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Exploration of Io wikipedia , lookup
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Planetary Orbits Mercury Venus Earth All planets in almost circular (elliptical) orbits around the sun, in approx. the same plane (ecliptic). Sense of revolution: counter-clockwise Sense of rotation: counter-clockwise (with exception of Venus, Uranus) (Distances and times reproduced to scale) Orbits generally inclined by no more than 3.4o Exceptions: Mercury (7o) The Solar Nebula Hypothesis Basis of modern theory of planet formation. Planets form at the same time from the same cloud as the star. Planet formation sites observed today as dust disks of T Tauri stars. Sun and our solar system formed ~ 5 billion years ago. Two Kinds of Planets Planets of our solar system can be divided into two very different kinds: Terrestrial (earthlike) planets: Mercury, Venus, Earth, Mars Jovian (Jupiter-like) planets: Jupiter, Saturn, Uranus, Neptune Space Debris In addition to planets, small bodies orbit the sun: Asteroids, comets, meteoroids Sample of asteroids Terrestrial Planets Four inner planets of the solar system Relatively small in size and mass (Earth is the largest and most massive) Rocky surfaces Weak or no present atmospheres Few or no moons No ring system Surface of Venus can not be seen directly from Earth because of its dense cloud cover. Mercury Closest planet to the Sun but not the hottest. No atmosphere No moons It is smaller than a couple of moons however it is more massive since it is made mostly of metals. Notable space missions: Mariner 10 MESSENGER Venus Clouds of SO2 Similar in size and mass to the Earth No moons Dense atmosphere containing mostly CO2 leading to a massive greenhouse effect. Hottest planet in the solar system. Rotates backwards and day is about 250 Earth days Visual wavelength image Venus Rocky surface is covered with volcanoes and craters. Volcanic activity is currently a mystery. In March 2014 infrared flashes were detected from the surface indicating outgassing. Notable space missions: -Venera (Russian) -Mariner (US) -Venus Express (ESA) Radar imaging of surface Surface of Venus from Venera 9 First image of the surface of another planet Surface craters Maat Mons Largest volcano on Venus Mars Olympus Mons Polar caps of CO2 and water ice. Half the radius of the Earth but equal in land surface area. Two “moons”. Weak atmosphere containing mostly CO2 and weak amounts of methane and ammonia. Similar rotational period (24hr 37m) and axial tilt to Earth (25.2°) Surface is most similar to Earth Host to many current space science missions Valles Marineris The Jovian Planets Complex satellite systems Thick atmospheres Much larger in mass and size than terrestrial planets Much lower average density All have rings (not only Saturn!) Mostly gas; no solid surface Jupiter Largest planet No solid surface Atmosphere is primarily hydrogen and helium with trace amounts of methane, ammonia and hydrogen sulfide. Faint system of rings Over 60 moons Gigantic magnetic field causes auroras at the poles. Great Red Spot – giant storm Large gravitational influence as a as solar system “vacuum cleaner” Visited by Pioneers, Voyagers, Galilieo spacecraft. Galilean satellites Io Europa Ganymede Callisto Jupiter from Voyager 1 - https://www.youtube.com/watch?v=9nf9nBtd2dM Jupiter in Motion - https://youtu.be/MyNkyL2mpmM?t=17m35s Jupiter Cloud Motion - https://www.youtube.com/watch?v=RdIfnymd9Aw Saturn Very similar in composition to Jupiter. Substantial ring system Largest satellite system with over 150 members. Titan is the largest moon. Sunlight reflected off liquid bodies on Titan Huygens Descent to Titan - https://youtu.be/9L471ct7YDo?t=37s Uranus Gas giant but contains a significant amount of ice. Bland atmosphere due to no internal heat source. As a result, high wind speed smooth out the atmosphere Color is mainly due to methane Weak ring system and around 27 satellites Visited only by Voyager 2 Neptune Gas giant but contains a significant amount of ice. Bland atmosphere due to no internal heat source. As a result, high wind speed smooth out the atmosphere Color is mainly due to methane Weak ring system and around 14 satellites Visited only by Voyager 2