Siding Spring Clears Mars, Program Which Discovered it is Shut Down

Siding Spring Imaged By MRO’s HiRISE Camera. Image Credit NASA/JPL-Caltech

The Siding Spring comet which gave Mars a close shave on Sunday was a bit smaller than many had predicted.

NASA Story on Siding Spring Image From MRO’s HiRISE camera:

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.

This composite image shows two versions of each of two of the best HiRISE images of the comet. Shown at top are images with the full dynamic range, showing the nucleus and bright coma near the nucleus. Shown at bottom are versions where the fainter outer coma is brightened, saturating the inner region. The images at left and right were taken about nine minutes apart.

These closest-approach images were made possible due to very precise pointing and slewing of the Mars Reconnaissance Orbiter by engineers at Lockheed Martin in Denver, based on comet position calculations by engineers at NASA’s Jet Propulsion Laboratory, Pasadena, California. HiRISE acquired three images 12 days before closest approach, when the comet was barely detectable above the “noise level” of the images. These early images indicated the comet was not quite at its predicted location. This new viewing angle on the comet was used to update its predicted location and timing at closest approach. Without this update, the comet may have been outside the HiRISE image area in the best images.

For more information on these images and future updates, see

End story.

2010 Infrared image of Siding Spring Credit: NASA/JPL/CAl-Tech

2010 Infrared image of Siding Spring
Credit: NASA/JPL-Caltech


It’s interesting to note that our fascination with Mars is so consuming that there were no less than seven separate spacecraft from three different space agencies working on or above the planet at the same time an Oort cloud comet came whizzing by. (NASA’s Opportunity and Curiosity rovers, the MAVEN, MRO, Mars Odyssey orbiters,  ESA’s Mars Express and India’s MOM)

Juxtapose that with the fact that Australia’s Siding Spring Observatory which first imaged the comet, is sufficiently threatened by light pollution from a proposed gas field project that it would be rendered “useless.” Better yet, the specific survey program at Siding Spring which actually found the comet which bears its name, has been canceled due to budget cuts.  NASA, participating with the Australian government, had partially funded the program, which searched the southern sky for potentially hazardous asteroids and comets, until 2013.  According to media sources, it is was the only one of its type in the Southern Hemisphere.

In other words, if the big one’s coming from southern half of infinity,  we can all just hang it up.

Perhaps time to highlight yet again, the B612 Foundation, whose Sentinel mission doesn’t limit the concept of planetary defense to the Northern Hemisphere.

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