Countdown to Mars: What we know about the Red Planet

It's the summer of Mars. Three countries – newcomers United Arab Emirates and China along with the US – separately will aim to launch robotic spacecraft to the red planet. Mars has fascinated mankind for centuries, but it's only in the last six decades - as robotic spacecraft have visited the red planet - that we've learned more about our neighbor in the solar system. Mars, the fourth planet in our solar system is about half the size of Earth - around 4,220 miles in diameter - and has two moons, named "Phobos" and "Deimos". Temperatures range from minus 140 degrees Celsius to plus 30 degrees Celsius. Gravity is about 62.5 percent less than what we're used to here on Earth. And the planet's atmosphere is composed almost entirely of carbon dioxide - 96 percent.