Seat thyself sultanically among the moons of Saturn, and take the high abstracted man alone; and he seems a wonder, a grandeur, a woe. But from the same point, take mankind in mass, and for the most part, they seem a mob of unnecessary duplicates, both comtemporary and hereditary. Herman Melville, Moby Dick

Assignment: Read in Explorations, pp. 285-295 Sign up for Observing Lab #3 Problem Set #9 is due Thursday at 1:00 pm

In Class: Question to Ponder To put the incredible ``thin-ness'' of Saturn's rings into perspective, consider the aspect ratio of some everyday objects. The aspect ratio is a just the ratio of an object's length to its thickness, so, for example, a square has an aspect ratio of 1, while a rectangle has an aspect ratio larger than 1, depending on how long and thin it is. Estimate the aspect ratio of a penny. a) 1 b) 2 c) 10 d) 100 For comparison, Saturn's rings have an aspect ratio of about 1,500,000. Saturn's Moons A pretty motley crew. Mainly composed of ice, and mainly pretty small. Mimas -- one really big crater covering almost a quarter of the moon's surface. Enceladus -- like Europa, very smooth -- maybe a subsurface ocean? Titan -- largest around Saturn by far, and one of the largest in our solar system. Titan Comparable in size to Mercury, Mars Has a substantial atmosphere (1.6 times Earth pressure) of methane and nitrogen. Can hold its atmosphere because it's so cold out here -- gases don't have enough kinetic energy to escape. Surface temps (~-180 C) warmed a bit by greenhouse effect. May allow methane to exist as solid, liquid, and vapor, (e.g., as water does here on Earth). Might produce an interesting analog to our hydrologic (e.g., weather ) cycle. The Cassini Mission to Saturn and Titan Similar mission to that of the Galileo spacecraft to Jupiter. Launched in 1997; arrived in 2004 Dropped the Huygens probe into Titan's opaque atmosphere Will orbit among Saturn's rings and moons for several years, much like the Galileo spacecraft did on the jovian system.