CSULB GEOG 494 - Mars: Basic Planetary Characteristics

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Mars: Basic Planetary CharacteristicsMars in SpaceSlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Mars: Data from Robotic MissionsSlide 11Slide 12C.M. Rodrigue, 2007Geography, CSULBMars: Basic Planetary CharacteristicsGeography 494-01S/07Dr. Christine M. RodrigueC.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsPlanetary orbits are ellipticalThe major focus of Mars' or Earth's orbit is inside the Sun The plane of that orbit is the eclipticThe diameter of the orbit along its long axis is the major axisHalf that distance is the semi-major axis (here shown as a)The diameter of the planet's orbit along its short axis is the minor axis Half that is the semi-minor axisC on this graph is the distance from the center of the orbit to one focusEccentricity is c/a – 0 for a perfect circleC.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s eccentricityMars has one of the greatest eccentricities in the solar system at 0.0934 Earth is one of the more circular at 0.0167C.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ solar irradiance and surface insolation averaged over the yearVery freaky: South polar regions get the most solar radiation due to greater axial tilt, greater eccentricity, and the greater length of day The length of day overcompensates for the lower sun angleGEOG 442 students can compare with Lab 1C.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s distance from the SunMars is about 227,936,640 km from the Sun averaged along the semi-major axisEarth is 149,597,890 kmSolar irradiance at Mars is about 590 W/m22 versus 1,350 W/m22 at Earth (~44%)C.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s distance from the SunSolar irradiance at Mars is about 590 W/m22 versus 1,350 W/m22 at Earth (~44%)C.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s distance from the SunSolar irradiance at Mars is about 590 W/m22 versus 1,350 W/m22 at Earth (~44%)Here, it would be like living on Earth at 54 N or S in March or SeptemberC.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s distance from the SunMars at perihelion is 206,600,000 km (Southern Hemisphere summer)Earth is 147,100,000 km (also Southern Hemisphere summer)Mars at aphelion is 249,200,000 kmEarth is 152,100,000 kmSo, Mars perihelion distance is only 82.9% of its aphelion distanceOn Earth, perihelion is 96.7% of aphelionOn Earth, this difference is a trivial influence, especially since perihelion hits during the more oceanic hemisphere’s summerOn Mars, it’s a major seasonal driverC.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s changes in eccentricityPlanets’ orbital shapes alternate between more circular and more ellipticalEarth’s varies from ~0.01 to ~0.05 over a cycle of ~100,000 yearsMars’ varies from close to 0.00 to ~0.14C.M. Rodrigue, 2007Geography, CSULBMars: Data from Robotic MissionsRotational characteristicsAxial tilt or obliquity:Mars: 2511’ 24” (25.19 ) from the vertical of the ecliptic Earth: 2326’24” (23.44) from the vertical of the ecliptic Mars’ axis precesses 360  in 93,000 Martian years or ~125,000 Earth yearsEarth’s axis precesses 1 per 71.6 years or 360 in 25,765 yearsC.M. Rodrigue, 2007Geography, CSULBMars: Data from Robotic MissionsSizeMars and Earth compared:Mars’ equatorial radius: 3,397 km (Earth: 6,378 km) Equatorial circumference: 21,344 km (Earth: 40,075 km) Volume: 163,140,000,000 km3 (Earth: 1,083,200,000,000 km3 Mass: 641.85 x 1018 metric tons (Earth: 5,973.70 x 1018 metric tons) Mean density: 3.94 g/cm3 (Earth: 5.52 g/cm3), where water = 1.00Equatorial surface gravity: 3.693 m/s2 (Earth: 9.766 m/s2) or about 38% of Earth’sEscape velocity: 11.18 km/sec (Earth: 5.02 km/sec)C.M. Rodrigue, 2007Geography, CSULBMars in SpaceSizeMars’ and Earth’s relative sizes


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