Discovery An image of Deimos taken by the Viking 1 orbiter. Viking 1 was the first of two spacecraft sent to Mars as part of NASA 's Viking program, and holds the record for the longest Mars surface mission Asaph Hall August 12, 1877 23,460 km 0. Asaph Hall ( October 15, 1829 &ndash November 22, 1907) was an American astronomer who is most famous for having discovered Events 1099 - First Crusade: Battle of Ascalon - Crusaders under the command of Godfrey of Bouillon defeat Fatimid Year 1877 ( MDCCCLXXVII) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common In Physics, an orbit is the gravitationally curved path of one object around a point or another body for example the gravitational orbit of a planet around a star In Geometry, the semi-major axis (also semimajor axis) is used to describe the dimensions of ellipses and hyperbolae The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand In Astrodynamics, under standard assumptions, any Orbit must be of Conic section shape 0002 1. The orbital period is the time taken for a given object to make one complete Orbit about another object 26244 d 1. A day (symbol d is a unit of Time equivalent to 24 Hours and the duration of a single Rotation of planet Earth with respect to the The orbital speed of a body generally a Planet, a Natural satellite, an artificial satellite, or a Multiple star, is the speed at which it 35 km/s 0. Inclination in general is the Angle between a Reference plane and another plane or axis of direction 93° (to Mars' equator)1. 793° (to the local Laplace plane)27. The Laplace plane, named after Pierre-Simon Laplace, is defined as the mean plane occupied by the orbit of a Satellite during a Precession cycle 58° (to the ecliptic) Mars 15. The ecliptic is the apparent path that the Sun traces out in the sky during the year A natural satellite or moon is a Celestial body that Orbits a Planet or smaller body which is called the primary. 0 × 12 × 10. 4 km 6. 2 km[2] 1. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object 48×1015 kg[3] 1. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 471 g/cm³[2] 0. For other uses of the words gram or gramme see Gram (disambiguation. A cubic centimetre or cubic centimeter (symbol cm3 —the abbreviation cc, though widely used is deprecated is a commonly used unit of Volume The surface gravity, g, of an astronomical or other object is the Gravitational acceleration experienced at its surface 0039 m/s² (3. 9 mm/s²)0. The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to 00040 g (400 µg) 5. g-force (also G-force, g-load) is a measurement of an object's Acceleration expressed in g s micro- ( µ) is a prefix in the SI and other systems of units denoting a factor of 10&minus6 (one Millionth. In Physics, escape velocity is the speed where the Kinetic energy of an object is equal to the magnitude of its Gravitational potential energy 6 m/s (20 km/hr)[3] synchronous 0. (For the South African airport with IATA code "KMH" see Johan Pienaar Airport. The rotation period of an astronomical object is the time it takes to complete one revolution around its Axis of rotation relative to the background stars In Astronomy, synchronous rotation is a planetological term describing a body orbiting another where the orbiting body takes as long to rotate The albedo of an object is the extent to which it diffusely reflects light from the sun 068[2] ≈233 K 12. Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 4 [4][2]

Deimos (pronounced /ˈdaɪməs/ DYE-məs, also /ˈdiːməs/ DEE-məs as in Greek Δείμος), is the smaller and outer of Mars’ two moons (the other being Phobos). A natural satellite or moon is a Celestial body that Orbits a Planet or smaller body which is called the primary. It is named after Deimos, a figure representing dread in Greek Mythology. In Greek mythology, Deimos ( Δεῖμος &ndash " dread " was the Personification of dread. Greek mythology is the body of stories belonging to the ancient Greeks concerning their gods and Heroes the nature of the world and the origins and significance Its systematic designation is Mars II. In ancient times only the Sun and Moon, a few hundred Stars and the most easily visible Planets had names

## Discovery

Asaph Hall, discoverer of Deimos. The discovery of the two moons of Mars, Phobos and Deimos, occurred in 1877 when American astronomer Asaph Hall Sr Asaph Hall ( October 15, 1829 &ndash November 22, 1907) was an American astronomer who is most famous for having discovered

Deimos was discovered by Asaph Hall, Sr. Asaph Hall ( October 15, 1829 &ndash November 22, 1907) was an American astronomer who is most famous for having discovered on August 12, 1877 at about 07:48 UTC (given in contemporary sources as "August 11 14:40" Washington mean time using the old astronomical convention of beginning a day at noon, so 12 hours must be added to get the actual local mean time). Events 1099 - First Crusade: Battle of Ascalon - Crusaders under the command of Godfrey of Bouillon defeat Fatimid Year 1877 ( MDCCCLXXVII) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common Events 2492 BC - Traditional date of the defeat of Bel by Hayk, progenitor and founder of the Armenian nation Washington mean time was the time at the meridian through the center of the old dome atop the main building at the old US Naval Observatory at Washington D [5][6][7][8] Hall also discovered Phobos at the same time, after deliberately searching for Martian moons.

The names, originally spelled Phobus and Deimus, respectively, were suggested by Henry Madan (1838–1901), Science Master of Eton, from Book XV of the Iliad, where Ares (the Roman god Mars) summons Dread (Deimos) and Fear (Phobos). Eton College, or just Eton, is a world-famous British Independent school for boys founded in 1440 by King Henry VI. The Iliad ( Greek: Ἰλιάς (Ancient Ιλιάδα (Modern is together with the Odyssey, one of two ancient In Greek mythology, Ares ( Ancient Greek:, Μodern Greek Άρης) is the son of Zeus and Hera. Mars was the Roman Warrior god, the son of Juno and Jupiter, husband of Bellona, and the lover of Venus. Phobos ( Ancient Greek, "Fear" is the embodiment of Fear and horror in Greek mythology. [9]

## Characteristics

Orbits of Phobos and Deimos (to scale)

Deimos, like Mars' other moon Phobos, has spectra, albedos and densities similar to that of a C or D-type asteroid. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies The albedo of an object is the extent to which it diffusely reflects light from the sun The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different C-type asteroids are Carbonaceous Asteroids They are the most common variety forming around 75% of known Asteroids {Fact|date=July 2008}} and an even higher D-type asteroids have a very low Albedo and a featureless reddish Electromagnetic spectrum. Like most bodies of its size, Deimos is highly nonspherical with dimensions of 15 × 12 × 10 km. It has a nearly circular orbit nearly in Mars' equatorial plane. In Astronomy and Navigation, the celestial sphere is an imaginary rotating Sphere of "gigantic Radius "

Deimos is probably an asteroid that was perturbed by Jupiter into an orbit that allowed it to be captured by Mars, though this hypothesis is still in some dispute. In Physics, an orbit is the gravitationally curved path of one object around a point or another body for example the gravitational orbit of a planet around a star [10][11]

As seen from the surface of Deimos, Mars would appear 1,000 times larger and 400 times brighter than the full Moon as seen from Earth, taking up one-eleventh of the width of a celestial hemisphere. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 In Astronomy and Navigation, the celestial sphere is an imaginary rotating Sphere of "gigantic Radius "

As seen from Mars, Deimos would have an angular diameter of no more than 2. The angular diameter of an object as seen from a given position is the "visual diameter" of the object measured as an angle 5′ and would therefore appear almost star-like to the naked eye. [12] At its brightest ("full moon") it would be about as bright as Venus is from Earth; at the first or third quarter phase it would be about as bright as Vega. The VENUS ( V ictoria E xperimental N etwork U nder the S ea project is a cabled sea floor observatory operated by the University Vega (α Lyr / α Lyrae / Alpha Lyrae ( or) is the brightest Star in the Constellation Lyra, the fifth brightest star in the night With a small telescope, a Martian observer could see Deimos's phases, which take 1. 2648 days (Deimos's synodic period) to run their course. The orbital period is the time taken for a given object to make one complete Orbit about another object [12]

Unlike Phobos, which orbits so fast that it actually rises in the west and sets in the east, Deimos rises in the east and sets in the west. However, the Sun-synodic orbital period of Deimos of about 30. 4 hours exceeds the Martian solar day ("sol") of about 24. Various schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars 7 hours by such a small amount that 2. 7 days elapse between its rising and setting for an equatorial observer.

Because Deimos’s orbit is relatively close to Mars and has only a very small inclination to Mars’ equator, it cannot be seen from Martian latitudes greater than 82. 7°.

### Solar transits

Deimos transits the Sun, as seen by Mars Rover Opportunity

Deimos regularly passes in front of the Sun as seen from Mars. The term transit or astronomical transit has three meanings in astronomy A transit is the astronomical event that occurs when one The Sun (Sol is the Star at the center of the Solar System. MER-B ( Mars Exploration Rover - B) known as Opportunity, is the second of the two rovers of NASA 's Mars Exploration A transit of Deimos across the Sun as seen from Mars takes place when Deimos passes directly between the Sun and a point on the surface of Mars obscuring The term transit or astronomical transit has three meanings in astronomy A transit is the astronomical event that occurs when one Due to its small size it cannot cause a total eclipse, appearing only as a small black dot traveling across the Sun. An eclipse is an astronomical event that occurs when one Celestial object moves into the shadow of another Its angular diameter is only about 2. 5 times the angular diameter of Venus during a transit of Venus from Earth. A transit of Venus across the Sun takes place when the Planet Venus passes directly between the Sun and Earth, obscuring a small portion of the On March 4, 2004 a transit of Deimos was photographed by Mars Rover Opportunity, while on March 13, 2004 a transit was photographed by Mars Rover Spirit. Events 51 - Nero, later to become Roman Emperor, is given the title Princeps iuventutis (head of the youth "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " MER-B ( Mars Exploration Rover - B) known as Opportunity, is the second of the two rovers of NASA 's Mars Exploration Events 1138 - Cardinal Gregorio Conti is elected Antipope as Victor IV, succeeding Anacletus II. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " MER-A ( Mars Exploration Rover - A) known as Spirit, is the first of the two rovers of NASA 's Mars Exploration Rover

## Physical characteristics

Deimos is composed of rock rich in carbonaceous material, much like C-type asteroids and carbonaceous chondrite meteorites. Asteroids, sometimes called Minor planets or planetoids', are bodies—primarily of the inner Solar System —that are smaller than planets but A carbonaceous chondrite or a C-type chondrite is a type of chondritic Meteorite which contains high levels of Water and Organic compounds It is cratered, but the surface is noticeably smoother than that of Phobos, caused by the partial filling of craters with regolith. In the broadest sense the term impact crater can be applied to any depression natural or manmade resulting from the high velocity impact of a projectile with larger body Regolith ( Greek: "blanket rock" is a layer of loose Heterogeneous material covering solid rock. The regolith is highly porous and has a radar estimated density of only 1. Porosity is a measure of the void spaces in a material and is measured as a fraction between 0–1 or as a Percentage between 0–100% 1 g/cm³. [13] The two largest craters, Swift and Voltaire, each measure about 3 kilometres across. Swift crater is a crater on Mars 's moon Deimos. It is about 3km in diameter

## Origin

The origin of the Martian moons is still controversial. [10] The main hypotheses are that they formed either by capture or by accretion. Because of the similarity to the composition of C- or D-type asteroids, one hypothesis is that the moons may be objects captured into Martian orbit from the asteroid belt, with orbits that have been circularized either by atmospheric drag or tidal forces,[14]. The asteroid belt is the region of the Solar System located roughly between the orbits of the Planets Mars and Jupiter. The tidal force is a secondary effect of the Force of Gravity and is responsible for the Tides It arises because the gravitational acceleration experienced Landis has suggested that the moons may have originated from a binary asteroid that separated due to tidal forces. Geoffrey A Landis works as a scientist and writer of Science fiction. A binary asteroid is a system of two Asteroids orbiting their common Center of mass, in analogy with Binary stars The first such system to be discovered [11]

## Named geological features

The two named craters on Deimos

Only two geological features on Deimos have been given names. The craters Swift and Voltaire, are named after two writers (Swift and Voltaire) who predicted the existence of Martian moons before they were discovered. Jonathan Swift (30 November 1667 François-Marie Arouet ( 21 November 1694 30 May 1778) better known by the Pen name Voltaire, was a French [1]

## References

1. ^ Jacobson, R. A. and Rush, B. (2006) MAR063 (2007-Jun-28). Planetary Satellite Mean Orbital Parameters. JPL/NASA. Retrieved on 2008-02-13. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1258 - Baghdad falls to the Mongols, and the Abbasid Caliphate is destroyed
2. ^ a b c d Planetary Satellite Physical Parameters. JPL (Solar System Dynamics) (2006-Jul-13). Retrieved on 2008-01-29. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 904 - Sergius III comes out of retirement to take over the papacy from the deposed Antipope Christopher.
3. ^ a b use a spherical radius of 6. 23 km; volume of a sphere * density of 1. The volume of any solid plasma vacuum or theoretical object is how much three- Dimensional space it occupies often quantified numerically 471 g/cm³ yields a mass (m=d*v) of 1. 48e15 kg and an escape velocity (sqrt((2*g*m)/r)) of 5. 6 m/s (20 km/hr
4. ^ Classic Satellites of the Solar System. (For the South African airport with IATA code "KMH" see Johan Pienaar Airport. Observatorio ARVAL. Retrieved on 2007-09-28. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 48 BC - Pompey the Great is assassinated on orders of King Ptolemy of Egypt after landing in Egypt.
5. ^ Hall, A. ; Observations of the Satellites of Mars, Astronomische Nachrichten, Vol. 91, No. 2161 (October 17, 1877, signed September 21, 1877) pp. Events 539 BC - King Cyrus The Great of Persia marches into the city of Babylon, releasing the Jews from almost Year 1877 ( MDCCCLXXVII) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common Events 1217 - The Estonian tribal leader Lembitu of Lehola was killed in a battle against Teutonic Knights. Year 1877 ( MDCCCLXXVII) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common 11/12–13/14
6. ^ Morley, T. A. ; A Catalogue of Ground-Based Astrometric Observations of the Martian Satellites, 1877-1982, Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), Vol. 77, No. 2 (February 1989), pp. 209–226 (Table II, p. 220: first observation of Deimos on 1877-08-12. 32526)
7. ^ Notes: The Satellites of Mars, The Observatory, Vol. 1, No. 6 (September 20, 1877), pp. Events 451 - The Battle of Chalons takes place in North Eastern France. Year 1877 ( MDCCCLXXVII) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common 181–185
8. ^ The Discovery of the Satellites of Mars, Monthly Notices of the Royal Astronomical Society, Vol. 38, No. 4, (February 8, 1878), pp. Events 421 - Constantius III becomes co- Emperor of the Western Roman Empire. Year 1878 ( MDCCCLXXVIII) was a Common year starting on Tuesday (link will display the full calendar of the Gregorian calendar (or a Common 205–209
9. ^ Hall, A. ; Names of the Satellites of Mars, Astronomische Nachrichten, Vol. 92, No. 2187 (March 14, 1878, signed February 7, 1878), p. Events 1489 - The Queen of Cyprus, Catherine Cornaro, sells her kingdom to Venice. Year 1878 ( MDCCCLXXVIII) was a Common year starting on Tuesday (link will display the full calendar of the Gregorian calendar (or a Common Events 457 - Leo I becomes emperor of the Byzantine Empire. 1074 - Battle of Montesarchio in which the Prince Year 1878 ( MDCCCLXXVIII) was a Common year starting on Tuesday (link will display the full calendar of the Gregorian calendar (or a Common 47/48
10. ^ a b J. A. Burns, "Contradictory Clues as to the Origin of the Martian Moons," in Mars, H. H. Kieffer et al. , eds. , U. Arizona Press, Tucson, 1992
11. ^ a b G. A. Landis, "Origin of Martian Moons from Binary Asteroid Dissociation," American Association for the Advancement of Science Annual Meeting; Boston, MA, 2001; abstract.
12. ^ a b Richardson, R. S., If You Were on Mars, Astronomical Society of the Pacific Leaflets, Vol. Robert Shirley Richardson (1902 &ndash 1981 was an American astronomer. 4, Leaflet No. 178 (December 1943), pp. 214–221
13. ^ Busch, M. W.. ; et al. (2007). "Arecibo Radar Observations of Phobos and Deimos". Icarus 186 (2): 581–584. doi:10.1016/j.icarus.2006.11.003. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.
14. ^ A. Cazenave, A. Dobrovolskis and B. Lago, "Orbital history of the Martian satellites with inferences on their origin," Icarus, Volume 44, No. 3, December 1980, pp 730-744