Lecture15 - 1 Astro 102/104 1 Lecture#15 • Mercury •...

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Unformatted text preview: 1 Astro 102/104 1 Lecture #15: • Mercury: • General properties. • Surface characteristics. • Interior and evolution. • Reading: – Chapter 7.1, 9.3, 10.3. Astro 102/104 2 The Main Point Mercury is a small, atmosphereless terrestrial planet with a large metallic core and evidence for a complex geologic history. Astro 102/104 3 Basic Properties of Mercury • Average Distance from Sun: 58,000,000 km (0.39 AU). • But: Orbital eccentricity = 0.206. • So: Distance varies from 46,000,000 to 70,000,000 km. • Orbital period: 88 days. • Period of Spin around axis: 58.65 days (2/3 orbit period!) • Mass = 3.3x10 23 kg = 0.055 M E . • Radius = 2440 km = 0.38 R E . • Density = 5.4 g/cm 3 (recall that Earth ~5.5 g/cm 3 ). • Surface Gravity = 3.7 m/sec 2 (38% of Earth's). • Surface Temperatures: -185°C (night), +430°C (day) [!] • Surface superficially lunar, but important differences. Astro 102/104 4 Observing Mercury in the Sky • Mercury is the innermost planet. • It never gets more than ~28° from the Sun. • Hard to see! – Twilight. – Haze/Smog. – Starlike. 2 Astro 102/104 6 What's up with that Density? • Mercury's density vs. size is distinctly different from that of the other terrestrial planets. • Implies a large metallic core ! Planet %Core Earth ~54% Moon ~10%?...
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This note was uploaded on 03/04/2008 for the course ASTRO 1102 taught by Professor Squyres,s/margot,j during the Spring '07 term at Cornell.

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Lecture15 - 1 Astro 102/104 1 Lecture#15 • Mercury •...

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