ocr: - / 9 OT MARS AND EARTH: A COMPARATIVE HISTORY THE SEARCH FON The question of life on Earth and Mars With growing proof that primitive life forms existed on Earth in its most distant past, scientists have gradually pushed back the date when they believe life. appeared on Earth. Today, we know that there were complex cells on Earth 3.7 billion years ago. Therefore, life developed in the first billion years after the Earth was formed. But. at that time, Mars and Earth were still very much alike. So couldn't life have also appeared on Mars? MARS BETAT
