It has fascinated us for hundreds of years. Named after the Roman God of war, Mars is more similar to Earth than any other planet we know of. Like Earth, Mars has a 24 hour day, an axis tilt that creates annual seasons, it has ice caps, valleys, volcanos, and canyons. Early in Mars' history, evidence suggests that liquid water flowed across the surface. Oceans, rivers, and lakes once existed here. Yet today Mars is a dry, cold world, with no evidence of any current surface water. Earth and Mars both formed in a similar way and both formed in the habitable zone, yet both worlds were destined down two different paths.
Earth is covered in water and is home to an abundance of life. Mars on the other hand is dry and cold, with no evidence that life has ever existed there. What happened? Why didn't Mars turn out like Earth? Scientists still don't know the full story, but there is quite a bit they do know. One important feature that Earth has that Mars does not is a magnetic field. Our magnetic field protects us from the deadly solar wind, and without a magnetic field, the solar wind would strip away our atmosphere. Early in Mars' history, it must have had a magnetic field. Mars is believed to have had a fairly thick atmosphere long ago, yet something happened to its magnetic field. Mars is smaller than Earth, so it lost much of its internal heat long ago. The once molten core froze over, and the magnetic field began to fail. Without a magnetic field, nothing could protect Mars from the solar wind. The solar wind stripped away the atmosphere, along with any surface water. If life did arise on Mars, it likely would have perished during this catastrophe unless it managed to stay alive deep underground.
Although Mars may no longer harbour oceans, its geology tells the story a lost world, that billions of years ago, was not so different from our own. Today Mars is a barren world, yet that doesn't make it any less interesting. The history of Mars is one of the most mysterious histories of any world we know, and there's still a lot more to find out.