Colonization of Mars

The colonization of Mars by humans is an ongoing debate. Some people want to colonize the planet Mars. Satellite imagery shows that there is frozen ground water on the planet. Mars also has a thin atmosphere. Because of this, it has potential to host humans and other organic life. That makes Mars the best choice for a thriving colony off the Earth. The Moon has also been proposed as the first location for human colonization but it is not known to have much air or water. It only has 0.16% air and has 14% water.
There are many factors humans on Mars will go through, such as the risks in landing on the planet within gravity wells.
Many organizations support the colonization of Mars.
Earth and Mars
The Earth is much like its "sister plant" Venus.
The Martian day (or sol) is similar to Earth days. A solar day on Mars is 24 hours 39 minutes 35 seconds and 244 milliseconds.
Mars has a surface area that is 28.4% of Earth's. It is slightly less than the amount of dry land on Earth (which is 29.2% or Earth's surface). The radius of Mars is half that of Earth and only one-tenth the mass. This means that it has a smaller volume (~15%). Mars also has a lower average density than Earth.
Mars has an axial tilt of 25.19deg. Earth's axial tilt is 23.44deg. This means that Mars has seasons similar to Earth. However, seasons on Mars last twice as long because the Martian year is about 1.88 Earth years. Mars' north pole currently points at Cygnus and not Ursa Minor.
Mars has an atmosphere. It is very thin (about 0.7% of Earth's atmosphere) it provides some protection from solar and cosmic radiation. It has also been used successfully for aerobraking of spacecraft.
Recent observations by NASA's Mars Exploration Rovers, ESA's Mars Express and NASA's Phoenix Lander has confirm water ice on Mars. Mars also has large quantities of all elements necessary to support life.
Differences from Earth
The surface gravity on Mars is 38% of that on Earth. It is unknown if this is enough for human health. Mars is much colder than Earth. Mars surface temperature is -63 degC and a low of -140 degC. The lowest temperature ever recorded on Earth was -89.2 degC, in Antarctica. There is no liquid water on the surface of Mars. Because Mars is further from the Sun, less solar energy reaches the upper atmosphere of Mars. Mars' orbit is more eccentric than Earth's.
The atmospheric pressure on Mars is ~6 mbar. This is far below the Armstrong Limit (61.8 mbar), so people cannot survive without pressure suits. Since terraforming cannot be expected within the century, humans must have their pressure suits. Mars' atmosphere has carbon dioxide. Mars has a very weak magnetosphere. This means that it does not do a good job getting rid of solar winds.
Habitability
Conditions on the surface of Mars are much closer to habitability than the surface of any other known planets or moons. Other planets such as Mercury has extreme hot and cold temperatures. Venus is very hot and all other planets and moons are very cold. There are some natural places on Earth, where humans have explored, that are similar to the conditions on Mars. The highest altitude reached by a balloon that was carrying humans, was 34,668 meters (113,740 feet), a record set in May 1961. The pressure at that altitude is about the same as on the surface of Mars. Extreme cold in the Arctic and Antarctic match all but the most extreme temperatures on Mars.
It may be possible to terraform Mars to allow a wide variety of living things. In April 2012, it was reported that lichen and bacteria survived for 34 days in conditions like those on Mars. This experiment was maintained by the German Aerospace Center (DLR).
Organizations
Many organizations support the colonization of Mars. They have also given different reasons and ways humans can live on Mars. One of the oldest organizations is the Mars Society. They promote a NASA program that supports human colonies on Mars. The Mars Society have set up Mars analog research stations in Canada and the United States. Other organizations include MarsDrive, who want to help fund settlements on Mars, and Mars to Stay. Mars to Stay advocates settlements on Mars. In June 2012, Mars One released a statement that they believe could help start a colony on Mars by 2023. SpaceX thinks it can launch astronauts to colonize Mars via Starship.