The two moons of Mars are Phobos and Deimos. These moons are likely asteroids captured from the main asteroid belt located between Mars and Jupiter. Phobos is the larger of the two, measuring 13,4 kilometers on its longest side, 11,2 kilometers wide, and 9,2 kilometers in diameter. It orbits at an altitude of 9380 kilometers from the center of Mars, or less than 6000 kilometers from the surface, every 7,5 hours. The satellite was discovered on August 18, 1877, by the American astronomer Asaph Hall (1829–1907).
In this article we are going to tell you everything you need to know about the Phobos satellite, its characteristics, discovery and importance.
Key features
Phobos, whose name means "fear" in Greek, was discovered in 1877 by the American astronomer Asaph Hall. It is the largest moon of Mars, but still quite small compared to other moons in our solar system, with a diameter of approximately 22 kilometers.
One of Phobos's most striking features is its irregular, elongated shape. Its surface is covered in craters, indicating a violent past and an interesting geological history. It also displays grooves and ridges, suggesting it may have undergone fracturing processes due to tidal forces generated by Martian gravity. For more information on other moons, you can consult our article on the moons of Venus.
Its orbit is extremely close to Mars. It is located at a distance of only 6,000 kilometers from the planet's surface, which is quite unusual for a natural satellite. This means that Phobos completes one orbit around Mars in approximately 7 hours and 39 minutes, much faster than the time it takes Mars to rotate on its own axis.
Due to its proximity to Mars, this satellite is undergoing orbital degradation. Over time, Martian gravity exerts tidal forces that are causing Phobos to drift ever closer to the planet. Scientists believe that, in a few million years, the satellite will eventually disintegrate due to tidal forces and become a ring around Mars. This is a fascinating phenomenon that relates to what we know about the Moon as a satellite.
The Russian space mission, called Phobos-Grunt, was intended to land on Phobos, collect samples, and bring them back to Earth. However, the mission suffered a technical failure and was unable to meet its objective.
Phobos Stickney Crater
This satellite is riddled with impact craters, like all terrestrial objects in the solar system. At 9 km in diameter, Stickney crater is the largest crater on a Martian moon and is almost half the diameter of Phobos.
The crater is named after Chloe Angelina Stickney Hall, a mathematician and astronomer and wife of Asaph Hall. Despite the low gravity (0,005 m/s²), it can be assumed that the material from the meteorite that struck Phobos slid slowly down the crater walls. The channels found on the surface of the moon are less than 30 meters deep, 100–200 meters wide, and up to 20 kilometers long.
Phobos and Deimos are topics of interest in planetary science. The characteristics of Phobos, along with its connection to the Mars exploration mission, highlight the importance of Mars in the study of the solar system.
Phobos and Deimos
The names of the two moons of Mars are derived from Greek mythology, Phobos (fear) and Deimos (terror), twins of the god Ares and the goddess Aphrodite. Deimos is covered by a thick layer of particles ejected by the meteorite impact, which obscures the relief of its gradual crater filling.
The two moons, likely from the asteroid belt, were captured during their close approach to Mars. Deimos is 23.460 kilometers from Mars and Phobos is 9.377 kilometers away . The gravity on Deimos' surface is very low (0,0039 m/s²). Its density is only 2,2 g/cm³. Its escape velocity is 22 km/h (6 m/s), which would allow a person to leave Deimos' surface simply by running.
Phobos is the larger of the two moons of Mars. It was also the closest to the red planet, taking 7 hours and 39 minutes. At the time of filming, Mars Express was 11 miles away, while Deimos was 800 kilometers away.
A notable distinction between these two moons is their shape. Phobos has an elongated, irregular shape, with a surface covered in craters and ridges. Deimos, on the other hand, has a more spherical and smooth shape, with fewer craters. This difference in shape may be due to the different geological histories of each satellite.
The orbits also differ significantly. Phobos orbits Mars at a distance of approximately 6,000 kilometers from the planet's surface, making it one of the closest satellites compared to others in our solar system. Deimos is at a much greater distance, orbiting about 23,500 kilometers from the Martian surface. This difference in orbital distances also translates into differences in the orbital periods of both satellites around Mars.
Regarding their origin, there are different theories. Some scientists suggest they could be asteroids captured by Mars' gravity , while others believe they could be remnants of a larger object that fragmented due to an impact. These theories remain the subject of research and debate within the scientific community.
landing mission
Phobos has been proposed as an early target for human missions to Mars. Human teleoperation of robotic explorers on Mars from Phobos could be accomplished without significant time delays, and planetary protection issues in early Mars explorations could be addressed in this way.
Landing on Phobos is much easier and less expensive than landing on the Martian surface. A lander heading to Mars must be able to enter the atmosphere and return to a subsequent orbit without any support facilities, or a support facility will need to be established on-site. In contrast, a lander on the moon could rely on equipment designed for lunar and asteroid landings. Furthermore, because it has very weak gravity, the delta-v required to land on Phobos and return is only 80% of that required to travel to and from the lunar surface.
I hope that with this information you can learn more about the Phobos satellite and its characteristics.
