a liquid metal core

Figure 1.3 shows a diagram of Mercurys interior. Mercury is one of the densest planets. Its relatively large, liquid core, made mostly of melted iron, takes up about 42% of the planets volume.



The smallest planet, Mercury, is the planet closest to the Sun. Because Mercury is so close to the Sun, it is difficult to observe from Earth, even with a telescope. However, the Mariner 10 spacecraft, shown in Figure 1.1, visited Mercury from 1974 to 1975. The MESSENGER spacecraft has been studying Mercury in detail since 2005. The craft is currently in orbit around the planet, where it is creating detailed maps. MESSENGER stands for Mercury Surface, Space Environment, Geochemistry and Ranging. (a) Mariner 10 made three flybys of Mercury in 1974 and 1975. (b) A 2008 image of compiled from a flyby by MESSENGER. As Figure 1.2 shows, the surface of Mercury is covered with craters, like Earths Moon. Ancient impact craters means that for billions of years Mercury hasnt changed much geologically. Also, with very little atmosphere, the processes of weathering and erosion do not wear down structures on the planet.


extreme temperatures

Mercury is close to the Sun, so it can get very hot. However, Mercury has virtually no atmosphere, no water to insulate the surface, and it rotates very slowly. For these reasons, temperatures on the surface of Mercury vary widely. In direct sunlight, the surface can be as hot as 427 C (801 F). On the dark side, or in the shadows inside craters, the surface can be as cold as -183 C (-297 F)! Although most of Mercury is extremely dry, scientists think Mercury is covered with craters, like Earths Moon. MESSENGER has taken extremely detailed pictures of the planets surface. there may be a small amount of water in the form of ice at the poles of Mercury, in areas that never receive direct sunlight.


short year long days

Mercury is named for the Roman messenger god, who could run extremely quickly, just as the planet moves very quickly in its orbit around the Sun. A year on Mercury the length of time it takes to orbit the Sun is just 88 Earth days. Despite its very short years, Mercury has very long days. A day is defined as the time it takes a planet to turn on its axis. Mercury rotates slowly on its axis, turning exactly three times for every two times it orbits the Sun. Therefore, each day on Mercury is 57 Earth days long. In other words, on Mercury, a year is only a Mercury day and a half long!

instructional diagrams

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compared to earth, mercury has _ years and _ days.

a) long; short

b) short; short

-->  c) short; long

d) long; long

which of the following is true about mercury?

a) the planet has two moons.

b) the surface has been smoothed over by lava flows in recent geologic history.

c) the planet has a thick atmosphere.

-->  d) the planet has an orbital period that is about one-quarter that of earth.

mercurys surface

a) is covered with impact craters.

b) hasnt changed much geologically for billions of years.

c) has undergone very little weathering and erosion.

-->  d) all of these.

planet mercury was named for the roman god mercury because it appears to travel rapidly across the face of the sun.

-->  a) true

b) false

on mercury, each year lasts only 1-1/2 days.

-->  a) true

b) false

mercury is the closest planet to earth.

a) true

-->  b) false

temperatures on mercury are _ because mercury _.

-->  a) extreme; has almost no atmosphere

b) moderate; has a thick atmosphere

c) similar to earths; has an earth-like atmosphere

d) extreme; has a thick atmosphere

the core of mercury is made mostly of melted

a) sulfur

-->  b) iron

c) mercury

d) silver

because mercury has a large core, the planet is

a) large.

-->  b) dense.

c) geologically dead.

d) all of these.

because mercury is so close to the sun, the entire planet is scorching hot.

a) true

-->  b) false

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