Lecture19 - Lecture #19: Mars Mars: Overview General...

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1 Astro 102/104 1 Lecture #19: Mars • Mars: Overview •General properties •Telescopic observations •Space missions •Atmospheric Characteristics • Reading: – Chapters 7.1 (Mars), 9.4, 10.4 Astro 102/104 2 The Main Point Changes in the Martian surface and atmosphere have been studied for centuries by telescopes, and more recently even more details have been discovered by spacecraft missions. Astro 102/104 3 Basic Properties of Mars • Average Distance from Sun: 227,900,000 km (a=1.52 AU) • Orbital period: 687 days • Period of Spin around axis: 24 hours, 37 minutes (= 1 Sol ) • Tilt of Martian spin axis: 25.2° (Mars has seasons ) • Mass: 6.7x10 23 kg = 0.11 M E ; Radius: 3397 km = 0.53 R E • Surface area of Mars Land area of Earth's continents • Density = 3.9 g/cm 3 (little metal; some ice? (Earth: 5.5)) • Surface Gravity = 3.7 m/sec 2 (38% of Earth's) • Thin CO 2 -rich atmosphere; Surface pressure ~1% Earth's • Average Surface Temperature: -60°C (-76°F); Δ T ~100°C • Complex surface geologic processes at work. .. Astro 102/104 4 Observations • Recall: Mars sometimes has a retrograde motion • Earth has a "close encounter" with Mars about once every 26 months – Distance varies because Mars' orbit is eccentric • During these times, Mars is a prominent bright "star" in the evening sky – It is noticeably red! – Hence its historic association with blood, war
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2 Astro 102/104 5 Telescopic Observations • Mars usually has a small apparent angular diameter in telescopes: 4" to 6" • Every 26 months or so, Mars' apparent size increases above 10" for a few months and astronomers can observe surface details And oh what details they have observed! Percival Lowell
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This note was uploaded on 03/04/2008 for the course ASTRO 1102 taught by Professor Squyres,s/margot,j during the Spring '07 term at Cornell University (Engineering School).

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Lecture19 - Lecture #19: Mars Mars: Overview General...

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