Besides the earth, what other planets are suitable for human survival?

Mars may indeed have liquid water and even life. The radar data of Mars Express and Mars Reconnaissance Orbiter show that there are a lot of water ice under the polar and mid-latitude surface. On July 3, 20081day, Phoenix confirmed the existence of water ice directly below the topsoil. On September 26th, 20 13, the rover Curiosity discovered that the Martian soil is rich in water, which is about 1.5-3 wt%, indicating that Mars has enough water resources for future immigrants.

At present (20 14), there are four probes in orbit on Mars, namely, the Mars Odyssey, the Mars Express, the Mars reconnaissance orbiter and the newly arrived MAVEN orbiter, the number of which is the largest in the solar system except the Earth. There are also many rovers and landers on the surface, including two Mars exploration rovers: Spirit and Opportunity, and Phoenix, which recently completed its mission. According to observational evidence, Mars may have covered a large area of water before. A similar phenomenon of groundwater gushing has been observed in recent ten years. Mars global surveyors have observed that the Antarctic crown has partially retreated.

Mars has two natural satellites: Phobos and Phobos, which are irregular in shape and may be captured asteroids. On earth, Mars is visible to the naked eye, and its brightness can reach -2.9, which is only darker than Venus, the moon and the sun, but it is darker than Jupiter most of the time. This provides a defense system, like the moon to block flying meteorites and so on, making survival possible.