1. ASTR-1010 Planetary Astronomy Day - 23

2. Announcements Smartworks Chapter 6: Due Monday, March 22. BSAS meeting Thursday March 18 – 7:30 pm Adventure Science Center – Nashville Mars Update – worth 8 points on next exam. 1 st Quarter Observing Nights: Tues & Thurs, March 23 & 25 -- 7:30pm Lab this week: Cratering - Next week: Earthquakes

3. ClassAction Stuff Splash page questions Solar System Temperatures Solar System Properties Impact Simulator

4. Condensation in the Solar Nebula

5. Temperature & Formation of Our Solar System Lecture Tutorial pg. 103 Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Take time to understand it now!!!! Come to a consensus answer you both agree on and write complete thoughts into your LT. If you get stuck or are not sure of your answer, ask another group.

6. Gathering Atmospheres Planets can gather gasses from the disk. This makes the primary atmosphere. Some planets later emit gasses from their interiors (e.g., from volcanoes). This can produce a secondary atmosphere.

7. Loss of Atmospheres Low-mass planets would lose their primary atmospheres. Recall that temperature measures the speed of motion of gas atoms. Low-mass planets have low escape velocities. Some gas atoms can go fast enough to escape small (or hot) planets.

8. Our Solar System The Sun’s planetary system fits this picture: Orbital planes have nearly the same orientation (planets formed in the disk). Inner planets are rocky/metallic. Outer planets can hold lots of gas. Asteroids and comets are planetesimals that still survive. Planetary moon systems are miniature versions of the Solar System.

9. Young Stars We can look at regions with a lot of gas and see stars with disks. These show the protostar/disk phase. Later the disk material should form planets. Often we see jets of material emitted from the system.

10. Concept Quiz  Hot Protostars We know that stars have different temperatures. Consider a newly forming star that was much hotter than the proto-Sun. What would we expect about its planets? A.The planets orbit at random angles around the star. B.Rocky planets might be formed over a wider range of distances than in our Solar System. C.The star would be “naked,” without a surrounding disk.

11. Cratered Planets Many planets and the Moon have craters. These come from the last stages of accretion. All inner planets would have started this way. Some planets have atmospheres and active geology. The activity would wipe out the craters. So cratered surfaces are old and unaltered.

12. Mercury’s Surface NASA / JPL / Northwestern University

13. Phobos Surface

14. Recent Collisions

15. Earth’s Surface