Why is Mars called the Earth's 'little brother'?

Mars is so called because among all the planets of the solar system it resembles the Earth the most. Our neighbouring planet rotates at the same speed as the Earth. It means that one day on Mars is approximately the same as one day on the Earth, Mars has seasons too. Even the landscape is similar to that of the Earth. The Mars landscape is a dry, rocky surface coated with fine red dust. Traces of water, and at least some land features that may have been shaped by water, have too been discovered. The highest mountain of the solar system. the 4000 km long and 200 km wide Valles Marineris. Even the rocks on Mars are similar to the ones found on the Earth. We know this because small robots such as the Sojourner sent to Mars have sent back reports about its surface.