Mars（火星） is the fourth planet from Sun. It is home to both the highest mountain and the deepest, longest valley（山谷） in the solar system（太阳系）. Olympus Mons, the highest mountain on Mars, is about 27 kilometers high, about three times as tall as Qomolangma. And the deepest valley on Mars reaches as deep as 10 kilometers and runs east west for about 4, 000 kilometers, about one fifth of the distance（距离） around Mars and close to the width（宽） of Australia.
Mars is much colder than Earth because it's farther away from Sun. The highest temperature can reach 20℃ while the lowest can be as low as —140℃. Just like Earth, Sun gives Mars seasons. However, the seasons that Mars experiences are different from Earth's. For example, when Mars is the farthest from Sun, the southern part of Mars experiences a very long and cold winter, about six months on Earth.
Mars lies farther from Sun than Earth does, so the Red Planet has a longer year— 687 days compared to 365 for our home world. However, the two planets have similar day lengths, 24 hours and 40 minutes for Mars and 24 hours for Earth.
Mars is far from Earth and it's not an easy planet to reach. But many countries like the USA, Russia, China and Japan are always trying to send people there. Robots have got the tickets to Mars and it's believed that Man will get the tickets by the 2030s, although it is still a big challenge now. And scientists say it will take at least six months for people to travel to Mars.
