An Impetus For Iapetus

Can the radical difference in albedo between the two hemisphers of Saturns moon Iapetus be seen at the eyepiece? I cant find anything telling me if this satellite has a face locked towards Saturn, or if it's freely rotating. Ideally, I'd like
to see its brightness vary over observing session(s), if thats possible. I'd
guess if its tidally locked with Saturn that the eyepiece view will be more
consistent night after night.

Mike Clemens

Attached Image:

Mike,

Iapetus is Saturn's third largest satellite (892 miles diameter) and orbits at a distance of a little over 2.2 million miles from the ringed planet (over 9 times the Earth-Moon distance!). Iapetus is in a synchronous orbit (tidally locked) with Saturn (79.3 days).

Iapetus was discovered by Giovanni Domenico Cassini in 1671 who was able to see the satellite at western elongation (10.2 magnitude) but not over it's eastern elongation (11.9 magnitude). Cassini correctly deduced that the leading hemisphere was darker than it's trailing hemisphere (albedo of 0.04 (or 4%) versus 0.60 (60%)). The origin of this discrepancy between the two hemispheres is still debated. It was thought to be due to material from Saturn's outermost satellite Phoebe, but further analysis of the respective surfaces do not match. Another explanation for the discrepancy was active (tectonic) processes within Iapetus producing the dark material. We still do not know the origin to date.

Interesting links on Iapetus may be found at;
http://solarviews.com/eng/iapetus.htm
http://en.wikipedia.org/wiki/Iapetus_%28moon%29
http://saturn.jpl.nasa.gov/science/moons/moonDetails.cfm?pageID=7
http://en.wikipedia.org/wiki/Giovanni_Domenico_Cassini
http://www.otastro.org/iapetus/

I hope that this summary helps.

Carlos