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
NASA Earth Science NASA Earth Science NASA Earth Science, formerly called the NASA Earth Science Enterprise (ESE), formerly called Mission To Planet Earth (MTPE), is a NASA research program "to develop a scientific understanding of the Earth system and its response to natural and human-induced changes to enable improved prediction of climate, weather, and natural hazards for present and future generations". "To improve life here" and "To understand and protect our home planet," NASA supports research in the Earth Sciences and, as part of its Earth Observing System (EOS), launches and maintains Earth observing satellites to monitor the state of the climate, atmospheric