The Solar System Missions

The Missions

http://www.jpl.nasa.gov/solar_system/index.cfm

planets not shown to scale >>

                                                                                                                                          

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

Mean Distance from the Sun (AU) 0.3871 0.7233 1 1.524 5.203 9.539 19.19 30.06

Sidereal period of orbit (years) 0.24 0.62 1 1.88 11.86 29.46 84.01 164.79

Mean Orbital Velocity (km/sec) 47.89 35.04 29.79 24.14 13.06 9.64 6.81 5.43

Orbital  Eccentricity 0.206 0.007 0.017 0.093 0.048 0.056 0.046 0.010

Inclination to ecliptic (degrees) 7.00 3.40 0 1.85 1.30 2.49 0.77 1.77

Equatorial Radius (km) 2439 6052 6378 3397 71490 60268 25559 25269

Polar Radius (km) same same 6357 3380 66854 54360 24973 24340

Mass of planet (Earth=1) 0.06 0.82 1 0.11 317.89 95.18 14.53 17.14

Mean density (grams/centimeter³ ) 5.43 5.25 5.52 3.95 1.33 0.69 1.29 1.64

Body rotation period (hours) 1408 5832 23.93 24.62 9.92 10.66 17.24 16.11

Tilt of equator to orbit (degrees) 2 177.3 23.45 25.19 3.12 26.73 97.86 29.6

Number of observed satellites 0 0 1 2 >28 30 24 8

Mercury is the planet nearest to the sun. It is difficult to observe from the Earth because it rises and sets within two hours from the sun. It is estimated that Mercury was formed about 4 billion years ago. Scientist are still not exactly sure because very little was know about it until about 1974. The estimate was based on the craters on Mercury's surface. It is said that the older the planet is the more craters the surface has. Mercury has a very dense and thin atmosphere of hydrogen, helium, potassium and sulfur surrounds the planet. Mercury revolves around the Sun of 87.97 Earth days.

Mercury

Mercury

Mercury

Mercury's successive positions during March of 2004. Each picture was taken from the same location in Leeds, England exactly 33 minutes after sunset.

Mercury is the fastest traveling planet so in mythology, he is referred to as the messenger of gods because of his agility. His symbol represents a snake entwined on a staff for protection. Mercury ís Greek name is Hermes and is the son of Jupiter and Maia, the goddess of the fields born in the cave of Arcadia. Mercury was given a staff, winged sandals, etc. When Mercury stole Apollo's cows, he was known as the god of thieves, travelers, commerce, athletes, etc. Jupiter, later gave him a place in the Olympian home. Mercury was part of many myths; he saved Dionysus and had four children, and he helped Pluto by guiding the spirits of the dead into the underworld. In astrology, Mercury symbolizes intelligence, communication and transportation. The element mercury is named after the god.

Mercury

Messenger of gods

Mercury Facts Sheet:

Type: Terrestrial

Mass of planet (Earth=1) =0.06Mean density (grams/centimeter³ ) = 5.43

Interior: Metallic core about ¾ of the planet’s radius, rocky mantle and crust

Surface: heavily cratered

Water: Frozen ice in permanently shadowed portion of north and south poles

Atmosphere: No significant atmosphere

Moons: 0

Mercury

Mercury is an important part of the Solar System puzzle, yet we know less about it than any other planet, except Pluto. Mercury is the smallest of the inner, rocky planets (Mars, Earth, and Venus) and the closest to the Sun. Its relatively high density (5.4 grams per cubic centimeter) indicates that it has a large metallic core (about 3/4 of the planet's radius) compared to its rocky mantle and crust. The surface is heavily cratered like the highlands of the Moon, but some areas are smooth and less cratered, possibly like the lunar maria (but not as dark). Radar data suggest that Mercury, like the Moon (see PSRD article Ice on a Bone Dry Moon), has deposits of water ice in permanently shadowed areas at the poles. Unlike the Moon, where water is only at the south pole, Mercury has ice at both poles. (The water composing the ice deposits probably came from comets hitting the surface.)

Mercury’s Interior

So far, observations of Mercury from ground-based observers and the Mariner 10 spacecraft have not shown evidence of a significant atmosphere compared to other planets. Mariner 10 did observe a tiny amount of helium 1000 km above the surface, but this is probably produced by capturing particles from the solar wind and radioactive decay of Mercury's crust. Other elements observed in Mercury's extremely tenuous atmosphere (which exerts a pressure one million billionths that of Earth) include sodium, potassium and oxygen. When these gases are ionized by solar radiation, they are lost to the atmosphere through the interaction of the planet's magnetic field with the solar wind. Temperatures at the surface range between -300 and 800oF (hot enough for lead to melt). This large range in surface temperature is possible because Mercury is so close to the Sun (a year is only 88 Earth days long) and does not have sufficient atmosphere present to moderate the range in surface temperature.

Mercury’s Atmosphere

http://www.psrd.hawaii.edu/Jan97/MercuryUnveiled.html

The smooth areas inside the larger craters in this photo of Mercury may be volcanic plains, somewhat like the maria on the Moon. There are many such smooth plains on Mercury. Some scientists hbave suggested that the plains were formed by rapidly-flowing material ejected from immense impact craters (called basins). However, the plains have smaller numbers of craters on them than do the ejecta blankets of impact basins, indicating a younger age. On some smooth plains, such as those inside the Caloris Basin, sinuous rilles occur, which are thought to be either lava channels or collapsed lava tubes, again suggesting a volcanic origin for the smooth plains.

Mercury’s Volcanoes (?)

Most important, the blue area has fuzzy boundaries that seem to grade into the surroundings. This is what one would expect for a pyroclastic deposit. It is also similar to debris from an impact, but there is no crater in the center that would act as a source for the deposited material. In fact, the dark blue materials lie along a straight segment of a border of Homer, similar to some volcanic fissures on the Moon.

This 1959 pyroclastic eruptionat Kilauea volcano in Hawaiisent lava up to 550 meters intothe air.

Mercury’s Atmosphere

Venus

Venus is the closest planet to the Earth, it is also most similar to Earth in mass, size and density. Venus rotates once every 243 days in a retrograde motion- which means that it rotates in a direction opposite to the rotation of the other planets. (Clockwise when viewed from above the Earth's North Pole). When Earth and Venus meet in their orbit around the Sun, Venus is always facing Earth with the same side. Venus atmosphere is mostly made up of carbon dioxide. The surface temperature is about 450 C which is even hotter than Mercury's "noon" temperature. Scientists believe that Venus is only about 400 million years old. 

Venus

Venus

Venus was a very special goddess in Greek and Roman mythology. She is named after a woman, and her symbol represents a hand mirror. Venus was named after the goddess of love and beauty. In Greek, her name was Aphrodite. The Chinese called Venus Tai-pe, which means "the beautiful white one", the Babylonians called Venus Ishtar, which means "the bright torch of heaven". Venus was born in the sea and was carried to the Greek island of Cyprus. Venus was so beautiful that the gods of Olympus each presented her with a gift to marry him. Jupiter put Venus with the ugly and lame god, Vulcan, who made a magic girdle for her that made her irresistible. Venus fell in love with Mars instead. She had a child Cupid or Eros, who is the god of love. Venus also had many lovers and children. Venus loved the glamour of love. Her son, Cupid married Psyche, a daughter of a king. Venus originally came from Western Asia into Greek mythologies. Her planet has two names: Phosperous "Morning Star" and Hesperus "Evening Star". Some symbols of Venus are the myrtle tree, the swan, sparrow, dove, turquoise and the emerald. Venus represents femininity, love, aesthetics, grace and beauty in astrology.

Venus

Goddess of Love and Beauty

Venus

Venus Facts Sheet:

Type: Terrestrial

Mass of planet (Earth=1) = 0.82Mean density (grams/centimeter³ ) = 5.25

Interior: Iron core about 3000 km radius, rocky mantle and crust

Surface: volcanic and cratered

Water: Probable in the past

Atmosphere: Very thick, primarily Carbon Dioxide, clouds of sulfuric acid

Moons: 0

VenusVenus is the second planet from the Sun, and is Earth's neighbor in the solar system. Venus is the brightest object in the sky after the Sun and the Moon, and sometimes looks like a bright star in the morning or evening sky. We can't see the surface of the planet because it has a very thick atmosphere filled with clouds that strongly reflect sunlight. Observations of Venus in the ultraviolet show cloud features that relate to characteristics of the planet's atmosphere. Venus is slightly smaller than Earth, and considering its neighboring position in the solar system might be expected to be similar to Earth. We think that the internal structure of Venus is similar to Earth, with a metallic core, rocky mantle, and crust. The atmosphere of Venus produces hostile conditions at the planet's surface, where temperatures can reach more than 460C (900F), atmospheric pressure is 90 times that at the Earth's surface, and clouds filled with sulfuric acid surround the planet. Nonetheless, space missions sent to Venus have managed to land on and photograph the surface while the Magellan spacecraft mapped the surface of the planet from above. These maps reveal a surface covered with craters, over 1600 major volcanoes, mountains, large highland terrains, and vast lava plains.

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. Recent results from the Magellan gravity data indicate that Venus' crust is stronger and thicker than had previously been assumed. 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. Venus has no magnetic field, perhaps because of its slow rotation. Venus has no satellites, moons. Venus is usually visible with the unaided eye. Sometimes (inaccurately) referred to as the "morning star" or the "evening star", it is by far the brightest "star" in the sky. There are several Web sites that show the current position of Venus (and the other planets) in the sky. More detailed and customized charts can be created with a planetarium program such as Starry Night.

VenusThe atmosphere of Venus is very hot and thick. If you were on the surface of the planet, the air above you would be about 90 times heavier than the Earth's atmosphere. This is like what a submarine experiences at 3000 ft below the surface of the Earth's ocean. The atmosphere is composed mainly of carbon dioxide (96%), 3.5% nitrogen, and less than 1% is made up of carbon monoxide, argon, sulfur dioxide, and water vapor.

All this carbon dioxide in the air has produced at strong greenhouse effect, which traps heat in the atmosphere. A small amount of sunlight can penetrate the planet's thick cloud layer (about 2%) without being reflected by the sulfuric acid clouds or absorbed by the atmosphere. Whatever sunlight does make it through heats the surface, and is reemitted in the infrared. But virtually all energy emitted by the planet in the infrared (heat radiation) is absorbed by the carbon dioxide rich air. The result is unusually high surface temperatures of about 460C (860F). Why should Venus and not the Earth have a hot and thick atmosphere? Some scientists call it the Goldilocks phenomenon.

Measurements made by probes which travelled through the atmosphere have shown that temperature varies no more than a few degrees from the equator to the poles, and that the atmospheric temperature remains nearly constant through the long dark night. Thus there are no significant daily, seasonal, or latitudinal temperature gradients in the atmosphere.

Venus

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 kilometers thick composed of sulfuric 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. There are strong (350 kph) winds at the cloud tops but winds at the surface are very slow, no more than a few kilometers per hour. Venus probably once had large amounts of water like Earth but it all boiled away. It is now quite dry. Earth would have suffered the same fate had it been just a little closer to the Sun. We may learn a lot about Earth by learning why the basically similar Venus turned out so differently.

Most of Venus' surface consists of gently rolling 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 Aphrodite Terra along the equator (about the 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.

Venus

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. Recent results from the Magellan gravity data indicate that Venus' crust is stronger and thicker than had previously been assumed. 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. Venus has no magnetic field, perhaps because of its slow rotation. Venus has no satellites, moons. Venus is usually visible with the unaided eye. Sometimes (inaccurately) referred to as the "morning star" or the "evening star", it is by far the brightest "star" in the sky. There are several Web sites that show the current position of Venus (and the other planets) in the sky. More detailed and customized charts can be created with a planetarium program such as Starry Night.

Venus

Magellan's images show a wide variety of interesting and unique features including pancake volcanoes which seem to be eruptions of very thick lava and coronae which seem to be collapsed domes over large magma chambers.

Venera Lander (USSR)

Earth

Earth is the only planet known to have the right temperature and the right atmosphere to support the kind of life humans know. Some scientists believe that millions of planets in the Milky Way, (the galaxy that contains the Earth), maybe able to support life, yet no one can predict anything. Many plants and animals have developed on Earth.. Many people believe that Earth is the only planet in the solar system that can support life. The Earth takes 365 days to orbit the Sun. Most of the earth is composed of water. Only about 1% of that is good for human-kind to drink.

Earth is known as Terra Mater in Roman and Gaea in Greek. Her symbol is a sphere or the earth. She was the first goddess on earth. She gave birth to Uranus, whoís also known as ìfather skyî. Gaea and Uranus had children, the hundred-headed, the Cyclops and then the Titans who were very powerful. Since Uranus thought that his children were ugly, he was very cruel to them. Gaea got angry and told one of the Titans to overthrow their father with a scythe. He created the giants, Erinnyes and the beautiful Venus with his blood. Cronus, the Titan, ruled the universe. He had children with his sister, and had children, which included Jupiter, Demeter, Pluto, Neptune, Hera, etc. Jupiter and his sisters and brothers had a war with their father for trying to eat them, but legend says that the one who overthrows his father, their children will overthrow them. Gaea gave birth to another monster called Typhon, which Jupiter easily defeated with his lighting and bolt. Gaea is known as the Goddess of Death because she is like the Earth which eventually brings the dead back to life.

Earth

Goddess of Death

This photo was taken in December 1972 by the Apollo 17 crew. The spacecraft was traveling between the Earth and the Moon. The redish landmass is Africa and Saudi Arabia which is desert. The white is both clouds and the ice covering Antarctica. (Courtesy NASA/JPL)

This United States is a mosaic prepared by using 16 images from the Advanced Very High Resolution Radiometer (AVHRR) sensors on the meteorological satellites NOAA-8 and NOAA-9. The images were taken between May 24, 1984 and May 14, 1986. On false-color infrared mosaics, vegetation appears in red instead of green. The "redness" indicates vegetation density, type and whether growing on dry land or in a swamp. Grasslands appear light red, deciduous trees and croplands appear red, and coniferous forests appear dark red or maroon. Desert areas appear white and urban areas appear bluish green. Lakes, rivers and oceans appear in various shades of blue, dark blue for deep water and light blue for shallow or turbid water. (Courtesy USGS)

Image of clouds taken by the STS-63.

This is an image of the sunrise from space over the South China Sea. An astronaut would see something like this; clearly defined bands of color through the atmosphere as the sun rises. High-peaking cumulus clouds, topping out in anvil-head cirrus can be seen as black shadows against the sunlit horizon. The brightness of the colors in the atmosphere in this photograph is due to the amount of dust in the atmosphere. More dust is found in near the equator. There are various sources for such upper level

This is an image taken of cumulonimbus clouds in the atmosphere. Aris Multimedia Entertainment, Inc. 1994

This is an image of a Cyclonic Storm. Aris Multimedia Entertainment, Inc. 1994

This is an image of a tropical storm. (courtesy of Aris Multimedia Entertainment, Inc. 1994)

This is a satellite image taken of Mount St. Helens Volcano on October 16, 1994 from STS-64. This volcano erupted on May 18, 1980 in Washington. Corel Photography

This is an image of the sun reflecting on the ocean Aris Multimedia Entertainment, Inc. 1994

This is a picture of the Colorado River. Aris Multimedia Entertainment, Inc. 1994

This image shows the topography of the ocean floor. (the Clausthal Mineral Collection, Institute for Mineralogy and Mineral Resources, Technical University of Clausthal; phbotograph by A.K. Schuster.)

Mars

Since ancient times Mars has been an interest to astronomers. Mars is about half the size of Earth. Its atmosphere is composed mostly of carbon dioxide. Liquid water does not exist on Mars because of low temperature and pressure. Water exists only at ice form on the poles of Mars. Another thing about Mars is that it has the largest volcano in our solar system, Olympus Mons. At a height of 27 kilometers, the volcano is 3 times higher than Mount Everest and it covers an area the size of Arizona.

Mars

God of War

Mars is the god of war. His Greek name is Ares and the son of Jupiter and Hera. Mars never married but had three children with Venus. Mars loved war and battle, so many people saw him as a violent god. His animal is the vulture and the tree but it was said to be a dog. Mars is the opposite of Venus and his sign is the male symbol, which represents a shield and a spear. In astrology, Mars shows your energy, strength, courage and passion. 

Mars

Mars Facts Sheet:

Type: Terrestrial

Mass of planet (Earth=1) = 0.11Mean density (grams/centimeter³ ) = 3.95

Interior: rocky

Surface: volcanic, cratered, evidence of river systems

Water: ????

Atmosphere: Primarily Carbon Dioxide, clouds consist of water ice condensed on dust

Moons: 2

Mars

Mars has an average diameter of 4,217 miles. This is about half the size of Earth, and about twice the size of Earth's moon. Despite its small size, Mars has approximately the same land area as Earth, primarily due to an absence of liquid water on its surface. The mass of Mars is about 10 percent that of Earth, and its gravity is about 38 percent as strong as our planet. The density of martian land is 3.9 times greater than liquid water -- on Earth, land density is 5.5 times greater. Mars has no detectable magnetic field.

The martian atmosphere is composed of 95.3 percent carbon dioxide, 2.7 percent nitrogen and 1.6 percent argon. This would be sufficient to suffocate a human in a matter of minutes. The atmospheric pressure there is about 1 percent that of Earth's. Surface winds have been measured to a maximum of 80 m.p.h. -- comparable to hurricane force on Earth. Dust storms occur frequently on Mars. These can be local, regional or can cover the entire planet. Dust can reach as high as six miles above the surface and settles very slowly. Surface temperatures average -64 degrees Fahrenheit, measured from a minimum -199 degrees Fahrenheit during polar night to a maximum +80 degrees Fahrenheit at the martian equator.

Mars

The uniquely red global surface of Mars is marked by many interesting features - some like those on the Earth and others strangely different. The reddish color is caused by rust (iron oxide) in the soil. Some of these features are; volcanoes, canyon systems, river beds, cratered terrain, and dune fields. Of these features, the most interesting includes the apparently dead volcano Olympus Mons, which rises 23 km (~75,000 ft) above the surrounding plains and is the highest known peak in the Solar System. Valles Marineris is a giant canyon system that runs about 2,500 miles across the surface of the planet and reaches depths of 6 km or 4 miles (for comparison, the Grand Canyon is not more than 1 mile deep).

MarsThe atmosphere of Mars is much thinner than that of Earth, with a surface pressure averaging 1/100th that at the surface of the Earth. Surface temperatures range from -113oC at the winter pole to 0oC on the dayside during summer. Although the length of the Martian day (24 hours and 37 minutes) and the tilt of its rotational axis (25 degrees) are similar to the values for these parameters on Earth (24 hours and 23.5 degrees), the eccentric orbit of the planet about the Sun impacts the lengths of the seasons the most. The atmosphere is composed mainly of carbon dioxide (95.3%), nitrogen (2.7%), and argon (1.6%), with trace amounts of other gases. Oxygen, which is so important to us on earth, makes up only 0.13% of the atmosphere at Mars. There is only one-fourth as much water vapor in the atmosphere. Although small, this is thought to be enough to allow water ice to be frozen into the near subsurface at mid to high latitudes. With so little water, clouds are rarely seen in the Martian sky. The possible role in the distant past of liquid water in forming the dry river beds which we can see is still unknown, particularly because water ice is not plentiful on the surface of the planet.

HST

Olympus Mons

Olympus Mons

Viking Landing Site

South Candor Chasm

Valles Marineris

Valles Marineris

South Polar Ice Cap

Viking Lander 1

Sand Dunes Near South Pole

Martian Clouds from Pathfinder

Sunset on Mars

Surface features and soils observed by pathfinder

This stunning image features the heat shield impact site of NASA's Mars Exploration Rover Opportunity. This is an approximately true-color mosaic of panoramic camera images taken through the camera's 750-, 530-, and 430-nanometer filters.

Spirit and Opportunity

Scientists working with NASA's Mars Exploration Rover Spirit decided to examine this rock, dubbed "Wishstone," based on data from the miniature thermal emission spectrometer.

Spirit and Opportunity

Deimos (left) and Phobos (right)

Phobos

The Question of Water

'Pack ice' suggests frozen sea on Mars11:48 21 February 2005 NewScientist.com news service Kelly Young A frozen sea, surviving as blocks of pack ice, may lie just beneath the surface of Mars, suggest observations from Europe's Mars Express spacecraft. The sea is just 5° north of the Martian equator and would be the first discovery of a large body of water beyond the planet's polar ice caps.Images from the High Resolution Stereo Camera on Mars Express show raft-like ground structures - dubbed "plates" - that look similar to ice formations near Earth's poles, according to an international team of scientists. But the site of the plates, near the equator, means that sunlight should have melted any ice there. So the team suggests that a layer of volcanic ash, perhaps a few centimetres thick, may protect the structures."I think it's fairly plausible," says Michael Carr, an expert on Martian water at the US Geological Survey in Menlo Park, California, who was not part of the team. He says scientists had previously suspected there was a past water source north of the Elysium plates. "We know where the water came from," Carr told New Scientist. "You can trace the valleys carved by water down to this area." He says the evidence is "compelling" for past flooding near the plates. "Maybe the ice is still there in the ground, protected by a volcanic cover, as they suggest," he says.There is abundant evidence for the past presence of water on Mars but today it appears relatively dry, with water ice confined to the planet's polar caps. Remote observations of hydrogen atoms by NASA's Odyssey spacecraft in 2002 hinted that ice might be locked in the top metre of soil at lower latitudes. But the evidence was inconclusive as the signal could have come from minerals exposed to water in the past.

Mars – Hot off the Presses 2005

Mars – Hot off the Presses 2006

Dustdevils

http://science.nasa.gov/headlines/y2005/14jul_dustdevils.htm

Mars – Hot off the Presses 2009

Recent Running Water

This Chasm is about 1.25 M years old, and is believed to have contained running water

Mars – Hot off the Presses March 2009

Water

Several photographs taken by NASA’s Phoenix Mars spacecraft show what look like water droplets clinging to one of its landing struts.

Mars – Hot off the Presses 2009

Recent Running Water

1.25 M years ago, who on Earth cares????

And, of course, the Faces on Mars