Facts About Deimos' Origin, Composition, Discovery And More


Deimos - Mars smallest moon
Deimos - The smallest moon of Mars

Deimos is the smallest and the outermost moon of the two potato-like Martian moons. At the height of 23,460 km or 14,580 mi from Mars' surface, it completes its one orbit in 30.3 hours. With a dimension of 15 km × 12.2 km × 11 km, it is one of the smallest moons in the inner solar system. Deimos is named after one of the sons of the Greek god Ares (Mars) and Aphrodite (Venus), who represent terror. Deimos composition is rich in carbonaceous material, which makes it similar to C-type asteroids and carbonaceous chondrite meteorites.

Facts About Deimos

Deimos Profile

Name Deimos
Moon of Mars
Distance from Mars (avg) 23,460 km
Mean Radius 6.2 km
Volume 999.78 km3
Mass 1.47 × 1015 kg
Surface area 495.15 km2
Gravity 0.003 m/s2
Temperature (avg) -40 °C or -40 °F
Length of day 30.312 h (earth time)
Discovered by Asaph Hall
Discovered on 12 August 1877

Quick Facts About Deimos

  1. Deimos' gravity is not so strong to round its body into a spherical shape.
  2. Deimos has no Atmosphere.
  3. Although there are a number of craters on Deimos, but it has a relatively smoother surface than Phobos.
  4. There are only two geological features have been named, the craters Swift and Voltaire.
  5. Both the craters named after authors who predicted the two Martian moon in their story.
  6. From the surface of Mars, the small moon has a star-like appearance.
  7. It is 56% smaller than the Mars largest moon, Phobos.
  8. When it is shining brightly on the full moon, it is like Venus from Earth.
  9. It also goes through phases that can be observed by a telescope from Mars.
  10. Several space-crafts have observed and taken close-up images of Deimos, whose primary mission to explore the red planet.
  11. However, Many missions to Deimos has been planned.
  12. In 1997 and 1998, a $247.7 million cost mission, named "Aladdin," was planned to visit Phobos and Deimos and collect samples. However, MESSENGER spacecraft, a probe to Mercury, was chosen.
  13. Another sample collection mission has been proposed called "Gulliver," which would collect 1 kilogram of material and return to the earth.
  14. NASA is planning to send Human-mission to the Martian moons in the 2030s.
  15. However, solar eruptions could charge the surface to hundreds of volts. But it is expected that it could not injure the astronomers but might affect sensitive equipment. So, they are designing suits that minimise such hazards.

Detailed Facts About Deimos

  • Deimos was the first discovered Martian moon

Asaph Hall - The discoverer of Mars and its moons
Asaph Hall - The discoverer of Mars and its moons

Using a 26-inch refractor telescope at the U.S. Naval Observatory in Washington, D.C., Asaph Hall discovered Deimos on 12th August 1877. He first discovered Deimos, and after six days of observation, he found the largest Martian moon - Phobos.

Although, in the 12th century, Johannes Kepler hypothesis that there should be two Moons of Mars, by observing the moons of our Earth and Jupiter's moon. However, due to the small size, the two moons were hidden from astronomers for decades.
  • Deimos was named by a Science Master

The smallest of the two Martian moon Phobos was named after the Greek personification of terror. The name was selected by Henry Madan, who was a Science Master of Eton. He picked the name from Homer's ancient poem, "The Iliad," where Phobos and Deimos accompanied their father, Ares, (Mars for Greeks) into the battle.
  • Deimos cannot be seen on Mars' poles

Orbits of Phobos and Deimos
Orbits of Phobos and Deimos

Like Phobos, Deimos has a nearly a circular orbit rather than an ellipse. The difference between the farthest point and the closest point to Mars is only a few meters, about 25 m. The moon completes its one orbit around Mars in 30.4 hours. Due to its relative closeness to Mars and has an orbit almost at the equator, an observer at latitudes greater than 82.7°, cannot see Deimos.
  • Eclipses caused by Phobos only lasts for minutes

Transits of Deimos captured by Opportunity and Spirit rover from Mars
Transits of Deimos captured by Opportunity and Spirit rover from Mars

The event when Deimos passes between the sun and Mars is referred to as a transit of Deimos or partial eclipse of the Sun by Deimos. Although the angular diameter of Deimos is one-tenth of the Sun's, so this event is more referred to as a transit. In a transit, Deimos can be seen as a dark spot moving rapidly across the sun's disk.

Deimos transit has been observed and photographed by Opportunity rover on 4 March 2004 and Spirit rover on 13 March 2004. Due to its rapid orbit, the transits only last for less than two minutes and causes fewer transits than Phobos. At the same time, an observer at latitudes higher than 82.7° N or 82.7° S neither see Deimos nor its transits.
  • The origin of Deimos is controversial

Voltaire and Swift - The Two named geographical features on Deimos
Voltaire and Swift - The Two named geographical features on Deimos

By observing the composition of Deimos, which is like that of C- or D-type asteroids, researchers theorised that they came from the asteroid belt. Deimos is thought to be an asteroid that was kicked out from the Asteroids Belt by Jupiter's immense gravity. However, after captured, their orbit was highly ellipse. But to form today's circular orbit from a highly elliptical orbit takes much time and a thick atmosphere to provide an atmospheric break. But due to Mars thin atmosphere, many researchers think that they should have other origins.

Another thought is that they were dust and rocks, which were drawn together by gravity, and the tiny moons we're formed. Some astronomers also think that Deimos was formed when a celestial body collided into Mars, and the dust and rocks ejected by the collision were coalesced to form Deimos, just like our moon formed.
  • In about 100 million years, there will be no moon to Mars

Image of Deimos captured by Viking 2 orbiter in October 1977
Image of Deimos captured by Viking 2 orbiter in October 1977

Phobos is slowly going away from Mars because of tidal acceleration. In about 100 million years, the tiny moon will eventually escape the red planet's gravity. Whereas the closer and the bigger moon, Phobos, is coming closer to Mars. It is estimated that within 50 million years, Phobos will collide with the Martian surface or make a ring. So, Mars will be alone without any moon in its future.

More Phobos Facts

Those are the interesting facts about Deimos. Check out these links to explore more about Deimos:

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