inner vs. outer planets

the outer planets

The four planets farthest from the Sun are the outer planets. Figure 1.2 shows the relative sizes of the outer planets and the Sun. These planets are much larger than the inner planets and are made primarily of gases and liquids, so they are also called gas giants. The gas giants are made up primarily of hydrogen and helium, the same elements that make up most of the Sun. Astronomers think that hydrogen and helium gases comprised much of the solar system when it first formed. Since the inner planets didnt have enough mass to hold on to these light gases, their hydrogen and helium floated away into space. The Sun and the massive outer planets had enough gravity to keep hydrogen and helium from drifting away. All of the outer planets have numerous moons. They all also have planetary rings, composed of dust and other small particles that encircle the planet in a thin plane. Click image to the left or use the URL below. URL: This image shows the four outer planets and the Sun, with sizes to scale. From left to right, the outer planets are Jupiter, Saturn, Uranus, and Neptune.


the inner planets

The inner planets, or terrestrial planets, are the four planets closest to the Sun: Mercury, Venus, Earth, and Mars. Figure 1.1 shows the relative sizes of these four inner planets. Unlike the outer planets, which have many satellites, Mercury and Venus do not have moons, Earth has one, and Mars has two. Of course, the inner planets have shorter orbits around the Sun, and they all spin more slowly. Geologically, the inner planets are all made of cooled igneous rock with iron cores, and all have been geologically active, at least early in their history. None of the inner planets has rings. Click image to the left or use the URL below. URL: This composite shows the relative sizes of the four inner planets. From left to right, they are Mercury, Venus, Earth, and Mars.


instructional diagrams

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which of these is not an inner planet?

a) venus

b) mars

-->  c) jupiter

d) earth

together, all of the planets equal the mass of the sun.

a) true

-->  b) false

why is earths natural satellite unique among the inner planets?

a) no other inner planet has a satellite.

-->  b) no other inner planet has a large, planet-like satellite.

c) no other inner planet has a captured asteroid for a satellite.

d) none of the above.

the inner planets are made of

-->  a) an igneous rock mantle with an iron core.

b) iron and nickel metal in the mantle and core.

c) a metal core with a metamorphic and igneous rock mantle.

d) a metamorphic rock mantle and an igneous rock core.

all of the inner planets were geologically active at some time in their history.

-->  a) true

b) false

the outer planets are called the _ and the inner planets are called the __.

a) rocky planets; gas giants

b) gassy planets; rocky planets

-->  c) gas giants; terrestrial planets

d) large planets; small planets

gas giants are primarily made up of _____.

a) helium and lithium

b) oxygen and carbon dioxide

c) carbon dioxide and methane

-->  d) hydrogen and helium

saturn is unique in the solar system because it is the only planet with rings.

a) true

-->  b) false

compared to the outer planets, the inner planets have

a) slower orbits.

b) slower spin.

c) few or no satellites.

-->  d) all of the above.

planetary rings are made up of

a) metal

-->  b) dust and small rocks

c) gases and ices

d) all of the above

diagram questions

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