The Terrestrial Planets Chapter 23, Section 2

Mercury: The Innermost Planet  Mercury, the innermost and smallest planet (not counting Pluto), is hardly larger than Earth’s moon and is smaller than 3 other moons in the solar system  Mercury has no atmosphere, and reflects only 6% of sunlight that hits it  There are cratered highlands, and some smooth terrains  It is a very dense planet, suggesting a large iron core  Mercury revolves around the sun quickly, but it rotates slowly (1 Mercury day = 59 Earth days), so a night on Mercury (-173ºC) lasts for three months and a day (427ºC) lasts for three months  Mercury has the greatest temperature extremes of any planet

Mercury

Venus: The Veiled Planet  Venus orbits the sun in a nearly perfect circle every 255 Earth-days  Venus is covered in thick clouds that visible light cannot penetrate, instead we use radar to view topography  Basaltic volcanism and tectonic activity shape Venus’s surface  Based on the low density of impact craters, these forces must have been very active during the recent geologic past  On Venus, the greenhouse effect has heated the planet’s atmosphere to 475ºC; the main reason for the runaway greenhouse effect is that Venus’s atmosphere consists of 97% carbon dioxide

Venus

Mars: The Red Planet  The Martian atmosphere has only 1% the density of Earth’s and is made primarily of carbon dioxide with some water vapor  Although the atmosphere of Mars is very thin, extensive dust storms occur and may cause the color changes observed from Earth  Hurricane-force winds up to 270 kilometers per hour can persist for weeks  Mars’ northern hemisphere contains several volcanoes (Olympus Mons is the size of Ohio and is 2 ½ times larger than Mt. Everest)  The southern hemisphere is dominated by a large canyon called Valles Marineris  Some areas of Mars exhibit drainage patterns similar to those created by streams on Earth (water = life)  The present Martian atmosphere only contains trace amounts of water

Mars

Assignment  Read Chapter 23, Section 2 (pg )  Do Section 23.2 Assessment #1-6 (pg. 653)