Earth Sciences 1086F/G Lecture Notes - Lecture 9: Caloris Planitia, Mariner 10, Exosphere
11 Jun 2020
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Chapter 9-Mercury
→no satellites, small
Mariner 10: only spacecraft to made it close to Mercury, where most our knowledge is
collected from
Messenger: where most of our current data comes from
• objective to determine surface material, composition, investigate reflective materials at
poles, analyze magnetic fields and determine if there is liquid outer core
o succeed in mapping entire surface
Orbital Chaos
• Mercury was tidally coupled to sun like moon is to Earth
• orbital pattern is eccentric of all planets, planet rotates 1.5x, we always count 1yr as
complete orbit around sun
→1 full mercury day is 2 yrs long
o due to eccentric orbit so its takes 2 full rotations to come back to same hemi
being lit up by sunlight
Mercury’s Surface
Surface Temp
Perihelion: point in orbit when closest to sun
Aphelion: point orbit when furthest from sun
• orbit and fact that days are long, and cause its too small for atmosphere means temp
variations is most extreme on mercury
Atmosphere
• thin atmos consisting of atoms blasted off its surface by solar wind, its constantly being
replenished
• contains Na, K, Ca and Mg
Exosphere: sparse atmosphere
Craters & Plains
• unlike moon, has enormous cliffs, smooth plains cover 40% surface from eruptions
Caloris Basin: largest basin in Mercury, multi-ring impact basin
*most striking diff b/w mercury and moon is that mercury lacks dark lava plains
Inter-crater plains: less cratered areas, produce by lava flows that buried older terrain
Smooth plains: younger than inter-crater plains, appear to be acient lawa flows
Evidence
• plains are solidified lava flows, unlike maria, lava plains are no darker than rest of crust
• mercury doesn’t reflect as much light as moon
Albedo: proportion of light that gets reflected by planet, so mercury has low albedo
Document Summary
Mariner 10: only spacecraft to made it close to mercury, where most our knowledge is collected from. Messenger: where most of our current data comes from: objective to determine surface material, composition, investigate reflective materials at poles, analyze magnetic fields and determine if there is liquid outer core, succeed in mapping entire surface. Orbital chaos: mercury was tidally coupled to sun like moon is to earth, orbital pattern is eccentric of all planets, planet rotates 1. 5x, we always count 1yr as complete orbit around sun. 1 full mercury day is 2 yrs long: due to eccentric orbit so its takes 2 full rotations to come back to same hemi being lit up by sunlight. Perihelion: point in orbit when closest to sun. Aphelion: point orbit when furthest from sun: orbit and fact that days are long, and cause its too small for atmosphere means temp variations is most extreme on mercury.
