The Terrestrial Planets

Exploration of Mercury

Mercury Half-Mapped

Mercury’s Orbit Fairly eccentric with e=0.21 –Perihelion distance = 0.31 AU –Aphelion distance = 0.47 AU Resonance –So Mercury rotates 3 times for every 2 orbits around the Sun –This is a tidal effect from the Sun

The Mercurian Day

Advance of Mercury’s Orbit

General Properties of Mercury Temperature –100 K at night to 700 K by day Magnetic Field –Surprisingly strong at ~0.5% of Earth’s –Magnetic field and high average density suggest a large iron core Atmosphere –None Interior –Large iron core - 1/3 by volume, extending to about 70% of radius

Degas Impact crater about 45 km wide Imaged by the Mariner 10 flybys

Surface Effects Scarps are seen on Mercury. Useful for relative dating and history of the surface.

Caloris Basin

Interior of Mercury

Origin Model for Mercury