Study Material - Astro Quest 2018-2019 - Corpus Christi School

Astro Quest 2018-2019

Study Material
Class 3rd and 4th
Scientific Development and Research Organisation, New Delhi

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Topics
   1. Inner Planets
   2. Outer Planets

Inner Planets

Earth‖s inner solar system companions, Mercury, Venus, the Moon, and Mars, are diverse bodies,
each of which provides data critical for understanding the formation and evolution of habitable
worlds like our own. These terrestrial (or rocky) planetary bodies have a range of compositions
and geologic histories—each is a unique world that reveals information crucial for understanding
the past, present, and future of Earth.

Within the past decade, initial results from the MESSENGER spacecraft have revealed aspects of
the complex early history of Mercury. Venus, with its greenhouse atmosphere, Earth-like size,
and volcanic surface, has been a focus of recent international missions but remains a challenge
for in situ exploration. Recent exploration of the Moon has revealed a geochemically complex
surface and polar volatiles (e.g., hydrogen or ice), leading to significant unanswered questions
about the Earth-Moon system. The detailed study of Mars over the past 15 years has greatly
increased our understanding of its history, which in turn has allowed us to formulate specific
questions to constrain terrestrial planet origin, evolution, and habitability.

Thus, the initial reconnaissance of the terrestrial planets is transitioning to more in-depth, in
study. In this new phase, specific observations can be made to allow the testing of hypotheses
and significant progress in finding answers to basic questions that can lead us to an improved
understanding of the origin and evolution of all of the terrestrial planets, including Earth.
All three of the cross cutting science themes for the exploration of the solar system include the
inner planets, and studying the inner planets is vital to answering several of the priority
questions in each of the three themes. The building new worlds theme includes the question,
What governed the accretion, supply of water, chemistry, and internal differentiation of the inner
planets and the evolution of their atmospheres, and what roles did bombardment by large

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projectiles play? The planetary habitats theme includes the question, Did Mars or Venus host
ancient aqueous environments conducive to early life, and is there evidence that life emerged?
The workings of the solar systems theme includes two questions that can be answered by the
study of the inner planets. First, the lunar impact record holds key information of relevance to
the question, What solar system bodies endanger Earth‖s biosphere, and what mechanisms shield
it? Second, studies of Venus and Mars relate directly to the question, Can understanding the
roles of physics, chemistry, geology, and dynamics in driving planetary atmospheres and climates
lead to a better understanding of climate change on Earth? Questions about how the inner
planets formed, about their composition, and about the processes by which they have evolved
are a major part of the question, How have the myriad chemical and physical processes that
shaped the solar system operated, interacted, and evolved over time?

Mercury

Mercury‖s orbit is not a perfect circle like most of the other planets. It‖s actually egg-shaped. At
times, Mercury‖s orbit brings it closer to the Sun than other times, while all the other planets
that have circular orbits are always the same distance from the Sun.

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The planet Mercury is the closest to the sun and the quickest to revolve around it. It‖s a very
dense planet with a solid iron core and a thick crust. That said, Mercury is small overall and so
has weak gravity. It can‖t even hold onto an atmosphere! This makes it unable to regulate its
temperature such that it fluctuates dramatically.

How Did Mercury Get its Name?
In Roman mythology, Mercury was the messenger of the Gods. He was super quick, often
depicted wearing winged sandals. Likewise, Mercury is the fastest of the planets. Its orbit of 88
days is the shortest in our Solar System.

A Dense Planet
Despite its speed, Mercury is awfully dense. The inside of the planet is almost entirely iron,
either solid or in the form of magma. The earth‖s core has a similar makeup, but it also has a
large mantle which Mercury does not. Instead, it has only two very thin layers above the core.

This imbalanced structure has to do with how the Solar System is arranged. Planets on the
inside, like Mercury and Venus, are metallic and rocky. That‖s because, long ago, the sun pushed

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away or destroyed anything lighter. Gas got thrown outwards, and any ice close to the center
melted. Mercury, the closest planet to the sun, has none of these things. It‖s pretty much just
metal.

Mercury has a Wrinkle!
Like the layers of the Earth, Mercury‖s layers interact with each other. Yet, as Mercury‖s core is by
far the largest and most powerful layer, these interactions aren‖t what we might expect.

The most significant of them is core shrinkage. Mercury‖s outer core is liquid, similar to the
earth‖s. But, it‖s also cooling slowly. As solids are denser than liquids, this means that the
planet‖s core is getting smaller over time.

In fact, the whole planet is shrinking as compression of Mercury‖s inner layers pulls the top ones
down. Of course, its crust is a solid and can‖t just ―shrink.‖ Rather, it gets crushed up as it
descends. This has lead to the creation of what we call lobate scarps on the planet‖s surface.
These odd landforms are basically just wrinkles in the crust.

Mercury Has No Atmosphere
Another notable feature about Mercury is that it has no atmosphere. That

means it doesn’t trap gas around it; it has no ‘air.’This is the result of two

things. The first is pretty simple. Although mercury is dense, it doesn’t have

a lot of mass overall. As a result, it has weak gravity and can’t hold things

down very well. In fact, if you went there, you would only weight about ⅓ as

much as you do on earth.

The second reason Mercury has no atmosphere has to do with the sun. The sun emits lots of
radiation as part of what‖s called solar wind. On earth, our atmosphere protects us from these
winds in a sacrificial manner. The wind destroys our atmosphere instead of hitting us.

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Although light gets through our atmosphere, solar wind does not. This filtering saves our lives
every day

Temperature Extremes
For many planets, having an atmosphere allows them to trap heat. This keeps them within a
certain temperature range. But of course, Mercury doesn‖t have an atmosphere. Its temperature
depends upon its exposure to the sun.

On the side that‖s facing the sun, things can get really hot. The surface climbs to temperatures of
up to 870 degrees Fahrenheit! Oppositely, Mercury‖s dark receives very little heat. It can become
as cold as -300 degrees Fahrenheit.

Venus

The Planet Venus is the second planet from the sun and the hottest in our solar system. It‖s a dry
world whose water has all evaporated due to rampant climate change. Yet, you‖d never suspect
after seeing it in the sky. Venus appears as a bright, beautiful object which we can observe
directly at sunrise. For this reason, it‖s often called the Morning Star.

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In Roman mythology, Venus was the goddess of love and beauty. The Romans might have given
the planet this name because it shined so beautifully!
Yet, the Romans had no idea what Venus is really like when they named it. Until Russia sent
spacecraft to the planet, no one did. That‖s because it‖s covered in extremely thick clouds.
Venus‖s atmosphere is actually 90x thicker than that of the Earth!So, for a long time, its features
were a mystery to us. Nowadays, having photographed the surface, we know that it‖s anything
but lovely.

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Not So Beautiful After All
When people first sent spacecraft to Venus (in the 70‖s), we found out that it‖s really an awful
place! For starters, it‖s extremely hot – hotter even than Mercury, which is closer to the sun. This
makes Venus a fiery wasteland. It‖s totally covered in volcanic features, too. That‖s because its
heat keeps lava warm and liquidy so that it can flow great distances.

A Deformed Surface
Where there‖s not just lava, Venus is marked by distorted landforms. We can find craggy
landmasses called tessera throughout. They‖re kind of like warped mountain ranges. Yet, they‖re
also the size of continents here on earth. This gives much of Venus a shifting, hilly topography.

All of this planetary messiness has to do with Venus‖s structure. Unlike Earth, Venus doesn‖t
seem to have a tectonic system.Yet, it did use to have extremely strong volcanism. For a long
time, magma kept upwelling through its surface, bending the land out of shape. Scientists don‖t
know if this is still going on or if it has completely stopped. Regardless, it has already made
Venus a frightening sight.

Venus’s Atmosphere
The atmosphere on Venus is even worse than its surface. It‖s made up of a thick blanket of
clouds. Clouds aren‖t that bad, right? Wrong – these clouds are literally made out of acid and
carbon dioxide! Their toxic mixture ensures that no life like that on Earth could survive on
Venus.
But, it wasn‖t always like this. Astronomers, like Carl Sagan, believe that Venus was actually
habitable a long time ago. And this kind of makes sense. The planet‖s composition is similar to
the earth‖s, and it‖s not that much closer to the sun. So, what makes it so inhospitable now?

Global Warming

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Venus‖s unbearable heat comes from a terrible cycle of climate change. Before it all began, the
planet may have been quite like the Earth. The main difference was just that it was a little closer
to the sun. But, as it turns out, that difference mattered A LOT.

This has to do with what‖s called the greenhouse effect. Here‖s how it works: When the sun‖s
heat reaches a planet, its atmosphere will trap some of it. Certain gases help to trap heat better
than others. Carbon dioxide and water vapor are the best at doing so.

On Earth, the heating is regulated by other processes (glacial cooling, oceans absorbing heat,
etc.). But, Venus‖s slightly increased temperature upset this balance. Its warmer climate caused a
lot of the water there to evaporate. Of course, this made even more water vapor, further heating
the planet. And so, a vicious cycle of heating began.
Eventually, all of the water on Venus evaporated. It became like a giant oven, trapping tons of
heat and baking its own surface. The end result: Venus is now a terribly hot, inhospitable place.

Did You Know?
On Venus, the sun rises in the east and sets in the west. This is the opposite of how the sun
appears to move from earth.

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Earth

The Earth is the planet we all live on! As far as we know, it is the only planet in our solar system
that can support life. This is just one of many interesting facts about Earth!

The Earth Orbits and Rotates

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The Earth is the third planet from the Sun. Even though it is one of the closer planets, it is still
93 million miles away from the sun. Since it‖s so far away, it takes the Earth about 365 days to
circle all the way around the sun. That‖s why a year is 365 days long!
The Earth doesn‖t just orbit the sun, it also spins like a top! This rotation is the reason why we
get night and day. Imagine drawing a line from the North Pole to the South Pole. The Earth
rotates around that line, or axis. If you‖re having trouble imagining that, think of a globe! A globe
spins around its axis the same way the Earth does.

The Earth is on a Tilt!
Another important fact about Earth is that it‖s tilted! If we compare the line we drew earlier to
Earth‖s orbit, our line wouldn‖t be exactly up and down. Instead, it would tilt slightly to one side,
much like it is on the globe!

This means that parts of Earth are closer to the Sun than others. But the part that is closest
changes as the Earth moves around the Sun! The part that is closer during a certain part of the
year will be warmer than the part that is farther away. This is why we have seasons!

How Big is the Earth?
The Earth is the biggest of all the terrestrial planets. The terrestrial planets are the dense, rocky
planets found in the inner Solar System. But the Earth is much smaller than the gas planets, like
Saturn and Jupiter, that are in the outer solar system. If you cut a piece of string long enough to
wrap it around the Earth, it‖d be 24,901 miles long. That‖s longer than 365,000 football fields!

Earth’s Gravity
Gravity is the force that holds us down to Earth‖s surface so we don‖t go drifting off into space! It
also plays a lot of important roles in the solar system. For example, it holds all the planets in
orbit around the sun.

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The amount of gravity a planet has depends on its mass. The bigger and denser a planet is, the
more gravity it has! Earth‖s size means it has enough gravity to hold onto an atmosphere.
Smaller planets, like Mars and Mercury, either have a very small atmosphere or none at all!

Earth’s Atmosphere
Earth‖s atmosphere is very important for keeping us alive! First, it contains the oxygen we need
to breathe. But it also protects us from the dangers of space!
The atmosphere blocks harmful radiation from the sun from reaching the Earth‖s surface. If you
get sunburnt from being outside, it‖d be much worse without an atmosphere!

The atmosphere also prevents most meteors from reaching the Earth‖s surface. Small meteors
burn up in the atmosphere before they get anywhere near the surface!

The Magnetized Earth
Another cool fact about Earth is that it has a magnetic field! The magnetic field exists because of
movement of material in the Earth‖s inner and outer core. The magnetic field protects the Earth
from solar wind, which is a stream of material released from the Sun. Without the magnetic field,
the solar wind would knock off parts of the atmosphere.

The Moon

The Earth is the only planet in our solar system that
has only one moon! Just like gravity holds the planets
in orbit around the sun, the Earth‖s moon stays in its
orbit because of Earth‖s gravity.

The moon also has some important effects on the
Earth. For example, the moon‖s gravity causes the tides
in our oceans.

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Life on Earth
The Earth‖s temperature, atmosphere, and many other factors are just right to keep us alive.
The Earth is just far enough away from the sun that it is at the right temperature to have liquid
water on its surface. In fact, most of Earth‖s surface is covered in water, which is very important
for living things.
Mars

This red planet is the fourth in the Solar System, and actually the second smallest. The now
desolate Mars shows signs that it had liquid water and a similar atmosphere to the Earth‖s at one
time. For these reasons, Mars is one of the most similar planets to Earth in the Solar System!

Numbers to Know
1 Orbit of Sun           686.98 Days
1 Rotation               24 hours 37 mins
Mass                    10% of Earth
Volume                  15% of Earth

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Escape Velocity         18,024 km/h (11,200 mph)
Distance From Sun       229 million kilometers (142 million miles)
Max Temperature         36°C (98°F)
Min Temperature         -123°C (-190°F)
Atmosphere              CO2 95.32%, N2 2.7%, Ar 1.6%, O2 0.13%, CO 0.08%
Diameter                6794 Kilometers (4,222 Miles)

Deep Canyons to Sky High Mountains
Mars has higher mountains and deeper canyons than any other planet in our solar system. Its
biggest canyon is Valles Marineris. On Earth this canyon would stretch from New York City to Los
Angeles, making the Grand Canyon look tiny.

Mars also has the Solar System‖s biggest volcano, Olympus Mons. This young volcano is nearly 3
times larger than Mount Everest. Olympus Mons age leads scientists to believe it‖s still active,
which means it could erupt!

How Did Mars Get its Name?

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You may sometimes hear Mars referred to as the “Red Planet” because the planet‖s surface
appears red. The soil color comes from the high levels of iron oxide minerals in the rock.

The planet actually got its name from its color. Roman astronomers saw the red color and
thought of blood. For this reason, they named the planet after the Roman god of war.

What is the Gravity Like on Mars?
Mars has less mass than the Earth, so it has less gravity too. The gravity is measured to be about
3.7 m/s² while the Earth‖s gravity is about 9.8 m/s². This means you would only experience 38%
of the gravity you feel on Earth. So if you weighed 100 pounds on the Earth, you would only
weigh 38 pounds on Mars.

Weighing 62% less would make moving a lot more fun. This is because our muscles and bones
have become used to working harder on Earth. With lower gravity, you could jump higher and
throw things like baseballs much farther!

The Planet

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Mars excites scientists because the surface shows signs of water erosion. Pictures taken by
spacecraft have led scientists to believe that there were once lakes, rivers, and oceans on the
planet. This is important because it means there could have been life on Mars. Liquid water is
one of the indicators that scientists look for in their search for extraterrestrial life.

The planet doesn‖t have liquid water on its surface anymore, which decreases the probability of
there being life on Mars. This is because the gravity isn‖t strong enough to hold onto the gases in
the atmosphere. As Mars‖ atmosphere slowly depleted into outer space, all the water evaporated.
Today, the only water left on the dusty planet is either frozen in the polar caps or underground.

The Moons of Mars

Mars has two different moons, Deimos and Phobos. Mars‖ moons were both found by an
astronomer named Asaph Hall. Hall searched and found the moons with a telescope in August
1877.

Exploration
The ways scientists have been exploring Mars has changed a lot since the 1960‖s. At first, the
only way modern explorers could study the planet was with satellites. These satellites would fly

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close to the surface and take pictures. They would then send these pictures back to Earth for
scientists to look at.

Eventually, scientists were able to put spacecraft into orbit around the planet. These types of
missions allowed researchers to get even more information on the Mars.

Today, scientists and researchers are able to land spacecraft on the surface of Mars. The most
recent spacecraft to land there is the Curiosity Rover. The rover launched from Earth in 2011 and
landed in 2012. Since then, the Curiosity Rover has given scientists a lot of insight into the
habitability of the planet.

Outer Planets

There is a very great distance between the inner and outer planets. This region is called the
Asteroid Belt and large chunks of rock swarm around and around in it.

Except for Pluto, the outer planets are alike in a lot of ways. They are much bigger than the inner
planets. They are made mostly of hydrogen and helium. The hydrogen and helium are in the
form of gas in the planets' atmospheres. The outer planets have a lot of atmosphere.

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The outermost part of these planets may be slushy. Below the surface, hydrogen and helium are
in a liquid form. At the center is a rocky core. Each of these huge planets has its own system of
moons.

Rings around Saturn have been seen for many years. They are probably made mostly of water,
ice, and other icy particles. Recently, rings have been discovered around two more giant planets
— Jupiter and Uranus. Scientists expect to find rings around Neptune, too.

Jupiter
Jupiter is the Roman name for Zeus, the king of gods in Greek mythology. He overthrew his
father Saturn to become king of the gods. He then split the Universe with his brothers Neptune
and Pluto.

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How much would you weigh on Jupiter?
If you traveled there on vacation, you would be very heavy. If you weigh 70 pounds (32 kg) on
Earth, on Jupiter you would weigh 185 pounds (84 kg). This is because Jupiter is much bigger
than Earth and so has stronger gravity.

The Planet
Jupiter is by far the largest planet in our Solar System. It could fit over 1000 Earths inside!

Jupiter is a very stormy planet. There are storms found throughout the atmosphere, and most of
the storms seem to never end. The many different cloud formations and storms in the
atmosphere also make Jupiter a very colorful planet.
The Great Red Spot, visible in the picture above to the right, is where a giant storm has been
raging for at least 300 years. This red spot is also called “The Eye of Jupiter” because of its
shape. This storm‖s super hurricane winds blow across an area larger than the Earth.

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Jupiter is a gas giant because it does not have a solid surface. Don‖t be fooled, though, you
couldn‖t just travel through Jupiter! Its center has so much pressure that the hydrogen actually
can become liquid and even solid!

Did you know Jupiter has rings?
They are faint and are only visible when Jupiter
passes in front of the Sun. This is because the
light from the Sun lights them up for us to see
here on Earth.
There are three rings in all. They are the
Gossamer Ring, Main Ring, and Halo Ring.

Moons

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Jupiter has 50 official moons and 12 provisional (unofficial) moons. The four largest and most
well-known were discovered by Galileo in the year 1610. Their names are Io, Europa, Ganymede,
and Callisto. Some of the other moons are Adrastea, Ananke, Carme, Elara, Himalia, Leda,
Lysithea, Metis, Pasiphae, Sinope, and Thebe.

Saturn

Saturn’s Outer Rings
The outer rings of Saturn are not as visible as the inner rings. That is because the outer rings do
not reflect as much light as the inner rings. Scientists are still discovering rings around Saturn.
There is a theory among astronomers that planetary rings are only temporary. The rings may
only last a few million years. In comparison to the age of the Solar System of roughly 4.5 billion
years, that isn‖t very long. If this is true then in the distant future the rings will disappear.
Perhaps another planet will have a set of rings instead.

Let’s Meet the Outer Rings
These rings of Saturn are over 85,000 miles away. There are a few interesting facts to note
about these rings. For example, the F Ring is very narrow and we don‖t know why. Rings usually
spread out and become wider. This is because the particles in the rings will collide with one
another and then move away. There is a similar thin ring around Uranus. Scientists believe that
the thinness of this ring might be due to the shepherding moons.

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The E-ring is centered on Saturn‖s moon Enceladus. The thickest area of the E ring is right at
Enceladus‖ orbit. This suggests that Enceladus is the source of the particles in the E ring. Turns
out, this is correct. On the south pole Enceladus there is a geyser. This geyser shoots out jets of
water particles into space. These particles are what created the E-ring. Astronomers are still
unclear on how the geyser works or where this water originates.

F RING
Distance from Saturn (miles): 87,104
Width (miles): 19-311
Description: Active ring with features that change every few hours.
Named after: None

JANUS/EPIMETHEUS RING
Distance from Saturn (miles): 92,584 – 95,691
Width (miles): 3,107
Description: Faint dust ring around the region occupied by the orbits of Saturn‖s moons. These
moons are Janus and Epimetheus.
Named after: Saturn‖s moons Janus and Epimetheus

G RING
Distance from Saturn (miles): 103,148 – 108,740
Width (miles): 5,592
Description: Thin, faint ring that lies between the F ring and E ring.
Named after: None

METHONE RING ARC
Distance from Saturn (miles): 120,689
Width (miles): Unknown
Description: A faint ring arc thought to have come from dust ejected from impacts with Saturn‖s
moon Methone.

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Named after: Saturn‖s moon Methone.

ANTHE RING ARC
Distance from Saturn (miles): 122,823
Width (miles): Unknown
Description: A faint ring arc thought to have come from dust ejected from impacts with Saturn‖s
moon Anthe.
Named after: Saturn‖s moon Anthe.

PALLENE RING
Distance from Saturn (miles): 131,109 – 132,663
Width (miles): 1,553
Description: A faint dust ring thought to have come from dust ejected from impacts with Saturn‖s
moon Pallene.
Named after: Saturn‖s moon Pallene.

E RING
Distance from Saturn (miles): 111,847 – 298,258
Width (miles): 186,411
Description: Outermost ring and extremely wide.
Named after: None

PHOEBE RING
Distance from Saturn (miles): ~2,485,485 – > 8,077,826
Width (miles): None
Description: A disk of material close to the orbit of Saturn‖s moon, Phoebe.
Named after: Saturn‖s moon Phoebe.

Note: Remember that “~” means “around” or “approximately” and “>” means “greater than” or
“more than”.

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Uranus
This blue planet is the seventh from the Sun in our Solar System. Uranus spins on its side, so its
rings rotate up and down around the planet. This is different from the rings that rotate around
the middles of Saturn and Neptune. The planets odd rotation probably exists because of a
collision with an object the size of Earth.

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Who Discovered Uranus?
Astronomer William Herschel first saw Uranus in 1781 while looking for stars. Herschel initially
thought what he was seeing was a comet, so he began to track it. When he reported his findings,
a man named Anders Lexell used Herschel‖s observations to calculate the orbit.

The two astronomers determined that the object must be a planet past Saturn. This made Uranus
the seventh planet in the Solar System, and the first found with a telescope.

How Did Uranus Get its Name?
Uranus is the god of the sky and the only planet with a name based on Greek mythology. The
planet wasn‖t named until 70 years after it‖s discovery. William Herschel wanted to name the
planet Georgium Sidus after King George. Very few scientists liked this name so it was rarely
used.

Astronomers thought the name Uranus made sense because it follows the pattern of mythology
and planets in the Solar System. In the mythology, Uranus is the Greek version of Caelus. Caelus
is the father of Saturn, and Saturn is the father of Jupiter. In the Solar System, Uranus is the
seventh planet, Saturn is the sixth, and Jupiter is the fifth.

Gravity on Uranus
Compared to other planets in the Solar System, Uranus has similar gravity to Earth. Uranus‖
gravity is 8.9 m/s² while Earth‖s gravity is 9.8 m/s². The gravity on Uranus is only a little bit
weaker than the gravity on Earth. For example, if you weigh 100 pounds on Earth, you would
weigh about 91 pounds on Uranus.

Why is Uranus Blue?
The atmosphere of Uranus has methane in it. When hit by light from the Sun, the methane
absorbs the red light and reflects back the blue light. This reflected blue light is what our eyes
are able to see.

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What is Uranus Made of?
Unlike other gas giants, Uranus‖ mantle is mostly icy water and ammonia. Because of all the ice,
the planet is often times called an ice giant instead of a gas giant.

The ice in the mantle isn‖t like what you find in your freezer, this ice is hot! The ice can‖t melt
because of the extreme pressure on the planet that squishes molecules together. This forms a
kind of hot slush called a water-ammonia ocean.

Beneath the ice scientists believe there is a layer of liquid diamond! This forms when carbon in
the atmosphere condenses into diamonds and rains down. The best part? The huge solid
diamonds floating in the ocean.

Beneath the ice and diamond mantle, there is a small rocky core made of iron and nickel. Above
the ocean, there is an atmosphere made of hydrogen, helium, and methane gases and an outer
atmosphere made of hydrogen.

Unlike all the other planets in our Solar System, Uranus spins on its side. The main theory for the
odd rotation is a collision with a developing planet. When the Solar System was young, a
runaway protoplanet smashed into the top of the ice giant. The crash was so powerful that it
completely changed the direction of Uranus‖ planetary rotation.
Moons

The collision would also explain Uranus‖ inner moons. The protoplanet was likely made of rock
and water ice. During the collision, all the debris flew up and got caught in an orbit around the
planet. This debris combined to form small icy moons.

Uranus‖ outer moons are larger and a different material than the inner moons. This leads
scientists to believe that the outer moons are actually asteroids that Uranus captured with its
gravitational pull.

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Rings
Uranus also has rings, though they don‖t stretch out as far as the rings of Saturn. The inner 9
rings contain mostly dark dust particles and large rocks. These dust particles make the inner ring
system appear grey. Uranus also has two outer rings, the inner one red and the outer one blue.

Neptune
Neptune is the Roman god of fresh water and the ocean. His counterpart in Greek mythology is
the god Poseidon. Neptune was the brother of Jupiter and Pluto.

How much would you weigh on Neptune?
If you weigh 70 pounds (32 kg) on the Earth, you would weigh 78.5 pounds (36 kg) on Neptune.
Neptune‖s gravitational factor relative to Earth is 1.19.

The Planet
For many, centuries people did not know that this planet even existed. Neptune was discovered
in 1846. Here is where it gets a little tricky. Johann Gottfried Galle, using Urbain Le Verrier and
John Couch Adams calculations, found Neptune. What this means is that Neptune‖s discovery is a
joint British-French-German discovery.

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Neptune is the smallest of the four gas giants in our Solar System. Much like Saturn and Uranus,
Neptune‖s atmosphere contains hydrogen, helium, and methane. Because of the methane in
Neptune‖s outer atmosphere, all the red light from the Sun gets absorbed but the blue light gets
reflected back. Thus, Neptune appears blue.
We didn‖t know much about Neptune until the spacecraft Voyager 2‖s expedition on August 25,
1989. Voyager 2 took many pictures of the planet. Much of what we know today about Neptune
came from this single visit. We saw a brilliant blue planet with a few thin white clouds laced
around its surface.

Clouds and Storms
In Neptune‖s atmosphere, there is a large white cloud that moves around rather quickly. The
“scooting” of this cloud around the atmosphere is why it‖s named “Scooter.”

When Voyager 2 visited Neptune, its pictures showed a giant storm much like the storm on
Jupiter. This storm isn‖t the “Great Red Spot”, it‖s the “Great Dark Spot”. It appears as a dark oval
shape on the surface of the planet. We do not know how long this storm has been active or if it
is still present.

More recently, the Hubble Space Telescope sent pictures and there was no sign of the Great Dark
Spot. These pictures did show two other dark spots that eventually faded away.

Extreme Winds
Neptune is a very windy place. No other planet in the Solar System has winds that are as strong
as Neptune‖s. The winds near the Great Dark Spot could have reached nearly 1,200 miles per
hour (approx 1931 km per hour). Perhaps this windy atmosphere contributes to the appearance
and disappearance of the great dark spots.

An Odd Orbit

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Neptune‖s circular orbit is offset from the Sun. At times, Neptune‖s orbit takes it further from the
Sun than any other planet in the Solar System. In 2011, Neptune completed its first orbit around
the Sun since it was discovered in 1846.

Rings
Neptune has six rings which circle the planet. Scientists believe these rings are fairly new. The
rings are more irregular than the rings of other planets. There are areas of varying thickness
throughout the rings.

Moons
Neptune has 14 moons that we know of. Because Neptune is so far away, it is difficult to see any
of these moons. There are probably many more moons orbiting this blue planet. We just haven‖t
seen them yet.

The first moon discovered was Triton. An amateur astronomer in England named William Lassell
discovered it. He found it only 17 days after Galle discovered Neptune in 1846.

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The other moons are: Despina, Galatea, Halimede, Laomedeia, Larissa, Naiad, Nereid, Neso,
Proteus, Psamathe, Sao, and Thalassa. Discovered July 1, 2013, the current name of the newest
moon of Neptune is S/2004 N 1.

Additional Resources:
   1.   https://spaceplace.nasa.gov/all-about-mercury/en/
   2.   https://www.space.com/29281-messenger-spacecraft-mercury-crash.html
   3.   http://www.planetsforkids.org/planet-venus.html
   4.   https://www.ducksters.com/science/venus.php
   5.   https://www.youtube.com/watch?v=euhLuWNEi0g
   6.   https://spaceplace.nasab.gov/all-about-earth/en/

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    7. https://www.ducksters.com/science/mars.php
    8. https://space-facts.com/mars/
    9. https://solarsystem.nasa.gov/planets/jupiter/overview/
    10. https://www.youtube.com/watch?v=4mKtiK4PKBE
    11. https://spaceplace.nasa.gov/all-about-uranus/en/
    12. https://space-facts.com/uranus/
    13. https://www.youtube.com/watch?v=VM22MyLaRSs

Credits: Alexa Wnorowski, Sabryne Fattouh, Jesus Cervantes and Sarvesh Bhardwaj

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