The 8 Planets – Part 4: Mars



A very belligerent planet. Mars. Named after the Roman god of war, Mars appears as a fiery battle-stained planet. Out of the seven planets (excluding Earth), Mars seems to be the most habitable planet. Although much smaller than Earth, Mars has an atmosphere (though thinner), ice caps (though mainly dry ice, or frozen carbon dioxide), and evidence that water once flowed on its surface. Astronomers have yet to find life on Mars, but sci-fi authors have long contemplated the possibility of life on Mars in the present or future (e.g. The Martian Chronicles). Don’t let the name fool you. Mars, the god of war, leaves no one alive while Venus, the goddess of love, often has a soft heart. In the solar system, Venus is a deadly planet while Mars is relatively benign.

The fourth planet from the Sun and the last terrestrial planet, Mars, the “Red Planet,” is actually the second smallest planet and the most explored aside from Earth. Distinguishable by its red color from an abundance of iron oxide, Mars has a thin atmosphere blanketing a surface filled with impact craters, volcanoes, valleys, deserts, and polar ice caps. Mars is also home to Olympus Mons, the tallest mountain in the solar system, and Valles Marineris, a large crack on Mars’ surface and one of the largest canyons. Dark patches on its surface suggest presence of large quantities of liquid water in the past. Though similar to Earth in surface features and climate, Mars is only about half the size of Earth, with 15% of Earth’s volume and 11% of mass. Because of its similar axial tilt, Mars has Earth-like seasons, though with a colder climate. Barren, Mars has the largest dust storms in the solar system. Mars is bigger than Mercury but less dense because of an iron sulfide core composed of lighter elements. The core is surrounded by a silicate mantle and the mantle by a thick crust. With no evidence of a global magnetic field, Mars, however, has some magnetized crust that has reversed polarity like Earth’s ocean floors. Mars’ geological history is split into three periods: Noachian period (4.5 – 3.5 billion years ago, oldest surfaces with impact craters and extensive flooding of water), Hesperian period (3.5 to 2.9 – 3.3 billion years ago, extensive lava plains), Amazonian period (2.9 – 3.3 billion years ago to present, few impact craters, Olympus Mons forms, lava flows). On Martian Soil, light silica-rich streaks appear on steep slopes, perhaps the dark underlying layers of soil exposed after dust avalanches. As Earth speeds Mars, Mars appears to move in a retrograde motion, or backwards with respect to the stars. Mars has two moons: Phobos and Deimos.


Phobos and Deimos

Mars’ two moons look more like asteroids than Earth’s moon. Named for Mars’ sons and attendants in battle, Phobos and Deimos mean “fear” and “panic,” respectively. Because of their low albedo, carbonaceous chondrite composition, and irregular shapes, scientists have proposed the capture theory. Stray asteroids from the Trojan belt may have been pulled into Mars orbit. Phobos is below synchronous position, so Mars’ tidal forces will eventually cause Phobos to crash into Mars’ surface, either forming an impact crater or a dust ring in 50 million years. On the contrary, Deimos is outside synchronous position, so the moon is slowly spiraling away from Mars. In about 50 million years, Mars may have no moons!

MISSIONS*: Mariner, Mars, Viking, Mars Global Surveyor, Mars Pathfinder, Mars Odyssey, Mars Express, Spirit, Opportunity, Rosetta, Mars Reconnaissance Orbiter, Phoenix, Dawn, Mars Science Laboratory

* Successful Missions


  • Order in Solar System: #4
  • Number of Moons: 2
  • Orbital Period: 687 days
  • Rotational Period: 24 hours, 39 minutes, 35 seconds
  • Mass: 6.4185 x 10^23 kg (0.107 Earths)
  • Volume: 1.6318 x 10^11 km³ (0.151 Earths)
  • Radius: 3,396 km (0.533 Earths)
  • Surface Area: 1.45 x 10^8 km² (0.284 Earths)
  • Density: 3.9335 g/cm
  • Surface Pressure: 0.636 kPa
  • Eccentricity of Orbit: 0.093315
  • Surface Temperature (Average): 210 K
  • Escape Velocity: 5.027 km/s
  • Apparent Magnitude: +1.6 to -3.0

3 thoughts on “The 8 Planets – Part 4: Mars

  1. Mars is one of my favorites, possibly because of it’s arbitrary location to the planet earth, making it compelling. You have to feel a little sorry for the moons however. Mars is fascinating for so many reasons while it’s moons just sort of hang out, or hang on depending on their respective locations, sad really, no sonnets for Phobos or Deimos. Sigh! I enjoyed this very much Tina, many thanks for the work you put into each post, it is very appreciated ~ take care of you, Penny

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