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 SpaceOrbital CharacteristicsPlanetary orbits are ellipticalThe major focus of Mars' or Earth's orbit is inside the Sun The plane of that orbit is the eclipticThe diameter of the orbit along its long axis is the major axisHalf 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 axisC on this graph is the distance from the center of the orbit to one focusEccentricity is c/a – 0 for a perfect circleC.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s eccentricityMars 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 SpaceOrbital CharacteristicsMars’ solar irradiance and surface insolation averaged over the yearVery 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 angleGEOG 442 students can compare with Lab 1C.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s distance from the SunMars is about 227,936,640 km from the Sun averaged along the semi-major axisEarth is 149,597,890 kmSolar irradiance at Mars is about 590 W/m22 versus 1,350 W/m22 at Earth (~44%)C.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s distance from the SunSolar irradiance at Mars is about 590 W/m22 versus 1,350 W/m22 at Earth (~44%)C.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s distance from the SunSolar 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 SpaceOrbital CharacteristicsMars’ and Earth’s distance from the SunMars 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 kmEarth is 152,100,000 kmSo, Mars perihelion distance is only 82.9% of its aphelion distanceOn Earth, perihelion is 96.7% of aphelionOn Earth, this difference is a trivial influence, especially since perihelion hits during the more oceanic hemisphere’s summerOn Mars, it’s a major seasonal driverC.M. Rodrigue, 2007Geography, CSULBMars in SpaceOrbital CharacteristicsMars’ and Earth’s changes in eccentricityPlanets’ orbital shapes alternate between more circular and more ellipticalEarth’s varies from ~0.01 to ~0.05 over a cycle of ~100,000 yearsMars’ varies from close to 0.00 to ~0.14C.M. Rodrigue, 2007Geography, CSULBMars: Data from Robotic MissionsRotational characteristicsAxial tilt or obliquity:Mars: 2511’ 24” (25.19 ) from the vertical of the ecliptic Earth: 2326’24” (23.44) from the vertical of the ecliptic Mars’ axis precesses 360 in 93,000 Martian years or ~125,000 Earth yearsEarth’s axis precesses 1 per 71.6 years or 360 in 25,765 yearsC.M. Rodrigue, 2007Geography, CSULBMars: Data from Robotic MissionsSizeMars 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 = 1.00Equatorial surface gravity: 3.693 m/s2 (Earth: 9.766 m/s2) or about 38% of Earth’sEscape velocity: 11.18 km/sec (Earth: 5.02 km/sec)C.M. Rodrigue, 2007Geography, CSULBMars in SpaceSizeMars’ and Earth’s relative sizes
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