INTRO: Deimos, the smaller of Mars’ two moons, often captivates the imagination of astronomers and space enthusiasts alike. Despite its modest size and dim appearance, Deimos possesses a fascinating set of characteristics that make it an intriguing subject of study. Here are ten compelling facts about this enigmatic celestial body.
Deimos is the Smaller of Mars’ Two Moons at Just 12 km Wide
Deimos is the diminutive companion of Mars, measuring approximately 12 kilometers (about 7.5 miles) in diameter. This makes it significantly smaller than its larger sibling, Phobos, which is around 22 kilometers (about 13.7 miles) wide. Deimos is so small that it would take roughly three Deimoses placed side by side to equal the length of a typical football field. Its small size and irregular shape contribute to its classification as a "moonlet," a term used for small natural satellites orbiting larger planets.
It Takes Deimos 30.3 Hours to Orbit Mars Completely
Deimos has a unique orbital period, taking approximately 30.3 hours to complete one full orbit around Mars. Interestingly, this orbital time is longer than the Martian day, which lasts about 24.6 hours. As a result, Deimos rises in the west and sets in the east, contrary to the typical east-to-west movement observed in most celestial bodies. This peculiar behavior is a consequence of Deimos’s slow orbital speed relative to Mars’s rotation.
Deimos Has a Surface Covered with a Layer of Regolith
The surface of Deimos is predominantly covered by a thick layer of regolith, which is a mix of dust, soil, and broken rock. This regolith is believed to be composed mainly of carbon-rich materials, making it dark and unreflective. The presence of regolith suggests that Deimos has been bombarded by meteoroids over billions of years, resulting in a surface that is pockmarked with craters and other geological features. This layer plays a vital role in protecting the underlying rock from further impacts.
The Moon’s Name Comes from Greek Mythology, Meaning "Terror"
The name "Deimos" is derived from Greek mythology, where he is known as the god of terror and the personification of dread. Deimos is often depicted as accompanying his brother Phobos, the god of fear, in their role as attendants of the war god Ares (Mars in Roman mythology). The choice of names reflects the moons’ association with the aggressive nature of Mars, known for its reddish color and connection to warfare.
Deimos is One of the Least Reflective Bodies in the Solar System
Deimos is known for its low albedo, which is a measure of reflectivity. With an albedo of about 0.07, it is one of the least reflective bodies in the solar system. This means that it reflects only about 7% of the sunlight that hits its surface. The dark, carbonaceous material that constitutes much of its regolith contributes to this low reflectivity, making Deimos appear dim and nearly indistinguishable from the background of space to the naked eye.
Its Orbit is Gradually Eroding, Moving Away from Mars
Deimos’s orbit is not static; it is gradually drifting away from Mars at a rate of about 1.8 centimeters (0.7 inches) per year. This slow process is similar to what is observed with Earth’s moon, which also moves away from our planet. As Deimos continues to recede, it could eventually reach a point where it might break apart due to tidal forces or be captured by Mars’s gravity and spiral inward, leading to an uncertain fate.
Deimos Was Discovered by American Astronomer Asaph Hall
Discovered on August 12, 1877, by American astronomer Asaph Hall, Deimos was identified during his examination of Mars. Hall’s work on Mars and its moons marked a significant milestone in the study of celestial bodies. Using a telescope at the United States Naval Observatory, Hall was able to find Deimos just days after discovering its larger sibling, Phobos. His findings greatly contributed to our understanding of Mars as a complex planetary system.
The Moon’s Surface Features Include Craters and Valleys
Deimos’s surface is marked by various geological features, including craters and shallow valleys. The most prominent crater, Swift, is about 2.3 kilometers (1.4 miles) wide and serves as a testament to the moon’s bombardment history. The presence of these craters indicates that Deimos has been subjected to impacts over billions of years. Additionally, the moon’s surface features demonstrate a lack of significant geological activity, suggesting it has remained relatively unchanged for a long time.
Deimos Completes a Full Rotation in Approximately 2.7 Days
The rotational period of Deimos is quite slow, taking approximately 2.7 Earth days to complete one full rotation on its axis. This slow rotation is synchronous with its orbit around Mars, meaning that the same side of Deimos always faces the planet. This phenomenon creates a unique perspective for potential future explorers, as one side of Deimos would be perpetually "daylight" while the other remains in constant "night."
It is Believed That Deimos May Be a Captured Asteroid
Many scientists believe that Deimos may have originated as a captured asteroid from the asteroid belt located between Mars and Jupiter. Its irregular shape, low density, and composition support this theory. The idea that Deimos is a captured body suggests that it may share characteristics with other small celestial bodies in the solar system, providing insights into the early formation of planetary systems and the processes that govern celestial mechanics.
OUTRO: Deimos, with its intriguing size, surface features, and unique orbital characteristics, continues to be a subject of scientific interest. As we advance in our exploration of Mars and its moons, understanding Deimos not only sheds light on its own history but also enhances our knowledge of planetary formation and the dynamics of celestial bodies in our solar system.