Homework Set 5 -- Solutions
DUE: Tuesday, June 25
Some of these questions entail looking up concepts and numbers in the book. Answers to these questions may also be sought by looking in astronomy books in the library, and at the astronomy links given on the course Web site.
1. Why does Venus have such a thick atmosphere compared to the Earth? Please be thorough but brief with your answer.
There is no water on Venus, which dissolved the CO2 on the Earth, and then reacted with rocks on the bottom of the ocean. So the CO2 stayed in Venus' atmosphere. There is about as much CO2 in Venus' atmosphere as all the CO2 tied up in rocks on the Earth
2. Come up with five differences that you can think of between the properties of comets and those of asteroids. This includes the bodies themselves and their orbits.
comets asteroids
long period orbits short period orbits
further out closer in
high inclinations in the plane of the solar system
high eccentricity more circular orbits
ice and rock mostly rock
3. How close is Venus during its nearest approach to Earth? How many times farther is this than the distance to the Moon? How close is Mars during its nearest approach to Earth, and how many times farther is this than the distance to the Moon?
Venus gets to within 0.28 AU of the Earth. This is 109 times the Earth-Moon distance
Mars gets to within 0.52 AU of the Earth (ignoring eccentricity -- it can actually get closer). This is about 202 times the Earth-Moon distance.
4. Compare photos of craters on Mars and on the Moon
a. Which body has smoother-edged craters, and why?
Mars has smoother edged craters, due to erosion by wind and water
b. What does this say about the lunar versus Martian environments?
Mars has an atmosphere, and had running water, both of which are responsible for the difference in crater appearance. Mars therefore had a more Earth-like environment
5. Since all planetary material condensed from the same nebula, why do meteorites have different chemical and geological properties than rocks you might find in your yard?
Rocks on the surface of the Earth come from the mantle and crust, which are products of the differentiation of the planet. Although some meteorites have come from parent bodies that have differentiated, we get samples from the cores, mantles and crust of these parent bodies, as well as undifferentiated ones, like the carbonaceous chondrites.
6. Use the theory of the origin of the solar system to explain the solar system characteristics listed in Table 14-1 of your book.
1. The planets formed from a flattened disk around the Sun
2. The Sun was the central part of this disk, and rotated with it as the Sun and planets formed.
3. The disk was circular in shape, and the accretion of the planets led to circular orbits
4. All the planets orbit in the same direction because they all came from the same disk, which was rotating one direction
5. Condensation sequence
6. Condensation sequence
7. Meteorites were not all formed from differentiated parent bodies
8. Angular momentum in the solar nebula favored rotation of the planets in the same sense that the disk itself rotated. Uranus and Venus may have been hit by giant impactors, which changed their spin
9. Conservation of angular momentum
10. Bode's rule is probably a result of the planetary accretion process sweeping up planetesimals in the region where each planet formed
11. Large planets as they formed heated the solar nebula around them. This caused a condensation sequence around them, and formation process for the moons similar to the one that created the planets around the Sun
12. Comets in the Oort cloud were formed from the left over planetesimals in the vicinity of Uranus and Neptune, and then ejected out. Comets in the Kuiper belt formed there without accreting into planets (due to too small a density of planetesimals), and stayed there.
13. Angular momentum was transferred to the orbiting planets due to the magnetic field of the early sun
6/21/96