Satellites Of MARS: Phobos And Deimos

There are two moons of Mars. They are Phobos and Deimos. They both have a completely irregular shape. American astronomer Asaph Hall in August 1877 discovered these two Moons. In this post, we will discuss these Satellites of Mars in detail.


Astronomers used computers to understand the orbits of both Phobos and Deimos. During observations, scientists found that they crossed paths at some point between one and 2.7 billion years ago.



This study confirmed that these two small moons having a potato-like shape, but have the same origin.

Scientists believed that both Phobos and Deimos were two parts of one big moon. Which later was shattered due to a large impact. An asteroid or any other astronomical object perhaps did that.


At first, both satellites of Mars Phobos and Deimos were one single Martian satellite. The big moon may have blown apart due to a collision, mentioned in a study by scientists.


Before one to 2.7 billion years ago a powerful explosion occurred between the Martian moon and an asteroid. As a result of this explosion two chunks of this blast captured by Mars by its gravitational force and now they are Phobos and Deimos.



At first, Phobos was thought to be an asteroid. In 1959, observations of Deimos by the Infrared Astronomical Satellite produced results that strongly suggested that Phobos is not a natural object. The existence of the moons was confirmed by spacecraft in 1973 and 1981. In November 2010, Nasa reported it is a rocky body more than 10 kilometers (6.2 mi) in diameter.


In 2016, scientists from the University of Hawaii reported that Phobos’s gravitational pull is sufficient to reshape the entire satellite. While this may not be enough to alter the moon’s orbit. They reported that the moon’s orbit may be altered enough to affect its lifetime, adding that it is at risk of being ripped apart by the solar wind in about 10 million years.


Astrophysical Journal Letters published the study. The moon was originally designated as asteroid 4560 Pallas and then renamed Phobos by Asaph Hall in 1877. It was finally given its current name by the International Astronomical Union (IAU).


Deimos is a satellite of Mars discovered by Gerard Kuiper in January 1892 and originally named Aten, an Ancient Greek term meaning “beacon of the sun.” The current names are a Latinisation of the Greek.


Satellites Of MARS Phobos


Phobos is the larger moon of Mars. It orbits Mars once every 13.8 hours. It is currently on the opposite side of Mars from Earth and lies directly between Mars and the Sun in the same hemisphere. That makes it impossible for spacecraft to see both moons at the same time.


The minimum orbital distance is 1,900 km (1,180 mi) and the average orbital distance is 1,900 to 2,050 km (1,140 to 1,390 mi). The moon’s mean radius is about 1,710 m (5,200 ft), with a diameter of 581 m (1,890 ft).


The surface of Phobos is as red as that of the lunar maria but is constantly being covered with a dusting of fine Martian material.


About 10 km (6.2 mi) or so in altitude, the concentration of dust rises to more than three times the amount in the atmosphere above the surface.


On November 15, 2014, NASA reported that the dust cloud, named the “Great Dust Storm of 2014”, had subsided after four Martian years. Phobos is dark red and the smaller moon is surrounded by a cloud of fine dust. The Martian moons, Deimos and Phobos, are little more than scraps of rock. 


Phobos is dark red in color. The surface has been altered by impact processes and by radiation. It has a mean radius of 1,710 m (5,200 ft), and a diameter of 581 m (1,890 ft). The surface of the satellite is characterized by scattered rock debris




The smallest and outermost satellite of Mars is Deimos. It was discovered on 6 January 1801 by Édouard Stephan and it orbits Mars at a mean distance of about 64.2 million kilometers in an oval orbit, once every 5.65 days, with an eccentricity of 0.1334 and an inclination of 1° with respect to the ecliptic.

The typical orbital period is 3.96 years and, since it is not precisely known with certainty, the eccentricity cannot be computed precisely.

Deimos orbits further to Mars than its larger companion Phobos.


This satellite of Mars has a mean distance from the planet is about, approximately 1.4 times that of Phobos. Its orbit can be inferred by examining Mars’ natural satellites, as orbital analysis of Phobos and Deimos was possible through observation of the discrepancies in their orbital periods and eccentricities.


At present, it is the nearest satellite of the planet to the Sun. That is why its name is the “northern moon”.


Its low inclination, making Deimos the closest object to the Sun for most of the year, is due to the fact that it is currently near the aphelion of its orbit.


Deimos has a volume of about 60,000 m. Its surface is reported as white with a light-grey albedo of 0.112. Although, by comparison with Phobos, Deimos has relatively little soil.


Its surface topography is dominated by a few elongated depressions (some with their diameters more than 1 km) that are about 200 m in diameter.


Only the most recent Mars Global Surveyor observations suggest the existence of a possible small impact crater at the eastern terminus.


From about 1980 to 2002, several transient shadows appeared on Deimos’ surface that is believed to be trails made by a rocket engine during a time when the spacecraft was passing very close to the Red Planet.


They lasted from several seconds to several minutes each and were caused by drag forces.


These shadows on Deimos were probably caused by the rear end of the spacecraft (or a small rocket engine) orbiting Mars, so that its exhaust blasted the spacecraft’s shadow onto the surface.


During that period, Mars and the Sun were in alignment, and the spacecraft’s engines were not moving as quickly as at present. The shadow path is about long.


The name “Deimos” is Greek for “desert”. It may be named after Deimos, a central character in Greek mythology.



Updated: April 3, 2021 — 5:41 pm

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