Ch. 22

Briefly describe the origin of the Moon.

A bolide the size of Mars collided with a young, molten Earth, causing ejected debris to be thrown into orbit around the Earth. Eventually this material condensed into the Moon.

Differentiate among the following solar system bodies: meteoroid, meteor, and meteorite.

A meteoroid is a small, solid particle that has entered Earth's atmosphere from space. A meteor is the streak of light seen as the meteoroid burns in the atmosphere. A meteorite is the remains of a meteoroid that makes it all the way to Earth's surface.

Compare and contrast asteroids and comets.

Asteroids are made of rocky and/or metallic material and are similar in composition to the terrestrial planets. Comets are less consolidated and made of ice, dust, and small rocky particles more typical of the outer portion of the solar system.

Where are comets thought to reside? What eventually becomes of comets that orbit close to the Sun?

Comets are thought to reside in the Oort cloud and the Kuiper belt. Comets that orbit close to the Sun eventually vaporize.

What accounts for the large density differences between the terrestrial and Jovian planets?

Different chemical compositions

Why are impact craters more common on the Moon than on Earth, even though the Moon is a much smaller target and has a weaker gravitational field?

Earth has a more substantial atmosphere than the Moon, causing more incoming bolides to burn up in the atmosphere before impact.

What body in our solar system is most like Mercury?

Earth's moon

Name three bodies in the solar system that exhibit active volcanism.

Earth, Venus, Io.

List the major stages in the development of the modern lunar surface.

Formation of the original crust, excavation of the large impact basins, filling of maria basins, and formation of rayed craters.

Where are most asteroids found?

In the asteroid belt.

When did the solar system experience the period of heaviest planetary impacts?

In the early time of formation

What are the three main sources of meteoroids?

Interplanetary debris missed by the gravitational sweep of the planets during the solar system formation, material that is ejected from the asteroid belt, and the rocky and/or metallic remains of comets that once passed through Earth's orbit.

What is the nature of Jupiter's Great Red Spot?

It is a giant cyclonic storm.

What is distinctive about Jupiter's satellite Io?

It is one of only three volcanically active bodies other than Earth known to exist in the solar system.

By what criteria are planets considered either terrestrial or Jovian?

Location, size, and density.

Compare and contrast the Moon's maria and highlands.

Maria are smooth, basaltic plains. Highlands are elevated several kilometers above the maria and are breccias. The maria tend to appear dark and the highlands appear light from Earth.

Why are the largest volcanoes on Earth so much smaller than the largest ones on Mars?

Mars lacks plate tectonics; successive volcanic eruptions will accumulate in the same place rather than the volcanoes being relocated by way of plate motion.

Why was Pluto demoted from the ranks of the officially recognized planets?

Pluto was reclassified as a dwarf planet. It was not large enough to clear its orbit of other debris, and other, larger Kuiper belt objects were discovered. Pluto also has an orbit that is dissimilar to the other 8 planets.

What evidence suggests that Mars had an active hydrologic cycle in the past?

Stream-like features with teardrop shaped islands suggest flowing water, valleys that appear to have been made by catastrophic flooding, dendritic drainage networks, and minerals that form only in the presence of water are all found on Mars.

Explain why the terrestrial planets have meager atmospheres, as compared to the Jovian planets.

Terrestrial planets were formed in a region where it was too hot for ice and gas to condense but the Jovian planets formed in colder locations. The terrestrial planets also are too small to exert the gravitational pull required to hold very light gases in their atmospheres.

Compare and contrast the processes of weathering and erosion on Earth with the same processes on the Moon.

The Moon lacks an atmosphere so erosion is largely from tiny particles from space bombarding the surface. There is no weathering as there is on Earth, which is a result of atmospheric processes.

Briefly outline the steps in the formation of our solar system, according to the nebular theory.

The Sun and planets began to form in a rotating cloud of nebular gas and dust. These materials eventually clumped together with a hot protosun at the center and chunks of planetesimals rotating around it. Through repeated collisions, the planetesimals grew into protoplanets, and eventually the solar system came about.

How is crater density used in the relative dating of surface features on the Moon?

The greater the crater density, the older the feature is supposed to be.

What do you think would happen if Earth passed through the tail of a comet?

There would be more particulate matter in the atmosphere and perhaps some meteor showers due to burning up of comet particles in the atmosphere.

How are maria on the Moon similar to the Columbia Plateau in the Pacific Northwest?

They are both made from fluid basaltic lavas that spread across a flat area.

How are Saturn's satellite Titan and Neptune's satellite Triton similar to one another?

They are both the only satellites in the solar system known to have substantial atmospheres.

How are Jupiter and Saturn similar to one another?

They both have dynamic atmospheres made of hydrogen and helium, both have rings, both have many satellites, and both are the two largest planets.

What two roles do ring moons play in the nature of planetary ring systems?

They exert gravitational pull on rings by altering their orbits and they also sweep up ring particles and subsequently eject them.

Why are many of Jupiter's small satellites thought to have been captured?

They revolve in the opposite direction of the largest moons and have eccentric orbits.

Why are the Galilean satellites of Jupiter so named?

They were discovered by Galileo.

Venus was once referred to as "Earth's twin." How are these two planets similar? How do they differ from one another?

Venus and Earth are of very similar sizes. Both are terrestrial planets, with volcanic activity, surface topography, and mantle upwelling. However, the atmospheres of these two planets are very different, as are the surface temperatures, with Venus being much hotter. As a result, Venus has volcanoes that are shorter and wider.

Why are the surface temperatures so much higher on Venus than on Earth?

Venus has a thick atmosphere of carbon dioxide that causes an extreme greenhouse effect.

What surface features do Mars and Earth have in common?

Volcanoes, polar ice caps, lava plains, and sand dunes.