Illustration depicting the ecosphere, or \life zone\", of the Sun. The ecosphere is defined as that zone of space around the Sun (or other star) in which a planet experiences conditions that are compatible with the development of life. The conditions that define the boundaries of the ecosphere are the heat radiation from the Sun (too hot when close, too cold when far away), and the intense solar particle flux close to the Sun. The illustration shows Earth well within the ecosphere (left of centre). Mars (lower right of centre) still orbits just within the tenuous outer edge of the ecosphere. The ecosphere concept does not allow for conditions on the planet itself."