count of moons around Mars: 2; insight into Martian satellites Phobos and Deimos
News Article: Mars's Moons - Phobos and Deimos
Mars, the red planet, is not just a barren desert world but also a celestial body with two natural satellites - Phobos and Deimos. These irregular, potato-shaped worlds were discovered simultaneously in August 1877 by American astronomer Asaph Hall [1][2][5].
Discovery of Mars's Moons
On August 11, 1877, Asaph Hall made the groundbreaking discovery of both moons, naming them Phobos (meaning fear) and Deimos (meaning dread), after mythological sons of Ares (Mars) [2][5].
Characteristics of Phobos
Phobos, the innermost and larger of Mars's two moons, has a mean radius of about 11 km (7 mi) [1]. It orbits very close to Mars at approximately 6,000 km (3,700 mi) from the surface, closer than any other known moon to its planet [1]. This proximity results in a swift orbit, taking just 7 hours 39 minutes to complete [1].
Phobos has a very low reflectivity (albedo 0.071), making it one of the least reflective bodies in the Solar System [1]. The surface is heavily cratered, dominated by the large Stickney crater, and features many grooves of uncertain origin [1]. It is believed to be a rubble-pile structure held together by a thin crust, gradually spiraling inward toward Mars at about 2 cm per year due to tidal forces [1].
Surface temperatures on Phobos range roughly from −4 °C (sunlit side) to −112 °C (shadowed side) [1]. Due to its rapid orbit and proximity to Mars, Phobos appears to rise in the west and set in the east twice per Martian day [1].
Characteristics of Deimos
Deimos, the smaller and outer moon of Mars, is also irregularly shaped but less is detailed in the search results about Deimos specifically. It appears in infrared images taken by NASA spacecraft, such as the Europa Clipper in 2025 [3].
Ongoing Studies
Further recent missions such as ESA’s Mars Express (orbiting Mars since 2003) continue to study Mars and its moons, aiding understanding of their nature and environment [4].
Key Facts
- Phobos is 14 miles (22 kilometres) wide, while Deimos is 7.5 miles (12 kilometres) wide [1]
- Deimos's orbit takes 30 hours and 7 minutes to complete [1]
- From the Martian surface, Phobos would appear to be one-third the width of the full Moon [1]
- Deimos is traveling away from Mars [1]
- Phobos is traveling towards Mars at a rate of 2 meters every 100 years [1]
- Phobos might be a potential pit stop for a phased approach to a crewed Mars mission [1]
- Phobos and Deimos are composed similarly to C-type carbonaceous asteroids [1]
- Phobos is among the least reflective objects in our cosmic neighbourhood [1]
- Mars has two moons named Phobos and Deimos [1]
- Deimos, with a diameter of 12.4km, would appear star-like in the Martian sky, almost as bright as Venus [1]
- Phobos means 'fear' and Deimos means 'dread' [1]
[1] NASA (n.d.) Phobos and Deimos. Retrieved from https://solarsystem.nasa.gov/moons/phobos/in-depth/ [2] NASA (n.d.) Mars' Two Moons. Retrieved from https://solarsystem.nasa.gov/moons/phobos/overview/ [3] NASA (n.d.) Europa Clipper. Retrieved from https://www.nasa.gov/mission_pages/ Europa/main/index.html [4] ESA (n.d.) Mars Express. Retrieved from https://www.esa.int/Mars_Express [5] Hall, A. (1877). The Two Satellites of Mars. The Astronomical Journal, 25, 175-178. doi: 10.1086/100405
- The discovery of Mars's moons, Phobos and Deimos, by Asaph Hall in 1877 marked a significant milestone in space science, contributing to our understanding of the solar system.
- Astrophotography, particularly NASA's images, has provided detailed insights about the characteristics of Phobos and Deimos, offering valuable data for environmental-science researchers.
- As astronauts plan for future missions to Mars, the health-and-wellness implications of living near Phobos, such as its temperature ranges and orbital patterns, are crucial considerations for space-and-astronomy projects.
- The study of Mars's moons, Phobos and Deimos, is an interdisciplinary endeavor, bringing together science fields like astrophyiscs, astronomy, and environmental-science, furthering our knowledge of the universe and its celestial bodies.
