The Phoenix lander returned data showing Martian soil to be slightly alkaline and containing elements such as magnesium, sodium, potassium and chlorine. These nutrients are found in gardens on Earth, and are necessary for growth of plants. Experiments performed by the Lander showed that the Martian soil has a basic pH of 8.3, and may contain traces of the salt perchlorate.
Streaks are common across Mars and new ones appear frequently on steep slopes of craters, troughs, and valleys. The streaks are dark at first and get lighter with age. Sometimes, the streaks start in a tiny area which then spread out for hundreds of metres. They have also been seen to follow the edges of boulders and other obstacles in their path. The commonly accepted theories include that they are dark underlying layers of soil revealed after avalanches of bright dust or dust devils. Several explanations have been put forward, some of which involve water or even the growth of organisms.