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The Planets
The Solar System in which we belong contains many varied worlds all with their different story to tell,
in this document we will try and explore this worlds and bring some of there exotic features to you. The
solar system has nine planets in, some might argue that the 9th – Pluto is not actually a planet but a
Kuiper belt object, but we will assume that Pluto is a planet.
The Solar System is 4.5 billion years old. It was initially a rotating gas cloud, as time passed gravity
became the dominant force, hence began to contact and angular momentum was conserved. The cloud
flattened and material drifted towards the centre forming a ‘protosun’. Temperature kept rising until
fusion began.
For the gas giants the most probable explanation to their formation is that gravitational instabilities lead
to the collapse of gas left over form the creation of the Sun. The rocky planets probably formed by the
planetisimal theory i.e. dust grains collide and merge together and gradually larger bodies associate
together.
The planets travel around the Sun in elliptical orbits, a fact first noticed by Johannes Kepler in 1609.
An inferior planet is one which has an orbit that is inside that of the Earth and the others are sad to be
superior. The inner solar system is defined as being: Mercury, Venus, Earth, Mars (asteroid belt) and
the outer solar system is: Jupiter, Saturn, Uranus, Neptune and Pluto (which has a maximum distance
from the sun of 7,375 million km.
We shall start with the closest and work our way outwards, to the edge of the solar system and the Oort
cloud.
Mercury
Orbit
Diameter
Mass
Satellites
Magnetic Field
57,910,000 km (0.38 AU) from Sun
4,880 km
3.30e23 kg
None
Approx 1% of the Earth’s
Mercury is the closest planet to the Sun and also the eight largest. Mercury has
been known of since at least the time of the Sumerians (about 3rd millennium
BC). It was given two names by the Greeks: Apollo for its apparition as a
morning star and Hermes as an evening star. Greek astronomers knew, however,
that the two names referred to the same body. Some Greek astronomers even
believed that Mercury and Venus orbited the Sun, not the Earth which is
contrary to the popular belief at the time. In Greek mythology Hermes is the
messenger of the Gods and the Roman counter part is Mercury; he god of
commerce, travel and thievery. The planet probably received this name because
it moves so quickly across the sky.
Spacecraft:
Mercury has been visited by only one spacecraft, Mariner 10. It flew by three
times in 1974 and 1975. 45% of the surface was mapped. In more recent times it has been
suggested that it should be mapped by the Hubble Space Telescope (HST), unfortunately, it
is too close to the Sun to be safely imaged by HST.
There are a few future missions to go back and map the rest of Mercury in the pipeline. The
first is NASA’s Messenger (http://messenger.jhuapl.edu/index.html), which is due to be
launched in 2004 and will start orbiting Mercury in 2004.
The second is BepiColombo which is ESA’s first visit to the innermost planet, the
objectives for this space craft are 1st dual Mercury orbiters, 1st Mercury lander, 1st
European deep-space probe using electric propulsion.
The point of Mercury's orbit closest to the Sun (perihelion) moves around the Sun faster
than predicted by Newton's theory of gravity. The motion of Mercury remained a mystery
until Albert Einstein overhauled the theory of gravity in 1915. BepiColombo will
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measure Mercury's motion more accurately than ever before and thus provide one of the most rigorous
tests ever of Einstein's theory. BepiColombo is named after Professor Giuseppe (Bepi) Colombo
(1920-1984) from the University of Padua, Italy, a mathematician and engineer of astonishing
imagination. He was the first to see that an unsuspected resonance is responsible for Mercury's habit of
rotating on its axis three times for every two revolutions it makes around the Sun.
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 perihelion of its orbit 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. It was thought that another planet (sometimes called
Vulcan) might exist in an orbit near Mercury's to account for the discrepancy. The real answer turned
out that this discrepancy could only be accounted for when General Relativity is was applied to the
system.
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 the Earth. 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, so Mercury's
atmosphere is constantly being replenished.
One of the largest features on Mercury's surface is the Caloris Basin; 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. The plains of Mercury are relatively smooth, probably due to some ancient volcanic
activity but possible due to the result of the deposition of ejecta from cratering impacts.
There is even a suggestion of water ice in the protected shadows of some craters around the
north pole of Mercury’s surface; this is from radar observations as this region was not mapped
by Mariner 10.
Venus
Orbit
Diameter
Mass
Satellites
Magnetic Field
108,200,000 km (0.72 AU) from Sun
12,103.6 km
4.869e24 kg
None
Zero
Venus is the second planet from the Sun and the sixth largest. Venus' orbit is
the most nearly circular of that of any planet, with an eccentricity of less than
1%. Venus is the name of the Roman (Greek: Aphrodite; Babylonian: Ishtar)
goddess of love and beauty The planet is so named probably because it is the
brightest of all the planets known to the ancients. The majority of the surface
features on Venus are named after female figures.
Venus is usually visible with the unaided eye. Sometimes referred to as the
‘morning star’ or the ‘evening star’, it is by far the brightest ‘star’ in the sky.
Venus has been known since prehistoric times. Except for the Sun and the
Moon it is the brightest object in the sky. Like Mercury, it was popularly
thought to be two separate bodies: Eosphorus as the morning star and
Hesperus as the evening star, but the Greek astronomers of the time knew
like they did with Mercury that the two bodies are the same object.
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Venus is an inferior planet, which means when viewed from the perspective of the Earth it shows
phases. This was first observed by Galileo and his observation of the phenomenon was important
evidence in favour of Copernicus’s heliocentric theory of the solar system.
Venus has a strange rotation, it is very slow (243 Earth days per Venus day, slightly longer than Venus'
year) and retrograde. In addition, the periods of Venus' rotation and of its orbit are synchronized such
that it always presents the same face toward Earth when the two planets are at their closest approach.
Whether this is a resonance effect or merely a coincidence is not known.
Spacecraft:
In 1962 the first spacecraft visited Venus, this was Mariner 2. It has since been visited by more
than 20, including Pioneer and the Soviet Venera 7 which was the first spacecraft tot land on
another planet. Venera 9 was the first to return photographs of the surface (see right). To get a
better picture of what is going on under the clouds of Venus the Magellan spacecraft mapped
the surface of Venus using radar (see main image of Venus).
Venus is sometimes regarded as Earth's sister planet. In some ways they are very similar. Venus is only
slightly smaller than Earth (95% of Earth's diameter, 80% of Earth's mass). Both have few craters
indicating relatively young surfaces. Their densities and chemical compositions are similar. Since
Venus seems so similar to the Earth, it was thought that below its dense clouds Venus might be very
Earthlike and even have life; however detailed study of Venus reveals that in many important ways it is
quite drastically different from the Earth.
The pressure of Venus' atmosphere at the surface is 90 atmospheres (about the same as the pressure at a
depth of 1 km in Earth's oceans). It is composed mostly of carbon dioxide. There are several layers of
clouds many kilometres thick composed of sulphuric acid. These clouds completely obscure our view
of the surface. This dense atmosphere produces a run-away greenhouse effect that raises Venus' surface
temperature by about 400 degrees to over 740 K (hot enough to melt lead). Venus' surface is actually
hotter than Mercury's despite being nearly twice as far from the Sun.
In the upper atmosphere there are strong winds (350kph) but at the surface they are very slow, no more
than a few kilometres per hour.
Venus' surface consists mostly of gently plains with little relief. There are also several broad
depressions: Atalanta Planitia, Guinevere Planitia, Lavinia Planitia. There two large highland areas:
Ishtar Terra in the northern hemisphere (about the size of Australia) and along the equator Aphrodite
Terra (size of South America). The interior of Ishtar consists mainly of a high plateau, Lakshmi
Planum, which is surrounded by the highest mountains on Venus including the enormous Maxwell
Montes.
Data from Magellan's imaging radar shows that much of the surface of Venus is covered by lava flows.
Recently announced findings indicate that Venus is still volcanically active, but only in a few hot spots;
it has been geologically rather quiet for the past few hundred million years.
There are no small craters on Venus, the small meteoroids burn up in Venus' dense atmosphere. Craters
on Venus seem to come in bunches indicating that large meteoroids that do reach the surface usually
break up in the atmosphere.
The interior of Venus is probably very similar to that of Earth: an iron core about 3000 km in radius, a
molten rocky mantle comprising the majority of the planet. Like Earth, convection in the mantle
produces stress on the surface which is relieved in many relatively small regions instead of being
concentrated at plate boundaries as is the case on Earth.
Earth
Orbit
Diameter
Mass
Satellites
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by definition, 1 AU, or 149.6 million km from Sun
12,756.3km
5.972^24 kg
The Moon (Lunar)
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Earth is the fifth-largest planet. Most of mass is in the layer called the mantle, and
if you know any more geography than the author you’ll know what that is. Earth is
the only planet on whose surface water can exist in liquid form. Obviously, it has
just the one natural satellite, and all spacecraft have been there!
The earth's magnetic field interacting with solar wind causes aurora borealis and
australis, and also the magnetic field to move and occasionally reverse completely.
The geomagnetic north pole is currently in northern Canada.
Mars
Orbit
Diameter
Mass
Satellites
Magnetic Field
227,940,000 km (1.52 AU) from Sun
6,794 km
6.4219e23 kg
2; Phobos and Diemos
Weak
This planet was not covered in the talk since this was covered in a
specific talk already for more information please see the Mars
document
which
currently
can
be
found
at:
http://students.bugs.bham.ac.uk/astrosoc/educational/Mars.pdf
Jupiter
Orbit
Diameter
Mass
Satellites
Magnetic Field
778,330,000 km (5.20 AU) from Sun
142,984 km (equatorial)
1.900e27 kg
about 40
Huge magnetic field
Jupiter is the largest planet in our Solar system, being over 1000 times greater in volume and
300 times greater in mass than the Earth. It is the Earth’s saviour; asteroids that would be
extinction level events (ELEs) if they impacted the Earth have instead been swallowed up by
the giant planet. This is probably partly why life was able to develop as it is on Earth. It is
composed mainly of Hydrogen and Helium.
Through a good telescope it appears as yellowish dish crossed by dark streaks which are
known as the ‘cloud belts’. The most stable of the bright bands have been named. Like all the
other giant planets it spins very quickly causing an equatorial bulge producing a shape which is
described as oblate.
The most famous feature on its surface is the Great Red spot, which is know to have persisted for over
300 years. It is not stationary and drifts over time. It is roughly 3 times greater than the radius of the
Earth. There are many theories as to its origin but one of the most promising is a ‘solitary wave’ which
is an isolative permanent wave which can flow between tow layers of a fluid when there is a velocity
difference between the layers. The wave takes its energy from the velocity gradient.
The temperature of Jupiter is between 104 and 105 K.
Spacecraft: Pioneer 10 1972, Pioneer 11 1974, Voyager 1 1977, Voyager 2 1977
Satellites:
There are currently 40 known moons around Jupiter. The four most famous and the largest are the
Galilean moons; Io, Europa, Ganymede and Callisto (in order of distance from Jupiter, can be
memorised via ‘I Eat Green Cheese’). These moons are so large that they are comparable to the smaller
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planets such as Mercury and are found on an almost circular orbit in Jupiter’s equatorial plane. They
are called Galilean as they were first discovered by Galileo in 1610.
Io
It is the most dense of the Galilean satellites been about as dense as the
moon (3.5×103 kgm-3). As the closest moon it is subject to a strong
gravitational attraction from Jupiter on the one side and on the other that of
the rest of the Galilean satellites. This causes its surface to flex and the
resulting friction produces heat to cause a molten interior.
Europa
The smallest Galilean moon. Its very high albedo (reflectivity) suggests that it has an icy surface.
There are very few craters on its surface which suggests that it may have remained in a slushy
state until the main bombardment era was over. It suffers from similar gravitational force as Io
(only 10% of the strength that Io receives) which may have lead to a water or slushy region
beneath the surface which many people postulate that there may be life there.
Ganymede
It is the largest and brightest Galilean satellite. The overall density is less
that that of water there it is inferred that if consists of around ½ rock and ½
ice. It is believed that there may be a convective mantle or water below the
100km thin crust.
Callisto
The least dense of the Galilean moons being one of the lowest satellite densities
measured. Also has a low albedo and so appears much fainter than tits companions. It is
thought to have a thin crust 200 to 300 km thick below which there is a convection layer
or water or soft ice, similar to that of Ganymede. Its surface is saturated with craters and
is thought to be approximately 4000 million years old, this makes it the oldest landscape
surfaces in the whole solar system.
Saturn
Orbit
Diameter
Mass
Satellites
Magnetic Field
429,400,000 km (9.54 AU) from Sun
120,536 km (equatorial)
5.68e26 kg
30 named
Significant
Saturn is the sixth planet from the Sun and the second largest.
In Roman mythology, Saturn is the god of agriculture. In Greek mythology Saturn was
the god, Cronus, who was the son of Uranus and Gaia and the father of Zeus (Jupiter).
Saturn is the root of the English word ‘Saturday’. Saturn has been known of since
prehistoric times.
In 1610 Galileo was the first to observe it with a telescope; he was confused by its
rather odd. It seems that early observations of Saturn were complicated by the fact that
the Earth passes through the plane of Saturn's rings every few years as Saturn moves in its orbit. This
means that a low resolution image of Saturn will change drastically. It took another 50 years after
Galileo first observed Saturn for Christian Huygens (in 1659) correctly inferred the geometry of the
rings. Saturn was believed to be the only planet with rings until in 1977 when faint rings were
discovered around Uranus and then shortly afterwards around Jupiter and Neptune.
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Saturn was first visited by Pioneer 11 in 1979 and later by Voyager 1 and Voyager 2.
Cassini, now on its way, will arrive in 2004.
Saturn is visibly flattened (oblate) when viewed through a small telescope; its
equatorial and polar diameters vary by almost 10% (120,536 km vs. 108,728 km). This is the result of
its rapid rotation (differential rotation) and fluid state. The other gas planets are also oblate, but not so
much so.
Saturn is the least dense of the planets; its specific gravity (0.7) is less than that of water. Like Jupiter,
Saturn is about 75% hydrogen and 25% helium with traces of water, methane, ammonia and "rock",
similar to the composition of the primordial Solar Nebula from which the solar system was formed.
Saturn's consists of a rocky core, a liquid metallic hydrogen layer and a molecular hydrogen layer; this
is similar to that of Jupiter. Traces of various ices are also present.
Saturn's interior is hot (12000 K at the core) and Saturn radiates more energy into space than it receives
from the Sun. Most of the extra energy is generated by the Kelvin-Helmholtz mechanism, the slow
gravitational compression of the planet, as in Jupiter. But this may not be sufficient to explain
Saturn's luminosity; some additional mechanism may be at work, perhaps the ‘raining out’ of helium
deep in Saturn's interior.
Saturn has bands in the atmosphere, like Jupiter but in the case of Saturn they are much wider near the
equator and far fainter. Most of the details are not visible from the Earth so it was not until the Voyages
encounters that any detail of Saturn’s atmospheric circulation could be studied.
Saturn also exhibits long-lived ovals (e.g. Red Spot on Jupiter). In 1990, the Hubble Space Telescope
(HST) observed an enormous white cloud near Saturn's equator which was not present during the
Voyager encounters.
From the Earth two prominent rings (A and B) and one faint ring (C) can be seen. The gap between the
A and B rings is known as the Cassini division. The fainter gap in the outer part of the A ring is known
as the Encke Division (but this was very likely never seen by Encke). The Voyager pictures show four
additional faint rings. Saturn's rings are extraordinarily thin, only about one kilometre thick. Voyager
confirmed the existence of puzzling radial inhomogeneities in the rings called ‘spokes’ which were first
reported by amateur astronomers. The nature of these ‘spokes’ remains a mystery, but may have
something to do with Saturn's magnetic field.
There are complex tidal resonances between some of Saturn's moons and the ring system. Some of the
moons, such as the ‘shepherding satellites (e.g. Atlas, Prometheus and Pandora) are important in
keeping the rings in place. Mimas seems to be responsible for the paucity of material in the Cassini
division.
Saturn's Satellites
Saturn has 30 named satellites plus one discovered in 2003 and as yet unnamed. Of these Titan is the
largest.
Titan
Titan is the fifteenth of Saturn's known satellites and the largest: In Greek mythology the Titans
were a family of giants, the children of Uranus and Gaia, who sought to rule the heavens but
were overthrown and supplanted by the family of Zeus. Titan was discovered by Huygens in
1655.
It was long thought that Titan was the largest satellite in the solar system but recent
observations have shown that Titan's atmosphere is so thick that its solid surface is slightly
smaller than Ganymede's. Titan is nevertheless larger in diameter than Mercury and larger and
more massive than Pluto.
Alone of all the satellites in the solar system, Titan has a significant atmosphere. At the surface, its
pressure is more than 1.5 bar. It is composed primarily of molecular nitrogen with 6% argon and a few
percent methane. There are also trace amounts of other organic compounds (e.g. ethane, hydrogen
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The Planets
cyanide, carbon dioxide) and water. In many ways, this is similar to the conditions on Earth early in its
history when life was first getting started.
It seems likely that the ethane clouds would produce a rain of liquid ethane onto the surface perhaps
producing an "ocean" of ethane (or an ethane/methane mixture) up to 1000 meters deep.
Uranus
Orbit
2,870,990,000 km (19.218 AU) from Sun
Diameter
Mass
Satellites
Magnetic Field
51,118 km
8.683^25 kg
27 named
Unusual (see below)
Uranus is the first planet whose discovery is recorded, i.e. the first planet
discovered which, while visible with the naked eye, is too insignificant to have
been noticed. Although the Hindus believed in nine planets, they thought one was
the Sun and the two they could not see were "nodes" of the motion of the Moon,
and there is no evidence that they knew of Uranus, Neptune or Pluto.
Uranus was discovered by William Herschel, on March 13, 1781. It had been seen
before but mistaken for a star. The earliest recorded sighting was by John
Flamsteed, who called it 34 Tauri in 1690. Herschel named it “the Georgian
planet” in honor of George III, others named it after the discoverer. Bode proposed
the name Uranus, and it was in common use by 1850.
Uranus was visited by Voyager 2 on January 24 1986.
The axis of Uranus’ rotation is almost parallel to the plane of its rotation, oddly, so the polar regions
receive more light. However, by an unknown mechanism, the
equatorial regions remain hotter. The magnetic field unusual in that it is
at 60 degrees to the axis of rotation. There is some disagreement as to
which of Uranus’ poles is its north!
Uranus is composed of rock and ices, and its atmosphere is about 83%
hydrogen, 15% helium and 2% methane. The methane is concentrated
in the upper atmosphere, giving the planet its blue colour.
All of the named moons in the solar system are named after characters
(e.g., assorted nymphs) or types of being (e.g. Neptune’s Nereid,
named after a type of nymph, not an individual) from Greco-Roman
mythology with the exception of the Earth’s and Uranus’ moons. The Earth’s moon is not named after
anything, and Uranus’ moons, unusually, have been named from the writings of Shakespeare and Pope.
You will be disappointed to learn that Uranus has as yet no moon named Bottom.
Uranus has 11 rings, and 27 known satellites, as follows: Cordelia, Ophelia, Bianca, Cressida,
Desdemona, Juliet, Portia, Rosalind, Belinda, Puck, Miranda, Ariel, Umbriel, Titania, Oberon, Caliban,
Stephano, Trinculo, Sycorax, Prospero, and Setebos.
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Neptune
Orbit
Diameter
Mass
Satellites
Magnetic Field
4,504,000,000 km (30.06 au) from the Sun
49,532 km
1.0247^26 kg
13
Unusual (see below)
Neptune is also visible with the naked eye, but insignificant. Pluto's eccentric orbit
means that sometimes Neptune is the furthest from the sun.
After discovery of Uranus, something was noticed to be disturbing its orbit. Adams
and Le Verrier predicted its location and it was found very near there by Galle and
D'Arrest on 24 September 1846. The English and the French squabbled over
discovery rights and are now jointly credited. The original predicted orbit diverges
quickly from actual orbit, so it was lucky that they observed the planet before it
moved from near the predicted orbit.
It was nearly discovered over 200 years earlier by Galileo in 1613, but he mistook it for a star. In fact,
he did notice a small movement on two successive nights, but on following nights the weather was bad
and he was prevented from following its motion. Had it not been cloudy he would probably have
identified it as a planet.
Neptune was visited by Voyager 2 on August 25 1989. A dark spot was observed, about twice the
size of Earth and probably a storm like the spot on Jupiter. However subsequent HST
observations have failed to locate it.
The planet is similar in composition to Uranus. The blue colour is also from methane, but some
other unknown chemical makes the clouds a particularly rich hue. Neptune has the fastest winds in the
solar system at up to 2000 km/hour (no Uranus jokes please!). It radiates twice as much energy as it
gets from the Sun. Like Uranus, it has rings and an oddly oriented magnetic field generated by motions
of conductive material (probably water) in its middle layers One ring has a twisted structure.
Neptune has 13 known satellites: Naiad, Thalassa, Despina, Galatea, Larissa, Proteus, Triton, and
Nereid, plus 5 unnamed ones.
Pluto
Orbit
Diameter
Mass
Satellites
5,913,520,000 km (39.5 AU) from the Sun (average)
2,274 km
1.27e22 kg
1; Charon
After the discovery of Neptune in 1846 there were still slight
perturbations in the movements of the outer planets. During 1930
Clyde Tombaugh used a blink-microscope and took photos on two
different nights and compared them, the stars would remain in the same
relative positions but a planet would shift during the interval and its
motion would be revealed. The planet was named Pluto after the God
of the underworld and Darkness, as suitable name for the most remote
planets in the solar system.
Pluto is smaller than the moon and has one satellite called Charon
which is around half the size of Pluto, hence it is often said that they may be a double planet or even a
double asteroid. Pluto has a very eccentric orbit which when Pluto is at perihelion it is closer to the Sun
than Neptune. Pluto does have a tenuous atmosphere of methane, but this may be a cyclic phenomenon
so that when Pluto moves towards aphelion the temperature may fall and the methane may condense
onto the surface. It has an orbit of 124 years.
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Mythology
Here we examine what amounts to being the history of astronomy. In ancient times there was a lot that
people didn’t understand, and most of it was attributed to the supernatural or the divine. While today
we know that Venus is just a lump of rock with a sulphurous atmosphere, the Mayans thought it was a
bringer of war that should be feared intensely, and the Greeks thought it was the celestial avatar of love
itself.
With the exception of Earth, all of our planets are named after Roman gods. Roman mythology, in fact,
is almost exclusively Greek, although they took over some Celtic lore where they found it (here in
Britain there are many ruined Roman buildings dedicated to indigenous deities whom the Romans had
incorporated into their belief system). The Romans were fascinated by the Greeks and basically took up
all of the ancient Greek religion. Where possible they assimilated the Greek gods to gods of their own
invention, which is why many Roman divinities have two names: the original Greek name and the
name of the Roman god whom the Romans felt best fitted the attributes of the Greek god they wanted
to make their own. Where possible we will speak of old Roman mythology, but in many cases there is
bugger-all information on Roman beliefs independent of ancient Greek religion.
To further add to the confusion, Greek mythology drew influence itself from Mesopotamian mythology
(the ancient region of Mesopotamia corresponds approximately to modern-day Iraq and Kuwait).
Mercury
Mercury (or Alipes) was the Roman god of commerce, and was originally the god of the corn trade.
The Germans identified him with their god Wodan, and the Celts with Lugh. He was later equated with
the Greeks’ Hermes, who was the messenger of the gods, and the god of travel and trade. The Greeks
called the planet Apollo (after Hermes’ brother) in the morning but were aware that it was the same
planet. In fact, Heraclitus even proposed that it and Venus orbited the sun. The planet was probably
named Mercury because it moves rapidly across the sky, and messengers have to be quick. The Hindus
associated the planet with the god Budha.
Venus
Venus was the Roman goddess of vegetation, who later became the goddess of love and beauty and
was eventually assimilated with the Greek goddess of love Aphrodite. Aphrodite was born from the
splash created when Cronus threw his father’s severed genitals into the sea. Baffled? We’ll get to that
later. Aphrodite, in folkloric terms, was related to the Mesopotamian goddess Ishtar and the Etruscan
goddess Turan. From Aphrodite we get the word ‘aphrodisiac’ and from Venus the term ‘venereal
disease’ (i.e. a disease of love).
When it appeared in the morning, the Romans named the planet Lucifer, meaning “light-bearer.”
The Hindus associated the planet with a god called Sukra, who knew the secret to bringing the dead
back to life.
In pre-Islamic times in the Middle East God was believed to have daughters, one of whom, a goddess
called Uzza, was associated with Venus.
In Latvian mythology (yes, Latvian), the planet Venus was associated with a god called Auseklis, who
may at some point have been a goddess. He was going to marry the Sun’s daughter, but she ran off with
the Moon!
Old German stories tell of a diminutive and kindly people called the Venusleute (people of Venus),
who aided lost children.
In Aztec mythology, a god called Tlahuizcalpantecuhti was associated with Venus when it appeared in
the morning, and believed to be an incarnation of a feathered serpent called Quetzalcoatl. The Aztecs
and Toltecs associated it with a god called Xolotl when it appeared in the evening. He was believed to
be a dog-headed man or a skeleton.
The Incas identified the planet with a virgin goddess Chasca.
The Mayans called the planet Kukulcan, associated it with warfare and feared it to the point where they
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blocked up their chimneys to prevent its light entering their houses!
When Venus appeared above the crescent moon, the Sumu Indians said that it was the wife of Udo, the
god of the Moon.
In Polynesia Venus was called Malara in the morning. Malara was believed to be seeking wives. It is
said that the Maori people sailed from Polynesia to their current home of New Zealand, guided by the
planet Venus.
Earth
Earth is the only planet not named after a Roman god. Its name is Old English/Germanic. The Moon is
also not named after a god, and being such an important object in the sky its mythology is so extensive
that it deserves to be left for a different article.
The Greeks associated the Earth with a goddess called Gaia (whom the Romans equated with their
goddess Tellus). She came out of Chaos and created everything.
The ancient Egyptians believed the Earth was a god called Geb, Keb or Seb, the provider of crops and
healer of ailments. In a sadistic twist, his laughter caused earthquakes. He was a green- or blackskinned bearded man with a goose on his head! Another Egyptian Earth god was Tatenen, who
represented the first sign of Earth appearing from the primordial waters. He also had green skin, as well
as a crown of feathers and ram’s horns.
The Aztecs associated the Earth with a goddess called Coatlicue, meaning "serpent skirt", who was the
goddess of life and death, wore a skirt made of serpents (duh) and a necklace of hearts and wanted
regular human sacrifices. The moon was the head of a daughter who tried to kill her, which Coatlicue
bit off and spat out. There was also an earth and cave god, Tepeyollotl, associated with the jaguar, who
caused earthquakes and echoes.
The Inca Earth goddess was the generous Pachamama, wife of the Sun god. The Yuncas had an Earth
god called Pachacamac, whose wife was Mama Pacha. The Incas adopted him, presumably explaining
the origins of Pachamama. Another Inca Earth goddess, or perhaps another name for the
aforementioned, was Mama Allpa, who had many breasts!
In Norse mythology the Earth was called Midgard, and was the body of a giant called Ymir killed by
the god Odin and his brothers Vili and Ve. The goddess of the Earth was Gerd.
Slavic lore told of an Earth goddess called Mokos, who may have been an evolution of an older
goddess called “Damp Mother Earth,” Mati Syra Zemlya. In what is now Eastern Europe many similar
Earth goddesses were worshipped, probably derived from an old Indo-Iranian goddess called “Humid
Mother of the Earth,” Ardvi Sura Anahita. In Russia, Mokos may live on unofficially in Orthodox
Christianity in the form of Saint Paraskeva-Piatnitsa.
In old Islamic folklore, the earth was said to be held in the horns of a giant bull, which stands on the
head of a big fish called Labuna! Angels bring food for the fish every day, but the author has been
unable to discover what the bull was supposed to eat.
The Japanese had/have an Earth god called Kenro-Ji-Jin, meaning “Solid Earth Being.” There was also
a god called Sarudahiko who had a red face, round eyes, and a long, phallic nose.
Most Earth deities are associated with fertility in some way, for obvious reasons, and most seem to be
female. At this point the author is going to resort to simply listing Earth deities about which there is
little to say or little (interesting) information available:
Zemepates and Zemyna – Lithuanian god and his goddess sister
Hwanin – Korean god, also god of Heaven, sent his son to Earth to found a city near modern-day
Pyongyang
Armaiti – Persian goddess, also associated with the dead because they are buried underground
Erda – ancient German goddess
Chibirias – Mayan goddess
Colel Cab – Mayan goddess
Etugan – Mongol virgin goddess
Audial – goddess from Caroline Islands
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The Planets
Zempat – Prussian god, also god of cattle
Eseasar – African goddess
Altan-Telgey – Mongol god
Enlil – Sumerian, also god of the air
Papa – Maori goddess, a.k.a. Fakahotu
Awitelin Tsta – goddess of the native American Pueblo Zeni tribe
Hou Ji – Chinese, also god of cereal crops
Anatu – Mesopotamian goddess, also queen of the sky
Jian Lao – Chinese god, also god of permanence
Tanen – Egyptian, the god Ptah in his ‘Earth god’ aspect
Onamuji – Japanese god
Itchita – Yakut goddess who lives in a beech tree and prevents illness
Atugan - Mongol
Nokomis – Algonquin goddess, ‘grandmother’
Prisni – Hindu goddess, also goddess of darkness
Humban – Elamite god
Ninhursag – Sumerian goddess, ‘queen of the mountain’
Mars
Mars, a.k.a. Ultor and Mavors, began as a Roman god of fertility and growth, later becoming a
chthonic (meaning of, or in the earth) god. Some earth gods became associated with death because the
dead are buried in the ground, and this happened to Mars. From here we can see how he finally became
associated with warfare, and was then associated with the Greeks’ Ares. Ares was one of two wardeities in Greek mythology, the other being Athena. However Athena was interested solely in
upholding justice, where as Ares simply enjoyed bloodshed. Ares was accompanied by his sister Eris
(Roman: Discordia), goddess of strife, an older war goddess called Enyo, and his sons Phobos and
Deimos, ‘panic’ and ‘fear’, after whom the planet’s two moons are named.
Mars was also associated with Cariocienus, an old Hispanic god, and Camulus, Teutates and BelatuCadros, Celtic gods.
Mars was the father of the legendary wolf-nursed founders of Rome, Romulus and Remus. From the
god Mars we get the name of the month of March. Many cultures associate the planet Mars with war,
because it is red, like blood.
The Hindus named the planet Mangala, and associated it with the god Karttikeya. He was created from
six babies born from six sparks from the eyes of the god Shiva. The babies were nursed by the Pleiades.
Shiva’s wife Parvati hugged the babies so hard that they stuck together into a single god, Karttikeya,
who had 12 arms and 6 heads, was the god of war and rode a peacock!
The Babylonian god of Mars was Salbatanu.
The Mayans depicted Mars as a serpent snaking across the sky, possibly referring to its motion
throughout the year.
Jupiter
Jupiter (a.k.a. Jove, Stator, and about a million other things) may be no more than a Romanised name
for Zeus, Greek king of the gods and god of lightening and light. The planet may be named after him
because it's a very bright object in the sky. Jupiter was associated with Jessis, a Slavic god, Hadad, a
Syrian god, Tinia, an Etruscan god, and Taranaich and Bussumarus, Celtic gods. His hobbies were
cheating on his wife (in fact he ate his first wife!) and creating innovative ways to avoid getting caught
(e.g., changing himself and his target into animals). Jupiter’s moons are named after nymphs (beautiful
female semi-divine beings from whom we derive the term ‘nymphomania’) with whom he had sex.
Gods associated with Jupiter:
Jessis – Slavic
Hadad – Syrian
Tinia – Etruscan
Taranaich – Celtic
Bussumarus – Celtic
Thor – Norse
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The Planets
Donar - Teutonic
In Judaic lore, Zadkiel is the angel of the planet Jupiter.
The planet was associated by the Sumerians with their fertility god Sulpa’e.
The Hindus had a god of Jupiter called Devapurohita, or Brivaspati.
The name of the Chinese god Tai-Sui-Xing, “Star of the Big Year,” refers to Jupiter, with its twelveyear orbit.
From the god Jupiter’s other name, Jove, we get the term ‘jovial’, as Zeus was supposed to be a jolly
fellow. From Thor we get the name of the day of the week Thursday.
Saturn
Saturn was the Roman god of agriculture and particularly corn. He was associated with the Phoenician
fertility god Baal-Hammon. He was equated with the Greek Cronus, who was the bringer of old age
and god of agriculture. Cronus was always shown carrying a sickle, the instrument with which he
carried out the harvest but also castrated his father. As such he was perhaps very much a god of
regeneration – only when the old has been disposed of can we bring in the new. After castrating his
father Uranus, Cronus succeeded him as king of the gods. Unfortunately his own behavior left him with
a paranoia that his children would depose him, and hence he would eat all of his children as soon as
they were born. However in the case of Zeus his wife (who was also his sister) tricked him into
swallowing a rock instead, and his paranoia turned out to be justified when Zeus did indeed stage a
coup and seize power. If you are wondering how a rock could be mistaken for a newborn child, don’t
ask us because we don’t know.
From the god Saturn we get the name of the day Saturday.
The Hindu god of the planet Saturn was Sani, known as 'the evil-eyed one' because his gaze could burn.
The following three planets have no real history, as they are fairly modern discoveries. However we
shall briefly discuss the mythology behind their names.
Uranus
Uranus is a purely Greek god – the Romans equated him with their god Coelus, but for some reason we
still use the Greek term. Uranus was the god of the sky, created by the Earth Mother goddess Gaia as a
husband after she appeared alone out of the primordial Chaos. Uranus impregnated his wife, and did
not ‘withdraw’ himself for so long that his children grew adult inside their mother, unable to be born.
In order to allow them exit, one of the children, Cronus, cut off his father’s penis with a sickle his
mother had given him. Having been emasculated, Uranus the Sky separated from Gaia the Earth.
Uranus is a sky-blue planet, and the author stipulates that the planet may have been named after the sky
god for this reason.
Neptune
Neptune was the Roman god of the sea, who may have evolved from the Etruscan water-god Nethuns.
He became assimilated with the Greek god Poseidon. Poseidon was the god of the sea and the bringer
of earthquakes. He was bad-tempered, a womanizer and a rapist. He even had sex with the Gorgon
Medusa, famous for her snake-hair and lethal gaze (Poseidon being immortal had no need to fear this),
from which union was produced the flying horse Pegasus. Neptune’s moons are named after random
mythological characters and beings. Neptune was probably suggested as a name for this planet because
it is blue, like the sea.
Pluto
The Roman Pluto, the Etruscan Aita and the Greek Hades are essentially identical. Hades was the god
of the underworld, where the dead reside. Even the other gods avoided him. The ancients didn’t like to
speak of him for fear of attracting his attention. His pet dog Cerberus had three heads. Pluto’s moon,
Charon, is named after the immortal who ferried the newly dead and occasional visitors such as
Hercules/Heracles and Orpheus across the river Acheron which separated the kingdoms of life and
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The Planets
death. The planet may be named after Pluto not only because it is a horrible icy rock, but also because
the first two letters are the initials of Percival Lowell, the namesake of the observatory at which the
planet was discovered.
Images
Cover Image: http://codep.ucsc.edu/planets.gif
Messenger Spacecraft:
http://messenger.jhuapl.edu/the_mission/artistimpression/images/orbitwithplanet.jpg
Mercury: http://www.jb.man.ac.uk/public/mercury.gif
Caloris Basin: starchild.gsfc.nasa.gov/ .../mercury_know.html
Venus: http://www.solarviews.com/browse/venus/venus1.jpg
Saturn: http://www.solarviews.com/eng/saturn.htm
Uranus: http://www.solarviews.com/browse/uranus/uranus.jpg
Uranus Atmosphere: http://hubblesite.org/newscenter/newsdesk/archive/releases/1996/15/
Uranus Satellites: http://www.lpi.usra.edu/research/outerp/usat.gif
Earth: http://seds.lpl.arizona.edu/nineplanets/nineplanets/gif/Earthbig.jpg
Jupiter: http://www.star.le.ac.uk/edu/planets/jupiter.gif
Europa: http://seds.lpl.arizona.edu/nineplanets/nineplanets/europa.html
Ganymede: http://www.solarviews.com/raw/jup/ganymede.gif
Callisto: http://pds.jpl.nasa.gov/planets/captions/jupiter/callval.htm
Io: http://www.jpl.nasa.gov/galileo/ganymede/P47971_full.jpg
Mars: http://oposite.stsci.edu/ftp/pubinfo/jpeg/Mars95.jpg
Neptune: http://pds.jpl.nasa.gov/planets/images/full/neptune/fullnep.jpg
Neptune Spot: http://pds.jpl.nasa.gov/planets/jpeg/nep/gdspot2.jpg
Pluto: http://www.seds.org/nineplanets/nineplanets/pluto.html
Contributors:
Samuel George
Scott Porter
Alexandra Yannacopoulou
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The Planets