There is evidence that, when the solar system was young, conditions on Mars and Venus may have been suitable for life. The surface of Mars has clearly been altered by water in the past and it may still exist deep underground. Venus is the nearest planet to Earth and is almost identical to Earth in both size and geological composition. Recent research has suggested that, long ago, Venus could have been Earth’s sister planet, complete with rivers and life. (With thanks to our sponsor 'Curriculum Press' for providing content for this podcast)