E X T E N S I O N IS THERE LIFE ON MARS? MARS FACTFILE Orbit 227,940,000 km mean distance from the Sun Diameter 6,794 km Martian day 24 hours, 37 mins 22 seconds Martian year 669 Martian days, 687 Earth days Average temperature -55° C Minimum temperature -133° C Maximum temperature 27° (summer dayside) Surface area 144 x 106 km2, about the same as the land area of Earth Atmospheric pressure at surface 6.35 mbar, that is less than one hundredth Earth s atmospheric pressure Atmospheric composition 95.32% carbon dioxide, 2.7% nitrogen, 1.6% argon, 0.13% oxygen Moons Phobos diameter 22 km, orbit 5981 km from surface Deimos diameter 12 km, orbit 20,062 km Mars perhaps first caught the public imagination in the late 1870s, when Italian astronomer Giovanni Schiaparelli reported that using a telescope he had observed canali , or channels, on Mars. A possible poor translation of this word as canals1 may have fired the imagination of Percival Lowell, an American businessman with an interest in astronomy. Lowell founded an observatory in Arizona, where his observations of the red planet convinced him that the canals were dug by intelligent beings. By the end of the century, popular songs told of sending messages from Earth to Mars by way of very big signal mirrors and H.G. Wells 1898 novel The War of the Worlds described an invasion of the Earth by technologically superior Martians desperate for water. When the first robotic spacecraft were sent to Mars in the 1960s, the pictures showed a desolate world. However, after the Earth, Mars is the planet with the most hospitable climate in the solar system. So hospitable that perhaps once it had primitive, bacteria-like life. Channels 1. canals: long passages dug in the ground and filled with water. 27