6The Solar System The Planets: An Overview The terrestrial planets are planets that are small and rocky—Mercury, Venus, Earth, and Mars. The Jovian planets are the huge gas giants—Jupiter, Saturn, Uranus, and Neptune. Pluto does not fit into either the Jovian or the terrestrial category.
9The terrestrial planets are also called the Rocky or the Inner planets. The Jovian planets are also called the Giant or the Outer or the Gas planets.
10Orbits of the PlanetsThe Sun’s gravitational pull guides the elliptical orbitsof the planets in our Solar System.Makes no sense without caption in book
11The Solar System The Planets: An Overview Size is the most obvious difference between the terrestrial and Jovian planets.Earth’s mass is 1/17th of the mass of Neptune (the smallest Jovian planet). Density, chemical makeup, and rate of rotation are other ways in which the two groups of planets differ.
20The Atmosphere of the Planets • The Jovian planets have very thick atmospheres of hydrogen, helium, methane, and ammonia.
21By contrast, the terrestrial planets, including Earth, have thin, meager atmospheres at best.
22Gases can escape from its planet’s gravity if it reaches escape velocity. For Earth, escape velocity is 11 km/s.For Jovian planets, the escape velocities are between km/s. So it is more difficult for gases to escape a Jovian planet’s gravity.
24Scale of the PlanetsMakes no sense without caption in book
25The Solar System Formation of the Solar System Nebular Theory • A nebula is a cloud of gas and/or dust in space.A nebula often consists of 92% H, 7% He, and <1% heavier elements.
26According to the nebular theory, the sun and planets formed from a rotating disk of dust and gases. As the speed of rotation increased, the center of the disk began to flatten out and become more concentrated. This eventually became our sun!!
28The Hubble Telescope captured this picture of a nebula near a dying star (450 light years away in the constellation Aquarius) (these are two gases colliding)
29Formation!The Solar System was formed from the contraction of a pre-solar nebula, a vast cloud of gas and dust.The center of the nebula became the Sun and the outer parts accreted to form the planetesimals.
30The Solar System Formation of the Solar System • Planetesimals are small, irregularly shaped bodies formed by colliding matter.Over time, these planetisimals will collect enough material/mass to have their own gravitational pull.The inner planets (close to the sun) were too hot for ice to form and only rocky material accreted.The outer planets (far from the sun) had both solid matter and ice to accrete.
31Formation of the Universe Makes no sense without caption in book
32Planetary Composition, Distance from the Sun, and Melting Point Makes no sense without caption in book
37Because Mercury is so small, the gravity on Mercury is 38% of the gravity on Earth. A 100 pound person would weigh only 38 pounds on Mercury. To calculate your weight on Mercury, just multiply your weight by 0.38
38Orbit: very elliptical with no seasons (because no tilt) Mercury orbits the sun every 88 days and has a rotation of 59 days.
39Surface Features• Mercury has cratered highlands, much like the moon, and vast smooth terrains that resemble maria.
41Surface Temperatures Mercury has a very, very thin atmosphere. This means that it has no shielding from the sun’s energy (on the light side) and no way to hold this energy (on the dark side).Mercury has the greatest temperature extremes of any planet.
42Since the atmosphere is so thin, the sky would appear pitch black (except for the sun, stars, and other planets, when visible), even during the day.
43Mercury has a daytime temperature of about 400⁰ C and a nighttime temperature of about -200 ⁰ C, a mere 73 degrees above absolute zero.
44Mercury’s SurfaceMakes no sense without caption in book
45If you were on the surface of Mercury, the Sun would look almost three times as big as it does from Earth!
47VenusMercury was visited by NASA's Mariner 10 in 1973 and 1974 (robotic space probe that visited both Venus and Mercury). Mariner is STILL orbiting the Sun, but is no longer transmitting (and is probably horribly damaged by the Sun’s energy.)
57Venus’ AtmosphereVenus has the densest atmosphere (93 times denser than Earth’s) of all the terrestrial planets, consisting mostly of carbon dioxide (97%).Venus is covered with an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light.
58Revolution and Rotation Venus’ orbital length is Earth days.Venus’ rotational period is 243 Earth days (slowest of any major planet).Also, Venus is the only planet to rotate clockwise!!!
59Surface TemperaturesThe average surface temperature of Venus reaches 475oC. There is little variation between night and day because of the thick atmosphere and slow rotation.There is minimal tilt so essentially no seasons.
63Mars is the Red Planet because of the iron oxide in the crust Mars is the Red Planet because of the iron oxide in the crust . Iron oxide is reddish in color.
64Mars: The Red Planet! The Martian Atmosphere The Martian atmosphere has only 1 percent of the density of Earth’s.Although the atmosphere of Mars is very thin, extensive dust storms occur and may cause the color changes observed from Earth.
65Surface FeaturesMost Martian surface features are old by Earth standards.The highly cratered southern hemisphere is probably 3.5 billion to 4.5 billion years old.
66Mars’ MoonsMars has two moons, Phobos and Deimos, which are small and irregularly shaped.
67Orbiting spacecraftMars is currently host to three functional orbiting spacecraft: Mars Odyssey, Mars Express, and the Mars Reconnaissance Orbiter. This is the most of any planet (other than Earth).
68Surface LandersThe surface is also home to the two Mars Exploration Rovers (Spirit and Opportunity) and several inert landers and rovers, both successful and unsuccessful. The Phoenix lander recently completed its mission on the surface.
71The Polar Landers have determine water on Mars!!!
72Water on MarsMakes no sense without caption in book
7323.3 The Outer Planets Jupiter: Giant Among Planets Jupiter has a mass that is 2 1/2 times greater than the mass of all the other planets and moons combined. Structure of Jupiter• Jupiter’s hydrogen-helium atmosphere also contains small amounts of methane, ammonia, water, and sulfur compounds.
74Jupiter and the Great Red Spot Makes no sense without caption in book
7523.3 The Outer Planets Jupiter: Giant Among Planets Jupiter’s Moons • Jupiter’s satellite system, including the 28 moons discovered so far, resembles a miniature solar system. Jupiter’s Rings• Jupiter’s ring system was one of the most unexpected discoveries made by Voyager 1.
76Jupiter’s Largest Moons Makes no sense without caption in book
7723.3 The Outer Planets Saturn: The Elegant Planet The most prominent feature of Saturn is its system of rings. Features of Saturn• Saturn’s atmosphere is very active, with winds roaring at up to 1500 kilometers per hour.• Large cyclonic “storms” similar to Jupiter’s Great Red Spot, although smaller, occur in Saturn’s atmosphere.
78Cassini Approaching Saturn Makes no sense without caption in book
7923.3 The Outer Planets Saturn: The Elegant Planet Saturn’s Rings • Until the discovery that Jupiter, Uranus, and Neptune have ring systems, this phenomenon was thought to be unique to Saturn.• Most rings fall into one of two categories based on particle density. Saturn’s Moons• Saturn’s satellite system consists of 31 moons.• Titan is the largest moon, and it is bigger than Mercury.
80Saturn’s RingsMakes no sense without caption in book
8123.3 The Outer Planets Uranus: The Sideways Planet Instead of being generally perpendicular to the plane of its orbit like the other planets, Uranus’s axis of rotation lies nearly parallel with the plane of its orbit.
8523.3 The Outer Planets Pluto: Planet X Pluto’s orbit is highly eccentric, causing it to occasionally travel inside the orbit of Neptune, where it resided from 1979 through February 1999.
8623.4 Minor Members of the Solar System Asteroids: Microplanets23.4 Minor Members of the Solar System An asteroid is a small, rocky body whose diameter can range from a few hundred kilometers to less than a kilometer. Most asteroids lie between the orbits of Mars and Jupiter. They have orbital periods of three to six years.
87Irregular Orbits of Asteroids Makes no sense without caption in book
8823.4 Minor Members of the Solar System Comets23.4 Minor Members of the Solar System Comets are small bodies made of rocky and metallic pieces held together by frozen gases. Comets generally revolve about the sun in elongated orbits.
8923.4 Minor Members of the Solar System Comets23.4 Minor Members of the Solar System Coma• A coma is the fuzzy, gaseous component of a comet’s head.• A small glowing nucleus with a diameter of only a few kilometers can sometimes be detected within a coma. As comets approach the sun, some, but not all, develop a tail that extends for millions of kilometers.
90Comet’s Tail Points Away from the Sun Makes no sense without caption in book
9123.4 Minor Members of the Solar System Comets23.4 Minor Members of the Solar System Kuiper Belt• Like the asteroids in the inner solar system, most Kuiper belt comets move in nearly circular orbits that lie roughly in the same plane as the planets. Oort Cloud• Comets with long orbital periods appear to be distributed in all directions from the sun, forming a spherical shell around the solar system called the Oort cloud.
9223.4 Minor Members of the Solar System Comets23.4 Minor Members of the Solar System Halley’s Comet• The most famous short-period comet is Halley’s comet. Its orbital period is 76 years.
9323.4 Minor Members of the Solar System Meteoroids23.4 Minor Members of the Solar System A meteoroid is a small, solid particle that travels through space. A meteor is the luminous phenomenon observed when a meteoroid enters Earth’s atmosphere and burns up, popularly called a shooting star. A meteorite is any portion of a meteoroid that reaches Earth’s surface.
9423.4 Minor Members of the Solar System Meteoroids23.4 Minor Members of the Solar System Most meteoroids originate from any one of the following three sources: (1) interplanetary debris that was not gravitationally swept up by the planets during the formation of the solar system, (2) material from the asteroid belt, or (3) the solid remains of comets that once traveled near Earth’s orbit.
95Major Meteor ShowersMakes no sense without caption in book