June 26, 1997. Copyright, 1997, Graphic News. All rights reserved 329 words total The Earthlings are comingÉ By Danny Sullivan If there be Martians, theyÕd better look out. Earth is returning to the Red Planet on July 4, and this time itÕs going mobile. Probes have landed before on Mars, but they have always been stationary. NASAÕs Pathfinder mission has both a lander and six-wheeled robot-rover named Sojourner that will cruise by remote control to investigate the planet. The question on everyoneÕs minds is whether traces of life will be detected. A paper released last summer suggesting that life once lived on Mars has fueled speculation. Scientists found what they believe to be fossils of micro-organisms in a meteorite that came from Mars. Debate continues over the findings. The Pathfinder mission could settle the matter, if it finds evidence of life during the month-long period it is expected to operate. A number of scientific instruments on both the lander and the rover will be investigating the atmosphere and soil of Mars. Mars does not seem hospitable to life. Temperatures rarely climb above 0 degrees Fahrenheit (minus 18 degrees Centigrade) and can drop as much as 212¡F (100¡C) from day to night, NASA scientists say. However, life has been found in inhospitable places on Earth, such as the depths of the ocean floor. Even if life is not found, traces of life from the past may exist, perhaps from when water flowed on the planet. The landing site, Ares Valles, is a dramatic example of this. It is a flood plain, at the mouth of a channel formed when huge amounts of water inundated the area. ÔIt would be as if all the water in the Great Lakes was forced into a narrow channel to the Gulf of Mexico in about a two-week period,Õ said Matthew Golombek, chief project scientist for Pathfinder. Pathfinder will be the fourth probe to land on Mars. First was the Soviet UnionÕs Mars 3 probe, which ceased operating 20 seconds after landing in 1971. NASAÕs two Viking probes landed in 1976 and are still functioning