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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