Mars is the fourth planet from the sun and has a distinct rusty red appearance and two unusual moons. The Red Planet is a cold, desert world within our solar system. Mars — the fourth planet from the Sun — is a dusty, cold, desert world with a very thin atmosphere. This dynamic planet has seasons, polar ice caps, extinct volcanoes, canyons, and weather. Mars formed along with the other planets approximately 4.5 billion years ago. During the martian Noachian period (4.5 to 3.5 billion years ago), its surface was marked by meteor impacts, valley formation, erosion, the possible presence of water oceans and the loss of its magnetosphere. Mars is the fourth planet in the solar system in order of distance from the Sun and the seventh in size and mass. It is a periodically conspicuous reddish object in the night sky. There are intriguing clues that billions of years ago Mars was even more Earth-like than today. Mars coverage from Scientific American, featuring news and articles about advances in the field. Today we know that this wandering red star is not a star at all but a world—an entire planet orbiting the Sun, cold and dusty, yet filled with landscapes that rival the most dramatic features on Earth. That planet is Mars. Mars has fascinated astronomers, writers, and dreamers for generations. In this article, we’ll tell you everything you need to know about Mars and answer the most common questions related to the Red Planet: why Mars is red, how big it is, what it looks like, and when it’s best to observe it. Mars is the most Earth-like planet in our solar system. It has seasons, weather patterns, polar ice caps, and a 24-hour day cycle. Evidence strongly suggests that billions of years ago, Mars had a thicker atmosphere, warmer temperatures, and liquid water flowing across its surface. Mars is the fourth planet from the Sun, orbiting at an average of 228 million kilometres away from the star. The planet moves at a speed of around 24 kilometres per second, making it slightly slower than Earth. It has an elliptical orbit, meaning it is egg- or oval-shaped. A guide to the Red Planet, Mars, including facts about its geology, a history of Mars missions and images captured by astrophotographers.