Science Library - free educational site


Mars is the first planet outside the Earth's orbit, with a year 1.88 Earth years long. It has a very thin carbon dioxide atmosphere, and a mean surface temperature of a chilly -63°C.

    Vital statistics:
  • Mass: 6.4 x 1023 kg = 0.107 Earths/8.8 Moons
  • Diameter: 6779 km = 0.53 Earth's
  • Density: 3.93 tonnes/m3 = 0.713 Earth's density
  • Surface gravity: 3.7 m/s2 = 0.38g
  • Distance from Sun: 207 - 249 million km (227.9 Mkm semi-major axis) = 1.38 - 1.67 AU (Earth-Sun distances)
  • Period of orbit: 687.0 Earth days / 1.88 Julian years
  • Period of rotation: 1.03 Earth days (24.62 h)
  • No. of moons: 2
  • Atmosphere: 0.64 kPa (0.63% Earth's atmosphere), 96.0% CO2, 1.9% argon, 1.9% nitrogen, 0.15% O2, and trace gases, including 210 ppm (parts per million) water vapour.


Mars has two natural satellites, the small moons Phobos and Deimos.

Phobos, moon of Mars
Phobos, moon of Mars

Content © Andrew Bone. All rights reserved. Created : October 25, 2015 Last updated :December 27, 2015

Latest Item on Science Library:

The most recent article is:

Air Resistance and Terminal Velocity

View this item in the topic:


and many more articles in the subject:

Subject of the Week


Information Technology, Computer Science, website design, database management, robotics, new technology, internet and much more. JavaScript, PHP, HTML, CSS, Python, ... Have fun while learning to make your own websites with

Computer Science

Great Scientists

Charles Darwin

1809 - 1882

Charles Darwin is one of the most famous of all scientists, and a true hero of science. His theory explaining the mechanisms of evolution were published in his book On the Origin of Species (1859), which launched a storm of controversy from religious dogma adherents.

Portrait: Charles Darwin

Quote of the day...

He who understands Archimedes and Apollonius will admire less the achievements of the foremost men of later times.

ZumGuy Internet Promotions

Yoga in Mendrisio