The Solar System

1. The Solar System SOL 6.8

2. Introduction In this presentation we will : - explore the nine planets and their features. - compare and contrast the similarities and differences of the �inner� and �outer� planets. - examine the location of the solar system in the universe and explore theories about its beginning. - take a detailed look at comets, asteroids, and  moons as significant members of our solar system.

3. Let�s start with the Sun A G2 typical yellow dwarf star Diameter: 1.4 million kilometers Contains 99.8% of the mass of the solar system The volume of the Sun could hold 1 million Earths. Composition: 75% hydrogen, 25% helium Surface Temperature: 5500 oC Core Temperature: 15 million degrees Celsius Rotates on its own axis once every 25.4 days at the equator. Revolves around the center of the Milky Way Galaxy once every 225 million years.

4. How about the planets? The solar system is divided into two basic groups. The inner and outer planets. The inner planets lie inside of the asteroid belt and consist of Mercury, Venus, Earth, and Mars. They are four of the five smallest planets in the solar system and are often called terrestrial planets because of their similarities with Earth. They have high densities because of heavy metal cores. Lets take a closer look at each one.

5. Mercury Mercury is the eighth largest planet (or second smallest) in the Solar System. Mercury is a heavily cratered planet, composed of rock with a central iron core that is three-quarters of the diameter of the planet (3,600 km). Following the Earth, Mercury is the second densest planet in the Solar System. Covered with thousands of craters, the surface of Mercury closely resembles the Earth's Moon. Mercury has few non-cratered areas on the surface, with the exception of the large flat area known as the Caloris Basin, and a few other small areas. The Caloris Basin, the result of an asteroid impact, is 1300 km in diameter.

6. More on Mercury The surface temperature of Mercury is characterized by major fluctuations. The daytime side of the planet reaches over 400 degrees C (752 degrees F), but on the night side the temperature falls to -170 degrees C (-274 degrees F). Mercury has no atmosphere and no known satellites. The only visit to Mercury was made by the Mariner 10 spacecraft in 1974. Mercury was believed by the Greeks to be two different stars. Mercury's appearance in the morning was called Apollo, and its evening appearance was referred to as Hermes. Mercury, often identified with the Greek god, Hermes, is the messenger of the gods in Roman mythology. Mercury is often characterized with winged sandals.

7. How About Venus Venus is the sixth largest planet in the Solar System. Similar in size, density, and mass, Venus and Earth often referred to as sister planets. However the surface and atmosphere of the two planets are drastically different. The atmosphere of Venus is primarily composed of carbon dioxide (96%) and nitrogen (3%), with traces of other gases and little to no water vapor. Venus would have a cold climate if it weren't for the high concentration of carbon dioxide in its atmosphere (96%). The high albedo on Venus reflects the majority of the solar radiation that reaches it, but carbon dioxide, a well known greenhouse gas, keeps the planet extremely warm. In fact the surface temperature of Venus is over 480 degrees C (900 degrees F).

8. More about Venus The clouds in Venus' atmosphere are composed of sulfuric acid which causes the planet to reflect 65% of the sunlight that reaches it. Thus, Venus the third brightest object in the sky (third only to the Sun and the Moon). The atmospheric pressure on the surface of Venus is 90 times the pressure on Earth.. The surface of Venus is very dry with flat plains, highland regions, and depressions. The interior of Venus is composed of a central iron core and a molten rocky mantle, similar to the composition of Earth. The rotation of Venus is very slow. A day on Venus (243 Earth days) is longer than a year (224.7 Earth days). The rotation is also opposite from that of Earth, with the Sun rising in the West.

9. The Russians photographed the surface first with their Venera probe

10. And a little more Venutian info� Venus has been visited by over 20 spacecrafts. The first visit was made by Mariner 2 in 1962. The Soviet Venera 7, which visited Venus in 1970, was the first spacecraft to land on another planet. A recent visit made by the Magellan, launched in 1989, produced high resolution maps of the surface using radar. Venus is named after the Roman goddess of love and beauty.

11. The Third Planet - Earth Diameter: 12.7 thousand kilometers Mass: 6.0 x 1024 kilograms or six sextillion metric tons Composition: water, silicon, carbon, heavy metal iron-nickel core Atmosphere: nitrogen, water vapor, oxygen, carbon dioxide Surface Temperature: -13 � 37oC Called the �Blue Planet� because of the color of nitrogen in it�s atmosphere.

12. More on the Earth The Earth rotates on an axis that is tilted 23 � degrees relative to the orbital or ecliptic plane. It�s period of rotation is one day or 23 hours and 56 minutes. The period of revolution around the Sun is a year or 365 and one-quarter days.

13. Earth (continued) Earth is the fifth largest planet in the Solar System. The Earth is around 4.6 billion years old. Earth is the only presently known planet in the Solar System to support life. The earliest fossil evidence for life dates back 3.5 billion years ago. 71% of Earth's surface is covered in water. The Earth is the densest planet in the Solar System. The Earth travels at an orbital speed of 108,000 km (67,000 miles) an hour. The Earth has only one satellite, the Moon. The Moon is the second brightest object in the sky.

14. How about the Red Planet - Mars Mars is the seventh largest planet in the Solar System. Known as the Red Planet, Mars is characterized by its red, dusty landscape. In observation of Mars seasonal changes and river channels on the surface, many scientists hoped for a possibility of Martian life. They speculated that the composition of Mars' was similar enough to Earth to support life. However, the atmosphere on Mars is very different than Earth's, with only small amounts of life supporting oxygen and water. The atmosphere on Mars is very thin, composed mainly of carbon dioxide(95%), nitrogen(2.7%), and argon(1.6%), with traces of oxygen and water.

15. More on Mars Mars has polar ice caps, composed of solid carbon dioxide, that advance and retreat with the changing seasons. Temperatures on Mars vary from a maximum of 0 degrees C (32 degrees F) to minimum -100 degrees C (-148 degrees F). The terrain on Mars is complex and varied, with deep canyons, mountains, volcanoes, and craters. Olympus Mons, the largest mountain in the Solar System, stands on Mars with an altitude of 24 km (78,000 feet) with a base that is 600 km across. Valles Marineris is a system of canyons that stretch out over the surface of Mars for nearly 2,500 miles (4000 km). The canyons can get up to 200 km wide and 6 km deep in some areas.

16. Mars (continued) Mars was first visited by the Mariner 4, in 1965, which transmitted 22 pictures of the Martian surface back to Earth. The pictures revealed that there was no water or life on the cold surface, shattering hopes to find life on Mars. There has been no proof to date that there was ever life on Mars. Mars has two small satellites named Phobos and Deimos. Mars is the god of war in Roman mythology.

17. What have you learned? Name the inner planets. Which one is smallest? Which one is biggest? Which ones have water? Which is the densest? Which one is the �red planet? Which have no moons? Which one has two moons? Which has no atmosphere? Which has an atmosphere of sulfuric acid? Which is the brightest object in the night sky after the Sun and Moon? Which has one moon? Which has the tallest mountain?

18. The Outer Planets The outer planets consist of four gas giants, Jupiter, Saturn, Uranus, and Neptune, and the outermost planet called Pluto.

19. Another 1-2 AUs and we�ll be in the Asteroid Belt Asteroids are small rocky objects that move in elliptical orbits in the asteroid belt between the orbits of Mars and Jupiter. Their average distance from the Sun is about 2.9 astronomical units (A.U.) Asteroids are also called minor planets. Giuseppe Piazzi discovered the first asteroid, Ceres, on January 1, 1801. Take a look.

21. More on Asteroids Asteroids range in size from Ceres, which has a diameter of about 1000 km, down to the size of pebbles. Sixteen asteroids have a diameter of 240 km or greater. They have been found inside Earth's orbit to beyond Saturn's orbit. Most, however, are contained within a main belt that exists between the orbits of Mars and Jupiter. Astronomers have calculated that, the chances of a collision between Earth and an asteroid averages out to only one collision about every 300,000 years.

22. On to Jupiter Jupiter, the largest planet in our solar system, is 318 times larger than Earth. It has 62 moons. The largest four were discovered by Galilei Galileo. Io, Europa, Ganymede and Callisto Jupiter is the fourth brightest object to be seen in the sky. Occasionally Mars will appear to be brighter than Jupiter in the Earth's sky.

23. More on Jupiter Jupiter spins faster on its axis than any other planet in our solar system. One day on Jupiter is 9.8 Earth hours Jupiter is a gas planet, composed largely of hydrogen (89%) and helium (11%), with traces of methane, water vapor, and ammonia. The gas gets denser with depth turning into liquid toward the center. The tops of the gas clouds in the atmosphere make up the colorful texture on Jupiter. The Great Red Spot is a high pressure region with clouds, moving in a counter-clockwise direction, thought to contain red phosphorus. The cloud tops in the Spot are higher than the surrounding clouds. The Great Red Spot is about 12,000 by 25,000 km.

24. Still More About Jupiter The Pioneer 10 was the first spacecraft to visit Jupiter in 1973, and was followed by visits from Pioneer 11, Voyager 1, Voyager 2, and Ulysses. The Galileo probe arrived in the Jovian system in late 1995 and will remain in orbit there until 1997 (two years). Jupiter, sometimes called Jove, was the King of the gods in Roman mythology and the son of Saturn. Like Saturn, Jupiter has rings, though they are much smaller, fainter, and darker. Jupiter's rings were discovered by the Voyager 1 in 1979. Take a look!

26. How about Saturn Saturn is the sixth planet from the Sun and the second largest. Saturn is flattened at the poles, due to a fast rotation on its axis. Galileo discovered Saturn in 1610, and was confused by its strange appearance in his telescope. Saturn is a gas planet, like Jupiter, and is large enough and far enough away from the Sun to retain its original primitive gases. The atmosphere on Saturn is primarily composed of hydrogen, with small amounts of helium and methane.

27. More about Saturn Saturn is the only planet in our solar system that is less dense that water. Saturn is well known for it's beautiful ring system, which are composed of millions of particles and large chunks of ice and snow. The ring system is divided into various parts, including rings and gaps. The bright A and B rings are separated by a large gap called the Cassini Division. Radial "spokes" composed of fine particles, about the size of dust specks, were found in the B-Ring by the Voyager. Saturn was the god of agriculture in Roman mythology. Saturn is also the father of Jupiter, the king of the Roman gods.

28. Mission to Saturn This photo was taken by the Cassini-Huygens Probe on a mission to Saturn and its largest moon, Titan.

30. How About Uranus? The atmosphere of Uranus is composed of hydrogen, helium, and methane. The methane in the atmosphere absorbs red light, giving the planet a blue-green color. Uranus is considered unusual because the planet is tipped on its side. The poles actually point towards the Sun. This is due to the fact that its magnetic field is tilted 60 degrees from the axis of rotation. Like Venus, Uranus spins from east to west, which is opposite from the spin of Earth.

31. More About Uranus Uranus has rings that are composed of fine dust, rocks, and ice boulders. The rings are very faint and remained undiscovered until the Voyager 2 spacecraft visited the planet in 1986. Voyager 2 is the only spacecraft to have visited Uranus. Uranus is named after the Greek god of the sky. Uranus was the husband of Gaia, the goddess of the Earth. Take a look at the rings of Uranus.

32. Nine rings�Can you Count them?

33. Now on to Neptune Neptune is the fourth largest planet in the Solar System. The only spacecraft ever to visit Neptune was the Voyager 2 in 1989. Neptune is a gas planet, composed of hydrogen, helium, methane, with traces of ammonia and water. The blue color of the planet is due to the absorption of red light by methane in the atmosphere.

34. More about Neptune Neptune has actually been the most distant planet from the sun since 1979 to 1999, due the fact that Pluto's orbit is highly eccentric. Pluto is now the most distant planet from Sun the again. Neptune has the stronger winds than any other planet in the Solar System. Blowing in a westerly direction, winds on Neptune get up to 2,000 km/hour (1,200 miles/hour). "The Scooter" is a cloud that moves around Neptune about every 16 hours. Neptune is the god of the sea in Roman Mythology.

35. Can you see the faint rings of Neptune?

36. On to Pluto Pluto is the smallest planet in our Solar System. Not a very good picture..huh? It�s just too far away. Pluto is named after the Greek lord of the underworld, Hades. It's only satellite, Charon, is named after the boatman who ferried the dead across the River Styx to Hades.

37. More on Pluto Pluto's moon, Charon, is 12,200 miles from the planet and has a diameter of 1,200 km (740 miles). Charon was first seen from Earth in 1978. Pluto and Charon are similar in size, and they orbit each other like a double planet, with the same sides permanently facing each other. Check this out.

38. Pluto and Charon

39. Planetary Moons (9/2003)

40. How about Comets Comets are small, fragile, irregularly shaped bodies composed of a mixture of non-volatile grains and frozen gases. They are thought to come from places in the Solar system called the Kuiper belt, and the Oort Cloud. The Kuiper Belt is a disk-shaped region past the orbit of Neptune extending roughly from 30 to 50 AU from the Sun containing many small icy bodies. It is now considered to be the source of the short-period comets. Occasionally the orbit of a Kuiper Belt object will be disturbed by the interactions of the giant planets in such a way as to cause the object to cross the orbit of Neptune or cross into the inner solar system. The statistics imply that the Oort cloud may contain as many as a trillion (1e12) comets. Unfortunately, since the individual comets are so small and at such large distances, we have no direct evidence about the Oort Cloud.

41. The Anatomy of a Comet

42. Space Missions to Comets Deep Space 1: NASA. Launched in 1998. DEEP SPACE 1 flew within 10 miles (16 kilometers) of Asteroid 1992 KD Braille on July 28, 1999. The mission is mainly a test of new propulsion and navigation technology. The extended mission was to include flybys of two comets, Wilson-Harrington and Borrelly, but a problem with the tracking system meant that priority is now being given to Comet Borrelly. Stardust: NASA. Launched 1999. STARDUST will fly past comet Wild 2 and capture dust grains blown from the comet's surface. These will be returned to Earth for analysis.