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Mars: Basic Planetary Characteristics

Mars: Basic Planetary Characteristics. Geography 494-01 S/07 Dr. Christine M. Rodrigue. Mars 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

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Mars: Basic Planetary Characteristics

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  1. Mars: Basic Planetary Characteristics Geography 494-01 S/07 Dr. Christine M. Rodrigue C.M. Rodrigue, 2007 Geography, CSULB

  2. Mars 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 circle C.M. Rodrigue, 2007 Geography, CSULB

  3. Mars 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 0.0167 C.M. Rodrigue, 2007 Geography, CSULB

  4. Mars 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 1 C.M. Rodrigue, 2007 Geography, CSULB

  5. Mars 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/m2 versus 1,350 W/m2 at Earth (~44%) C.M. Rodrigue, 2007 Geography, CSULB

  6. Mars in Space • Orbital Characteristics • Mars’ and Earth’s distance from the Sun • Solar irradiance at Mars is about 590 W/m2 versus 1,350 W/m2 at Earth (~44%) C.M. Rodrigue, 2007 Geography, CSULB

  7. Mars in Space • Orbital Characteristics • Mars’ and Earth’s distance from the Sun • Solar irradiance at Mars is about 590 W/m2 versus 1,350 W/m2 at Earth (~44%) • Here, it would be like living on Earth at 54 N or S in March or September C.M. Rodrigue, 2007 Geography, CSULB

  8. Mars 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 driver C.M. Rodrigue, 2007 Geography, CSULB

  9. Mars 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 ~0.14 C.M. Rodrigue, 2007 Geography, CSULB

  10. Mars: 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 years C.M. Rodrigue, 2007 Geography, CSULB

  11. Mars: 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, 2007 Geography, CSULB

  12. Mars in Space • Size • Mars’ and Earth’s relative sizes compared C.M. Rodrigue, 2007 Geography, CSULB

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