An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A → stochastic process, based on the classical → random walk concept, in which the probabilities of occurrence of various future states depend only on the previous state of the system and not on any of earlier states. Also called Markov process and Markovian principle.

Named after Andrey Andreyevich Markov (1856-1922), a Russian mathematician, who introduced this model in 1906; → chain.

A method for sampling from → probability distributions using → Markov chains. MCMC methods are widely used in data modeling for → Bayesian inference and numerical integration in physics, chemistry, biology, statistics, and computer science.

→ Markov chain; → Monte Carlo Method.

Fourth planet from Sun and the seventh largest. Mass 6.42 × 10²⁶ g (0.11 Earth's), radius 3397 km. Mean distance from Sun 1.52 → astronomical units. → Sidereal period 687 days, → synodic period 779.9 days. Surface temperature 248 K., → rotation period, or → sol, 24h37m22s.6. Mars' → obliquity is currently 25.19 degrees, but has changed dramatically over billions of years since solar system formation. Atmosphere more than 90% CO₂, traces of O₂, CO, H₂O. Two tiny satellites (→ Phobos and → Deimos), both of which are locked in → synchronous rotation with Mars.

Late M.E., from L. Mars the Roman god of war, Ares in Gk. mythology.

Bahrâm, from Mid.Pers. Vahrâm, from Vahrân "god of victory," from Av. vərəθraγna- "victory, breaking the defence, the god of victory." The first element vərəθra- "shield, defensive power," cf. Skt. vrtrá- "defence, name of a demon slain by Indra," Arm. vahagan name of a god (loanword from Iranian). The second element γna-, from Av., also O.Pers., jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Mod.Pers. zadan, zan- "to strike, beat;" Mid.Pers. zatan, žatan; Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike," phonos "murder;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *g^when- "to strike, kill."

The → zero point of elevation on Mars. It is the elevation at which the atmosphere pressure is 6.1 millibars, or 610 → Pascals. Atmosphere pressure has to be used because Mars has no ocean, and "sea level" cannot be used like on Earth. More formally, the datum is a fourth-order, fourth-degree surface of equal → gravitational potential (determined from the Viking orbiter spacecraft) such that the pressure of the atmosphere is 6.1 millibars (source: Lunar and Planetary Institute, USRA).

→ Mars; → datum.

A member of the family of → asteroids located at either of the stable → Lagrangian points (L4 or L5) of the orbit of → Mars.

→ Mars; → Trojan asteroid.

A special calendar for time reckoning on Mars in which the year consists of 668 → sols (687 Earth days) and each sol has 24h 39m 35s. For convenience, sols are divided into a 24-hour clock. Each landed Mars mission keeps track of local solar time at its landing site, which depends upon the lander's longitude of Mars. The Martian year begins when Mars arrives at the → vernal point of the orbit in its northward journey; in other words, when the solar longitude Ls is 0°. Mars' other seasons begin when Ls = 90° at → summer solstice, 180° at → autumn equinox, and 270° at → winter solstice. The year counts begin at Mars Year 1, at the northern → vernal equinox of April 11, 1955. The second half of that year was marked by a major dust storm (→ Mars' dust storm). February 7, 2021 marked the start of Year 36 on Mars. Year 37 will start on Dec. 26, 2022, and Year 38 on Nov. 12, 2024. On Earth, spring, summer, autumn, and winter are all similar in length, because Earth's orbit is nearly circular (→ eccentricity = 0.0167), so it moves at nearly constant speed around the Sun. By contrast, Mars' elliptical orbit (→ eccentricity = 0.0934) makes its distance from the Sun change with time, and also makes it speed up and slow down in its orbit. Mars is at → aphelion (249,200,000 km from Sun) at Ls = 70°, near the northern summer solstice, and at → perihelion (206,700,000 km) at Ls = 250°, near the southern summer solstice. The Mars dust storm season begins just after perihelion at around Ls = 260°.

→ Mars; → calendar.

A violent atmospheric disturbance on Mars marked by high amounts of dust, especially during spring and summer seasons of the planet southern hemisphere. The elongated orbit of Mars has several important consequences. During southern spring and summer, Mars travels near its → perihelion, while its southern pole is tilted toward the Sun. Therefore, its surface receives much more heat . The atmosphere's temperature near surface raises and since the upper layers of the atmosphere are cold, warm air moves up and takes dust particles upward. Each several years big storms occur and cover significant portions of the planet such that dust stays in the atmosphere for several weeks or months. See also → Mars' calendar.

→ Mars; → dust; → storm.

A quake on the → planet Mars, probably caused by some phenomena other than → tectonic plate motions. Unlike Earth, Mars seems to lack tectonic plates. Therefore, its quakes are thought to arise from the slow cooling of the planet over time, which causes the → crust to contract and develop fractures. These quakes can also come from the impact of → meteorites and possibly the movement of → magma deep below the surface. On April 6, 2019, the instrument called Seismic Experiment for Interior Structure (SEIS) on NASA's Mars → InSight Mission lander recorded quakes that appear to have come from inside the planet, the first time ever a likely marsquake.

→ Mars; → quake.

Of, relating to, or like the planet → Mars.

M.E. marcien, from L. Marti(us) of, belonging to → Mars + -an a suffix of adjectives.

A piece of rock that was ejected from the Martian surface into space by the impact of an asteroid or comet, and landed on Earth. So far about 100 Martian meteorites have been collected. These meteorites have elemental and isotopic compositions that match those of the Martian crust as measured by NASA's Mars exploration missions.

→ Martian; → meteorite.

A slender, cloudy projection sometimes seen to extend from the surface of → Mars to very high altitudes. Noted and confirmed by amateur astronomers on photos of Mars in March 2012, possibly similar plumes have been found on archived images as far back as 1997. The plumes reach 200 km up, which seems too high for them to be related to wind-blown surface dust. Since one plume lasted for more than 10 days, it seemed too long lasting to be related to → aurora. The origin of this phenomenon is not yet known.

→ Martian; → plume.

A region on the surface of the → Moon where the → gravitational attraction is slightly higher than normal due to the presence of dense rock.

Short for mass concentration; → mass; → concentration.

1) Having qualities appropriate to or usually associated with a man.
2) Of, relating to, or constituting the gender that ordinarily includes most words or grammatical forms referring to males (Merriam-Webster.com).

M.E. masculin, from O.Fr. masculin "of the male sex," from L. masculinus "male, of masculine gender," from masculus "male, masculine; worthy of a man," diminutive of mas "male person, male," of unknown origin.

Narin, from nar, → male.

1) A source of very intense, narrow-band, coherent microwave radiation involving → stimulated emission, as in the → laser.
2) A device that generates such radiation.
3) In astronomy, maser emission detected from a number of molecules and associated with several environments: the vicinity of newly forming stars and → H II regions (OH, water, SiO, and methanol masers); the circumstellar shells of evolved stars, i.e. red giants and supergiants (OH, water, and SiO masers); the shocked regions where supernova remnants are expanding into an adjacent molecular cloud (OH masers); and the nuclei and jets of active galaxies (OH and water masers). The hydroxyl radical (OH) was the first interstellar maser detected (Weinreb et al. 1963).

Maser stands for Microwave Amplification by Stimulated Emission of Radiation; → laser.

An emission arising from the → maser process.

→ maser; → emission.

1) Something that serves to cover or conceal.
Electronics: A pattern used to control the configuration of conducting material deposited or etched onto a semiconductor chip.
2) Electronics: To override one signal with a stronger one.

From M.Fr. masque "covering to hide or guard the face," from It. maschera, from M.L. masca "mask, specter, nightmare," of uncertain origin.

1) Mâsk, loan from Fr., as above; 2) with verb zadan "to make, to do," originally "to strike, beat; to do; to play an instrument" (Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *g^when- "to strike, kill").

1) A method of improving → spatial resolution of images. → pupil masking; → unsharp masking.
2) Computers: The process of specifying a number of values that allow extracting desired information from a set of characters or bits while suppressing the undesired information.

Verbal noun of → mask.

1) A measure of the amount of material in an object, defined either by the inertial properties of the object or by its gravitational influence on other bodies. See also → inertial mass, → gravitational mass.
2) A considerable assemblage, number, or quantity.

From O.Fr. masse "lump," from L. massa "kneaded dough, lump," from Gk. maza "barley cake, lump, mass, ball," related to massein "to knead."

Jerm, from Ar. jirm.
Qond "assembled, collected; a crowd," related to gondé "coarse, thick; big;" Mid.Pers. gund "troop, group, gathering;" loaned into Arm. gund and Ar. jund.
Tudé "heap, stack, tumulus;" cf. Kurd. tavda "all, total;" Tati tâya "heap, mass;" Sogd. tuδē "heap, mass." Perhaps related to PIE *teuta- "people, tribe;" cf. Lith. tauta, Oscan touto, O.Irish tuath, Goth. þiuda, O.E. þeod "people, folk, race."
Anbuh "numerous, abundant," from Proto-Iranian *ham-buH- "to come together," from ham- "together," → com- + *buH- "to be , become," Av. ham.bauu- "to come together, unite," from ham- as above + bauu-, bu- "to be, become," O.Pers. bav- "to be, become," Mod.Pers. budan "to be," Skt. bhavati "becomes, happens," PIE base *bheu-, *bhu- "to grow, become;" cf. Gk. phu- "become," P.Gmc. *beo-, *beu-, E. be.

A measure of the rate of absorption of radiation, expressed as the linear absorption coefficient divided by the density of the medium through which radiation is passing.

→ mass; → absorption; → coefficient.

The difference between the rest mass of an atomic nucleus (made up of protons and neutrons) and the sum of the masses of its individual protons and neutrons. The mass difference is equal to the released binding energy. Also called mass deficiency

→ mass; → defect.