Lecture_6

Lecture_6 - Comparing the sizes of Earth, Moon, and Mars...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
Comparing the sizes of Earth, Moon, and Mars
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Terrestrial Planets Demoted!!
Background image of page 2
Rotation • Mercury rotates 3 times every 2 “years” • Venus rotates slowly retrograde in 243 days • Earth – 24 hour with 23.5 o axial tilt • Mars – 24.6 hours with 24 o axial tilt • Thus Mars has seasons like the Earth, although twice as long, and somewhat complicated by its eccentric orbit
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Terrestrial Planet Atmospheres Where do atmospheres come from? Volcanoes outgas nitrogen, carbon dioxide, and water. Comets may add more water and carbon dioxide. On Earth oxygen is produced by plant life. If the plant life died, the oxygen supply would combine with rocks in about 2000 years. Mercury and the Moon are too small to hold atmospheres; the molecules escape from the upper parts. Mars is marginal. Venus holds a thick atmosphere, and the Earth a moderate one, but even these two planets cannot hold the light elements hydrogen and helium. Venus Approx. 100 At. of CO 2 Runaway Greenhouse: Water photodissociated; hydrogen escaped. Earth 1 At. 78% N 2 , 21% O 2 Mars 1/100 At. of CO 2 , The CO 2 washed out by rain, combined with rocks but not recycled. Mars cooled faster and volcanos ended. Nitrogen was lost by dissociative-recombination .
Background image of page 4
Runaway Greenhouse Effect In the runaway greenhouse effect, as the surface of Venus heated up, rocks evolved more carbon dioxide, increasing the warming effect, releasing more carbon dioxide, etc. Any surface water boiled away, and ultraviolet radiation photodissociated the water vapor in the upper atmosphere into hydrogen and oxygen. The hydrogen escaped and the oxygen combined with other elements. Thus, Venus lost all
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/03/2008 for the course ASTR 3 taught by Professor Hauser during the Winter '07 term at UCLA.

Page1 / 49

Lecture_6 - Comparing the sizes of Earth, Moon, and Mars...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online