Extraterrestrial skies Mars appears to be the angular diameter as seen from Earth (0.35°), and sends 40% of the light, approximately the brightness of a slightly cloudy afternoon on Earth. On June 3, 2014, the "Curiosity" rover on Mars observed the planet Mercury transiting the Sun, marking the first time a planetary transit has been observed from a celestial body besides Earth. Mars has two small moons: Phobos and Deimos. From the Martian surface, Phobos has one-third to one-half the angular diameter of the Sun while Deimos is barely more than a dot (only 2′ angular diameter). The orbital period of Phobos
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.)