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What comes to mind when you hear the word ‘planets’?
Are you interested in the planets?
What do you think of the planet names?
What do you think is the most mysterious planet?
Do you think there’s life on other planets?
Would you like to visit another planet?
Do you think we should look for life on other planets?
How are all the planets different?
What do the names of the planets mean?
Would you like to see our planet from space?
What are planets?
How are planets formed?
Why doesn’t life exist on other planets in our solar system?
What do you think of the idea of moving to another planet after we’re finished with Earth?
Do you know anyone who’s from another planet?
Do you think it will be possible one day to go to planets in other solar systems?
Do you think there’ll ever be a war between planets – Star Wars?
What fictional planets do you know of from books and movies?
Do you think our planet will survive?
Do you think Earth is a good name for our planet? Is it the same in your language?
1.What are the 9 planets?
1) Mercury 水星 shuǐxīng Mercury is the closest planet to the Sun and the eighth largest. Mercury is slightly smaller in diameter
than the moons Ganymede and Titan but more than twice as massive. orbit: 57,910,000 km (0.38 AU) from Sun
diameter:
4,880 km
mass: 3.30e23 kg In Roman mythology Mercury is the god of commerce, travel and thievery, the Roman counterpart
of the Greek god Hermes, the messenger of the Gods. The planet probably received this name because it moves so quickly across the
sky. Mercury has been known since at least the time of the Sumerians (3rd millennium BC). It was sometimes given separate names
for its apparitions as a morning star and as an evening star. Greek astronomers knew, however, that the two names referred to the same
body. Heraclitus even believed that Mercury and Venus orbit the Sun, not the Earth. Since it is closer to the Sun than the Earth, the
illumination of Mercury's disk varies when viewed with a telescope from our perspective. Galileo's telescope was too small to see
Mercury's phases but he did see the phases of Venus. Mercury has been now been visited by two spacecraft, Mariner 10 and
MESSENGER. Marriner 10 flew by three times in 1974 and 1975. Only 45% of the surface was mapped (and, unfortunately, it is too
close to the Sun to be safely imaged by HST). MESSENGER was launched by NASA in 2004 and will orbit Mercury starting in 2011
after several flybys. Its first flyby in Jan 2008 provided new high quality images of some of the terrain not seen by Marriner 10.
Mercury's orbit is highly eccentric; at perihelion it is only 46 million km from the Sun but at aphelion it is 70 million. The position of
the perihelion precesses around the Sun at a very slow rate. 19th century astronomers made very careful observations of Mercury's
orbital parameters but could not adequately explain them using Newtonian mechanics. The tiny differences between the observed and
predicted values were a minor but nagging problem for many decades. It was thought that another planet (sometimes called Vulcan)
slightly closer to the Sun than Mercury might account for the discrepancy. But despite much effort, no such planet was found. The real
answer turned out to be much more dramatic: Einstein's General Theory of Relativity! Its correct prediction of the motions of Mercury
was an important factor in the early acceptance of the theory. Until 1962 it was thought that Mercury's "day" was the same length as
its "year" so as to keep that same face to the Sun much as the Moon does to the Earth. But this was shown to be false in 1965 by
doppler radar observations. It is now known that Mercury rotates three times in two of its years. Mercury is the only body in the solar
system known to have an orbital/rotational resonance with a ratio other than 1:1 (though many have no resonances at all). This fact
and the high eccentricity of Mercury's orbit would produce very strange effects for an observer on Mercury's surface. At some
longitudes the observer would see the Sun rise and then gradually increase in apparent size as it slowly moved toward the zenith. At
that point the Sun would stop, briefly reverse course, and stop again before resuming its path toward the horizon and decreasing in
apparent size. All the while the stars would be moving three times faster across the sky. Observers at other points on Mercury's surface
would see different but equally bizarre motions. Temperature variations on Mercury are the most extreme in the solar system ranging
from 90 K to 700 K. The temperature on Venus is slightly hotter but very stable. Mercury is in many ways similar to the Moon: its
surface is heavily cratered and very old; it has no plate tectonics. On the other hand, Mercury is much denser than the Moon (5.43
gm/cm3 vs 3.34). Mercury is the second densest major body in the solar system, after Earth. Actually Earth's density is due in part to
gravitational compression; if not for this, Mercury would be denser than Earth. This indicates that Mercury's dense iron core is
relatively larger than Earth's, probably comprising the majority of the planet. Mercury therefore has only a relatively thin silicate
mantle and crust. Mercury's interior is dominated by a large iron core whose radius is 1800 to 1900 km. The silicate outer shell
(analogous to Earth's mantle and crust) is only 500 to 600 km thick. At least some of the core is probably molten. Mercury actually
has a very thin atmosphere consisting of atoms blasted off its surface by the solar wind. Because Mercury is so hot, these atoms
quickly escape into space. Thus in contrast to the Earth and Venus whose atmospheres are stable, Mercury's atmosphere is constantly
being replenished. The surface of Mercury exhibits enormous escarpments, some up to hundreds of kilometers in length and as much
as three kilometers high. Some cut thru the rings of craters and other features in such a way as to indicate that they were formed by
compression. It is estimated that the surface area of Mercury shrank by about 0.1% (or a decrease of about 1 km in the planet's radius).
One of the largest features on Mercury's surface is the Caloris Basin (right); it is about 1300 km in diameter. It is thought to be similar
to the large basins (maria) on the Moon. Like the lunar basins, it was probably caused by a very large impact early in the history of the
solar system.
That impact was probably also responsible for the odd terrain on the exact opposite side of the planet (left). In addition to the heavily
cratered terrain, Mercury also has regions of relatively smooth plains. Some may be the result of ancient volcanic activity but some
may be the result of the deposition of ejecta from cratering impacts. A reanalysis of the Mariner data provides some preliminary
evidence of recent volcanism on Mercury. But more data will be needed for confirmation. Amazingly, radar observations of Mercury's
north pole (a region not mapped by Mariner 10) show evidence of water ice in the protected shadows of some craters. Mercury has a
small magnetic field whose strength is about 1% of Earth's. Mercury has no known satellites. Mercury is often visible with binoculars
or even the unaided eye, but it is always very near the Sun and difficult to see in the twilight sky. There are several Web sites that
show the current position of Mercury (and the other planets) in the sky. More detailed and customized charts can be created with a
planetarium program.
2) Venus 金星 jīnxīng Venus is the Roman goddess of love and beauty. She is known as Aphrodite in Greek
mythology. The planet is so named probably because it is the brightest of the planets known to the ancients.
This is the symbol for Venus:
Venus is the second planet from the Sun, and the sixth largest of all the nine planets. Venus' hot temperature is due to what we call
"the Greenhouse Effect." The large amount of carbon dioxide in Venus' atmosphere acts like a blanket. The heat gets trapped
underneath the thick layer of clouds. Because the heat has nowhere to go, Venus gets hotter and stays hot. Venus probably once had
large amounts of water like Earth, but it all boiled away. The same thing would have happened to the Earth had it been just a little
closer to the Sun. Because Venus is so similar to our Earth, we sometimes call it Earth's "sister planet." In what ways are they similar?
~ Venus is only slightly smaller than Earth
~ Both have few craters indicating relatively young surfaces.
~ Their densities and chemical compositions are similar. Most of Venus' surface consists of gently rolling plains. You won't find many
mountains or hills Data from the Magellan spacecraft shows that much of Venus' surface is covered by lava flows. There are many
large volcanoes (like the ones in Hawaii) such as Sif Mons (right). Scientists have recently found that there are still many active
volcanoes on Venus! Magellan's images show a wide variety of interesting and unique features including the "pancake volcanoes."
(left) Look for Venus! Venus is usually visible with the naked eye. Though it's not correct to call it so, Venus is sometimes called the
"morning star" or the "evening star." It is by far the brightest "star" in the sky.
3) Earth 地球 dìqiú Earth is the only planet whose English name does not derive from Greek or Roman mythology.
The name comes from Old English and Germanic language. There are, of course, hundreds of other names for the
planet in other languages.
This is the symbol for Earth:
Earth is the third planet from the Sun, and the fifth largest of the nine planets Earth, of course, can be studied
without the aid of spacecraft. It was not until the twentieth century that we had maps of the entire planet.
Pictures of our planet taken from space are very important! They are a big help in predicting the weather especially in tracking and predicting hurricanes. They are also extraordinarily beautiful. The Earth's surface is
very young. This means that the Earth's surface has changed a lot from when it was first formed. Erosion and
tectonic processes (like earthquakes) destroy, recreate and reshape most of the Earth's surface. 71 % of the
Earth's surface is covered with water. Earth is the only planet on which water can exist in liquid form on the
surface. Water is essential for life as we know it. The Earth's vast oceans keep temperatures stable - important
for life on our planet. Water is also responsible for most of the erosion and weathering of the Earth's continents,
a process unique in our solar system. The Earth's atmosphere is 77% nitrogen, 21% oxygen, with traces of argon,
carbon dioxide and water. The carbon dioxide in the Earth's atmosphere is very important. Carbon dioxide helps to
maintain the Earth's temperature by way of the "Greenhouse Effect." The Greenhouse Effect warms the Earth's
temperature; without it, the oceans would freeze and life as we know it would be impossible. Besides being the
most interesting and unique of all the planets, our Earth is also the most beautiful. From space, the Earth's white
clouds, blue oceans and brown lands seem to shine against the black backdrop of our solar system.
4) Mars 火星 huǒxīng Mars is the god of War. In Greek mythology, he is known as Ares. The planet probably got
this name due to its red color; Mars is sometimes referred to as the "Red Planet." The name of the month March
derives from Mars.
This is the symbol for Mars:
Mars is the fourth planet from the Sun, and the seventh largest of the nine planets. Mars comes in second place
(Earth being in first) for having the most highly varied and interesting terrain of any of the terrestrial planets.
Check out some of these spectacular features: Olympus Mons - The largest mountain in the Solar System! Olympus
Mons rises a full 24 km (78,000 ft.) above the surrounding plain. Its base is more than 500 km across and is
rimmed by a cliff 6 km (20,000 ft) high!
Valles Marineris - A network of canyons that run 4000 km long and stand from 2 to 7 km tall!
Tharsis - A huge bulge on the Martian surface. It's about 4000 km across and 10 km high!
Though there is no water on Mars now, it is thought that large lakes or even oceans may have once existed on this
planet. Clear evidence of water erosion can be seen in old river channels and floodplains. It seems that water was
only around for a very short while and very long ago. The southern hemisphere of Mars is mostly ancient cratered
highlands (left) - much like our own Moon. In contrast, most of the northern hemisphere consists of plains which
have undergone changes since the planet was first formed. The northern hemisphere is also lower in elevation. On
Aug 6, 1996, David McKay announced the first identification of organic compounds in a Martian meteorite. It is
suggested this may be evidence of ancient Martian life. This sounds exciting, but always remember that
"extraordinary claims require extraordinary evidence." Scientists must do much more studying and research before
we can be confident about this claim. Look for Mars! When it is in the nighttime sky, Mars is easily visible with the
naked eye. Its brightness varies greatly depending on where it is relative to the Earth.
5) Jupiter 木星 mùxīng Jupiter (a.k.a. "Jove") was the King of the Roman Gods and the patron of the Roman state.
To the ancient Greeks, he was known as Zeus, ruler of the Greek Gods and Mount Olympus.
This is the symbol for Jupiter:
upiter is the fifth planet from the Sun and by far the largest of all nine planets. Jupiter is more than twice as
massive as all the other planets combined - It's 318 times bigger than the Earth! Jupiter does not have a solid
surface due to its gaseous composition. The swirls and bands we see when looking at Jupiter are the tops of clouds
high in its atmosphere Jupiter has high speed winds that whip by at more than 400 mph! These winds are trapped in
the planet's wide bands of latitude. Each band has a slightly different chemical make-up and temperature from the
others. This gives it a color which is different from surrounding bands. The light colored bands are called "zones."
The dark colored bands are called "belts." The vivid colors seen in Jupiter's clouds are probably the result of
subtle chemical reactions in Jupiter's atmosphere. The clouds are a different color, depending on its altitude. Blue
clouds are lowest, followed by brown and white clouds. Red clouds are the highest. Sometimes we see the lower
cloud layers through holes in the upper cloud layers. Jupiter's most outstanding and interesting feature is called
"The Great Red Spot." The Great Red Spot is an oval about 12,000 km by 25,000 km - big enough to hold two
Earths! Jupiter also has other smaller similar spots. The Great Red Spot is a high-pressure region whose cloud tops
are much higher and colder than the surrounding areas. Jupiter has faint rings like Saturn's, but much
smaller. Unlike Saturn's, Jupiter's rings are dark. They're probably composed of very small grains of rocky
material. Look for Jupiter! When it is in the nighttime sky, Jupiter is often the brightest "star" in the sky (it is
second only to Venus, which is seldom visible in a dark sky). The four large Galilean moons are easily visible with a
pair of binoculars. You can even see a few of Jupiter's bands and the Great Red Spot with a small astronomical
telescope!
6) Saturn 土星 tǔxīng In Roman mythology, Saturn is the god of agriculture. He is known as Cronus in Greek
mythology. Cronus was the father of Zeus (Jupiter). Saturn is the root of the English word "Saturday."
This is the symbol for Saturn:
Saturn is the sixth planet from the Sun, and the second largest of the nine planets Like Jupiter, Saturn has bands
(left). Saturn's bands, however, are much fainter. The bands are also much wider near the equator. Saturn has
long-lived "spots" as well (right). Just like Jupiter's "Great Red Spot," they are areas where big storms are
occurring. Saturn's rings, unlike the rings of the other gas planets, are very bright. Though they look "solid" or
continuous from the Earth, the rings are actually composed of many, many small particles circling Saturn at their
own speeds. They range in size from a centimeter to several meters. A few kilometer-sized objects are also
likely! Saturn's rings are extraordinarily thin. Even though they measure about 250,000 km across, they're no more
than 1.5 kilometers thick. Despite their impressive appearance, there's really very little material in the rings. If
the rings were compressed into a single body it would be no more than 100 km across! When viewing Saturn through
a small telescope, it appears a bit "squished." This is because its structure isn't very rigid (it's mostly gas and
liquid), and it becomes slightly "compressed" as it spins very quickly. Look for Saturn! When it is in the nighttime
sky, Saturn is easily visible to the naked eye. Though it is not nearly as bright as Jupiter, it is easy to identify as a
planet because it doesn't "twinkle" like the stars do. The rings and the larger moons are visible with a small
astronomical telescope.
7) Uranus 天王星 tiānwángxīng Uranus is the ancient Greek God of the Heavens - the earliest supreme god. He was
the father of Cronus (also known as Saturn in Roman mythology) and of the Cyclopes and Titans (predecessors of
the Olympian gods).
This is the symbol for Uranus:
Uranus is the seventh planet from the Sun and the third largest of the nine planets (in size). Uranus is larger in
size but smaller in weight than Neptune. Like the other gas planets, Uranus has bands of clouds that blow around
rapidly. Uranus' bands are very, very faint. They can only be seen with special treatment of pictures obtained by
the Voyager 2 spacecraft. Here are examples of what Uranus looks like before and after image
enhancement. Uranus' blue color is the result of a gas called "methane" found in the planet's upper atmosphere.
Uranus may have colored bands like Jupiter's, but they are hidden from view by the overlaying methane
layer. Like the other gas planets, Uranus has rings. Uranus' rings are very dark like Jupiter's rings. The rings are
made up of fairly large particles ranging up to 10 meters across in addition to fine dust - much like the rings of
Saturn. There are 11 known rings, all are very faint. Uranus' brightest ring is known as the "Epsilon" ring. Look for
Uranus! Uranus is sometimes just barely visible with the naked eye on a very clear night; it is fairly easy to spot
with binoculars (if you know exactly where to look). A small astronomical telescope will show a small disk.
8) Neptune 海王星 hǎiwángxīng In Roman mythology Neptune was the god of the Sea. He is known as Poseidon in
Greek mythology. The planet was probably named after the sea gods because of its deep blue color.
This is the symbol for Neptune:
Neptune is the eighth planet from the Sun and the fourth largest (by size) of the nine planets. Neptune is smaller
in size but it's heavier than Uranus. Neptune's blue color is the result of a gas called "methane" in its atmosphere.
Like the other gas planets, Neptune has rapid winds trapped in "bands" of latitude and large storms. Neptune's
winds are the fastest in the solar system, reaching 2000 km/hour! At the time of Voyager's flyby, Neptune's most
outstanding feature was the "Great Dark Spot" in the southern hemisphere. It was about half the size as Jupiter's
"Great Red Spot" - about 1 Earth would fit into it. Neptune's winds blew the Great Dark Spot westward at 300
meters/second (700 mph)! Voyager 2 also saw a smaller dark spot in the southern hemisphere and a small irregular
white cloud that zipped around Neptune every 16 hours or so now. This feature is known as "The Scooter." Recently,
however, the Hubble Space Telescope (HST) showed that the Great Dark Spot has disappeared! Scientists think
that it has either dissipated (like our storms do) or is currently being hidden by Neptune's atmosphere. Also, HST
discovered a new dark spot in Neptune's northern hemisphere. This shows that Neptune's atmosphere changes
rapidly. Neptune also has rings. The Voyager 2 spacecraft showed scientists that Neptune indeed has complete
rings with bright clumps. Like Uranus and Jupiter, Neptune's rings are very dark and very faint. Scientists still
haven't figured out what they are made of yet. Look for Neptune! Neptune can be seen with binoculars (if you
know exactly where to look) but a large telescope is needed to see anything other than a tiny disk.
9) Pluto 冥王星 míngwángxīng In Roman mythology, Pluto is the god of the underworld. In Greek mythology, he is
known as Hades, ruler of the underworld. The planet received this name perhaps because it's so far from the Sun
that it is in perpetual darkness.
This is the symbol for Pluto:
Pluto used to be the farthest planet from the Sun (usually) and by far the smallest of the nine planets. Pluto is
smaller than seven of the solar system's moons!
Now it's officially not a planet at all, just a "dwarf planet". To date, not much is known about the planet, Pluto.
Most of the information we have is largely based on speculation and inference. Its moon, Charon, helps scientists
with various calculations relating to the properties and characteristics of Pluto. Pluto is so far away that even the
Hubble Space Telescope can make out only the largest features on its surface. This is why available pictures look
so blocky and ambiguous. ike Uranus, Pluto seems to be lying on its "side." Pluto's equator points straight up and one
of its poles point directly at the Sun. Look for Pluto! Pluto can be seen with an amateur telescope - but it is not
easy. You will need detailed charts and a few days of careful observations to actually find it.
COMPOSITION
ROCKY PLANETS (Mercury - Venus - Earth - Mars - Pluto)
The rocky planets are mostly made up of rock and metal. These planets are very heavy and move slowly. They also
do not have rings and very few moons.
GAS PLANETS (Jupiter - Saturn - Uranus - Neptune)
The gas planets are mostly made up of gases (hydrogen and helium). These planets are light for their sizes (just
like a big air balloon) and move quickly. They have rings and lots of moons.
SIZE
SMALL PLANETS (Mercury - Venus - Earth - Mars - Pluto)
The small planets have diameters less than 13000 km across. Mercury and Pluto are sometimes referred to as
lesser planets because they are so tiny.
GIANT PLANETS (Jupiter - Saturn - Uranus - Neptune)
The giant planets have diameters greater than 48000 km. The giant planets are sometimes also referred to as gas
giants.