Even with the largest telescopes it is very hard to see much detail on Mars. In the late 1800s, some scientists thought they could see straight lines crossing the planet's surface. These lines joined greenish areas that looked as if they were covered by plants. These scientists thought that the straight lines were canals built by Martians to carry water to their crops.
Spacecraft pictures have shown that these canals do not exist. There is no sign of any life – plants or intelligent Martians - on the planet. We now know that Mars is a very cold, dry planet, where liquid water cannot exist on the surface. However, there are large areas of water ice at the polar caps. There is also a lot of ice in the frozen ground – much like the permafrost areas of northern Canada and Russia.
Large, dry channels also show that there was once a lot of running water on the surface. Recent results from Mars Express and other spacecraft show that there may be liquid water deep underground. If Mars was once warmer and wetter, life may have begun on the red planet. Simple life, such as bacteria, may still exist beneath the frozen surface.
In 1996, a group of scientists told the world that they had found evidence of bacteria inside a meteorite that had come from Mars. However, this idea is not very popular with most other scientists. If life is found on Mars in the future, it would be the first proof that we are not alone in the Universe.