Transit of Phobos from Mars

A passage of Phobos from the sun, as seen from Mars, takes place when Phobos passes directly between the Sun and a point on the surface of Mars. Here, a large part of the sun's disc for an observer on Mars is covered. During a passage Phobos can be seen as large black disk of Mars, which is quickly absorbed through the sun.

The event can be described as a partial eclipse of the sun by Phobos. From the orbit of the penumbral shadow of Phobos can be observed that travels quickly across the surface of Mars. This shadow on the Martian surface was photographed by Mars probes on many occasions. A passage of Phobos as seen from Mars, takes account of its very rapid orbital period of about 7.6 hours normally only by 30 seconds.

Because the orbit of Phobos is only slightly inclined to the equatorial plane of Mars, but the equatorial plane is inclined similarly to the orbital plane of the planet by the earth, the shadow of Phobos is projected over the course of a year in different areas of Mars. For any given latitude on the surface of Mars between 70.4 ° ​​N and 70.4 ° ​​S, there are two time points in the Martian year to which the shadow of Phobos exceeding the corresponding latitude. During this time, a half-dozen passes Phobos at this position is taking place. During the " winter season " the shadow falls on the north side, during the vernal equinox and the autumnal equinox it crosses the equator. Thus, the passages of Phobos in the Northern Hemisphere occur approximately symmetrical around the winter solstice.

Close to the equator, it will take place at the autumn equinox and the spring equinox, far away from the equator, however, closer to the winter solstice. Generally on the surface of Mars there on most days of the year Mars passages of Phobos. However, missed a few days in the Martian year the shadow of Phobos the Martian surface in the north or south. Because it orbits so close to Mars, Phobos can be seen from 70.4 ° ​​S, 70.4 ° ​​N, not north of or south. Observer smaller at high latitudes than 70.4 ° ​​see a noticeably smaller Phobos because they are further away from him as an observer at the equator. Consequently cover passages of Phobos for such observers, the disk of the sun less.

• Mars ( Planet)
• Astronomical event