Mars

The slideshow is an introduction to the planet Mars.

Mars was once quite like Earth with a substantial atmosphere and greenhouse gases to keep it warm. There were clouds and rain, rivers and seas of liquid water. It is possible that primitive life developed there.

But, about 3.7 billion years ago, the iron core solidified, stopping the currents that produce a magnetic field. Without a magnetic field, the solar wind stripped away most of the atmosphere and much of the water. The planet then cooled and dried, producing what we see today.

Mars' atmosphere is now only 1% the thickness of the earth's. The recorded temperatures range from -155C to 20C.

The planet is home to the solar system's largest volcano, Olympus Mons, standing 27 km tall, and also to the canyon, Valles Marineris, 4000 km long, up to 300 km wide and up to 9 km deep.

Because it is easy to get to and with a relatively hospitable surface, Mars is the most explored planet other than Earth, and there are plans to send people there in the next few years.

Image: freesvg.org