Mars, the red planet, has two small and mysterious moons: Phobos and Deimos. Unlike Earth’s large and round moon, these two are tiny, irregularly shaped, and full of fascinating secrets. Scientists often call them the “doomed moons of Mars” because their future is uncertain. Phobos is slowly spiraling toward Mars, while Deimos drifts farther away. These moons are not just interesting because of their strange shapes and orbits—they also hold clues about the history of our solar system.
In this blog, we’ll explore 29 amazing facts about Phobos and Deimos. From their discovery to their possible origins and ultimate fate, these facts will help you understand why these moons are so special.
1. Phobos and Deimos Were Discovered in 1877
Astronomer Asaph Hall discovered Phobos and Deimos in August 1877. He named them after the Greek mythological figures Phobos (fear) and Deimos (panic), who accompanied the god of war, Ares (Mars in Roman mythology), into battle. Their discovery marked a significant milestone in the study of Mars.
2. They Are Among the Smallest Moons in the Solar System
Phobos is only 22 kilometers (14 miles) wide, while Deimos is even smaller at 12 kilometers (7.5 miles). Compared to Earth’s moon, which is 3,474 kilometers (2,159 miles) in diameter, these moons are tiny. Their small size makes them more like asteroids than traditional moons.
3. Phobos Is Slowly Falling Toward Mars
Phobos orbits Mars at just 6,000 kilometers (3,700 miles) above the surface, making it the closest moon to its planet in the solar system. However, it’s slowly spiraling inward and will likely crash into Mars or break apart in about 50 million years.
4. Deimos Is Drifting Away
While Phobos is falling toward Mars, Deimos is moving farther away. This is similar to how Earth’s moon is drifting away from us. Over time, Deimos’ orbit will become more distant, making it less affected by Mars’ gravity.
5. They Might Be Captured Asteroids
One theory suggests that Phobos and Deimos are captured asteroids from the asteroid belt. Their irregular shapes and dark, carbon-rich surfaces resemble some asteroids, supporting this idea. If true, they could provide valuable insights into the early solar system.
6. They Could Be Leftovers from a Giant Impact
Another theory proposes that the moons formed from debris after a massive object collided with Mars billions of years ago. This is similar to how Earth’s moon is thought to have formed. If correct, Phobos and Deimos could be fragments of Mars itself.
7. Phobos Has a Giant Crater Named Stickney
Phobos is covered in craters, but the largest is Stickney Crater, which is 9 kilometers (5.6 miles) wide. This massive impact almost destroyed the moon. The crater is named after Chloe Angeline Stickney Hall, the wife of Phobos’ discoverer, Asaph Hall.
8. Deimos Has a Smoother Surface
Deimos appears smoother than Phobos because it’s covered in a thick layer of fine dust and loose material called regolith. This dust fills in smaller craters, giving Deimos a less rugged appearance compared to its sibling moon.
9. Phobos Orbits Mars Faster Than the Planet Rotates
Phobos completes one orbit around Mars in just 7 hours and 39 minutes, which is faster than Mars’ rotation. As a result, Phobos rises in the west and sets in the east, unlike most moons in the solar system.
10. Deimos Takes 30 Hours to Orbit Mars
Deimos orbits Mars much more slowly than Phobos, taking about 30 hours to complete one orbit. It rises in the east and sets in the west, like most moons. Its slower movement makes it less noticeable in the Martian sky.
11. Phobos and Deimos Are Darker Than Coal
Both moons have very low reflectivity, meaning they don’t reflect much sunlight. Their surfaces are as dark as coal, which is another reason scientists think they might be captured asteroids. This darkness makes them difficult to observe from Earth.
12. They Were Named After Fear and Panic
The names Phobos and Deimos come from Greek mythology. They were the twin sons of Ares (Mars) and Aphrodite (Venus). In mythology, they symbolized fear and panic, emotions often associated with war, which ties to Mars’ identity as the god of war.
13. Phobos Has Strange Grooves
Phobos is covered in long, shallow grooves that stretch across its surface. Scientists believe these grooves might be cracks caused by the impact that created Stickney Crater or by tidal forces from Mars’ gravity pulling on the moon.
14. Deimos Is More Stable Than Phobos
Deimos has a more stable orbit than Phobos because it’s farther from Mars and less affected by the planet’s gravity. While Phobos is doomed to crash into Mars, Deimos is likely to remain in orbit for billions of years.
15. Phobos Could Become a Ring Around Mars
If Phobos breaks apart before crashing into Mars, its debris could form a ring around the planet. This would make Mars the only rocky planet in the solar system with a ring, similar to the rings of Saturn, Jupiter, Uranus, and Neptune.
16. Deimos Is Farther from Mars
Deimos orbits Mars at a distance of about 23,460 kilometers (14,580 miles), which is much farther than Phobos. This distance makes it less affected by Mars’ gravity and less likely to experience tidal forces.
17. They Were First Photographed in the 1970s
NASA’s Mariner 9 spacecraft was the first to capture close-up images of Phobos and Deimos in 1971. These photos revealed their irregular shapes, cratered surfaces, and other unique features, sparking further interest in studying these moons.
18. Phobos and Deimos Are Not Round
Unlike Earth’s moon, which is nearly spherical, Phobos and Deimos are irregularly shaped, resembling potatoes. Their small size and weak gravity prevent them from pulling themselves into a round shape, which is why they look so strange.
19. Phobos Has a Thin Atmosphere
Phobos has a very thin atmosphere made of dust and gas, but it’s so thin that it’s almost a vacuum. This makes it impossible to support life as we know it and creates a harsh environment for exploration.
20. Deimos Is Less Dense Than Phobos
Deimos has a lower density than Phobos, suggesting it might be made of lighter materials. This difference in density could provide clues about their origins and whether they are captured asteroids or fragments of Mars.
21. Phobos Blocks the Sun During Eclipses
Phobos is large enough to partially block the Sun when it passes in front of it, creating a solar eclipse on Mars. These eclipses are much shorter than those on Earth, lasting only about 30 seconds.
22. Deimos’ Eclipses Are Rare
Because Deimos is smaller and farther from Mars, it rarely causes eclipses. When it does, the eclipse is barely noticeable because Deimos appears as a tiny dot against the Sun.
23. They Are Covered in Dust
Both moons are covered in a thick layer of dust and loose material called regolith. This dust is created by constant impacts from micrometeoroids, which bombard their surfaces over millions of years.
24. Phobos Has Been Proposed as a Base for Mars Exploration
Some scientists have suggested building a base on Phobos to study Mars. Its low gravity and proximity to the planet make it an ideal location for a research station or a staging point for future Mars missions.
25. Deimos Is Harder to Study
Because Deimos is smaller and farther from Mars, it’s harder to study than Phobos. Most spacecraft focus on Phobos because it’s easier to reach and provides more opportunities for exploration.
26. Phobos and Deimos Could Contain Water
Some studies suggest that Phobos and Deimos might contain small amounts of water ice beneath their surfaces. If true, this water could be used for future space missions, making the moons valuable resources for exploration.
27. They Are Bombarded by Radiation
Without an atmosphere or magnetic field, Phobos and Deimos are constantly exposed to solar radiation and cosmic rays. This makes their surfaces extremely harsh and dangerous for any potential human exploration.
28. Phobos Has Been Visited by Several Spacecraft
Spacecraft like Mariner 9, Viking 1, and Mars Express have studied Phobos up close. These missions have provided valuable data about its surface, composition, and orbit, helping scientists understand its origins.
29. Deimos Has Been Less Explored
While Phobos has been the focus of many missions, Deimos has received less attention. Its smaller size and greater distance from Mars make it harder to study, but future missions may explore it in more detail.
Conclusion
Phobos and Deimos may be small, but they are full of big mysteries. Their strange shapes, unusual orbits, and uncertain futures make them some of the most fascinating objects in the solar system. As we continue to study these doomed moons of Mars, we may uncover new clues about the formation of planets, the behavior of asteroids, and the evolution of our solar system.
Their ultimate fate—whether Phobos crashes into Mars or becomes a ring, and whether Deimos drifts away forever—reminds us of the dynamic and ever-changing nature of space. By studying these tiny moons, we not only learn about Mars but also gain a deeper understanding of the universe itself. Who knows what secrets they still hold?
