Solar System: Planets: Mars

Mars is probably the most heavily studied planet in the Solar System. It is the second closest planet to us, but the conditions on the surface of Venus are very harsh and don't allow easy exploration. The closest that Earth and Mars come together is 0.38 AU, which happens with a period of 17 years. Some basic facts about Mars:

• Diameter of 6800 km
• Density of about 3900 kg/cubic meter
• Average distance from the Sun is 228 mil. km (1.52 AU), aphelion 249.1 mil. km, perihelion 206.5 mil. km
• Orbiting time 687 days
• Rotation period of 24 hrs. 37 mins.
• Rotational axis tilted at 25 degrees
• Mass is about 11% that of the Earth
• Atmosphere: Carbon Dioxide (95%), Nitrogen (3%), Argon (1%), Carbon Monoxide, Oxygen, Water Vapor (1%)
• Atmospheric pressure of 0.006 atm, thus very thin atmosphere, no solid water ice
• Seasonal North Polar carbon dioxide ice cap, possible remnant southern cap
• Temperature variatons from 310 degrees Kelvin at noon to 210 degrees Kelvin at night

It is believed that some time ago Mars did have a relatively extensive atmosphere, allowing the existance of surface ice and water, which caused the channels on its surface, which look like they were left by water streams. It is now believed that water might be still existent under the surface of Mars.

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