ASTR-1010 Planetary Astronomy

1. ASTR-1010Planetary Astronomy Day - 21

2. Announcements Smartworks Chapter 7 & 8: Due Thursday, Nov. 18 Exam 3 – Thursday Nov. 18 – Chapters 6, 7, 8 The LAST Observing Session is TONIGHT*! 7:00pm - Sundquist atrium (the weather will suck) 25 of you have not come yet! Tonight* is the last chance. If you don’t come tonight*, you can’t do the “visit to the observatory” report. • *The other option is the BSAS meeting Thursday night in Nashville – 7:30 Adventure Science Museum. Visit to the Observatory & Virtual Observations Reports due Tuesday Dec. 2

3. Spring Classes Spring 2011: ASTR 1010/1011 – Planetary Astronomy ASTR 1020/1021 – Stellar Astronomy + Honors ASTR 2020 – Problems in Stellar Astronomy ASTR 3020 – Cosmology ASTR 3040 – Astrobiology

8. Winds and Circulation • Parts of the Earth are heated differently. • Vertical circulation of air (convection) distributes surface heating. • Global winds carry heat from hot to cool regions. • On Earth, Venus, and Mars, the circulation depends on heating pattern and rotation period.

11. Layers in the Earth’s Atmosphere • Troposphere (surface to 10-15 km altitude). • Temperature, pressure decline with altitude. • Water vapor mainly here. • Tropopause (upper boundary of troposphere). Temperature stops declining with altitude. • Stratosphere (15-50 km) • Temperature rises with altitude. • Ozone absorbs light, heats stratosphere.

12. Layers (continued) • Mesosphere (50-90 km). • No ozone, temperature declines with altitude. • Upper mesosphere is coldest part of atmosphere. • Ionosphere (> 90 km) • Ultraviolet radiation and solar wind can ionize atoms. • Solar wind = flow of particles from the Sun. • Ionize = strip electrons from an atom.

13. Atmospheric Profiles

14. Venus • Hot, dense atmosphere, completely cloud-covered. • Surface pressure 92 times that on Earth. • Mainly CO2, strong greenhouse effect. • Surface temperature about 740 K. • Thick atmosphere means nearly uniform temperatures over the entire planet. • Rotates very slowly.

16. Mars • Cold, thin atmosphere. • No oxygen, no ozone. • Thin atmosphere = extreme temperature variations. • Equator: up to 293 K (20 C). • Pole: down to -150 C. • Consequently large winds, which can make big dust storms.

22. The Moon and Mercury • Almost totally airless. • Combination of temperatures and low escape velocity means any atmosphere is lost. • No erosion from wind, so old, cratered surfaces are retained.

23. Concept Quiz – The Moon Is Airless The Moon and the Earth have approximately the same average temperature. Why does the Moon lack an atmosphere? • Comets, which deliver water and air, collide only with the Earth. • The Moon has no life. Life produces the atmosphere. • The Moon never had any volcanism. • The Moon has a low escape velocity.

25. Concept Quiz – Earth’s Carbon The Earth started with about as much carbon as Venus has. In Venus, the carbon is mainly in the atmosphere. Where is it on the Earth? • In rocks, the ocean, and in life. • It was lost when the primary atmosphere escaped. • It evaporated from Earth’s atmosphere while other gasses were retained.

29. Greenhouse EffectLecture Tutorial Handout • 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. • 25 Minutes for this one.

30. Concept Quiz – Global Warming Burning oil and coal raises the CO2 content of our atmosphere. By 2100, the Earth’s average temperature should be 2 to 5 K higher than now. Which will be larger? • The rate Earth absorbs sunlight. • The rate Earth emits infrared light. • Both rates will be equal.

32. Size As Viewed From Earth

33. Seasons 25 degree tilt vs. 23.5 for Earth 0.093 orbital eccentricity 1.38 – 1.66 AU Strong winds driven by seasonal changes (temperature gradients)‏