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Mercury
Named after the messenger of the Roman Gods
Mercury is the planet closest to the Sun, coming as close as
46 million km on it’s closest approach. The surface temperature can reach as high as
427°C on the dayside and -183° C on the night side.
Mercury is the smallest planet, now that Pluto was re-classified as a dwarf planet, about
one-third the size of Earth. Mercury has no appreciable atmosphere.
Because of its location nearest the Sun and its orbital inclination, Mercury is difficult to
observe. The only time Mercury can be observed is during the day or just before sunset or
sunrise.
In the 1880’s Giovanni Schiapareli drew the first sketches of Mercury. The first
spacecraft to visit Mercury was Mariner 10 on March 29, 1974. Mariner 10 flew past
Mercury three times at a distance of approximately 705 kilometers. Taking a total of
2,700 pictures, Mariner 10 gave scientists their first good look at the planet.
The surface of Mercury is quite similar to that of our moon. A dusty rolling terrain, with
huge cliffs that rise for several kilometers and cover hundreds of kilometers. The surface
is covered with craters from constant bombardment from meteorites.
VENUS
Named after the Roman Goddess of Love & Beauty
Venus is considered Earth’s sister planet because it is similar in
size, mass, composition and distance from the Sun. That is where
the similarities end.
Earth and Venus were formed at about the same time. A dense atmosphere surrounds
Venus. It has no oceans and virtually no water vapor. Its clouds are composed of sulfuric
acid with a surface pressure that is 92 times greater than that of Earth's at sea level.
With a surface temperature of 485°C, hot enough to melt lead, the planet’s atmosphere
consists mainly of carbon dioxide with sulfuric acid clouds. The high temperature is due
to the greenhouse effect of the dense atmosphere of carbon dioxide. The greenhouse
effect happens when sunlight passes through the atmosphere and heats the planets
surface. The heat then bounces or radiates off the surface. Normally this heat would then
pass back out through the atmosphere and go into space. On Venus the heat is trapped,
making it hotter then Mercury.
Venus rotates in the opposite direction then that of Earth. This means that if you were
standing on Venus, wearing a special pressure suit to protect you, you would see the Sun
rising in the West and setting in the East.
Due to the thick atmosphere, scientists were, until recently, unable to see the planets’
surface. New radar imagery has allowed then to see through the atmosphere of carbon
dioxide and the clouds of sulfuric acid. What they found was a planet covered with
impact craters, lava flows, mountains, two highland areas and broad sweeping plains.
EARTH
Gaea or Ge was the Earth goddess of ancient Greece.
Earth, our home is the third planet from the Sun, the fifth
largest planet in the solar system, and the only known planet
to support life.
Earth rotates around it’s axis once every 23 hours 56 minutes,
or what we call one day. It takes the earth 365.3 days, or what we call one year, to travel
once around the Sun.
Our atmosphere consists of 78 % nitrogen, 21 % oxygen, H2O and 1 % trace amounts of
other gasses. It is our delicate atmosphere that is one of the reasons that life exists on
Earth. The atmosphere is what protects us from almost all the harmful radiation from the
Sun, and causes meteors to burn up before they impact Earth’s surface.
We think of Earth as a solid, safe, predictable home. But like the other planets in our
solar system, earth is dynamic and ever changing. 71 percent of the Earth’s surface is
made up of water. The other 29 percent is made up of solid material called terrestrial
plates that float over the Earth’s mantle. These plates, which are constantly moving, are
what we live on. The movement of these plates is so slow that we normally don’t notice
it. Earth quakes are the result of two plates moving apart. Rain, snow, wind, waves and
lightning are all a part of this dynamic, moving planet.
Until recently we believed that Earth was the only planet on which water existed. It is
now known that water exists, (in the form of ice) on Mars as well as a couple of moons,
including our own. Liquid water is essential to life as we know it.
In astronomical term Earth is quite young. It is estimated that the Earth is 4.5 - 4.6 billion
years old. The oldest known rocks are 4 billion years old. The earliest evidence of life on
this planet is 3.9 billion years old with the earliest evidence of “humans” at 5.8 - 5.2
million years ago.
Our planet has one moon named “ the Moon” or “Luna”. It is the brightest object in the
night sky. The moon orbits Earth once a month or once every 29.5 days. The moon has
quite an effect on Earth. Not only does it slow down the Earth rotation by 2 milliseconds
each year, but it’s gravitational pull is what causes the tides.
From our perspective living on the planet, we think of Earth as a large, unaffected,
divided, thriving planet teeming with life.
Astronauts returning to Earth after seeing the planet from space talk of a isolated, small,
fragile planet, floating in the middle of blackness. The atmosphere that protects us and
allows life to thrive is seen as only a thin layer above the planet. The boarders of the
different countries vanish. The effects of fires in the Amazon can be seen spreading
around the globe, indifferent to the political boundaries.
MARS
Named after the Roman God of War.
Mars, the red planet is probably the most well known of all
the planets. Early observations by astronomers such as
Giovanni Schiapparelli saw what they believed to be canals
carved by running water. The idea of running water on Mars
fueled the belief that life existed on the red planet. Science
fiction books, radio and movies have not helped dispel this myth.
The large number of books, movies, radio and folklore dedicated to the myth that life
exists on Mars make it the most talked about planet in our solar system. These carved
channels were believed to have been naturally made by running water or made by
intelligent life. This led to the belief that in either case life probably existed on the red
planet at one time. The 1938 radio broadcast “War of the Worlds” by Orsen Wells did not
help dispel the false information.
Mars's apparent seasonal changes, and the possibility that water once flowed on Mars
have made it a very interesting planet for scientists to study. The first spacecraft to land
on Mars was Mariner 4 in 1965. The pictures sent back by Mariner showed a dry dusty,
crater filled surface with naturally made channels, but no flowing water.
Scientists were still hopeful that if water once flowed on Mars that life might have
existed. In 1976 two spacecraft were sent to conduct biological experiments, testing for
evidence of microscopic life. The Viking Landers 1 & 2 landed on Mars where they
conducted chemical experiments of soil samples. No evidence of life was found. What
they did find was that the soil was saturated with ultraviolet radiation was extremely dry
and therefore could not support life.
Vales Marineris is a huge canyon that is 4000 km long and from 2-7 km deep. If it were
here on Earth it would stretch from Vancouver to Toronto.
Mars has the largest volcanic mountain in the solar system; Olympus Mons is 27 km
high, (3x the height of Mt Everest) and 600 km across, almost the distance between
Toronto and Montreal.
There is Water on Mars. The amount is much less than it is here on Earth, in all three
states of matter. Most of the water is locked in the permafrost and polar caps, so there are
no bodies of liquid water on the surface of the planet. Only a small amount of water
vapor is in the atmosphere.
Current conditions on the planet surface do not support the long-term existence of liquid
water. The average pressure and temperature are far too low, leading to immediate
freezing and resulting sublimation. Despite this, research suggests that in the past there
was liquid water flowing on the surface, creating large areas similar to Earth's oceans.
The question remains, where has the water gone?
There are a number of direct and indirect proofs of water's presence either on or under the
surface, e.g. stream beds, polar caps, spectroscopic measurement, eroded craters or
minerals directly connected to the existence of liquid water.
JUPITER
Named after the King of the Roman Gods and Lord of the Sky
Jupiter is the largest planet in our solar system. Jupiter is like
a small sun with its own miniature solar system. In the center
is Jupiter, a giant gas ball, composed of Hydrogen and Helium, encircled with 61 moons.
Unlike the Sun, Jupiter is too small and therefore does not emit light. If Jupiter had 80
times more mass, it could be a small star.
Jupiter is the first of what is called the outer gas giant planets. Unlike the inner planets
Mercury, Venus, Earth and Mars, Jupiter does not have a sold surface. It is a giant ball of
gas, with the gas getting denser and denser as you go deeper into the planet.
Jupiter is so large that if it were hollow, 1000 Earths could fit inside. It contains more
matter than all of the other planets put together.
Images of Jupiter reveal colourful bands that circle the planet. These bands are
atmospheric storms swirling around the planet at speeds of more then 640 kph. The
colours are probably the result of chemical reactions with elements in the atmosphere.
The patterns are continually changing, sometimes within hours or days. The lighter bands
are called zones while the dark bands are called belts.
Jupiter’s atmosphere is alive with lightning and huge storms that rage for days or years.
The largest of these storms is known as the Great Red Spot (GRS). The GRS has
persisted for at least 100 years and perhaps as long as 300 years. The GRS is between
12,000-25,000 km wide, so large that between 2 & 2.5 Earths could fit across its face.
Jupiter does have rings, but unlike the rings of Saturn, Jupiter’s rings are much fainter,
smaller and dark. The rings were discovered when Voyager 1 flew past the planet. The
rings are probably composed of very small grains of rock and dust.
Jupiter has 61 moons or satellites, the most of any of the nine planets in our solar system.
The four largest are Io, Europa, Ganymede, and Callisto. There are 12 smaller named
moons, and 45 more that have only recently been discovered and have yet to be
confirmed or named.
Being the largest planet in our solar system, Jupiter is often visible in the night sky. Its
four largest moon are also often visible using binoculars or affordable amateur
telescopes. With a good telescope some of the bands and the GRS can also be seen.
SATURN
Named after the Roman God of the Harvest
Saturn is most famous for its large and beautiful
ring system. Although 3 other planets have ring
systems, Saturn’s is the largest and most elaborate.
Saturn’s ring system is visible from Earth even with a low powered telescope. Saturn has
7 major ring divisions. The major rings contain hundreds of ringlets, with some rings
being braided, others being flanked with small moons, called shepards. The rings may be
remnants of moons destroyed by tidal interaction with Saturn’s gravity, or pieces of
comets that passed too close to Saturn and suffered the same fate.
From Earth the rings appear as one sold object circling the planet. In reality the ring
system is made up of millions of individual particles, each in it’s own orbit. Together
these particles make up the seven different rings. The brightest of these are called the A
and B rings with a C ring being fainter. Between these rings are gaps; the largest being
called the Cassini gap, which separates the A, and B, rings. The gap was named after
astronomer Giovanni Casinni who discovered the gap in 1675.
Spacecraft, like Voyager, that have been close to the rings have discovered that the rings
contain a significant amount of water. This has led to the theory that the rings may
contain icebergs or snowballs.
Saturn also has 30 moons, its largest Titan is a little bigger than Mercury, and is the only
moon to have an appreciable atmosphere. 12 of these moons have only recently been
discovered and so are unconfirmed and unnamed.
A gas giant, Saturn is composed of hydrogen and helium much like the Sun and Jupiter.
Saturn is the lightest of all the planets. If there was a pool large enough to hold it, Saturn
would float on water.
The winds on Saturn are even stronger than on Jupiter. At the equator where the winds
are the strongest, speeds of over 500 meters per second can be reached.
URANUS
Named after the old Roman God Uranus. He was the father of
Saturn and the Grandfather of Jupiter
Uranus, pronounced “YOOR a nus, not “your anus” or “urine
us” is the seventh planet from the Sun and the third largest.
Uranus was first thought to be a comet. Its diameter is four
times the size of Earth. Due to its distance from the Sun, temperatures remain around 220°C throughout the year. The planets bluish green colour is a result of methane in the
atmosphere. Winds on Uranus speed around most of the planet between 100-600 kph, and
will reach as high as 1040 kph at the equator. This is four times faster than the strongest
winds on Earth.
Like Saturn, Uranus has a ring system, but unlike Saturn Uranus’s ring system is dark,
making it very difficult to see. Uranus’s ring system is made up of at least 9 known rings
with the possibility of several smaller, or incomplete rings. The rings are made up of ice,
rock and dust, ranging in size from several meters to fine particles.
Discovered in 1781 by William Herchel, Uranus is considered to be the first planet
discovered in modern times. Originally named “Georgium Sidus” in honour of King
George III of England, it has also been called “Herchel” after it’s discoverer. The name
Uranus was finally decided upon, in keeping with other planetary names from classical
mythology.
All the planets in our solar system spin on an imaginary axis. Most planets, including
Earth, spin on an axis in line with the North and South poles. Uranus has the distinction
of being tilted and spinning on its side. The imaginary axis on Uranus is in line with the
equator instead of the poles. Scientists think that this change is due to a collision with a
planet sized body early in its life.
Uranus has 20 named moons or satellites plus 1 recently discovered, and unnamed moon.
Unlike most other moons, which are named after classical mythology, Uranus’s moons
are named after the writing of Shakespeare and Pope. NEPTUNE
Named after Roman God of the ocean, God of the Sea
Neptune is the smallest of the giant gas planets. Like
Jupiter, Neptune also has large hurricane-like storms
that appear as spots on its surface. The largest of these,
the Giant Dark Spot (GDS), is the size of Earth.
Neptune has the strongest winds with speeds up to
2000 kph. The majority of the winds blow westward,
opposite to the rotation of the planet. Voyager 2, the spacecraft that flew past and
recorded images and data from many of the planets, saw a small irregular white cloud
that flies around Neptune every 16 hours. Known as “Skooter” scientists do not fully
understand what or why this happens.
Neptune was discovered in September 1846 by Johann Gottfried Galle of Berlin and
Louis d’Arrest an astronomy student. Astronomers observed the orbit of Uranus was not
in keeping with the idea that it was the farthest planet. Using Newton’s laws it was
predicted that there had to be another planet farther out past Uranus. Calculating where
such a planet should be, Galle and d’Arrest, working independently, determined and then
found Neptune.
Composed of molten rock, liquid ammonia, hydrogen, helium, water, and methane, it is
the methane in the atmosphere that gives Neptune its green / blue colour.
Like the other gas giants, Neptune also has a ring system. Like Uranus, and Jupiter,
Neptune’s rings are small and very faint. The four rings are made up of dust particles
thought to come from the smashing of meteorites into Neptune’s moons.
Neptune has one large moon or satellite, Triton and 7 small moons.
PLUTO
Named after the Greek God of wealth, Pluto ruled
the dark underworld of myth.
Pluto used to be the smallest and coldest planet in
our solar system. In August 2006 the International
Astronomical Union (IAU) passed a resolution re-defining what a planet is. The new
definition excluded Pluto as a planet. Pluto was added as a member of a new category of
celestial bodies called "dwarf planet" along with Eris and Ceres. After the
reclassification, Pluto was added to the list of minor planets and given the number
134340.
A number of scientists continue to hold that Pluto should be classified as a planet.
Due to its great distance from the Earth it has not been visited by any spacecraft, YET,
and so we do not know as much about it.
Pluto is smaller then the Earth’s moon, and is composed of exotic snows of methane,
nitrogen and carbon monoxide.
Pluto has three moons, Charon which is almost half the size of Pluto, Hydra and Nix,
which were only discovered in 2005.
Pluto’ s orbit is such that for 20 years out of its 249-year orbit, Pluto is closer to the Sun
than Neptune. On January 21, 1979 Pluto crossed Neptune’s orbit, making Neptune the
planet farthest from the Sun. Pluto was closest to the Sun on September 5, 1989 and
remained within Neptune’s orbit until February 11, 1999. It has since crossed Neptune’s
orbit again making it farther out from the Sun.
Like Uranus, Pluto’s axis is perpendicular to its equator. When Pluto was first viewed
from Earth we saw a bright spot. This bright spot turned out to be Pluto’s south pole. Its
surface is composed of 50 - 70% rock mixed with ice. The icy surface is 98% nitrogen,
methane and traces of carbon monoxide.
The discovery of Pluto was both systematic and serendipitous. Astronomers were looking
for planet “X” out past Neptune. A 24-year-old lab assistant named, Clyde Tombaugh,
compared images he had taken of the night sky two weeks apart looking for object that
had shifted. On February 18, 1930 be discovered Pluto. Too small to be the mythical
planet”X”, a new planet was discovered.
In 2006 NASA launched a spacecraft to be the first to visit Pluto. The spacecraft, called
New Horizons will finally reach Pluto in July 2015.
MERCURY
VENUS
EARTH
MARS
JUPITER
SATURN
URANUS
NEPTUNE
PLUTO