INTRO: Mars, the fourth planet from the Sun, is known for its striking red landscape and intriguing features. Among these features are its two natural satellites, Phobos and Deimos, which have captivated astronomers and space enthusiasts alike. Despite their small sizes and irregular shapes, these moons harbor fascinating characteristics that contribute to our understanding of planetary science. Here are ten intriguing facts about Mars’ moons.
Mars Has Two Moons: Phobos and Deimos, Not One
Unlike Earth, which boasts a single natural satellite, Mars is accompanied by two moons: Phobos and Deimos. Discovered in 1877 by American astronomer Asaph Hall, these moons were named after the Greek mythology figures representing fear and dread, who were said to accompany the god of war, Ares, after whom Mars is named. While they may not be as prominent as Earth’s Moon, Phobos and Deimos play a significant role in enhancing our understanding of celestial mechanics and the history of our solar system.
Phobos is the Larger Moon, Measuring About 22 Kilometers Wide
Phobos, the larger of the two moons, measures approximately 22 kilometers (13.7 miles) across and exhibits a rugged, cratered surface. Its size makes it the 7th largest moon in the solar system. However, this is modest compared to many other moons, emphasizing the relatively small scale of Martian satellites. Phobos is so close to Mars that it appears three times larger in the Martian sky than our Moon does from Earth, creating a striking visual for any observer on the Martian surface.
Deimos is the Smaller Moon, Only 12 Kilometers in Diameter
Deimos, the smaller companion of Phobos, is about 12 kilometers (7.5 miles) in diameter. Despite its size, Deimos is notably smoother than Phobos, with fewer craters and a surface marked by a blanket of regolith that gives it a more rounded, albeit still irregular, appearance. This difference in surface characteristics suggests that Deimos may have undergone different processes over its history, providing insights into the geological history of Mars and its moons.
Both Moons Are Irregularly Shaped, Not Spherical Bodies
Unconventionally, both Phobos and Deimos are not spherical like many other moons in the solar system. Instead, they exhibit irregular shapes, resembling large, potato-like bodies. This irregularity is primarily due to their small sizes and relatively low gravitational forces, which are insufficient to mold them into a more rounded form. These shapes bear resemblance to asteroids, supporting the theory that they may be captured celestial bodies rather than remnants from Mars’ formation.
Phobos Orbits Mars Faster Than Mars Rotates in a Day
One of the most fascinating aspects of Phobos is its orbital speed; it orbits Mars at an astonishing pace, completing a full revolution in just about 7.6 hours. This rapid orbit means that Phobos rises in the Martian sky in the west and sets in the east, contrary to most celestial bodies. As a result, if you were standing on the surface of Mars, you would witness the moon moving quickly across the sky, making it an extraordinary sight.
Deimos Has a Slower Orbit, Taking About 30.3 Hours to Complete
In contrast to Phobos, Deimos has a much slower orbital period of approximately 30.3 hours. This means it takes nearly one and a half Martian days to complete a single orbit around the planet. As a result, Deimos rises in the east and sets in the west, similar to Earth’s Moon. The slower orbit allows Deimos to remain visible in the Martian sky for extended periods, providing a different experience for those on the Martian surface compared to its larger counterpart.
Both Moons Are Likely Captured Asteroids from the Belt
The prevailing theory about the origins of Phobos and Deimos suggests that they are captured asteroids from the asteroid belt located between Mars and Jupiter. Their composition, which includes carbon-rich materials, aligns with the characteristics of many asteroids found in that region. This theory not only sheds light on the formation of the Martian moons but also contributes to our understanding of the early solar system, where gravitational forces played a critical role in shaping celestial bodies.
Phobos Is Gradually Spiraling Inward, Facing Impending Doom
Phobos is on a collision course with Mars, gradually spiraling inward at a rate of approximately 1.8 meters (6 feet) every century. This trajectory suggests that Phobos will eventually disintegrate due to tidal forces or crash into the Martian surface in about 50 million years. This impending doom raises questions about the future of Martian studies, as Phobos may provide critical data before it meets its end.
Deimos Is Gradually Moving Away from Mars, at 1.8 Centimeters
Conversely, Deimos is slowly drifting away from Mars at an approximate rate of 1.8 centimeters (0.7 inches) each year. This gradual recession may eventually lead Deimos to escape Mars’ gravitational influence altogether, becoming a free-floating body in the solar system. The divergent fates of these two moons highlight the complex gravitational interactions that occur between celestial bodies and the intricate dynamics of our solar system.
OUTRO: Mars’ moons, Phobos and Deimos, may be diminutive in size compared to the vastness of the solar system, but their unique characteristics and behaviors provide valuable insights into planetary science. As our exploration of Mars and its moons continues, these celestial companions serve as fascinating subjects for further study, enriching our understanding of the universe and its many wonders.