Mars:
Mars is the fourth planet from the Sun. On average, it is about 140 million miles from the Sun (or about 17,700 planet Earths). The planet itself has a diameter of 4,196 miles, so just over half the size of Earth.
As you can see, Mars is about twice the size of our Moon but about half the size of the Earth.
Mars is often one of the most easily recognizable objects in the night sky. This is because of the massive amounts of iron oxide on the surface of the planet. Despite the iron oxide on the surface of the planet, Mars does not always appear to be red from the Earth. It often ranges anywhere from yellow, to orange, to red.
Photo of the Martian surface taken by the Spirit rover.
As you can see from the picture, Mars has a barren and rocky surface. Because of its great distance from the Sun, the temperatures on Mars range from about 23 degrees F to -125 degrees F. This bitterly cold climate is relatively similar to Earth's, in the sense that both planets have seasons. Due to Mars' distance from the Sun, the seasons last about twice as long as they do here on Earth. However, despite the fact that both planets have seasons, Earth and Mars have one very key difference: the Earth has a magnetosphere, Mars does not. Because of this, Mars is not shielded from the solar winds and has not been for the last 4 billion years. This leaves Mars completely exposed to radiation from the sun, from strikes by meteors, and is the most likely explanation for why Mars no longer has liquid water actively on its surface.
An artist's depiction of the protection that Earth's magnetosphere provides from the solar winds. And how Mars' (bottom planet) lack of one leaves it completely exposed.
Despite the fact that Mars has not had an atmosphere for billions of years now, liquid water may still in fact exist on the Martian surface. On April 4th, 2011, NASA released images that very likely could be seasonal water flows on the surface of Mars. While these images cannot be completely confirmed, scientists believe that these flows are made of very briny water, which would in fact lower its freezing point.
Whatever scientists eventually conclude about these images, one thing that is for certain is that the newest Martian probe will be landing on the surface of the planet this coming August. Currently, the Martian Rovers Spirit and Opportunity, have been operating on the planet searching for past evidence of liquid water; and they have been very successful. In August, the Curiosity Rover will be delivered to Mars with four major goals in mind: to study the geology of Mars, study the Martian climate, explore the possibility of future human missions, and answer questions concerning past life on the planet. Curiosity will offer great insights into many of the most difficult questions concerning Mars.
Finally, as a bit of an afterthought, I feel it necessary to mention a few things about the moons of Mars. Mars is the only other rocky planet besides the Earth to have any Moons, although they are not large enough to be gravitationally shaped into a sphere. However, both of Mars' moons, Phobos and Deimos, have a chaotic future ahead of them. Phobos, the larger of the Martian moons, is the closest moon in the solar system to its host planet. This close proximity to the planet will eventually cause Phobos to either crumble up as it nears the planet, or to directly crash into the surface. Mars' other moon, Deimos, is on course to no longer be a Martian Moon. Deimos, like Earth's moon is slowly moving away from its host planet. Deimos though, unlike our own moon, will eventually be gravitationally slingshotted into the vastness of space, never to be seen or heard from again.
Mars is so intriguing to scientists because there is strong evidence to suggest that the planet may have once supported water and life. Hopefully, the Curiosity rover will lead to some amazing discovery that changes our perspective on the universe.
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