Transcript 3A8 Week 10 Lecture 25

Planetary Geology 101
The Solar System
Formation of the Solar System
• The stages of solar system formation start
with a protostar embedded in a gas cloud,
then to an early star with a circumstellar
disk, to a star surrounded by small
"planetesimals" that are starting to clump
together to a solar system like ours today.
Formation of the Solar System
protostar
planetesimals
www.jwst.nasa.gov/birth.html
circumstellar disk
home
Credit: Shu et al. 1987
Structure
(from the inside out)
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Central star
Inner “terrestrial” planets
Asteroid belt
Outer “gas giant” planets
Outer “ice giant” planets
(Dwarf planets)
Trans-Neptunian objects (Kuiper belt,
scattered disk, Oort Cloud)
• Miscellaneous
The Sun
• “Yellow dwarf”, 1.4 million km in diameter
• Fuses 620 million tonnes/sec of H
• 8.3 light-minutes away
The Sun
Mercury
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Innermost planet, 4,880 km in diameter
Very dense, with its own magnetic field
Enigmatically large iron core
Recent evidence for volcanism
Mercury
Venus
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Regarded as Earth’s “Evil Twin”
Surface T: 460°C, P: 92 Bar
Subject to runaway greenhouse effect
Extensive resurfacing due to volcanism
Venus
Mars
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Diameter: ~6800 km (= Earth’s core)
Same surface area of all Earth’s continents
Deserts, ice caps, canyons, giant volcanoes
Upper hemisphere may be giant impact basin
Mars
Asteroid Belt
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Small bodies: asteroids/minor planets
>50% mass: Ceres, Vesta, Pallas, Hygiea
Protoplanets that orbited too fast to acrete
Mainly loosely-bound piles of rubble
Asteroid Belt
Jupiter
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Largest body after the Sun (D: ~143,000 km)
Primarily H, He, with putative rocky core
High-energy storms in its atmosphere
At least 63 moons
Jupiter
Saturn
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Second-largest planet, diameter ~121,000 km
Prominent set of rings
53 officially-named moons
Hosts largest moon in the system, Titan
Saturn
Uranus
• Larger of the two “ice giants”, D ~51,000 km
• Gas atmosphere + contains H20, NH3, CH4
• Axis of rotation inclined almost 90
Neptune
• Second “ice giant”, D ~49,000 km
• Same composition as Uranus (H20, NH3, CH4)
• Tenuous ring system, 13 known moons
Dwarf Planets
• Currently 5: Ceres, Pluto, Haumea,
Makemake, Eris
• Most occur beyond Neptune (except Ceres)
• Best known is Pluto (former planet)
Trans-Neptunian Objects (TNOs)
• Composed of 3 regions: Kuiper Belt,
scattered disk, and Oort Cloud
Trans-Neptunian Objects (TNOs)
• Composed of 3 regions: Kuiper Belt,
scattered disk, and Oort Cloud