Fourth planet from Sun and the seventh largest. Mass 6.42 x 10^26 g (0.11 Earth's); radius 3397 km. Mean distance from Sun 1.52 AU. Sidereal period 687 days; synodic period 779.9 days. Surface tempera
ture 248 K., rotational period 24h 37m 22.66s. Obliquity 23°59'. Atmosphere more than 90% CO_2, traces of O_2, CO, H_{2}O. Two tiny satellites (Phobos and Deimos), both of which are locked in synchronous rotation with Mars.
In geography, a marsh, or morass, is a type of wetland which is subject to frequent or continuous inundation. Typically a marsh features grasses, rushes, reeds, typhas, sedges, and other herbaceous pl
ants (possibly with low-growing woody plants) in a context of shallow water. A marsh is different from a swamp, which has a greater proportion of open water surface, and is generally deeper than a marsh. In North America, the term swamp is used for wetland dominated by trees rather than grasses and low herbs