Transit of Phobos from Mars north of 70.4°N; for some days in the year, its shadow misses the surface entirely and falls north or south of Mars. At any given geographical location on the surface of Mars, there are two intervals in a Martian year when the shadow of Phobos or Deimos is passing through its latitude. During each such interval, about half a dozen transits of Phobos can be seen by observers at that geographical location (compared to zero or one transits of Deimos). Transits of Phobos happen during Martian autumn and winter in the respective hemisphere; close to the equator they happen around
Lithobraking launched, including penetrators on the two Phobos probe landers targeted for Mars' moon Phobos and ones for Mars itself on Mars 96 and Deep Space 2, but so far none have succeeded. The cancelled LUNAR-A probe would have carried penetrators to the Moon. Lithobraking as a method for de-orbiting a spacecraft has not been used due to the extremely high orbital velocities of most bodies (e.g. for the Moon it is over 7000 km/h). However, some small moons and asteroids have very low gravity and it could conceivably be used there (e.g. Phobos has an "escape velocity" of 40 km/h.)