GEOL3045: Planetary Geology Lysa Chizmadia Mercury From Mariner 10 to Messenger Lysa Chizmadia Mercury From Mariner 10 to Messenger

Introduction  Closest planet to Sun  5.8 x 10 7 km (0.38 AU)  Diameter = 4880 km  Smaller than Ganymede & Titan  Mass = 3.3 x kg  Surface T: K  3:2 resonance with the Sun  3 rotations for every 2 orbits  88 days and 59 days  Closest planet to Sun  5.8 x 10 7 km (0.38 AU)  Diameter = 4880 km  Smaller than Ganymede & Titan  Mass = 3.3 x kg  Surface T: K  3:2 resonance with the Sun  3 rotations for every 2 orbits  88 days and 59 days Image from:  Orbit highly eccentric  Aphelion = 70 million km  Perihelion = 46 million km  Irregularities in orbit  Thought to be Vulcan  Supports general theory of relativity

Mercury vs. Moon  Similarities  Heavily cratered  Old surfaces w/ smooth terrains  Caloris basin simliar to Lunar Maria  Craters near poles in permanent shadow  Radar data suggest ice in N pole craters  Similarities  Heavily cratered  Old surfaces w/ smooth terrains  Caloris basin simliar to Lunar Maria  Craters near poles in permanent shadow  Radar data suggest ice in N pole craters  Differences  Mercury has much higher density  5.43 vs g/cm 3  2nd densest body in solar system  Indicates very large Fe core  km  ~75% volume  w/ very thin silicate crust  km  Very thin atmosphere  From solar wind Image from:

Mariner 10  Launched in 1974  3 orbits in 2 years  Mapped 45% of surface  Discovered escarpments  100’s km high  From surface shrinkage of ~0.1% (~1 km)  Reanalysis suggests recent volcanism  More data needed to confirm  Launched in 1974  3 orbits in 2 years  Mapped 45% of surface  Discovered escarpments  100’s km high  From surface shrinkage of ~0.1% (~1 km)  Reanalysis suggests recent volcanism  More data needed to confirm Image from: /spacecraft.html#marin10

Messenger  Launched in 3 Aug 2004  Will orbit starting in 2011  ~March 18th  First fly by January 2007  Launched in 3 Aug 2004  Will orbit starting in 2011  ~March 18th  First fly by January 2007 Images from: Previously unseen side Matisse Crater Surface Spectra

Messenger  Designed to answer following questions:  Mercury’s high density  Geological history  Nature of magnetic field  Structure of core  Whether there really is ice are poles  Determine source of tenuous atmosphere  Designed to answer following questions:  Mercury’s high density  Geological history  Nature of magnetic field  Structure of core  Whether there really is ice are poles  Determine source of tenuous atmosphere Image from:

Summary  Mercury closest to Sun  3:2 resonance with Sun  Highly eccentric orbit  Confirms general relativity  Similar to Moon  Heavily cratered & smooth terrains  Different from Moon  Tenuous atmosphere  High density  Large FeNi core  Mercury closest to Sun  3:2 resonance with Sun  Highly eccentric orbit  Confirms general relativity  Similar to Moon  Heavily cratered & smooth terrains  Different from Moon  Tenuous atmosphere  High density  Large FeNi core

Formation of Impact Craters  Three stages: Images from: Image from:

Formation of Complex Craters Images from:

Crater Rays  Filamentus, high- albedo material  Rays are ejecta from craters  Cratering exercise  Filamentus, high- albedo material  Rays are ejecta from craters  Cratering exercise Image from: