OK, so where were we? Oh, Comet ISON....no it hasn't adjusted its course to rendezvous with Phobos. In fact, NASA is still touting its "Comet of the Century" glory despite of all the data from observers to the contrary. We should see a spectacular show from all of NASA's space-based assets including the Mars Reconnaissance Orbiter, Solar Dynamic Observatory, SOHO, STEREO and others. Of course naked-eye visibility is still questionable. If we see a Northern Hemisphere equivalant of Comet Lovejoy, I will be thrilled. Somehow Lovejoy overcame the odds and the 'Roche Limit' by remaining mostly intact after a close encounter with Sol.

The 'Roche Limit' wiki:

[link to en.wikipedia.org]

per ISON-

If a comet passes too close to a planet or sun, the gravitational forces can tear it apart - this is called the Roche Limit. The Roche Limit for comets moving around the sun is 1.49 million miles, and Comet Ison will pass within 1.16 million miles - inside the Roche Limit.

It might not break up and we have no concerns. But if it breaks up and spreads out, several things can happen. It can lose speed and be pulled into the sun, or some of the pieces may be pulled into the sun while others escape. Escaping objects will probably be slowed due to the sun’s pull and their outbound speed and trajectories will change, increasing the chance of them crossing the Earth's orbit. Remote - probably. But a chance we should be studying.

Here's why. The real problem comes after Ison goes behind the sun and begins its return trip. When would the comet and/or pieces of comet hit the Earth? And where? Can JPL/NASA give us possible scenarios for comet breakup and potential impact? I think so - not precise, but useful for planning purposes. Then leaders can look at options for possible large-scale evacuations, and staging and storage of food and water. If we are in danger of getting hit by pieces of Ison, we should be planning for it now.
EDIT: {This, to me, is the only potential Doom-Factor from Comet ISON...and it's infinitessimaly remote, though theoretically possible}

[link to www.joelgraves.com]

On November 28, 2013 Comet ISON will be within 800,000 miles (1.2 million km) of the Sun's surface. This will be the closest the comet comes to the Sun. This position in the path of Comet ISON is known as its perihelion. From Earth's perspective, a tight grouping of Saturn and Mercury will be in the vicinity.

Comet ISON will pass within the Roche Limit, which means that the Sun's gravity or temperature may cause Comet ISON to disintegrate. If ISON can survive, it will shed an enormous amount of material and become the most spectacular of all comets in 2013. Some astronomers believe it even has a chance to become the "Comet of the Century" - rivaling Ikeya-Seki, which was the brightest comet in the 20th century.

[link to www.fallofathousandsuns.com]



[link to www.youtube.com]