Planets and Moon

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Planets and Moon

  1. 1. The Planets and the Moon
  2. 2. Mercury orbit: 57,910,000 km (0.38 AU) from Sun diameter: 4,880 km mass: 3.30e23 kg• closest planet to the Sun and the eighth largest• slightly smaller in diameter than the moons Ganymede and Titan but more than twice as massive
  3. 3. Mercury• has been known since at least the time of the Sumerians• given separate names for its apparitions as a morning star and as an evening star• Heraclitus even believed that Mercury and Venus orbit the Sun, not the Earth.
  4. 4. Mercury• Has the most extreme temperature variations in the solar system raging from 90K to 700K• is in many ways similar to the Moon: its surface is heavily cratered and very old; it has no plate tectonics.• Mercury is the second densest major body in the solar system, after Earth (much denser than the moon)
  5. 5. Mercury Mercury CratersThis indicates that Mercurys dense iron core isrelatively larger than Earths, probablycomprising the majority of the planet. Mercurytherefore has only a relatively thin silicatemantle and crust.
  6. 6. Mercury• Mercurys orbit is highly eccentric ; at perihelion it is only 46 million km from the Sun but at aphelion it is 70 million. The position of the perihelion precesses around the Sun at a very slow rate
  7. 7. Mercury19th century astronomers made very careful observations of Mercurys orbital parameters but could not adequately explain them using Newtonian mechanics. The tiny differences between the observed and predicted values were a minor but nagging problem for many decades. It was thought that another planet (sometimes called Vulcan) slightly closer to the Sun than Mercury might account for the discrepancy. But despite much effort, no such planet was found. The real answer turned out to be much more dramatic: Einsteins General Theory of Relativity! Its correct prediction of the motions of Mercury was an important factor in the early acceptance of the theory.
  8. 8. Venus Venus (Greek: Aphrodite; Babylonian: Ishtar) is the goddess of love and beauty• The planet is so named probably because it is the brightest of the planets known to the ancients. (With a few exceptions, the surface features on Venus are named for female figures.)
  9. 9. Venus• known since prehistoric times. It is the brightest object in the sky except for the Sun and the Moon• Like Mercury, it was popularly thought to be two separate bodies: Eosphorus as the morning star and Hesperus as the evening star , but the Greek astronomers knew better. (Venuss apparition as the morning star is also sometimes called Lucifer.)
  10. 10. Venus• 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.• once had large amounts of water like Earth but it all boiled away. Venus is now quite dry. Earth would have suffered the same fate had it been just a little closer to the Sun
  11. 11. Venus• Most of Venus surface consists of gently rolling plains with little relief. There are also several broad depressions: Atalanta Planitia, Guinevere Planitia, Lavinia Planitia.
  12. 12. Venus• 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)
  13. 13. Venus• 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.
  14. 14. Earth orbit: 149,600,000 km (1.00 AU) from Sun diameter: 12,756.3 km mass: 5.972e24 kg• Earth is the third planet from the Sun and the fifth largest• Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic.
  15. 15. Earth• 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.• once had large amounts of water like Earth but it all boiled away. Venus is now quite dry. Earth would have suffered the same fate had it been just a little closer to the Sun
  16. 16. EarthThe Earth is divided into several layers which havedistinct chemical and seismic properties (depths inkm): 0 – 40 Crust 40 – 400 Upper Mantle 400 – 650 Transition Region 650 – 2700 Lower Mantle 2700 – 2890 D” Layer 2700 – 5150 Outer Core 5150 – 6378 Inner Core
  17. 17. EarthMost of the mass of the Earth is in the mantle, mostof the rest in the core; the part we inhabit is a tinyfraction of the whole (values below x10^24kilograms): Atmosphere 0.0000051 Ocean 0,0014 Crust 0,026 Mantle 4.043 Outer core 1.835 Inner core 0.09675
  18. 18. Mars Mars (Greek: Ares) is the god of War. The planet probably got this name due to its red color• sometimes referred to as the Red Planet. (An interesting side note: the Roman god Mars was a god of agriculture before becoming associated with the Greek Ares; those in favor of colonizing and terraforming Mars may prefer this symbolism.)• The name of the month March derives from Mars.
  19. 19. Mars Mars’ Surface
  20. 20. Mars• Mars orbit is significantly elliptical. One result of this is a temperature variation of about 30 C at the subsolar point between aphelion and perihelion (major influence on its climate)• While the average temperature on Mars is about 218 K (-55 C, -67 F), Martian surface temperatures range widely from as little as 140 K (-133 C, -207 F) at the winter pole to almost 300 K (27 C, 80 F) on the day side during summer.
  21. 21. MarsThe interior of Mars is known only by inference from dataabout the surface and the bulk statistics of the planet. Themost likely scenario is a dense core about 1700 km inradius, a molten rocky mantle somewhat denser than theEarths and a thin crust. Data from Mars Global Surveyorindicates that Mars crust is about 80 km thick in thesouthern hemisphere but only about 35 km thick in thenorth. Mars relatively low density compared to the otherterrestrial planets indicates that its core probably containsa relatively large fraction of sulfur in addition to iron (ironand iron sulfide).
  22. 22. MarsMars has two tiny satellites which orbit very closeto the martian surface: Satellite (000 km) (km) (kg) Discover Year er Phobos 9 11 1.08e16 Hall 1877 Deimos 23 6 1.80315 Hall 1877
  23. 23. Jupiter Jupiter (a.k.a. Jove; Greek Zeus) was the King of the Gods, the ruler of Olympus and the patron of the Roman state.• Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus)The name of the month March derives from Mars• known since prehistoric times as a bright "wandering star".
  24. 24. Jupiter• 1610 when Galileo first pointed a telescope at the sky he discovered Jupiters four large moons Io, Europa, Ganymede and Callisto (now known as the Galilean moons)• This was the first discovery of a center of motion not apparently centered on the Earth.
  25. 25. JupiterIt was a major point in favor of Copernicussheliocentric theory of the motions of the planets(along with other new evidence from his telescope:the phases of Venus and the mountains on theMoon). Galileos outspoken support of theCopernican theory got him in trouble with theInquisition.
  26. 26. Saturn Saturn is the god of agriculture. The associated Greek god• Saturn has been known since prehistoric times. Galileo was the first to observe it with a telescope in 1610• Early observations of Saturn were complicated by the fact that the Earth passes through the plane of Saturns rings every few years as Saturn moves in its orbit
  27. 27. Saturn• Saturns rings remained unique in the known solar system until 1977 when very faint rings were discovered around Uranus (and shortly thereafter around Jupiter and Neptune• Saturn is visibly flattened (oblate) when viewed through a small telescope; its equatorial and polar diameters vary by almost 10% (120,536 km vs. 108,728 km). This is the result of its rapid rotation and fluid state. The other gas planets are also oblate, but not so much so.
  28. 28. Saturn• Saturn is the least dense of the planets; its specific gravity (0.7) is less than that of water.• Saturn is the least dense of the planets; its specific gravity (0.7) is less than that of water.• Saturns interior is similar to Jupiters consisting of a rocky core, a liquid metallic hydrogen layer and a molecular hydrogen layer. Traces of various ices are also present.
  29. 29. Saturn• Saturns rings are extraordinarily thin: though theyre 250,000 km or more in diameter theyre less than one kilometer thick. Despite their impressive appearance, theres really very little material in the rings -- if the rings were compressed into a single body it would be no more than 100 km across.
  30. 30. Uranus ancient Greek deity of the Heavens, the earliest supreme god• the first planet discovered in modern times, was discovered by William Herschel while systematically searching the sky with his telescope on March 13, 1781• (the earliest recorded sighting was in 1690 when John Flamsteed cataloged it as 34 Tauri)
  31. 31. Uranus• The name "Uranus" was first proposed by Bode in conformity with the other planetary names from classical mythology but didnt come into common use until 1850.• Uranus axis is almost parallel to the ecliptic.• Uranus south pole was pointed almost directly at the Sun. This results in the odd fact that Uranus polar regions receive more energy input from the Sun than do its equatorial regions.
  32. 32. Uranus• Uranus is composed primarily of rock and various ices, with only about 15% hydrogen and a little helium (in contrast to Jupiter and Saturn which are mostly hydrogen).• Uranus has bands of clouds that blow around rapidly. But they are extremely faint, visible only with radical image enhancement
  33. 33. Uranus Uranus’ Clouds
  34. 34. Uranus• Uranus blue color is the result of absorption of red light by methane in the upper atmosphere.• Uranian rings were the first after Saturns to be discovered. This was of considerable importance since we now know that rings are a common feature of planets, not a peculiarity of Saturn alone.
  35. 35. Neptune the god of the Sea.• . Neptune was first observed by Galle and dArrest on 1846 Sept 23 very near to the locations independently predicted by Adams and Le Verrier from calculations based on the observed positions of Jupiter, Saturn and Uranus
  36. 36. Neptune• Neptunes composition is probably similar to Uranus: various "ices" and rock with about 15% hydrogen and a little helium. Like Uranus• Neptunes blue color is largely the result of absorption of red light by methane in the atmosphere but there is some additional as-yet-unidentified chromophore which gives the clouds their rich blue tint.
  37. 37. Neptune• Neptune has rapid winds confined to bands of latitude and large storms or vortices. Neptunes winds are the fastest in the solar system, reaching 2000 km/hour.• Neptune has an internal heat source -- it radiates more than twice as much energy as it receives from the Sun.
  38. 38. Neptune• Neptunes rings have been given names: the outermost is Adams (which contains three prominent arcs now named Liberty, Equality and Fraternity), next is an unnamed ring co- orbital with Galatea, then Leverrier (whose outer extensions are called Lassell and Arago), and finally the faint but broad Galle.• Neptunes magnetic field is, like Uranus, oddly oriented and probably generated by motions of conductive material (probably water) in its middle layers.
  39. 39. NeptuneNeptune can be seen with binoculars (if youknow exactly where to look) but a largetelescope is needed to see anything otherthan a tiny disk. There are severalWeb sites that show the current position ofNeptune (and the other planets) in the sky,but much more detailed charts will berequired to actually find it. Such charts canbe created with a planetarium program.
  40. 40. Pluto orbit: 5,913,520,000 km (39.5 AU) from the Sun (average) diameter: 2274 km mass: 1.27e22 kg• In Roman mythology, Pluto (Greek: Hades) is the god of the underworld. The planet received this name (after many other suggestions) perhaps because its so far from the Sun that it is in perpetual darkness and perhaps because "PL" are the initials of Percival Lowell
  41. 41. Pluto• Pluto was discovered in 1930 by a fortunate accident• After the discovery of Pluto, it was quickly determined that Pluto was too small to account for the discrepancies in the orbits of the other planets• Fortunately, Pluto has a satellite, Charon
  42. 42. Pluto• Charon was discovered (in 1978) just before its orbital plane moved edge-on toward the inner solar system. It was therefore possible • The surface temperature on Pluto to observevaries between about -235 and -210 C over many transits of Pluto Charon and viceK). The "warmer"regions that (38 to 63 versa roughly correspond to the regions• Plutos orbit is highly optical wavelengths times it is appear darker in eccentric. At closer to the Sun than Neptune (as it was from January 1979 thru February 11 1999). Pluto rotates in the opposite direction from most of the other planets.
  43. 43. Pluto• The surface temperature on Pluto varies between about -235 and -210 C (38 to 63 K). The "warmer" regions roughly correspond to the regions that appear darker in optical wavelengths• Plutos composition is unknown, but its density (about 2 gm/cm3) indicates that it is probably a mixture of 70% rock and 30% water ice much like Triton. The bright areas of the surface seem to be covered with ices of nitrogen with smaller amounts of (solid) methane, ethane and carbon monoxide
  44. 44. PlutoLittle is known about Plutos atmosphere, but it probably consists primarily of nitrogen with some carbon monoxide and methane. It is extremely tenuous, the surface pressure being only a few microbars. Plutos atmosphere may exist as a gas only when Pluto is near its perihelion; for the majority of Plutos long year, the atmospheric gases are frozen into ice. Near perihelion, it is likely that some of the atmosphere escapes to space perhaps even interacting with Charon. NASA mission planners want to arrive at Pluto while the atmosphere is still unfrozen
  45. 45. Moon
  46. 46. Moon orbit : 384,400 km from Earth diameter : 3476 km mass : 7.35e22 kg• It is the second brightest object in the sky after the Sun
  47. 47. Moon• Moon orbits around the Earth once per month, the angle between the Earth, the Moon and the Sun changes; we see this as the cycle of the Moons phases. The time between successive new moons is 29.5 days (709 hours), slightly different from the Moons orbital period (measured against the stars) since the Earth moves a significant distance in its orbit around the Sun in that time.• Due to its size and composition, the Moon is sometimes classified as a terrestrial "planet" along with Mercury, Venus, Earth and Mars.
  48. 48. Moon• gravitational forces between the Earth and the Moon cause some interesting effects. The most obvious is the tides. The Moons gravitational attraction is stronger on the side of the Earth nearest to the Moon and weaker on the opposite side. Since the Earth, and particularly the oceans, is not perfectly rigid it is stretched out along the line toward the Moon.
  49. 49. Moon The Moon has no atmosphere. But evidence from Clementine suggested that there may be water ice in some deep craters near the Moons south pole which are permanently shaded. This has now been reinforced by data from Lunar Prospector. There is apparently ice at the north pole as well. A final determination will probably come from NASAs Lunar Reconnaissance Orbiter, scheduled for 2008.
  50. 50. Moon• The Moons crust averages 68 km thick and varies from essentially 0 under Mare Crisium to 107 km north of the crater Korolev on the lunar far side. Below the crust is a mantle and probably a small core (roughly 340 km radius and 2% of the Moons mass).
  51. 51. MoonThere are two primary types of terrain on the Moon: the heavily cratered and very old highlands and the relatively smooth and younger maria. The maria (which comprise about 16% of the Moons surface) are huge impact craters that were later flooded by molten lava. Most of the surface is covered with regolith, a mixture of fine dust and rocky debris produced by meteor impacts. For some unknown reason, the maria are concentrated on the near side.

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