Comet C/2013 A1 (Siding Spring) was discovered by Australian observer R. H. McNaught with the 0.5-m Uppsala Schmidt telescope on 2013, Jan. 03 (discovery magnitude +18.6). After its discovery, due to the uncertainty within the orbital calculations, there was thought to be a chance of a collision with Mars, but this possibility was excluded when its orbit was determined more accurately. Instead C/2013 A1 passed the planet Mars very closely on 2014, 19 October at 18:29UT. According to JPL website (With an observation arc of 733 days) the comet passed at a Nominal Distance of about 139,500 kilometers or 0.00094 AU (1 AU = ~150 million kilometers) from the Red Planet, that's closer than any previous known comet flyby of Earth or Mars.
You can read more info about this comet and its discovery circumstances on our previous post dated back to 2013, March 04.
Astronomers, amateur astronomers and NASA's fleet of orbiters and rovers at Mars were all ready to observe this event. Below you can see a short selection of some of the most significant/preliminary results and images obtained from the observation of this flyby. Click on each image for a bigger version.
Below a wide-field image obtained by N. Howes & R. Wodaski taken few hours before the close passage on October 19.
|Image credit: Nick Howes and Ron Wodaski - Tzec Maun Foundation|
"Researchers used the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity to capture this view of comet C/2013 A1 Siding Spring as it passed near Mars on Oct. 19, 2014. This image is from a 50-second exposure taken about two-and-a-half hours before the closest approach of the comet's nucleus to Mars. The sky was still relatively dark, before Martian dawn. At the time of closest approach, the morning sky was too bright for observation of the comet. A Martian dust storm to the west of Opportunity hampered visibility somewhat on Oct. 19, compared to the sky over Opportunity a week earlier." - For more info about Opportunity's image click here.
|Image Credit: NASA/JPL-Caltech/Cornell Univ./ASU/TAMU|
"These images were taken of comet C/2013 A1 Siding Spring by NASA's Mars Reconnaissance Orbiter on Oct. 19, 2014, during the comet's close flyby of Mars and the spacecraft. Comet Siding Spring is on its first trip this close to the sun from the Oort Cloud at the outer fringe of the solar system. This is the first resolved imaging of the nucleus of a long-period comet. The High Resolution Imaging Science Experiment (HiRISE) camera on Mars Reconnaissance Orbiter acquired images of this comet from a minimum distance of about 86,000 miles (138,000 kilometers), yielding a scale of about 150 yards (138 meters) per pixel. Telescopic observers had modeled the size of the nucleus as about half a mile, or one kilometer, wide. However, the best HiRISE images show only two to three pixels across the brightest feature, probably the nucleus, suggesting a size less than half that estimate." - For more info about HiRISE's image click here.
|Image credit: NASA/JPL/University of Arizona|
"NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft obtained this ultraviolet image of hydrogen surrounding comet C/2013 A1 Siding Spring on Oct. 17, 2014, two days before the comet's closest approach to Mars. The Imaging Ultraviolet Spectrograph (IUVS) instrument imaged the comet at a distance of 5.3 million miles (8.5 million kilometers).The image shows sunlight that has been scattered by atomic hydrogen, shown as blue in this false-color representation. Comets are surrounded by a huge cloud of atomic hydrogen because water (H2O) vaporizes from the icy nucleus, and solar ultraviolet light breaks it apart into hydrogen and oxygen. Hydrogen atoms scatter solar ultraviolet light, and it was this light that was imaged by the IUVS. Two observations were combined to create this image, after removing the foreground signal that results from sunlight being scattered from hydrogen surrounding Mars." - For more info about MAVEN's image click here.
|Image credit: NASA/Laboratory for Atmospheric and Space Physics/Univ. of Colorado|
All other results and news about this event will be posted here as soon as they are available!
by Ernesto Guido