Phobos vs The Moon (How Are They Different?)

The main differences between Phobos and the Moon are that Phobos is smaller with a diameter of 22.53km while the Moon has a diameter of 3,474.8km, the Moon orbits Earth while Phobos orbits Mars and the Moon is spherical in shape while Phobos is not.

There are numerous other differences between the two so, continue reading for a more detailed look at each of these natural satellites along with their similarities and differences below.

What Is The Moon Phobos?

Phobos is the larger and innermost of the Martian moons, named after the Greek God of fear and panic. This rocky satellite measures approximately 27 x 22 x 18 kilometers and possesses an irregular shape.

Flying only 270 km above Mars’s surface, Phobos orbits the Martian surface so closely that it spins around the planet three times a day (each orbit takes 7 hours and 39 minutes). And this proximity means that the moon cannot always be seen from Mars’ surface (it all depends on where you’re standing).

In general, Phobos rises in the west, passes through the sky in around 4 hours, and sets in the east. And this process occurs twice during one Martian day.

Phobos travels 1.8 m closer to Mars every 100 years, which means this doomed moon will one day crash into its planet or break up into rings. Still, this won’t happen for another 50 million years or so.

The moon is covered in streak patterns from impact craters, the most significant of which is the crater Stickney, with a diameter of 9.7 km. Phobos has weathered thousands of meteorite impacts, one of which almost shattered it to pieces.

It was first discovered by the American astronomer Asaph Hall on 17th August 1877. But, it can be difficult for astronomers to see as it is one of the least reflective bodies in the solar system with an albedo of 0.071.

Despite its small stature, Phobos experiences wildly varying temperatures on its dark side compared to the light side. Measurements on the light side of the moon suggest that temperatures can rise to -4 degrees Celsius, a sort of brisk winter’s day that would be cold but tolerable.

In contrast, temperatures on the dark side can drop to -112 degrees Celsius, even though the two areas are just a few kilometers apart. The probable cause is fine surface dust that cannot retain heat, allowing temperatures to drop rapidly.

The low density of Phobos suggests its composition is similar to carbonaceous chondrite meteorites, which could mean that Phobos is a captured asteroid.

What Is The Moon?

The moon is the gray celestial being that orbits our Earth. It is also tidally locked to Earth meaning that we only see one side of it at any time in our sky.

It takes the moon roughly 27 days to complete an orbit around Earth, which it does in an elliptical pattern. The Moon’s axial tilt is very straight at 1.5 degrees. As a result of the tidally locked status along with the effects that Earth has on its general rotational patterns, it takes the Moon roughly 29.5 days to complete a day.

In regards to its temperature, it fluctuates where it can be really hot at 127 degrees Celsius when the Sun is shining on it and to -173 degrees in areas where the Sun does not strike it. It’s core on the other hand is far hotter ranging between 1,327 to 1,427 degrees Celsius.

This is as a result of the lunar entity’s extremely thin to practically non-existent atmosphere, which not only results in these massive temperature shifts but, is also the reason why it has over 100,000 craters on its surface.

Speaking of the Moon’s surface, the entity is mostly made of rocks, iron, magnesium just like most of the other moons and terrestrial based planets in our solar system.

It is among the bigger moons in our solar system with a diameter of 3,474.8km and a mass of 7.35 × 10^22 kg, which actually places it fifth amongst all moons in our solar system and would also make it bigger than the dwarf planet Pluto.

Despite all the advancements in technology, the last time a manned mission was made to the Moon was on the Apollo 17 way back in December 1972 and no further missions have been done since, possibly as result of the political agendas behind the numerous countries vying for opportunities that we don’t know of.

Similarities Between Phobos And The Moon

As both are natural satellites, the Moon and Phobos do share a few similarities, which includes the following:

• Both have a rocky, terrestrial surface.
• Neither have rings surrounding them.
• Both are tidally locked to their planet.
• Both orbit their planet in an elliptical pattern.
• Neither have a magnetic field.
• Neither have tectonic plates

Differences Between Phobos And The Moon

As for the differences between the two so, they include the below:

• Phobos orbits Mars whilst the Moon orbits the Earth.
• The Moon is a spherical shape while Phobos is not.
• The Moon has a diameter of 3,474.8km whilst Phobos has a diameter of 22.53km.
• Phobos has no atmosphere whilst the Moon’s atmospheric composition consists of a thin layer with small amounts of helium, argon, and possibly neon, ammonia, methane and carbon dioxide.
• A day on Phobos takes 7 hours 39 minutes whilst a Moon day 29.5 days.
• It takes Phobos 7 hours 39 minutes to orbit Mars and around the Sun in 673 days whilst the Moon orbits Earth in 29.5 days and the Sun in 365 days.
• The Moon has an axial tilt of 5 degrees whilst Phobos’ axial tilt is closer to 0.
• Phobos’ temperature ranges between -4 to -112 degrees Celsius whilst the Moon’s is between 127 degrees and -173 degrees Celsius.
• The Moon orbits Earth at an average distance of 384,400 km whilst Phobos is 6,000km away from Mars.
• The Moon’s density is 3.34 g/cm³ whilst Phobo’s density is 1.88 g/cm³.
• The Moon’s mass is 7.35 × 10^22 kg whilst Phobos’ mass is 10.6 × 10^15 kg.
• Phobos’ gravitational strength is 0.0057 m/s² whilst the Moon’s is 1.62 m/s².
• Phobos only orbits Mars 6,000km away and is getting closer to the planet by 1.8 meters every 100 years.

Summary

The Moon and Phobos are both natural satellites that orbit a planet and are terrestrial, low density floating rocks but, there are still numerous differences between the two.

Whether it be in regards to mass, size, orbital periods, distance from their planets, their physical shape and more, so despite the numerous similar features these two share, they are still easy to tell apart due to their distinguishable features.