lecture_tan13 - Key Concepts Lectures 13 Terrestrial...

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Key Concepts: Lectures 13 Terrestrial Planets: Overview - How do the properties of planets depend on their mass? Mercury Mars The Planets • The Terrestrial Planets Mercury - Overview • Closest Planet to the Sun • Only a little bigger than the Moon Property Mercury Earth Radius 2430 km 6378 km Mass 3.3 x 10 23 Kg 6.0 x 10 24 kg Density 5430 kg/m 3 5520kg/m 3 Escape Speed 4.3 km/sec 11.2 km/sec Atmosphere (Very thin!!) Sodium, Potassium Nitrogen, Oxygen Magnetic Field 3.0 x 10 -7 T 4.0 x 10 -5 T Basically no atmosphere Exploration of Mercury • Telescopic Observations – Very difficult to observe since it is always near the Sun – Giocanni Schiaparelli made a map of subtle dark and bright areas (1877) • Space craft exploration – Mariner 10 (1973-1974) – Messenger (2008+)
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Orbit and Rotation Orbital Period = 88 days Most eccentric of any planet other than Pluto • 46 million km to 70 million km • Sunlight varies by factor of 2.3 [INVERSE SQUARE LAW: Flux from Sun = Luminosity/(4 ! r 2 ) , where r is distance from Sun] Was found to precess more than Newton’s Laws would predict Planet Vulcan? Never found Einstein's Theory of Relativity is the explanation (more later in the class) Rotation = 59 days Rotates 3 times in 2 orbits Tidally locked to Sun Structure of Mercury • No seismic data • Small planet - interior will be relatively cool and solid • Large metal core – Density roughly equal to Earth – Mercury has less gravity so material will be compressed less – Core should be relatively larger than the Earth’s • Thin solid mantle Surface of Mercury • Very similar to Moon • Lots of impact craters – Surface is very old – No plate tectonics thinner ejecta rims than lunar craters - due to higher gravity on Mercury than on the Moon
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lecture_tan13 - Key Concepts Lectures 13 Terrestrial...

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