ASTR-1010ASTR-1010Planetary AstronomyPlanetary Astronomy

Day - 21

AnnouncementsAnnouncementsSmartworks Chapter 7 & 8: Due Thursday, Nov. 18

Exam 3 – Thursday Nov. 18 – Chapters 6, 7, 8

The LASTLAST 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. 2due Tuesday Dec. 2

Spring ClassesSpring 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

Winds and CirculationWinds 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.

Layers in the Earth’s Layers in the Earth’s AtmosphereAtmosphere

• 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.

Layers (continued)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.

Atmospheric ProfilesAtmospheric Profiles

VenusVenus

• 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.

MarsMars• 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.

The Moon and MercuryThe 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.

Concept Quiz – The Moon Is Concept Quiz – The Moon Is AirlessAirless

The Moon and the Earth have approximately the same average temperature. Why does the Moon lack an atmosphere?

A. Comets, which deliver water and air, collide only with the Earth.

B. The Moon has no life. Life produces the atmosphere.

C. The Moon never had any volcanism.D. The Moon has a low escape velocity.

Concept Quiz – Earth’s CarbonConcept 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?

A. In rocks, the ocean, and in life.B. It was lost when the primary atmosphere

escaped.C. It evaporated from Earth’s atmosphere

while other gasses were retained.

Greenhouse EffectGreenhouse EffectLecture Tutorial Lecture Tutorial HandoutHandout

• 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.

Concept Quiz – Global WarmingConcept 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?

A. The rate Earth absorbs sunlight.

B. The rate Earth emits infrared light.

C. Both rates will be equal.

Size As Viewed From EarthSize As Viewed From Earth

Seasons25 degree tilt vs. 23.5 for Earth

0.093 orbital eccentricity 1.38 – 1.66 AU

Strong winds driven by seasonal changes (temperature gradients)