The fourth planet out from the Sun


  • Mars has a daytime temperature and atmosphere more like the Earth’s than any other planet.
  • sometimes, it calls the red planet because it is rust-red in colour – this comes from oxidized (rusted) iron in Mars’ soil.
  • Mars orbits at an average distance of 143 million miles – takes 687 Earth days  (nearly two years) to complete Mars orbit.
  • 4,246 miles in diameter and spins around once every 24.62 hours – almost the same time as the Earth takes to rotate in 23 hours 56 minutes.
  • Olympus Mons – Mars volcano is the biggest volcano in the all of Solar System – covering the same area as France and three times higher than Mount Everest. (diagram)
  • surface of Mars is dry, rocky and covered in dust – the wind blows up huge dust storms, sometimes covering the whole Mars; Dust devils, similar to small tornadoes – often race across the surface of Mars.
  • almost all the water on Mars is frozen into ice – there are ice caps at the poles, and thin clouds made of ice crystals in the sky.
  • Mars was probably warmer and wetter in the past; Spacecraft have spotted many dried-up riverbeds, gullies and lake beds; Mars Rover Spirit, and Opportunity have found minerals that normally form in water.
  • Global Surveyor Spacecraft has discovered two gullies on Mars where water and mud have gushed out onto the surface in the last few years.
  • in 2008, NASA’s Phoenix Lander confirmed the presence of water on Mars in the form of ice crystals just below the surface; the ice was found in a soil sample scooped from a 5cm deep trench nicknamed Snow White.


Mars’ moons

  • Mars has two moons – Phobos (photo) and Deimos (photo).
  • Phobos – nearly 17 miles in diameter.
  • Deimos – nearly 10 miles in diameter.
  • both moons have so little gravity that an astronaut could leap off them and into space using muscle power alone.
  • Phobos and Deimos are highly irregular in shape – every appearance of being asteroids that were formed when the Solar System was created and afterwards captured by Mars’ gravity.
  • both moons follow very low regular orbits around Mars; Deimos is at an average distance of 14,680 miles, while Phobos orbits less than 3,750 miles above Mars’ surface.
  • large impact craters caused by meteorites mark the surface of Phobos – Stickney; 6¼ miles in diameter.
  • meteorite craters on Deimos have mostly been filled with dust and broken rock and none are more than nearly two miles across.
  • due to Mars extremely low orbit; Phobos is being gradually slowed by Mars’ gravity and is falling towards Mars ‘ surface at a rate of 18 metres per century – Phobos will crash into surface of Mars in around 40 million years time.


Back to The Solar System page.


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