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Key Terms:

Notes: (27-1)

Within our sun centered solar system there are nine planets.  These planets can be distinctly separated into two categories;

inner (terrestrial) planets - Mercury, Venus, Earth, Mars
rocky crusts, dense mantle, & very dense core
outer (Jovian) planets - Jupiter, Saturn, Uranus, Neptune
gaseous (outer layer consisting mostly of H gas), liquid H core, less dense that terrestrial planets, ring systems
not dense enough to be terrestrial, not large enough to be Jovian

A montage of the Solar System.  JPL / Nasa


planet nearest the sun
shortest period - 88 days
turns on its axis every 59 days
causes extremely high daytime temps - 400oC
causes extremely low nighttime temps - -200oC
~1/3 the size of Earth
magnetic field is ~1% as strong as Earth
lack of a significant atmosphere
very weak gravity 
nearness to the sun
surface consists of craters and smooth plains
formed much like our moon

(www.jb.man.ac.uk/public/ mercury.gif)



Earth's twin (sister)
similar mass, diameter, & gravity
very weak magnetic field
rotates E to W (unlike other planets)
thick atmosphere obscures its surface from telescopes
surface mapped using radar (Magellan satellite)
surface consists of volcanoes, faults, and lava flows
oldest crust is estimated to be ~800 million years old
atmosphere is about 96% CO2 and 3% N2
atmospheric pressure is ~90 times greater than Earth
the greenhouse effect of the CO2 gives venus a comfortable temperature of ~475oC
Often called the evening and morning stars
brightest body in space (other than the sun)

(www.solarviews.com/raw/ venus/venus.gif) 



fourth planet from the sun
period - 687 days
tilted axis is very similar to Earth
gives Mars 4 seasons
has polar ice caps like Earth
northern may be water, southern is most likely frozen CO2
freezing and melting cause large global winds
mild daytime temps in the summer - 27oC
mild to extreme nighttime temps -  can go as low as -125oC in the winter
~1/2 the size of Earth
very weak magnetic field 
gravity is ~ 40% of Earths
atmosphere is about 95% CO2 and 5% N2 & argon
atmospheric pressure is <1% of Earths
surface is made up of smooth low lands and crater filled highlands much like our moon
has some very large visible volcanoes
Olympus Mons
26km high 
may have had frozen water in the past
probably evaporated as Mars' atmosphere disappeared









Last modified: May 09, 2003