Phobos is one of the two natural satellites of the planet Mars. It is the larger of the two and it orbits Mars at a distance of about 9,378 km (5,827 mi) from the planet's center, which is closer than any other known planetary moon in the solar system. Phobos is irregularly shaped and heavily cratered, with a diameter of about 27 x 22 x 18 km (17 x 14 x 11 mi).
Examples of Phobos missions include:
- Phobos-Grunt, a Russian spacecraft mission launched in 2011, which aimed to study Phobos and return samples of its surface material to Earth, but it failed and crashed back to Earth.
- NASA's Mars Reconnaissance Orbiter (MRO) has been studying Phobos from orbit since 2006, using its high-resolution camera to study the moon's surface and its properties.
- The European Space Agency (ESA) and Roscosmos have a joint mission planned to study Phobos called the Phobos and Deimos & Mars Sample Return mission, which aims to launch in 2026 and return samples of Phobos back to Earth for analysis.
- The China National Space Administration (CNSA) is planning a mission to Phobos in 2028 to study the moon's surface and to return samples of its soil to Earth.
Phobos is of interest to scientists and space agencies due to its proximity to Mars and its potential to provide insights into the planet's geology and history, as well as its potential as a resource for future manned missions to Mars.