Why Do You Think All the Terrestrial Planets Were So Hot in the Past? Isn’T Space Rather Cold?
Terrestrial Planets
Discussion
Why do you think all the terrestrial planets were so hot in the past? Isn’t space rather cold?
Discussion
What’s a silicate? Give and example of a silicate.
Discussion
How do you think we know what the internal structure of the Earth is when our deepest mines and wells have not made it deeper than the Earth’s crust? Earthquakes
Earthquakes produce three types of waves that travel through the Earth.
1. Surface waves 2. Primary waves, or P waves 3. Secondary waves, of S waves Discussion
Which type a wave do you think will travel be er through a liquid and why?
Discussion
How do you think we know that the Earth’s inner core is solid? Planetary Magne c Fields
Caused by mo on of charged par cles
Requires, moderately rapid rota on, molten core and convec on Planets internal structure
Two tools without seismic data:
1) Mean density
2) Gravita onal mapping – mascons
Discussion
Which of the terrestrial worlds likely was the ho est during forma on? Why?
Planetary Size and Cooling
Larger planets lose heat more slowly than do smaller planets. Discussion
Larger planets have larger surface areas, and a larger surface area should radiate more energy into space? So shouldn’t larger planets cool faster? Why do larger planets cool more slowly than smaller planets? Geologic ac vity
Internal heat drives geologic ac vity on the planets’ surfaces. Discussion
Because heat is radiated from the surface of a planet, the surface is cooler than the interior.
How does the heat from the core of the planet get to the surface?
Plate tectonics Geologic processes
1) Impact cratering
2) Volcanism
3) Tectonics
4) Erosion Impact Craters and Surface Age
The more impact craters on a surface, the older that surface is. Discussion
Which area on the Moon is older, the light region to the le or the dark region in the center of the picture?
Discussion
Rank the terrestrial planets (include the Moon) in terms of the age of their surfaces from youngest to oldest to try and predict which planets will have the most craters. 1. Earth 2. Venus 3. Mars 4. Mercury 5. Moon
Smaller planets retain less heat and therefore have less geologic ac vity.
Discussion
Why do you think Earth’s oceans have so few impact craters as compared to Earth’s con nents?
Venus radar map Mars laser al meter map
Types of craters
1) Simple
2) Complex
3) Mul -ringed basin
Moltke Crater (7 km) Bessel crater (16 km) Euler Crater (25 km)
King Crater (77 km) Copernicus Crater (95 km) Schrodinger (320 km) Mare Orientale (930 km)
Mare Imbrium (1100 km) Mercury
Colaris basin Mercury (1550 km)
Chao c terrain forma on Meteor Crater (1.2 km) Arizona from the Shu le Wolf Creek (0.85 km) New Quebec Crater (3.4 km) Clearwater Lakes (26 km) Chichxulub Crater (250 km) Manicouagan Crater (100 km) Discussion
Why is the Manicouagan crater inverted, with a lower rim and higher center?
Hint: It is at high northern la tude and is rather old (212 million years) Radar images of Venus
Bright areas in radar images indicate rough terrain, while dark areas are smooth. Typically, rough terrain is younger than smooth terrain. Discussion
Why are rough areas younger? Adivar Venus (29 km) Meitner basin Venus (150 km) Unnamed crater Mars (2.3 km) Hellas basin Mars (2000 km)
Discussion
No ce the small size of this crater (about 12 km). On the Moon complex craters were about twice as large. What does this tell you about the surface material of Mars where this crater formed?
Why are craters important
• Numbers of craters provide rela ve ages
• Punch holes in crust
• Transi on size between simple and complex craters provides clues to the mel ng point/strength of the surface.