October 19th, 2014
Econintersect: On Sunday 19 October 2014 a comet known "Siding Spring" will pass within 87,000 miles of Mars. Such close encounters of comets with planets of the inner solar system are rare so scientists have a lot of measurement experiments planned to observe and learn from the event. The comet is named after Australia's Siding Spring Observatory, near Coonabarabran, New South Wales, which first obereved the comet in 2013.
From a NASA press release:
On October 19, a comet that has travelled many billions of miles will come within about 87,000 miles of Mars - about one-third of the distance of the Moon from Earth. Comet Siding Spring comes from the Oort Cloud, material left over from the formation of the solar system. "This comet is coming into the solar system straight from the Oort Cloud. It's likely this is its first time this close to the sun," said space scientist David Humm, of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland.
Oort cloud material, including comets, is scattered through a vast region that begins outside the orbits of Neptune and Pluto and extends a substantial fraction of the distance to Proxima Centauri, the closest neighboring star. Oort Cloud comets can tell scientists about the materials - including water and carbon compounds - that existed during the formation of the solar system some 4.6 billion years ago.
Studying this close encounter will be the largest fleet of orbiting scientific observatories ever flown to another world, orbiting around (and rolling on the ground of) Mars. These instruments will, for the first time ever, have the chance to make close-up observations of a comet new to the inner solar system. And though it will not be the easiest task, the teams operating these instruments and spacecraft have developed plans to take advantage of this rare opportunity.
- Comet Siding Spring's Rare Mars Flyby: Full Coverage (Space.com, 18 October 2014)
- CRISM Prepares For Mars-grazing Comet Siding Spring (Press release, Johns Hopkins Applied Physics Laboratory, NASA Mars Exploration, 09 October 2014)