AST 102 Lecture Notes - Lecture 20: Mariner 4, Permafrost, 600 Miles
Document Summary
A good on-line resource for information and images of mars is nasa"s space science data center mars page. Mars is about twice the diameter of the moon, and about half the diameter of the earth. As a result, mars retained its internal heat much longer than the moon did, and remained geologically active for much of its history. But as it is so much smaller than earth, it has cooled much faster. It does not appear to have much geologic activity any more. Mars has a number of other similarities with earth. Its rotation period is 24h 40m, nearly the same as. Its orbital period is 1. 88 yr. and its rotation axis is tilted by 25 degrees to its orbital plane (as compared to 23. 5 degrees for earth). Thus, mars has seasons, much like earth does. The surface pressure of the martian atmosphere is only about 0. 01 that of earth.
