Comet ISON, C/2012 S1 (ISON): Update On Mars Flyby Incoming (and Possibly Outgoing).

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. by Anura Guruge

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Incoming encounter, October 7, 2013. Orbital path diagrams from JPL. Click to access JPL database.

ISON will be ~ 0.0725 AU, 6.7 million miles (10.8 million km) from Mars.

That ~1/6th the 39.9 mile separation between ISON and Earth, when they are closest together on December 26, 2013.

Despite this apparent ‘adjacency’ this 6.7 million separation is plenty big enough, especially since Mars isn’t big enough to wield much gravitational heft.

Just for comparison: On January 3, 2013, ace comet discoverer Robert H. McNaught who had already discovered over sixty comets, found another, C/2013 A1 (Siding Spring), which per observations by another cometary luminary, Leonid Elenin, is expected to pass within 25,700 to 200,000 miles of Mars (not enough data as yet available to determine its exact trajectory) in October 2014. Now that is close.

In 1770, D/1770 L1, Lexell’s comet came within 1.4 million miles of Earth.

On June 12, 1983, C/1983 J1 (Sugano-Saigusa-Fujikawa) came within 5.8 million miles of Earth.

So, the 6.7 million mile flyby of Mars is definitely a ‘no cigar’ event.

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Outbound IF it survives perihelion.

Everything post perihelion depends on how ISON weathers its Solar sungrazing.

If it survives, as we all hope it does, it will be hurtling past Mars at the end of the year. Mars will be far, far away.