AST 301Introduction to AstronomyJohn LacyRLM [email protected] LiRLM [email protected] JeonRLM [email protected] site: www.as.utexas.eduGo to Department of Astronomy courses,AST 301 (Lacy), course websiteRearranged schedule for next few weeksThis week: Introduction to planets and a bit of geologyNext week: Planet formation and a bit on small bodiesThird week: Atmospheres9/27 Ch 710/4 Ch 8 (Prof. Dinerstein)10/11 Ch 1010/18 Ch 13 (back on schedule)Wednesday’s quizA red laser and a green laser. Both emit 1 mW of power.Red is longer wavelength.Green is higher frequency. (f = c/λ)Green photons have high energy. (E = hf)Same power (1 mW).Power = Energy/sec = Energy/photon x photons/sec,so you need more red photons to carry the same amountof power as the green photons.Topics for this weekDescribe and compare briefly the compositions and orbits ofthe terrestrial planets, Jovian planets, asteroids, andcomets.What is inside of the terrestrial planets?What determines the appearances of the surfaces of theterrestrial planets?How do we determine the age of the planets?Terrestrial PlanetsThe inner four planetsSizes similar to the Earth’sInteriors made of metals and rocksVery thin atmospheres (compared to the diameters of theplanets)Earth also has oceans (and Mars may once have). Thesealso make up a small fraction of the volume.The order from the Sun: Mercury, Venus, Earth, MarsJovian planetsThe next four planetsDiameters about 10 times the terrestrial planets’Interiors made of ices and gasses (probably with smallrocky cores)Jupiter and Saturn are mostly gas.Uranus and Neptune are mostly (partially melted) ices.The order from the Sun: Jupiter, Saturn, Uranus, Neptune(and then lots of smaller icy bodies like Pluto)“Flying” over VenusThe video was made from radar data from Venera andMagellan orbiters.Brightnesses correspond to radar reflectivities (generallyroughnesses).The vertical scale is exaggerated by a factor of 10.Most of the features are volcanic: domes, lava flows, andcalderas.Others are impact craters.Without liquid water, there is less erosion on Venus, socraters are more common and prominent than on Earth.Impact cratersWhy is it bright around the craters?What is the streak going to the left?Why is the surface between the craterssmooth?Shield volcanoes: Sapas Mons and Maat MonsMauna Loavisible light and radarWhat are the circular cracks?What are the pancake domes?Russian Venera on the surface of VenusWhy haven’t we been there?Mars movieThe data are from the Viking orbiters.Vertical scale is exaggerated by a factor of 5.The “flight” goes over Valles Marineris, the Tharsisvolcanoes, and Olympus Mons.Valles Marineris may have been cut by water, and is 1800miles long.Olympus Mons is 15 miles (75,000 ft) high and as wide asMissouri.Mars elevation mapWhy is the southern hemisphere higher and rougher?Olympus MonsValles Marinerisand TharsisvolcanoesValles MarinerisA QuestionWhy are the volcanoes of Mars so much larger thanvolcanoes on Earth?What is different about Mars that might cause its volcanoesto be larger?Ask your neighbors and come up with some
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