A view of coral-like formations called stromatolites are seen in the Poza Azul lake at Cuatro Cienegas, Mexico, February 18, 2007. The stromatolites' ability to harness oxygen, carbon, nitrogen and sulfates in early Earth's atmosphere at a time when phosphates had yet to be released into the oceans allowed them to form the basis of all life. Scientists at NASA say understanding Cuatro Cienegas may help us know how the Earth developed and hold clues to whether other planets like Mars have primitive, extraterrestrial life. Picture taken February 18, 2007. To match feature MEXICO-ENVIRONMENT