Review Worksheet Solutions

1. Describe the focus of comparative planetology and discuss its importance to solar system studies. Comparative planetology is the approach we use to study and understand our solar system. It involves comparing the worlds of our system, including planets, moons, asteroids, and comets, to one another. Its basic premise is that the similarities and differences among the worlds can be traced to common physical processes.

2. Briefly outline the theory or hypothesis which best explains the origin of the solar system and explain how the observable properties of the solar system are related to its process of formation. A large nebula began to collapse gravitationally. As it did so, it began to spin faster, and flattened into a disk and heated up. Planetisimals were formed by accretion of small particles that collided & stuck together growing larger.

The greater gravity of planetisimals attracted more materials and they grew larger, forming planets. Leftover debris became asteroids and comets.

All the orbital and rotational motions can be explained as preserving the original rotation of the nebula from which the solar system formed. Accretion explains planetary isolation. Temperature differences explain differentiation. Irregularities can be explained by collisions during the planetisimal era

3. Compare and contrast the formation of Jovian planets to that of terrestrial planets. The terrestrial planets are composed primarily of denser materials that condensed in the hotter part of the solar nebula. The Jovian planets contain not only the metallic and rocky compounds but also the hydrogen compounds which condensed in the colder part of the nebula, outside the frost line. Since these materials made up a larger percentage of the nebula, these planetisimals were able to accrete more material. This allowed their greater gravity to attract the lighter hydrogen and helium gas. As a result, the Jovian planets have thick atmospheres.

4. In the context of planet formation, what are asteroids and comets? Briefly explain why we find asteroids in the asteroid belt and comets in the Kuiper belt and Oort cloud. Asteroids and comets are the leftover planetisimals that never accreted enough material to form planets. Asteroids formed inside the frostline, comets formed outside the frost line. The asteroids are kept in the asteroid belt by the gravitational influence of Jupiter.

Comets that formed beyond the orbit of Neptune orbit in the Kuiper belt. Comets that formed where the Jovian planets are were flung into extreme orbits by Jupiter and the other large Jovian planets.

5. Summarize the basic differences between the terrestrial and the Jovian planets. Terrestrial planets are metallic or rocky in composition, close to the Sun, are warmer at the surface, have higher average density, have a solid surface, and have few if any moons. Jovian planets are gaseous in composition, lower in density, have no solid surface, are farther from the Sun, and have rings and moons

6. Describe and distinguish between space missions and discuss the advantages and disadvantages of each. flyby- lowest cost, easiest type of mission however, can’t do sustained studies, try to capture images/data on the fly Orbiter- costs more & takes more planning but allows for long term studies Lander – more costly & more planning, also requires extra fuel for descent to surface, more danger of damage but gives high res images of surface and can study samples. Can collect info on surface comp, temp, pressure, etc. Sample return- most expensive, heaviest load.

7. Describe how the moon formed and the evidence to support this hypothesis. The Moon formed from a giant impact of a Mars-size object with the earth. This impact destroyed the body and blasted material from the Earth’s mantle into orbit. This material eventually coalesced to form the Moon.

Three pieces of evidence are: the composition of the Moon is similar to that of the earth’s outer layers, the Moon is depleted of easily vaporized materials, as we would expect from the heat of an impact computer simulations show that the Moon could really have formed this way

8. Explain why the early Earth did not form with water, and how it gained it later in its formation. Earth, and all terrestrial planets, formed inside the frost line from rocky and metallic planetisimals. The temperature of the solar nebula was too hot for water ice to exist and the earth was too small to hold onto a substantial atmosphere of hot gases. Earth gained its water later during the heavy bombardment phase. Water-rich planetisimals (or comets) that formed beyond the frost line were scattered into the inner solar system, predominantly through gravitational encounters with Jupiter, and impacted the earth.

9. If a fossil is found to contain a sixteenth as much Carbon-14 as a living organism, what is the percent of Carbon-14 remaining? If the half life of Carbon-14 is 5, 715 years, how old is the fossil? 1/16 = (½ ) 4 so four half lives have gone by this means the fossil is about 5715 x 4 = 22,860 years old the percent remaining is (1/16) x 100 = 6.25 %