The journey to the moon had been the first step toward future exploration( 探险 ) in space. The distance between the Moon and Earth is very short indeed when compared with the distances between Earth and the other planets. Mars, the nearest planet to Earth is millions of miles away. Traveling to the planets will be man’s next aim. Such travels will be more challenging than the trip to the moon and certainly more adventurous. Recently, two American spaceships, Vikings 1 and 2, landed on Mars trying to discover whether that planet has any life on it. So far the signs of life on Mars has neither confirmed( 确认 ) nor ruled out. Russians have discovered that the surface of Venus( 金星 ) is so hot that it is almost certain that there is no life there. Also the atmosphere of Venus is extremely dense( 稠 ) and the pressure is nearly a hundred times greater than that of the Earth’s atmosphere. Scientists believe man may find planets which have the same conditions as those we have on Earth , but man should realize Earth will be his only home for a long time and begin to love and care for it.