However, to date, no evidence of life has been found. Mars takes 687 days to make one trip around the Sun. Because of its eccentric orbit, Mars's distance from the Sun can vary by about 36 million miles. Its distance from Earth can vary by as much as 200 million miles. Its gravity is one-third of Earth's.
Major constituents are carbon dioxide and nitrogen.
Water vapor and oxygen are minor constituents. Mars has four seasons like Earth, but they are much longer. For example, in the northern hemisphere, the Martian spring is 198 days, and the winter season lasts 158 days. Analysis of the reddish surface soil pointed to the presence of oxidized iron, indicating that the planet's surface is rusting. Sojourner samples of soil taken from several sites found their composition similar to those analyzed by the two Viking landers in 1976, indicating that the Martian winds have distributed the soil evenly over the planet.