The fourth planet from the Sun, Mars resembles Earth in many ways. Although it is only half the size of our globe and its ferrous core is smaller, it does have seasons which last about six months because the planet takes longer to complete an orbit around the Sun. Moreover, Mars features ice caps at the poles and possesses a thin atmosphere.
Observations of Mars may be traced back to the advanced civilizations of antiquity. It was probably because of its reddish blood-like color that the planet was given the name of the god of war, Ares or Mars. Early in the 17th century Johannes Kepler formulated his three laws, which describe the movements of the planets, on the basis of Mars position measurements made by the Danish astronomer Tycho Brahe which, although few in number, were highly precise for their time. Whenever Mars was in opposition in the last few centuries, it was common practice to compute the length of the astronomical unit (the distance between the Earth and the Sun) on the basis of trigonometric measurements of the distance between Earth and Mars. In 1877, Schiaparelli fell for an optical illusion when he thought he saw trenches and grooves on Mars which he called ‘canali‘. For many of Schiaparelli‘s contemporaries they simply had to be of artificial origin, and even much later, when the scientific world had long recognized the optical illusion for what it was, they led many to believe in an intelligent civilization on our planetary neighbor. Read more...

First sighting of the Martian moons, Deimos and Phobos, was reported in 1877 by Asaph Hall, an astronomer of the Naval Observatory in Washington. The increasing interest in Phobos, the larger of the two Martian moons, is not only due to the steadily increasing number of space based and earth based observations but also to its low orbit about Mars. Its motion and rotation are thus effected by the Martian gravity field and variation may lead to further clues of its origin and evolution. Furthermore, Phobos was identified as potential target for sample return missions by different mission planning groups.
The German Aerospace Center (DLR) was involved in an in-depth study of this natural satellite. Based on images of the multi-spectral line scanning High Resolution Stereo Camera (HRSC) and the Super Resolution Channel (SRC) – a frame camera – the department of Planetary Geodesy. Read more...