Mars is the planet in our Solar System that is most similar to the Earth

Primitive life could survive around hydro-thermal vents near the planet's surface

Nowadays it may be too cold for life to exist there. But organisms may have thrived in the past

In science fiction stories, Mars is the favourite home of aliens. No one has found any green Martians wandering over the planet. But many scientists believe that Mars may be the best place to look for simpler forms of life.

Of all the planets in the Solar System, Mars is the most similar to Earth.

Why is Mars like Earth?

It has a similar temperature
At present, it's too cold for liquid water to exist on the surface. But the planet may have been warmer in the past.

It has an atmosphere
The atmosphere is much thinner than on Earth. Plus there's not much ozone to protect the planet from the Sun's harmful UV rays. But the atmosphere may have been thicker millions of years ago.

It has a rocky surface
This makes it easier for life to get a foothold. On rocky planets, all the necessary chemicals for life can collect in one place, rather than floating freely through a gassy atmosphere.

It has polar ice caps
These expand and contract with the planet's seasons. Although the ice is mostly frozen carbon dioxide, there is probably water there too. So like the Earth, Mars could also have a water cycle.

Canals on Mars?

When 19th century astronomers looked at Mars, many saw lines criss-crossing the planet.

Percival Lowell was convinced that these lines were canals, built by a race of intelligent Martians. In fact, they were just an optical illusion.

Will we find life on Mars?

Were these gullies formed by liquid water?
Although it's probably too cold for life to exist on the surface of Mars, it could exist in warmer pockets below ground. Micro-organisms could be living around hydro-thermal vents near the planet's surface.

In the past, Mars was a very different world. The Mars Global Surveyor probe found evidence that there was running water on the planet's surface. This would have made the planet much more hospitable to life.

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