Bob Moler's Ephemeris Blog

C/2012 S1 (ISON)  is the official designation for Comet ISON, which will pass close to Mars on its inbound leg of its orbit of the sun.

Universe Today has two links on what to expect as Comet ISON nears the sun.

The Comet ISON, a Viewing Guide From Now to Perihelion:  http://www.universetoday.com/104818/comet-ison-a-viewing-guide-from-now-to-perihelion/

The comet’s coma (head) is turning green as it approaches.  That’s a good thing:  http://www.universetoday.com/105087/comet-ison-goes-green/

Here’s another site: The NASA Comet ISON Observing Campaign:  http://www.isoncampaign.org/ which answers some of your questions and details some of the world-wide and solar system wide attempts to observe Comet ISON as it makes its mad dash to and from the sun.

As Comet ISON approaches the Sun  it is doing so close to the ecliptic plane (plane of the earth’s orbit).  Situated in the morning sky, it will follow fairly close to the ecliptic, passing Mars and Saturn on the way in from our point of view.  It will physically pass close to Mars this week.  Expect photos of the comet from Mars by the end of the week.  What Martians are taking the photos?  Why we are.  NASA and the Europeans have assets on and around Mars who will, in their robotic way photograph and possibly analyze the comet as it passes by.  The apparent passage by Saturn is apparent from our point of view from the earth.  It is far in the background.  Comet Encke, the shortest of the periodic comets with a 3.3 year orbit will be in some of the photographs from earth.

Around the end of October Comet ISON will cross the earth’s orbit heading to perihelion on November 28th.  Comet will stay a morning comet after leaving the sun heading northward from the earth’s point of view.  We expect the comet be at its brightest, but rapidly fade in December.  But who knows.  I will be reporting what I know and see about the time the comet becomes visible in binoculars or a small telescope.  Stay tuned.