ASTR 100 Lecture 10: Planetary geology and atmospheres
Still in the innermost part of the Solar system
To understand the differences between Terrestrial planets, need to look at their structure differentiation
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
Internal and external forces shape planets Internal: Volcanism Tectonics Weather (Erosion) External: Collisions Tidal influences Space weather
Terrestrial planets come in two flavors: Geologically dead or geologically alive
Lithosphere the solid part of the mantle *Not to scale on Earth and Venus Thick lithosphere means No Volcanism and No Seismic activity
Thick lithosphere means No convection of liquid rock (or it just doesn t affect surface) No Volcanism and No Seismic activity http://www.youtube.com/watch?v=jmk6_6eac5o Smaller planets cool faster
Sources of heat: Contraction Differentiation Radioactivity Accretion (done) (mostly done) (still going) (it happens.) Sunlight NOT a significant source of heat
Lava plains on the Moon Evidence for ancient Volcanic activity http://content.usatoday.com/communities/sciencefair/post/2012/03/videonasa-reveals-history-of-the-moon-/1#.ulmwwbaqpl4
Tectonic activity on Mars
Erosion on Martian craters
Internal forces basically related to lithosphere Internal: Volcanism Tectonics Weather (Erosion)
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.
Where do atmospheres come from? 1) Outgassing 2) Evaporation 3) Surface ejection
Can t outgas w/o volcanism Less greenhouse gas
Earth: Man-made outgassing
How does one lose atmosphere? Condensation/Freezing Chemical reactions (oxidization) Solar wind stripping Thermal escape
Two loose ends: The role of the molten core Rapidly spinning liquid metal is like a magnet
Magnetosphere protects from solar winds
Aurora Borealis/Australis: Solar wind caught in the Earth s magnetosphere
http://youtu.be/httdxjyk7eq?t=3m10s http://www.youtube.com/watch?v=jeamkkrivlc Aurora from orbit (change to HD) http://www.youtube.com/watch?v=ev9opunaqxe
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
All of this still an area of active research. http://spacescience.arc.nasa.gov/mars-climate-modeling-group/past.html
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?
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)
MEDIOCRE EXAMPLE PRESENTATION
Earth has a magnetosphere due to its rapidly spinning liquid metal core. Bodies w/o a spinning liquid metal core shouldn t have one
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
Located on the Mare Crisium antipode (opposite side of the sphere) Scattered solar Wind up to 50% higher
WHO CARES? 1) A specific area with more protection from harmful solar rays would be preferred place for a moon base
WHO CARES? 2) The basic understanding of the structure of planets/moons and how they interact with their environment in the Solar System
Bibliography [1] Voisey, John. Moon s Mini-Magnetosphere." www.universetoday.com79781/moons-minimagnetosphere/. November 23, 2010. Web. Accessed Oct 8, 2013. [2] "Chandrayaan-1." Wikipedia, The Free Encyclopedia. Wikimedia Foundation, Inc. 15 September 2013. Web. Accessed Oct 12, 2013. [3] Martin Wieser et al., First observation of a minimagnetosphere above lunar magnetic anomaly using energetic neutral atoms http://arxiv.org/ftp/arxiv/papers/1011/1011.4442.pdf ArXiv. Accessed Oct 12, 2013