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

Curiosity to Land on the Red Planet

Curiosity: A model at the Discovery Science Center

The Mars Rover Curiosity will land on the Red Planet on August 5, 2012 (Pacific Time).

A collaboration between JPL (Jet Propulsion Laboratory) and NASA, Mars Rover Curiosity (SUV), otherwise known as Mars Science Laboratory (MSL), has technology that succeeds its predecessors, Spirit and Opportunity (golf carts) and Sojourner (microwave). NASA launched Curiosity on November 26, 2011 at the Cape Canaveral Air Force Station. Curiosity is expected to land on August 5, 2012 on the Aeolis Palus region of the Gale crater. Curiosity‘s four objectives are: 1) determine whether Mars is suitable for life; 2) study Mars’ climate; 3) study Mars’ climate; 4) plan future human mission to Mars.


  • Weight: 2,000 lbs.
  • Length: >9.8 ft.
  • Distance Covered (per day): ~600 ft
  • Lifetime: >687 Earth days (1 Martian year)


  • Power: Radioisotope Thermoelectric Generator (RTG) – uses the decay of plutonium-238 to generate 2.5 kilowatt hours per day
  • Heat Rejection System: To keep Curiosity at optimal temperatures since temperatures on Mars vary dramatically (30°C  to -127°C)
  • Computers: “Rover Compute Element” – tolerates extreme radiation from space; Inertial Measurement Unit (IMU) – rover navigation
  • Communications: X band transmitter – communicate directly with Earth; UHF Electra-Lite software defined radio – communicate with Mars orbiters
  • Mobility: 6 wheels in rocker-bogie suspension – serve as landing gear


  • Cameras: 1. MastCam – multiple spectra and true color imaging; 2. Mars Hand Lens Imager (MAHLI) – microscopic images of rock and soil; 3. MSL Descent Imager (MARDI) – color images to map the  surrounding terrain and landing location
  • ChemCam: laser to vaporize samples up to 7 meters away for analysis, with the laser-induced breakdown spectroscopy (LIBS) and micro-imager (RMI)
  • Alpha-particle X-ray spectrometer (APXS): map the spectra of X-rays to elemental composition of samples
  • Chemistry and Mineralogy (CheMin): identify and quantify abundance of minerals on Mars
  • Sample Analysis at Mars (SAM): analyze organics and gases from atmospheric and solid samples
  • Dynamic Albedo of Neutrons (DAN): measure hydrogen, ice, and water at and near Martian surface
  • Rover Environmental Monitoring System (REMS): measure atmospheric pressure, humidity, wind currents and direction, air and ground temperature, UV levels
  • MSL Entry Descent and Landing Instrumentation (MEDLI): measure aerothermal environments, sub-surface heat shield response, vehicle orientation, atmospheric density; detect heat shield separation
  • Hazard Avoidance Cameras (HazCams): use light to capture 3-D image to protect the rover from crashing
  • Navigation Cameras (Navcams): use visible light to capture 3-D images for navigation


Landing Sequence

  • EDL (Entry, Descent, Landing): also called the “7 minutes of Terror,” because any malfunction or any misstep means failure of the mission
  • Landing Sequence: “6 vehicles, 76 pyrotechnic devices, 500,000 lines of code, zero margin of error”; from 13,000 miles an hour to 0 miles and hour; 1,600 degrees upon entry
  • Mar’s atmosphere is 100 times thinner than Earth’s so it is harder for MSL to slow down
  1. Guided Entry: control the craft to approximate landing site region
  2. Parachute Descent: supersonic parachute (can withstand 65,000 lbs of force but only weighs 100 lbs.) deploys at 10 km altitude
  3. Powered Descent: cut parachute off and rocket thrusters (Mars Lander Engine, MLE) extend out and slow the descent
  4. Sky Crane: lower the rover with a 21-foot tether wheels down onto the Martian crater to prevent the rockets from making dust clouds; the bridle is cut and the rock thrusters fly away to a safe distance


  • Each wheel on Curiosity has a specific traction pattern that is Morse code for “JPL”
  • It takes 13 minutes and 46 seconds to relay signals from Earth to Curiosity


Grecius, Tony, ed. “Mars Science Laboratory.” NASA. NASA, July 2012. Web. 27 July 2012.