On 19 October 2014, Comet Siding Spring will come within about 139,500 km of Mars – less than half the distance between Earth and our moon and less than one-tenth the distance of any known comet flyby of our planet. This proximity will provide an unprecedented opportunity for astronomers to gather data on both the comet and its effect on the Martian atmosphere. The comet’s nucleus will come closest to the Red Planet around 2:27 p.m. EDT (11:27 a.m. PDT, 6:27 p.m. GMT, 8:27 p.m. CET), hurtling at about 56 km per second. The Slooh Observatory (at 2:15 p.m. EDT, 11:15 a.m. PDT, 6:15 p.m. GMT, 8:15 p.m. CET) and the Virtual Telescope (at 12:45 p.m. EDT, 9:45 a.m. PDT, 4:45 p.m. GMT, 6:45 p.m. CET) will have live stream coverage.
An artist’s concept of Mars and Comet Siding Spring (2013 A1). Image credit: NASA.
Also known as C/2013 A1, Siding Spring was discovered in 2013 by professional astronomer Dr Robert McNaught at Siding Spring Observatory using the 0.5-m Uppsala Southern Schmidt Telescope. At the time of discovery, it was 7.2 AU from the Sun and located in the constellation Lepus.
The comet came from the Oort Cloud, a region of space 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 our Solar System some 4.6 billion years ago.
Siding Spring will pass Mars at a distance of 139,500 km. The outer parts of the comet’s thin atmosphere will collide at high speed with the Mars’ atmosphere.
On 19 October 2014, as seen from Earth, Mars will be in the constellation Ophiuchus, near globular cluster NGC 6401.
Some of the best and most revealing images and science data will come from assets orbiting and roving the surface of Mars.
In preparation for the Siding Spring flyby, NASA scientists maneuvered Mars Odyssey orbiter, Mars Reconnaissance Orbiter, and the newest member of the Mars fleet, MAVEN, in order to reduce the risk of impact with high-velocity dust particles coming off the comet.
The period of greatest risk to orbiting spacecraft will start about 90 min after the closest approach of the comet’s nucleus and will last about 20 minutes, when Mars will come closest to the center of the widening trail of dust flying from the nucleus.
Siding Spring will be the first comet from the Oort Cloud to be studied up close by spacecraft.
