Mercury = Hermes Mythology Planet Mercury, Element, Mercredi God of Commerce, Messenger God, guide to Hades Winged sandals and staff
Mercury s Orbit Mercury never seen more than 28 from the sun Revolves/orbits 0.4 AU from sun in 88 days Rotates in 59 days (radar) 3 Rotations to 2 revolutions Resonance
Mercury Differentiation Small mass high temperature=no air Most dense planet except Earth Iron core 75% of radius Tiny magnetic field slow rotation? Liquid core? Melted - heat of formation & decay of radioactive elements
Impact Craters Heavy bombardment cratered surface Strange dark rimmed crater Crater with gullies run to/from
Intercrater Plains More craters than the Lunar Maria 3.5 Billion, but less than Highlands 4.5 Billion years
Caloris Basin Giant impact creates ringed basin Later flooded by lava Jumbled terrain on opposite hemisphere of planet Mariner 10&MESSENGER
Volcanism on Mercury Volcanic vent is kidney shaped depression
Lobate Scarps When Mercury cooled it shrunk & surface wrinkles formed Which pass through a previously (10 9 years) existing crater Smooth plains and intercrater plains (similar to maria) not saturated with craters so must be younger than other areas
Messenger on its way back to Mercury Launched Aug04; loops around sun 15 times, Earth once, Venus twice and Mercury 3 times Will finally orbit in 2011
Rotation of the Moon Revolves & rotates on axis in 27.3 days synodic=29.53d Always keeping one side facing the Earth Resonance due to tidal coupling
Flooding of Basins by Lava Lowlands = mare in blue 3.5 billion years old basalt Heavily cratered highlands in green 4.5 billion years old Farside of Moon has no Maria due to thicker crust
Impact Crater Formation Impactor has velocity 10 times rifle bullet Releases energy 10 times equal mass of dynamite Impactor vaporized when temperature reaches millions K Shock wave forms shocked quartz found only in impacts Rebound can launch rocks without destroying them
Craters Copernicus and Tycho Moon is covered by craters of all sizes Highlands are saturated with craters Mare/lowlands have fewer craters so are younger Notice rays, ejecta blankets, secondary craters
Largest Impacts - Mare Orientale Mare = sea in Latin are sites of major impacts Note: multiringed basin Which flooded with basalt @ 3.5 billion years ago = volcanism
Volcanism - Hadley Rille 150km long, 1.5km across, 300meters deep Formed by flowing lava 3.3 billion years ago
No Atmosphere to Soften Shadows No Atmosphere => no erosion by wind water Escape velocity too low Maximum temperature of 123C&min of -233C
Only Erosion Is Slow Surface Evolution Regolith is crushed rock/dust; covers surface to depth of a few meters Erosion by micrometeorites, solar wind etc. Breccias glued with glass from impacts
Formation of the Moon Fission Protoearth spun so fast that the moon budded off - but wrong angular momentum Coaccretion- formed near Earth from nebula - but no iron core and no volatiles Capture- formed somewhere else- wrong oxygen isotopes + hard to capture + no iron or volatiles Giant Impact- Earth hit by Mars sized asteroid
Formation of Moon by Giant Impactor Elapsed time is about a day; moon forms in a year Earth ends up spinning once in 5 hours, moon in low orbit Earth was differentiated so moon is made from mantle material Correct isotope ratio, no iron core, volatiles evaporate Robin Canup s simulation
Eagle Has Landed Apollo 11 lands in Mare Tranquillitatis Neil Armstrong and Buzz Aldrin 20 July 1969
One Small Step
Hammer and Feather 6 Moon missions &12 astronauts A week to get there Apollo 12 and Surveyor 3
Young Drives Moon Rover
Last Man on the Moon?
Giant Impactor Painting by Kaufmann Problem of the low density of the Moon Solved by Moon being formed from low density mantle material Is it Science? Testable Prediction = Disprovable
Fox TV Moon Hoax No stars: Not enough exposure Illuminated astronaut: bright background Parallel shadows: topography Flag waving: no atmosphere so waved longer & liked it wrinkled
Precession of Mercury s Orbit Most of the precession is due to other planets Part is due to General Relativity
No Atmosphere = No Erosion But Ice at Mercury s & Moon s Poles? VLA radar observations see echo from poles which resembles ice Surface temperature 100K to 700K, but inclination of rotation axes 0º South Pole of Moon with craters permanently in shadow in white Hydrogen detected from neutron spectrometer on Lunar Prospector
Lunar Impact