Telescopes like the Hubble Space Telescope have helped us understand and observe the solar system and space. There are 11 planets in our solar system including Earth and Mars, though there is no sign of life on other planets yet. Scientist believe life could exist on Mars or other terrestrial planets if certain conditions were present. Gas giants like Jupiter and Saturn are large planets made of gas, while terrestrial planets like Earth, Venus, Mercury and Mars are rocky bodies that could support life under the right conditions.