show in the form of a comet. On Oct. 19, Comet Siding Spring will come within about 87,000 miles of Mars, which is about one-third of the distance of the moon from Earth.

The comet itself is coming from the Oort Cloud, which is material left over from the formation of the solar system. The Oort Cloud is scattered through a vast region that begins outside the orbits of Neptune and Pluto and extends a fraction of the distance to Proxima Centauri, which is the closest neighboring star. What's interesting about the comet that's set to graze Mars is that it can tell scientists about the materials in the Oort Cloud that helped form the solar system about 4.6 billion years ago.

"The close fly-by of Mars by Comet Siding Spring is unique, unexpected and lucky for us," said David Humm, who serves as instrument scientists for the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), in a news release. "CRISM has a significant advantage due to its proximity to the comet at closest approach."

In fact, the researchers are taking advantage of this close fly-by to better understand the Oort Cloud. CRISM is both a spectrometer and a camera, which means that it can identify molecules by the light they emit and characterize minerals by the light that they reflect. The researchers plan to use this instrument to detect features and learn a bit more about the nature of the gas and dust in the Oort Cloud.

"I would have been very surprised if you had told me we were going to use CRISM to look at a comet," said Humm. "The likelihood of being this close to a new comet is really very small, and we're operating well beyond our design lifetime, so this exciting an opportunity is completely unexpected."

Currently, the scientists are gearing up to study this spectacular event. They're hoping to attain enough data in order to learn a bit more about the formation of our solar system.