Mars, the fourth planet from the Sun, is well-known for its distinctive reddish appearance and its intriguing surface features. However, beyond the planet itself, Mars also has two small moons orbiting it.
These moons are unique in many ways and have fascinated astronomers since their discovery.
Understanding the names and characteristics of Mars’ moons provides insight into the planet’s history and the broader dynamics of our solar system. This article explores the names of these moons, their origins, physical properties, and the stories behind their designations.
The Names of Mars’ Moons
Mars has two natural satellites, which are named Phobos and Deimos. Both names come from Greek mythology, specifically the mythological sons of Ares, the Greek counterpart to the Roman god Mars.
Phobos and Deimos were discovered in 1877 by American astronomer Asaph Hall. Their discovery was significant because, until then, Mars was believed to have no moons.
The naming of these moons reflects their mythological connection to war and fear, fitting for Mars’ association with the god of war.
“Phobos and Deimos perfectly embody the themes of war and terror, as they are the mythological companions of Ares who accompany him into battle.” – Astronomy Historian
Phobos
Phobos is the larger and closer of the two moons. It orbits Mars at a distance of about 6,000 kilometers from the planet’s surface, making it one of the closest moons to its planet in the entire solar system.
Phobos is heavily cratered and irregular in shape, resembling a large asteroid more than a typical spherical moon.
Deimos
Deimos is smaller and orbits much farther from Mars, approximately 20,000 kilometers away. It is smoother and less cratered than Phobos, with a more rounded shape.
Despite its size, Deimos still maintains an irregular form, indicative of its likely origin as a captured asteroid.
Mythological Origins of Phobos and Deimos
Both names have deep roots in mythology. Phobos means “fear” or “panic” in Greek, and Deimos translates to “terror” or “dread.” These two figures were said to be the sons of Ares (Mars) and Aphrodite (Venus), who accompanied their father into battle, instilling fear and terror among his enemies.
By naming the moons Phobos and Deimos, astronomers drew a symbolic connection between the planet Mars and its satellites, emphasizing the warlike and fearsome aspects associated with the god Mars.
| Moon Name | Meaning | Mythological Role | Parentage |
|---|---|---|---|
| Phobos | Fear, Panic | God of Fear, companion of Ares in battle | Son of Ares and Aphrodite |
| Deimos | Terror, Dread | God of Terror, companion of Ares in battle | Son of Ares and Aphrodite |
Physical Characteristics of Phobos and Deimos
Both moons are small and irregularly shaped, differing greatly from Earth’s large, spherical moon. Their size and shape have led scientists to hypothesize that they are captured asteroids from the nearby asteroid belt.
Phobos is about 27 kilometers in diameter at its widest point, while Deimos is smaller, measuring approximately 15 kilometers across. These diminutive sizes contribute to their weak gravitational pulls and unusual orbital behaviors.
| Feature | Phobos | Deimos |
|---|---|---|
| Diameter | ~27 km | ~15 km |
| Orbital Distance from Mars | ~6,000 km | ~20,000 km |
| Orbital Period | 7.66 hours | 30.35 hours |
| Shape | Irregular, heavily cratered | Irregular, smoother surface |
| Surface Composition | Carbonaceous chondrite-like material | Carbonaceous chondrite-like material |
Historical Discovery
Phobos and Deimos were discovered on August 12 and 18, 1877, respectively, by Asaph Hall, who was working at the United States Naval Observatory in Washington, D.C. Hall used a 26-inch refractor telescope to observe the moons, which he initially referred to as “Mars I” and “Mars II.”
Hall’s discovery was kept secret until September 1877, after which the names Phobos and Deimos were proposed and accepted. The selection of these names was suggested by Henry Madan, an Oxford scholar, who recommended the mythological names to maintain the tradition of classical nomenclature in astronomy.
“Asaph Hall’s discovery of Mars’ moons was a remarkable event, opening new avenues of exploration and understanding of the Martian system.” – NASA Historian
Why Are Mars’ Moons So Small?
Unlike Earth’s moon, which is quite large relative to Earth, Mars’ moons are tiny. Scientists believe that Phobos and Deimos are not original to Mars but were likely captured asteroids, pulled into orbit around Mars by its gravity.
Their size and irregular shapes support this theory, as captured asteroids tend to retain their small, non-spherical forms. Additionally, their composition resembles that of certain classes of asteroids found in the asteroid belt between Mars and Jupiter.
Future Exploration of Phobos and Deimos
Interest in Mars’ moons has grown as space agencies consider them potential stepping stones for human missions to Mars. Their low gravity and proximity to Mars make them attractive locations for scientific study and perhaps even bases for future explorers.
Several missions have been proposed to study Phobos and Deimos more closely. For example, Japan’s Martian Moons eXploration (MMX) mission aims to land on Phobos, collect samples, and return them to Earth.
This mission will help unlock mysteries about the moons’ origin and their relationship with Mars.
Summary
Mars is orbited by two small moons named Phobos and Deimos. These names are deeply rooted in Greek mythology, symbolizing fear and terror, fitting companions for the god of war, Mars.
Discovered in 1877 by Asaph Hall, these moons are irregularly shaped, likely captured asteroids, and are significantly smaller than Earth’s moon.
Their unique characteristics continue to intrigue scientists, who study them to better understand Mars and the solar system’s history. With upcoming missions planned, our knowledge of Phobos and Deimos is expected to expand dramatically in the coming decades.
