Name__________________________________________________________________

ASTR 1010 – Exam 4 – Spring 2009 – Prof. Magnani

April 24, 2009

There are 25 questions on this exam and you must attempt them all. Each question is worth 4 points. There is only one best answer to each question. A formula and constants sheet is included at the end of this exam. Please write right on the exam pages. You may use a calculator. Good luck!

1. The Earth’s mantle transports heat to the bottom of the lithosphere primarily by

a) radiation

b) radiative decay

c) conduction

d) convection

e) subduction

2. In order to generate a magnetic field, a terrestrial planet needs to have

a) solid metal core, rapid rotation

b) molten metal core, rapid rotation

c) molten metal core, slow rotation

d) solid metal core, ionosphere

e) molten metal core, ionosphere

3. Tectonic activity on Earth resurfaces the entire planet in about

a) 20 million years

b) 2 milion years

c) 250 million years

d) 2 billion years

e) 4.5 billion years

4. What is the most important characteristic for determining why the surface of a terrestrial type planet looks the way it does?

a) distance from Sun

b) rotation

c) magnetic field

d) axial tilt

e) size

5. To produce an atmospheric layer like the stratosphere, a planet needs a gas that will strongly absorb

a) ultraviolet radiation

b) optical light

c) infrared light

d) x-rays

e) all of the above

6. If a planet at a distance of 3.5 AU from the Sun has a surface temperature (not including the greenhouse effect) of 140 K, what is its reflectivity?

a) 0.06

b) 0.12

c) 0.23

d) 0.77

e) 0.86

7. What is the thermal velocity of an oxygen atom at a temperature of 290 K ? (The oxygen atom is 16 times more massive than a hydrogen atom).

a) 0.55 km/s

b) 0.30 km/s

c) 1.68 km/s

d) 3.00 km/s

e) 7.22 km/s

8. The main constituent of Earth’s atmosphere is

a) oxygen

b) nitrogen

c) carbon dioxide

d) methane

e) water vapor

9) Jupiter’s large magnetic field is produced by

a) a liquid metallic core

b) a solid metallic core

c) a layer of liquid helium

d) a layer of liquid metallic hydrogen

e) a layer of ice

10) Which of the following satellites has a sizeable atmosphere?

a) Io

b) Europa

c) Ganymede

d) Callisto

e) Titan

11) What type of radiation are greenhouse gases particularly good at absorbing?

a) x-rays

b) optical

c) ultraviolet

d) infrared

e) microwaves

12) How do the Galilean satellites resemble the formation of the Solar System?

a) The large and dense ones are closest to Jupiter

b) The small and dense ones are closest to Jupiter

c) They are gravitationally flexed by Jupiter

d) They have strong magnetospheres

e) They each have a family of satellites

13) The next 3 questions address the same issue: whether a planet can hold a particular atom in its atmosphere. Begin by determining the escape velocity of the planet in question. This planet is 6 times more massive than the Earth and has a radius twice that of Earth. Its exosphere ranges from 200-250 km above the surface. What is the escape velocity from the top of the exosphere?

a) 6.7 km/s

b) 11.2 km/s

c) 19.0 km/s

d) 24.1 km/s

e) 31.2 kms

14) At the top of the exosphere of the planet in question 13, the temperature is 300 K. What is the thermal velocity of the nitrogen molecule there? Nitrogen molecules are 28 times more massive than hydrogen.

a) 0.18 km/s

b) 0.42 km/s

c) 2.2 km/s

d) 5.6 km/s

e) 9.2 km/s

15) Which of the following statements is NOT correct?

a) The planet will retain its nitrogen.

b) The planet can retain gases heavier than nitrogen.

c) The planet would not lose its nitrogen if the temperature at the top of the exosphere was 290 K.

d) The planet would not lose its nitrogen if the temperature at the top of the exosphere was 310 K.

e) The planet would lose its nitrogen if the temperature at the top of the exosphere was 310 K.

16) Saturn gives off more heat than it receives from the Sun because

a) it is spinning rapidly

b) helium droplets form in the outer layers and descend closer to the center

c) it has an extensive ring system

d) it has a radioactive core

e) it is still contracting gravitationally

17) The strangest thing about Neptune’s satellite Triton is that

a) it is the largest satellite in the Solar System

b) it has a thick methane atmosphere

c) it has the strongest greenhouse effect in the Solar System

d) it is revolving about Neptune backwards

e) it has a small ring system

18) Why did Mars lose its atmosphere?

a) It died geologically and the atmosphere dissolved in the martian oceans.

b) Its volcanoes blew the atmosphere into space before the planet died geologically.

c) Its magnetosphere ionized all the gas which recombined with the surface soil.

d) It died geologically so that the mechanism for putting CO₂ back in the atmosphere were extinguished and the magnetic field weakened allowing the solar wind to strip the atmosphere.

e) All of the above.

19) Why is Io’s interior molten?

a) It contains lots of radioactive material at its center.

b) Jupiter’s magnetosphere heats and melts the interior.

c) Jupiter gravitationally flexes the satellite.

d) Jupiter’s heat provides enough energy to melt the interior.

e) All of the above.

20) Assume a planet orbiting the Sun has a reflectivity of 0.3. At what distance must this planet be for it to have a surface temperature in the absence of the greenhouse effect of 160 K?

a) 0.7 AU

b) 1.0 AU

c) 2.6 AU

d) 6.6 AU

e) 14.3 AU

21) Which of the following processes does NOT shape a planetary surface?

a) magnetic field reversal

b) impact cratering

c) volcanism

d) tectonics

e) erosion

22) Why do the spreading tectonic plates on the Earth’s surface not increase the overall surface area of the Earth?

a) There are many regions where one plate dives under the other and returns material to the lithosphere.

b) Two colliding plates buckle and produce a mountain range on each plate.

c) Erosion destroys the leading edge of colliding plates.

d) Volcanoes at the edge of colliding plates erupt and the ensuing magma flows destroy portions of the plates.

e) In actuality, the Earth’s surface is slowly increasing in area.

23) Which of the following surfaces is the youngest?

a) the lunar highlands

b) the lunar maria

c) the martian highlands

d) the martian volcanic region

e) the surface of Venus

24) The largest volcanoes in the Solar System are found on

a) Earth

b) Venus

c) Mars

d) Io

e) Titan

25) Choose the correct order from least geologically active to most geologically active:

a) Mercury, Mars, Venus, Earth

b) Mercury, Venus, Earth, Mars

c) Mars, Venus, Earth, Mercury

d) Mercury, Mars, Earth, Venus

e) Mars, Mercury, Venus, Earth

Constants and Formulas

Radius of Earth = 6378 km

Diameter of Earth = 12756 km

Radius of Sun = 6.95 x 10⁵ km

Diameter of Sun = 1.39 x10⁶ km

Radius of Moon = 1738 km

Diameter of Moon = 3476 km

S = dq / 206265

p² = a³

d_p = a(1 – e)

d_a = a(1 + e)

d_p + d_a = 2a

e = c/a

distance of Moon from Earth: 3.84 x 10⁵ km

distance of Sun from Earth/Moon system: 1.5 x 10⁸ km

1° = 60¢ = 3600²

1 AU = 1.5 x 10⁸ km = 1.5 x 10¹¹ m

1 year = 3.16 x 10⁷ s

Mass of Earth = 6.0 x 10²⁴ kg

Density = Mass/Volume

Volume of a sphere = (4/3)pr³

T = 280[(1 – reflectivity)/d²]^0.25

v_thermal = (2kT/m)^0.5

v_escape = (2GM/r)^0.5

k = 1.38 x 10^-23 J/K

G = 6.67 x 10^-11 Nt m²/kg²

Mass of Hydrogen = 1.67 x 10^-27 kg