2.3 THE SOLAR SYSTEM

1. 2.3 THE SOLAR SYSTEM

2. Formation of the Solar System • In space, a cloud of gas and interstellar dust is known as a nebula. • Often consists of 92% Hydrogen (H), 7% Helium (He), and less than 1% of remaining heavier elements. • These clouds rotate, contract gravitationally, and spin rather quickly.

3. Formation of the Solar System • Studies of these nebulae have led to a theory concerning the beginning of our solar system. • According to the Solar Nebula Theory, the Sun and planets formed from a rotating disk of dust and gases. • Also known as the Solar Nebula Disk Model (SNDM). • As speed increased, the center flattened out and matter became more concentrated until the Sun eventually formed.

5. Formation of the Solar System • The planets began their formation through a process known as accretion, where solid bits of matter collide and form together. • This colliding matter formed small, irregular shaped bodies known as planetesimals. • Inner planets (Terrestrial): Mercury, Venus, Earth, and Mars. • Relatively small, rocky, and dense. • Contain large percentages of heavy elements such as iron (Fe) and nickel (Ni). • Outer planets (Jovian): Jupiter, Saturn, Uranus, and Neptune. • Huge gas giants with relatively low densities. • Colder planets, having mainly light elements: hydrogen (H) and helium (He)  gases.

7. Planetary Data 67 62 27 13 3

8. Terrestrial Planets

9. Mercury: The Innermost Planet • Innermost and smallest planet. • NASA’s Messenger provides many images. • Absorbs most sunlight striking its surface due to the lack of an atmosphere (similar to Earth’s moon). • Exhibits cratered highlands, like our moon, and smooth terrains resembling maria of the moon. • Unlike the moon, Mercury is very dense implying it likely has a large iron core. • Greatest temperature extremes of any planet (slow rotation: 59 Earth days).

10. Venus: The Veiled Planet • Similar to Earth in size, density, mass, and location in the solar system thus commonly referred to as “Earth’s Twin”. • Covered in thick clouds, hiding the surface of the planet. • Volcanism and tectonic activity are believed to have impacted the surface (few impact craters, similar to Earth). • 80% of its surface is covered with volcanic flows.

11. Venus: The Veiled Planet • Radar-generated image of a large volcano on the surface. • Magellan spacecraft data. • Greenhouse Effect: the trapping of heat due to certain atmospheric gases. • On Venus, this effect has heated the planet to extreme temperatures; hottest planet in the solar system. • Atmosphere is 97% carbon dioxide (CO2), which is a greenhouse gas. • Lacks oceans, which could dissolve CO2, removing it from the atmosphere. • Responsible for the hot temperatures on the planet.

12. Mars: The Red Planet • The most pronounced feature of Mars is its white polar ice caps. • Data collected from probes concluded the ice caps are made of water ice, covered by frozen carbon dioxide. • Dust storms occur on the planet and much of the surface resembles a large desert. • Atmospheric composition similar to that of Venus. • Atmosphere is extremely thin and doesn’t trap heat like the atmosphere of Venus does, resulting in very cold temperatures on the planet.

13. Mars: The Red Planet • Also has several large inactive volcanoes, including the largest known in the solar system, Olympus Mons. • 3 times the elevation of Mt. Everest (approx. 90,000 ft.) • Several canyons are present as well, some even larger than Earth’s Grand Canyon. • Largest is the Valles Marineris, which is more than 5000 km. long and 8 km. deep.

14. Mars: The Red Planet • Some areas of Mars exhibit drainage patterns, quite similar to those created by streams and rivers on Earth. • Evaporite minerals have been found, as well as geologic formations associated with liquid water. • Present Martian atmosphere contains only slight traces of water. • Some scientists believe the stream-like valleys were created due to melting of ice along the polar ice caps. • Others believe Mars was once covered in flowing water. • Since water is essential to life, this exploration will continue for years to come.

15. Jovian Planets

16. Jupiter: Giant Among Planets • Largest planet of our solar system. • Mass is over 300 times Earth’s mass. • Hydrogen (H) and Helium (He) make up 92% of Jupiter  much like our Sun. • “Star That Failed” • Not enough mass to allow nuclear fusion to begin in its core. • Alternating light and dark bands are gases, such as ammonia (NH3) and methane (CH4) swirling around the planet at a quick pace. • Fastest rotation period of any planet • 9 hours, 50 minutes.

17. VOYAGER 1 Video data from approach to Jupiter in 1979

18. Jupiter: Giant Among Planets • Jupiter’s most distinctive feature is its Great Red Spot. • Giant rotating storm, similar to a hurricane on Earth (trace amounts of water present deep within the atmosphere). • Twice the size of Earth. • Several other smaller storms have been observed on Jupiter. • High wind speeds are caused by temperature differences from heat within the planet’s interior (liquid hydrogen  pressure).

19. Saturn: The Elegant Planet • Composition similar to Jupiter’s. • Voyager 1 and 2 spacecrafts collected various data. • Least dense (lightest) planet of the solar system. • Known for its rings, which are twice the planet’s diameter. • All the gas giants have faint rings, however, Saturn has the most complex and extensive ring system. • Made of billions of dust and ice particles. • Probably came from comets and other bodies traveling in space.

20. Uranus: The Sideways Planets • Unique orientation of the planet wasn’t discovered until 1986, when the Voyager 2 spacecraft passed by. • The planet is turned on its side. • Axis almost parallel to its plane of orbit. • Similar atmospheric composition to the other gas giants. • Blue-green color of the planet also shows a significant amount of methane (CH4) gas present.

21. Neptune: The Windy Planet • Neptune was named after the Roman God of the sea. • Voyager 1 and 2 also provided images of Neptune. • Dark blue in color due to its composition (H2, He, CH4). • Strongest known winds in the solar system. • The Great Dark Spotof Neptune is similar to Jupiter’s Great Red Spot, but not quite as large.

22. Objects Beyond Neptune • Pluto was discovered in 1930 and up until 2006, it was considered the 9th planet of our solar system. • It is now characterized as a dwarf planet, which is defined by meeting the following criteria: • An object orbiting the Sun • Is round because of its own gravity • Has not cleared the region around its orbit • Is not a satellite of another planet

24. Objects Beyond Neptune • In recent years, astronomers have discovered hundreds of objects beyond Neptune’s orbit and have termed them Trans-Neptunian Objects (TNO’s). • Most are just small chunks of ice. • TNO’s exist in a region known as the Kuiper Belt.

27. Satellites of Other Planets • Until the 1600’s, astronomers believed Earth was the only planet with a moon. • In 1610  Galileo discovered four major moons of the planet, Jupiter. • Since then, astronomers have discovered all planets within our solar system, with the exception of Mercury and Venus, have moons.

28. Moons of Mars Phobos • Mars has 2 known moons, named Phobos and Deimos. • Irregularly-shaped chunks of rock and are thought to be captured asteroids. • Surfaces are dark, like the maria of the moon. • Exhibit several craters, indicating possible asteroid contact and old age. Deimos

29. Moons of Jupiter • Jupiter has 67 known moons, including the largest 4, known as the Galilean Moons: IO EUROPA GANYMEDE CALLISTO

30. Io • Io is the innermost of Jupiter’s 4 major Galilean moons. • Several hundred active volcanoes exist on the surface. • Eject thousands of metric tons of material each second. • Most volcanic material is believed to be mainly sulfuric, due to the yellowish color of Io.

31. Europa • Europa is about the size of Earth’s moon and is slightly less dense than our moon. • Crust of ice covers the moon; believed to be about 100 km. in thickness. • Scientists believe a flowing ocean of liquid water may exist underneath this ice sheet. • If liquid water exists, simple life forms may exist as well. • Studies continue to this day of life potential on Europa. http://www.youtube.com/watch?v=6Nz9TdNVz0w

32. Ganymede • Ganymede is the largest known moon of the solar system. • Larger than the planet Mercury. • Much of the surface is covered with ridges and valleys. • A magnetic field is believed to be in existence around Ganymede. • Only moon in the solar system known to have its own magnetic field. • Surrounded by Jupiter’s much more powerful magnetic field.

33. Callisto • Callisto is similar to Ganymede in size, density, and composition, but has a much rougher surface. • One of the most densely cratered moons within our solar system. • Craters are the result of collisions from asteroids occurring early in the history of our solar system.

37. Moons of Saturn • Saturn has 62known moons, most of which are small, icy bodies with many craters. • Saturn’s largest moon is Titan, which is the 2nd largest moon in the solar system, next to Jupiter’s Ganymede. • Titan has a thick atmosphere, composed mainly of Nitrogen (N).

38. Moons of Uranus and Neptune • Uranus has 27 known moons, the most interesting being Miranda. • Originally believed to be split apart by asteroid impact then joined back together (process of accretion). • Further studies suggest tectonic activity does exist, causing the distorted appearance. • Neptune has 13 known moons, the largest being Triton. • Revolves around Neptune in a backwards, or retrograde, orbit (clockwise). Miranda Triton

39. Pluto’s Moons • Although no longer considered a planet, but rather a dwarf planet, Pluto does have at least five known moons. • The largest moon, Charon, is almost half the size of Pluto itself. • Exhibits synchronous rotation, just like Earth’s moon. • Pluto has four other moons. • Nixand Hydra were both discovered in 2005 by the Hubble Space Telescope. • P4 was discovered in 2011 and P5 in 2012. Charon

40. Asteroids Ceres • Asteroids are fragments of rock orbiting the Sun; largest minor bodies of the solar system. • More than 300,000 have been discovered. • Largest known is Ceres. • Exists within the Asteroid Belt between Mars and Jupiter. • Also considered a dwarf planet. • Composition can vary from Carbon (C), Iron (Fe), Nickel (Ni) and Silicon (Si) materials.

41. Comets • Small bodies of ice, rock, and cosmic dust following a highly elliptical orbit around the Sun are known as comets. • Most famous is Halley’s Comet, which passes by Earth every 76 years. • Most recent 1986; Next return in 2061. • Core (Nucleus): made of rock, metals, and ice. • Coma: cloud of gas and dust surrounding the core. • Tail: electrically charged gas particles (ions) resulting from sunlight changing the comet’s ice into gas (sublimation).

42. Oort Cloud • Most astronomers think comets originate in a spherical cloud of dust and ice surrounding out solar system known as the Oort Cloud. • Believed matter within this cloud was leftover from the time the solar nebula was formed. • Contains the nuclei of billions of comets.

43. Meteoroids, Meteors, and Meteorites • Smaller particles, possibly coming from asteroids or comets, orbiting the Sun are known as meteoroids. • Most have diameter < 1 mm. • When a meteoroid enters Earth’s atmosphere, friction heats the surface and causes it to burn up. • As it burns it produces a bright streak of light known as a meteor, which is commonly referred to as a “shooting star”. • Any part of a meteoroid making contact with Earth’s surface, is known as a meteorite. Meteoroid Meteor Meteorite