Download The Terrestrial Planets

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. 649-653)
 Do Section 23.2 Assessment #1-6 (pg. 653)