ASTR 100. Lecture 10: Planetary geology and atmospheres

Transcription

1 ASTR 100 Lecture 10: Planetary geology and atmospheres

2 Still in the innermost part of the Solar system

3 To understand the differences between Terrestrial planets, need to look at their structure differentiation

4 Core: Metals, Iron and Nickel Possibly molten, Possibly solid Mantle: Rocky later of minerals Possibly molten, Possibly solid Crust: Thin shell of low-density solid rock

5 Internal and external forces shape planets Internal: Volcanism Tectonics Weather (Erosion) External: Collisions Tidal influences Space weather

6 Terrestrial planets come in two flavors: Geologically dead or geologically alive

7 Lithosphere the solid part of the mantle *Not to scale on Earth and Venus Thick lithosphere means No Volcanism and No Seismic activity

8 Thick lithosphere means No convection of liquid rock (or it just doesn t affect surface) No Volcanism and No Seismic activity Smaller planets cool faster

9 Sources of heat: Contraction Differentiation Radioactivity Accretion (done) (mostly done) (still going) (it happens.) Sunlight NOT a significant source of heat

10 Lava plains on the Moon Evidence for ancient Volcanic activity

11 Tectonic activity on Mars

12 Erosion on Martian craters

13 Internal forces basically related to lithosphere Internal: Volcanism Tectonics Weather (Erosion)

14 Relationship between cooling/thick lithosphere and an atmosphere? Are you telling me that Mars stopped having: liquid water, significant weather, and an atmosphere because its lithosphere got a bit thicker?.yeah, basically.

15 Where do atmospheres come from? 1) Outgassing 2) Evaporation 3) Surface ejection

16 Can t outgas w/o volcanism Less greenhouse gas

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18 Earth: Man-made outgassing

19 How does one lose atmosphere? Condensation/Freezing Chemical reactions (oxidization) Solar wind stripping Thermal escape

20 Two loose ends: The role of the molten core Rapidly spinning liquid metal is like a magnet

21 Magnetosphere protects from solar winds

22 Aurora Borealis/Australis: Solar wind caught in the Earth s magnetosphere

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24 Aurora from orbit (change to HD)

25 No, seriously, did you make all that up? On what authority do people make these extravagant claims? Newton s law of Gravity F = GmM r 2 Density = Mass/Volume Earthquakes

26 All of this still an area of active research.

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30 Key terms: Differentiation, Core, Mantle, Crust, Atmosphere, Volcanism, Tectonics, Erosion, Lithosphere, Outgassing, Magnetosphere, Aurora Borealis/Australis Key Ideas: What are the main parts of a terrestrial planet? Why are some Terrestrial planets geologically dead? How does the thickness of the lithosphere affect a planet? Where does atmosphere come from? How does a magnetosphere form? What roles do the magnetosphere and atmosphere play? How do we know about the structure of the terrestrial planets?

31 Course presentations: 5 minutes/5% of your grade. 1) Find a space-related news article (or articles) 2) Send a link to me and ask is this a ight? 3) Once I ve approved article make and schedule presentation What s the article about/relate to class material Who did the research How did they do it Why did they do it and why do I care? (Optional: Your brief thoughts on the matter)

32 MEDIOCRE EXAMPLE PRESENTATION

33 Earth has a magnetosphere due to its rapidly spinning liquid metal core. Bodies w/o a spinning liquid metal core shouldn t have one

34 Chandrayaan-1 spacecraft launched by the Indian space organization in 2008 has been orbiting the moon and sees the solar wind is reflected in an area of the moon. About 20% of the incoming particles bounce back Corresponds to a magnetic field about 100x weaker than Earth s

35 Located on the Mare Crisium antipode (opposite side of the sphere) Scattered solar Wind up to 50% higher

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37 WHO CARES? 1) A specific area with more protection from harmful solar rays would be preferred place for a moon base

38 WHO CARES? 2) The basic understanding of the structure of planets/moons and how they interact with their environment in the Solar System

39 Bibliography [1] Voisey, John. Moon s Mini-Magnetosphere." November 23, Web. Accessed Oct 8, [2] "Chandrayaan-1." Wikipedia, The Free Encyclopedia. Wikimedia Foundation, Inc. 15 September Web. Accessed Oct 12, [3] Martin Wieser et al., First observation of a minimagnetosphere above lunar magnetic anomaly using energetic neutral atoms ArXiv. Accessed Oct 12, 2013