How Many Moons Does Mars Have?

By Eugenia Yordán, Natural resources technician. April 26, 2023
How Many Moons Does Mars Have?

Throughout the history of human exploration, our fascination with celestial bodies has driven us to uncover the secrets of the cosmos. Mars, often referred to as the "Red Planet," has held a special place in our collective imagination. In addition to its reddish hue and its potential as a future human habitat, Mars boasts an intriguing celestial entourage of its own: its moons.

In this article from thedailyECO, we seek to answer the question of how many moons does Mars have, as well as some other fascinating aspects of these enigmatic companions.

You may also be interested in: What Are the 27 Moons of Uranus Called?

The moons of Mars

Mars, at present, boasts two moons called Deimos and Phobos. Deimos takes its name from the Greek word meaning "flight" or "pain," while Phobos is derived from the Greek word for "fear" or "panic."

In 1972, NASA's Mariner 9 orbiter made a historic breakthrough by capturing the first satellite images of Mars, revealing the irregular, potato-like shapes of both moons. The distorted forms of Deimos and Phobos can be attributed to their feeble gravitational fields, which hinder them from acquiring a balanced, spherical structure.

These Martian moons harbor immense potential for future exploration endeavors. Firstly, they could serve as strategic outposts for space missions, providing a valuable platform for landing and conducting observations. Due to their weak gravitational fields, the energy required to maintain orbit is significantly lower than that needed for our own Moon.

Furthermore, the moons may contain water reserves, offering a vital resource for space travelers. By extracting and utilizing the water's hydrogen and oxygen components, future missions could reduce dependence on Earth for supplies.

Mars moon discovery history

Before 1877, it was widely believed that Mars had no moons as none had been identified up to that point Throughout history, various astronomers observed Mars, but no moons were identified. However, limited technology and observational capabilities hindered their detection.

In the 19th century, American astronomer Asaph Hall became determined to search for potential satellites of Mars. He worked at the United States Naval Observatory and had access to better telescopes and tools than his predecessors.

In the year 1877, Mars reached its closest proximity to Earth, a celestial event referred to as opposition. Opposition occurs when Mars and Earth are on opposite sides of the Sun, resulting in Mars being at its closest point to Earth in its orbit. This phenomenon happens approximately every two years and two months.

This alignment presented a remarkable opportunity for astronomers to conduct observations and significantly enhanced the likelihood of identifying any potential moons around Mars. It was during this auspicious period that Asaph Hall's unwavering determination bore fruit. On the 12th of August, 1877, utilizing a 26-inch refracting telescope, Hall spotted a minuscule and faint object in the vicinity of Mars. Undeterred, he continued his vigilant search, and on the subsequent night, the 13th of August, 1877, Hall's efforts were rewarded as he observed a second moon gracefully orbiting Mars.


Phobos is the larger of the two Martian moons, but it is still relatively small, measuring approximately 27 kilometers (17 miles) in diameter. It orbits very close to Mars, at an average distance of about 6,000 kilometers (3,700 miles) from the planet's surface. Phobos is the closest moon to its parent planet in the entire solar system.

The origin of Phobos is still a subject of scientific investigation and debate. One theory suggests that it may be a captured asteroid, while another hypothesis proposes that it formed from debris ejected during a large impact on Mars. Phobos is composed of carbonaceous chondrite-like material, similar to some types of primitive meteorites.

Phobos has an irregular, asymmetrical shape, resembling a lumpy potato or a heavily cratered rock. Its surface is covered with numerous impact craters, which is a characteristic of heavily bombarded celestial bodies. The largest crater on Phobos, named Stickney, is about 9 kilometers (5.6 miles) in diameter and is believed to have been caused by a significant impact event.

Phobos orbits Mars at a very close distance, completing a revolution in just 7 hours and 39 minutes. Due to its proximity, tidal forces from Mars are gradually causing Phobos to spiral inward. Scientists estimate that within approximately 30 to 50 million years, Phobos will either break apart or collide with Mars.

You might be interested in this other article, where we discuss why there are craters on the surface of the Moon.

How Many Moons Does Mars Have? - Phobos


Deimos is the smaller of the two Martian moons, with a diameter of approximately 15 kilometers (9.3 miles). It orbits Mars at an average distance of about 23,460 kilometers (14,580 miles) from the planet's center, making it the outermost moon of Mars.

Deimos also has an irregular shape. Its surface is marked by numerous craters, resulting from impacts over its long history. Although it is less cratered compared to Phobos, it still bears the scars of countless collisions.

Deimos is believed to be composed of a mixture of rock and ice. Its low density indicates the presence of significant void spaces or porous material beneath its surface. The exact composition of Deimos is still a subject of scientific investigation.

Deimos is thought to have originated in the outer regions of the solar system as a Kuiper Belt or asteroid belt object. It is theorized that it was captured by Mars' gravity, transitioning into its current orbit around the planet. This capture hypothesis helps explain the irregular shape and composition of Deimos.

Do not miss this other article, where we explain in more detail what a celestial body is.

How Many Moons Does Mars Have? - Deimos

An overview of Mars' features

Mars, commonly known as the "Red Planet," is the fourth planet from the Sun in our solar system, positioned between Jupiter and Earth in its orbital path. It is distinguished by its desert-like landscape, frigid temperatures, rocky topography, and its iconic reddish appearance, which arises from the prevalence of oxidized iron in its soil. Now, let's explore some prominent features of Mars:

  • Size: in terms of size, Mars is approximately half the diameter of Earth. Mars has a diameter of approximately 6,779 kilometers (4,212 miles).

  • Orbital period: Mars has a longer orbital period than Earth due to its larger orbital path. The average orbital period of Mars is approximately 687 Earth days, which is equivalent to 1.88 Earth years. This means that Mars takes about 1.88 Earth years to complete a full revolution around the Sun. It's worth noting that Mars' orbit is slightly elliptical, meaning that its distance from the Sun varies throughout its orbit.

  • Surface: Mars has a diverse and intriguing surface. It is home to various geological formations, including vast plains, towering volcanoes, deep canyons, and impact craters. The largest volcano in the solar system, Olympus Mons, resides on Mars. Valles Marineris, a system of enormous canyons, stretches across a distance of about 4,000 kilometers (2,500 miles).

  • Polar ice caps: Mars has polar ice caps at its north and south poles. These ice caps are primarily composed of water ice, but they also contain a significant amount of frozen carbon dioxide (dry ice). During the Martian winter, these caps grow in size as carbon dioxide freezes out of the atmosphere.

  • Atmosphere: Mars has a thin atmosphere compared to Earth. The Martian atmosphere is primarily composed of carbon dioxide, with traces of nitrogen, argon, and oxygen. The atmospheric pressure on Mars is about 0.6% of Earth's atmospheric pressure, making it inhospitable for human survival without the aid of specialized equipment.

  • Dust storms: Mars is known for its frequent dust storms, which can sometimes cover the entire planet. These storms occur when the surface of Mars heats up and causes changes in atmospheric pressure, leading to strong winds that stir up dust particles. Dust storms can vary in scale and duration, from small local events to planet-wide storms that last for months.

These are just a few of the main features of Mars. As our knowledge of the planet continues to evolve through space missions and scientific research, we can gain a deeper understanding of its geological history, potential habitability, and the possibilities it holds for future human exploration.

If you want to read similar articles to How Many Moons Does Mars Have?, we recommend you visit our Facts about Earth and the universe category.

  • Bagheri A, Khan A, Efroimsky M, Kruglayakov M, Giardini D. 2021. Dynamical evidence for Phobos and Deimos as remnants of a disrupted common progenitor . Available at:
  • Burns, J. A., and Showalter, M. R. (2006). Evolutionary Processes in the Small Natural Satellites of the Solar System. In F. Rasio and I. A. Zwart (Eds.), The Cambridge N-Body Lectures (pp. 120-140). Cambridge University Press.
  • Hartmann, W. K., and Phillips, R. J. (2001). The Martian Phobos and Deimos. Lunar and Planetary Institute.
  • Natural satellites of Mars . Tayabeixo. Available at:

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