phys0001_chapter08 - Chapter 8 Terrestrial Planets...

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Chapter 8 Terrestrial Planets Terrestrial planets or Earth-like planets are Mercury, Venus, Earth and Mars. They all have a solid surface and their sizes are relatively small. The following table shows their general properties. Mercury Venus Earth Mars Diameter (Earth=1) 0.38 0.95 1 0.53 Mass ratio (Earth=1) 0.06 0.82 1 0.11 Density (Water=1) 5.4 5.2 5.5 3.9 Revolution period 88 days 224 days 365 days 687 days Sidereal rotation period 59 days 243 days 24 hours 25 hours No. of satellites 0 0 1 2 Mercury Mercury has a thin layer of atmosphere, which is mainly made up of sodium and a little helium. The atmospheric pressure is almost zero. The presence of gaseous sodium means the temperature is high enough to allow sodium in rock be released. This is expected as Mercury is so near the Sun. Because the atmosphere is thin, there is a great difference between day and night temperatures. One of the most impressive surface features of Mercury is its full of craters . Most of them were formed by the impacts of meteorites. Impact craters have some special features, for example, there are some ray systems
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This note was uploaded on 10/14/2010 for the course BSC phy1001 taught by Professor Prof during the Spring '10 term at HKU.

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phys0001_chapter08 - Chapter 8 Terrestrial Planets...

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