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6,300 | In Vulgar Latin and the Romance languages, merged with . During the Classical Latin period this form of speaking was deliberately avoided by well-educated speakers. | https://en.wikipedia.org/wiki?curid=17730 |
6,301 | Syllables in Latin are signified by the presence of diphthongs and vowels. The number of syllables is the same as the number of vowel sounds. | https://en.wikipedia.org/wiki?curid=17730 |
6,302 | Further, if a consonant separates two vowels, it will go into the syllable of the second vowel. When there are two consonants between vowels, the last consonant will go with the second vowel. An exception occurs when a phonetic stop and liquid come together. In this situation, they are thought to be a single consonant, and as such, they will go into the syllable of the second vowel. | https://en.wikipedia.org/wiki?curid=17730 |
6,303 | Syllables in Latin are considered either long or short. Within a word, a syllable may either be long by nature or long by position. A syllable is long by nature if it has a diphthong or a long vowel. On the other hand, a syllable is long by position if the vowel is followed by more than one consonant. | https://en.wikipedia.org/wiki?curid=17730 |
6,304 | Latin was written in the Latin alphabet, derived from the Etruscan alphabet, which was in turn drawn from the Greek alphabet and ultimately the Phoenician alphabet. This alphabet has continued to be used over the centuries as the script for the Romance, Celtic, Germanic, Baltic, Finnic and many Slavic languages (Polish, Slovak, Slovene, Croatian, Bosnian and Czech); and it has been adopted by many languages around the world, including Vietnamese, the Austronesian languages, many Turkic languages, and most languages in sub-Saharan Africa, the Americas and Oceania, making it by far the world's single most widely used writing system. | https://en.wikipedia.org/wiki?curid=17730 |
6,305 | The number of letters in the Latin alphabet has varied. When it was first derived from the Etruscan alphabet, it contained only 21 letters. Later, "G" was added to represent , which had previously been spelled "C", and "Z" ceased to be included in the alphabet, as the language then had no voiced alveolar fricative. The letters "Y" and "Z" were later added to represent Greek letters, upsilon and zeta respectively, in Greek loanwords. | https://en.wikipedia.org/wiki?curid=17730 |
6,306 | "W" was created in the 11th century from "VV". It represented in Germanic languages, not Latin, which still uses "V" for the purpose. "J" was distinguished from the original "I" only during the late Middle Ages, as was the letter "U" from "V". Although some Latin dictionaries use "J", it is rarely used for Latin text, as it was not used in classical times, but many other languages use it. | https://en.wikipedia.org/wiki?curid=17730 |
6,307 | Classical Latin did not contain sentence punctuation, letter case, or interword spacing, but apices were sometimes used to distinguish length in vowels and the interpunct was used at times to separate words. The first line of Catullus 3, originally written as | https://en.wikipedia.org/wiki?curid=17730 |
6,308 | The Roman cursive script is commonly found on the many wax tablets excavated at sites such as forts, an especially extensive set having been discovered at Vindolanda on Hadrian's Wall in Britain. Most notable is the fact that while most of the Vindolanda tablets show spaces between words, spaces were avoided in monumental inscriptions from that era. | https://en.wikipedia.org/wiki?curid=17730 |
6,309 | Latin is a synthetic, fusional language in the terminology of linguistic typology. In more traditional terminology, it is an inflected language, but typologists are apt to say "inflecting". Words include an objective semantic element and markers specifying the grammatical use of the word. The fusion of root meaning and markers produces very compact sentence elements: , "I love," is produced from a semantic element, , "love," to which , a first person singular marker, is suffixed. | https://en.wikipedia.org/wiki?curid=17730 |
6,310 | The grammatical function can be changed by changing the markers: the word is "inflected" to express different grammatical functions, but the semantic element usually does not change. (Inflection uses affixing and infixing. Affixing is prefixing and suffixing. Latin inflections are never prefixed.) | https://en.wikipedia.org/wiki?curid=17730 |
6,311 | For example, , "he (or she or it) will love", is formed from the same stem, , to which a future tense marker, , is suffixed, and a third person singular marker, , is suffixed. There is an inherent ambiguity: may denote more than one grammatical category: masculine, feminine, or neuter gender. A major task in understanding Latin phrases and clauses is to clarify such ambiguities by an analysis of context. All natural languages contain ambiguities of one sort or another. | https://en.wikipedia.org/wiki?curid=17730 |
6,312 | The inflections express gender, number, and case in adjectives, nouns, and pronouns, a process called "declension". Markers are also attached to fixed stems of verbs, to denote person, number, tense, voice, mood, and aspect, a process called "conjugation". Some words are uninflected and undergo neither process, such as adverbs, prepositions, and interjections. | https://en.wikipedia.org/wiki?curid=17730 |
6,313 | A regular Latin noun belongs to one of five main declensions, a group of nouns with similar inflected forms. The declensions are identified by the genitive singular form of the noun. | https://en.wikipedia.org/wiki?curid=17730 |
6,314 | There are seven Latin noun cases, which also apply to adjectives and pronouns and mark a noun's syntactic role in the sentence by means of inflections. Thus, word order is not as important in Latin as it is in English, which is less inflected. The general structure and word order of a Latin sentence can therefore vary. The cases are as follows: | https://en.wikipedia.org/wiki?curid=17730 |
6,315 | Latin lacks both definite and indefinite articles so can mean either "the boy is running" or "a boy is running". | https://en.wikipedia.org/wiki?curid=17730 |
6,316 | There are two types of regular Latin adjectives: first- and second-declension and third-declension. They are so-called because their forms are similar or identical to first- and second-declension and third-declension nouns, respectively. Latin adjectives also have comparative and superlative forms. There are also a number of Latin participles. | https://en.wikipedia.org/wiki?curid=17730 |
6,317 | First- and second-declension adjectives are declined like first-declension nouns for the feminine forms and like second-declension nouns for the masculine and neuter forms. For example, for (dead), is declined like a regular first-declension noun (such as (girl)), is declined like a regular second-declension masculine noun (such as (lord, master)), and is declined like a regular second-declension neuter noun (such as (help)). | https://en.wikipedia.org/wiki?curid=17730 |
6,318 | Third-declension adjectives are mostly declined like normal third-declension nouns, with a few exceptions. In the plural nominative neuter, for example, the ending is "-ia" ( (all, everything)), and for third-declension nouns, the plural nominative neuter ending is "-a" or "-ia" ( (heads), (animals)) They can have one, two or three forms for the masculine, feminine, and neuter nominative singular. | https://en.wikipedia.org/wiki?curid=17730 |
6,319 | Latin participles, like English participles, are formed from a verb. There are a few main types of participles: Present Active Participles, Perfect Passive Participles, Future Active Participles, and Future Passive Participles. | https://en.wikipedia.org/wiki?curid=17730 |
6,320 | Latin sometimes uses prepositions, depending on the type of prepositional phrase being used. Most prepositions are followed by a noun in either the accusative or ablative case: "apud puerum" (with the boy), with "puerum" being the accusative form of "puer", boy, and "sine puero" (without the boy), "puero" being the ablative form of "puer". A few adpositions, however, govern a noun in the genitive (such as "gratia" and "tenus"). | https://en.wikipedia.org/wiki?curid=17730 |
6,321 | A regular verb in Latin belongs to one of four main conjugations. A conjugation is "a class of verbs with similar inflected forms." The conjugations are identified by the last letter of the verb's present stem. The present stem can be found by omitting the -"re" (-"rī" in deponent verbs) ending from the present infinitive form. The infinitive of the first conjugation ends in "-ā-re" or "-ā-ri" (active and passive respectively): , "to love," , "to exhort"; of the second conjugation by "-ē-re" or "-ē-rī": , "to warn", , "to fear;" of the third conjugation by "-ere", "-ī": , "to lead," , "to use"; of the fourth by "-ī-re", "-ī-rī": , "to hear," , "to attempt". The stem categories descend from Indo-European and can therefore be compared to similar conjugations in other Indo-European languages. | https://en.wikipedia.org/wiki?curid=17730 |
6,322 | Irregular verbs are verbs that do not follow the regular conjugations in the formation of the inflected form. Irregular verbs in Latin are "esse", "to be"; "velle", "to want"; "ferre", "to carry"; "edere", "to eat"; "dare", "to give"; "ire", "to go"; "posse", "to be able"; "fieri", "to happen"; and their compounds. | https://en.wikipedia.org/wiki?curid=17730 |
6,323 | There are six general tenses in Latin (present, imperfect, future, perfect, pluperfect and future perfect), three moods (indicative, imperative and subjunctive, in addition to the infinitive, participle, gerund, gerundive and supine), three persons (first, second and third), two numbers (singular and plural), two voices (active and passive) and two aspects (perfective and imperfective). Verbs are described by four principal parts: | https://en.wikipedia.org/wiki?curid=17730 |
6,324 | The six tenses of Latin are divided into two tense systems: the present system, which is made up of the present, imperfect and future tenses, and the perfect system, which is made up of the perfect, pluperfect and future perfect tenses. Each tense has a set of endings corresponding to the person, number, and voice of the subject. Subject (nominative) pronouns are generally omitted for the first ("I, we") and second ("you") persons except for emphasis. | https://en.wikipedia.org/wiki?curid=17730 |
6,325 | The table below displays the common inflected endings for the indicative mood in the active voice in all six tenses. For the future tense, the first listed endings are for the first and second conjugations, and the second listed endings are for the third and fourth conjugations: | https://en.wikipedia.org/wiki?curid=17730 |
6,326 | Some Latin verbs are deponent, causing their forms to be in the passive voice but retain an active meaning: "hortor, hortārī, hortātus sum" (to urge). | https://en.wikipedia.org/wiki?curid=17730 |
6,327 | As Latin is an Italic language, most of its vocabulary is likewise Italic, ultimately from the ancestral Proto-Indo-European language. However, because of close cultural interaction, the Romans not only adapted the Etruscan alphabet to form the Latin alphabet but also borrowed some Etruscan words into their language, including "mask" and "actor". Latin also included vocabulary borrowed from Oscan, another Italic language. | https://en.wikipedia.org/wiki?curid=17730 |
6,328 | After the Fall of Tarentum (272 BC), the Romans began Hellenising, or adopting features of Greek culture, including the borrowing of Greek words, such as (vaulted roof), (symbol), and (bath). This Hellenisation led to the addition of "Y" and "Z" to the alphabet to represent Greek sounds. Subsequently, the Romans transplanted Greek art, medicine, science and philosophy to Italy, paying almost any price to entice Greek skilled and educated persons to Rome and sending their youth to be educated in Greece. Thus, many Latin scientific and philosophical words were Greek loanwords or had their meanings expanded by association with Greek words, as (craft) and τέχνη (art). | https://en.wikipedia.org/wiki?curid=17730 |
6,329 | Because of the Roman Empire's expansion and subsequent trade with outlying European tribes, the Romans borrowed some northern and central European words, such as (beaver), of Germanic origin, and (breeches), of Celtic origin. The specific dialects of Latin across Latin-speaking regions of the former Roman Empire after its fall were influenced by languages specific to the regions. The dialects of Latin evolved into different Romance languages. | https://en.wikipedia.org/wiki?curid=17730 |
6,330 | During and after the adoption of Christianity into Roman society, Christian vocabulary became a part of the language, either from Greek or Hebrew borrowings or as Latin neologisms. Continuing into the Middle Ages, Latin incorporated many more words from surrounding languages, including Old English and other Germanic languages. | https://en.wikipedia.org/wiki?curid=17730 |
6,331 | Over the ages, Latin-speaking populations produced new adjectives, nouns, and verbs by affixing or compounding meaningful segments. For example, the compound adjective, , "all-powerful," was produced from the adjectives , "all", and , "powerful", by dropping the final "s" of and concatenating. Often, the concatenation changed the part of speech, and nouns were produced from verb segments or verbs from nouns and adjectives. | https://en.wikipedia.org/wiki?curid=17730 |
6,332 | The phrases are mentioned with accents to show where stress is placed. In Latin, words are normally stressed either on the second-to-last (penultimate) syllable, called in Latin or , or on the third-to-last syllable, called in Latin or . In the following notation, accented short vowels have an acute diacritic, accented long vowels have a circumflex diacritic (representing long falling pitch), and unaccented long vowels are marked simply with a macron. This reflects the tone of the voice with which, ideally, the stress is phonetically realized; but this may not always be clearly articulated on every word in a sentence. Regardless of length, a vowel at the end of a word may be significantly shortened or even altogether deleted if the next word begins with a vowel also (a process called elision), unless a very short pause is inserted. As an exception, the following words: "est" (English "is"), "es" ("[you (sg.)] are") lose their own vowel "e" instead. | https://en.wikipedia.org/wiki?curid=17730 |
6,333 | In ancient times, numbers in Latin were written only with letters. Today, the numbers can be written with the Arabic numbers as well as with Roman numerals. The numbers 1, 2 and 3 and every whole hundred from 200 to 900 are declined as nouns and adjectives, with some differences. | https://en.wikipedia.org/wiki?curid=17730 |
6,334 | The numbers from 4 to 100 do not change their endings. As in modern descendants such as Spanish, the gender for naming a number in isolation is masculine, so that "1, 2, 3" is counted as . | https://en.wikipedia.org/wiki?curid=17730 |
6,335 | The same text may be marked for all long vowels (before any possible elisions at word boundary) with apices over vowel letters, including customarily before "nf" and "ns" where a long vowel is automatically produced: | https://en.wikipedia.org/wiki?curid=17730 |
6,336 | Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin atmosphere (less than 1% that of Earth's), and has a crust primarily composed of elements similar to Earth's crust, as well as a core made of iron and nickel. Mars has surface features such as impact craters, valleys, dunes and polar ice caps. It has two small and irregularly shaped moons, Phobos and Deimos. | https://en.wikipedia.org/wiki?curid=14640471 |
6,337 | Some of the most notable surface features on Mars include Olympus Mons, the largest volcano and highest known mountain in the Solar System and Valles Marineris, one of the largest canyons in the Solar System. The Borealis basin in the Northern Hemisphere covers approximately 40% of the planet and may be a large impact feature. Days and seasons on Mars are comparable to those of Earth, as the planets have a similar rotation period and tilt of the rotational axis relative to the ecliptic plane. Liquid water on the surface of Mars cannot exist due to low atmospheric pressure, which is less than 1% of the atmospheric pressure on Earth. Both of Mars's polar ice caps appear to be made largely of water. In the distant past, Mars was likely wetter, and thus possibly more suited for life. It is not known whether life has ever existed on Mars. | https://en.wikipedia.org/wiki?curid=14640471 |
6,338 | Mars has been explored by several uncrewed spacecraft, beginning with "Mariner 4" in 1965. NASA's "Viking 1" lander transmitted in 1976 the first images from the Martian surface. Two countries have successfully deployed rovers on Mars, the United States first doing so with "Sojourner" in 1997 and China with "Zhurong" in 2021. There are also planned future missions to Mars, such as a Mars sample-return mission set to happen in 2026, and the "Rosalind Franklin" rover mission, which was intended to launch in 2018 but was delayed to 2024 at the earliest, with a more likely launch date at 2028. | https://en.wikipedia.org/wiki?curid=14640471 |
6,339 | Mars can be viewed from Earth with the naked eye, as can its reddish coloring. This appearance, due to the iron oxide prevalent on its surface, has led to Mars often being called the Red Planet. It is among the brightest objects in Earth's sky, with an apparent magnitude that reaches −2.94, comparable to that of Jupiter and surpassed only by Venus, the Moon and the Sun. Historically, Mars has been observed since ancient times, and over the millennia has been featured in culture and the arts in ways that have reflected humanity's growing knowledge of it. | https://en.wikipedia.org/wiki?curid=14640471 |
6,340 | The history of observations of Mars is marked by the oppositions of Mars when the planet is closest to Earth and hence is most easily visible, which occur every couple of years. Even more notable are the perihelic oppositions of Mars, which are distinguished because Mars is close to perihelion, making it even closer to Earth. | https://en.wikipedia.org/wiki?curid=14640471 |
6,341 | The ancient Sumerians named Mars Nergal, the god of war and plague. During Sumerian times, Nergal was a minor deity of little significance, but, during later times, his main cult center was the city of Nineveh. In Mesopotamian texts, Mars is referred to as the "star of judgement of the fate of the dead." The existence of Mars as a wandering object in the night sky was also recorded by the ancient Egyptian astronomers and, by 1534 BCE, they were familiar with the retrograde motion of the planet. By the period of the Neo-Babylonian Empire, the Babylonian astronomers were making regular records of the positions of the planets and systematic observations of their behavior. For Mars, they knew that the planet made 37 synodic periods, or 42 circuits of the zodiac, every 79 years. They invented arithmetic methods for making minor corrections to the predicted positions of the planets. In Ancient Greece, the planet was known as . Commonly, the Greek name for the planet now referred to as Mars, was Ares. It was the Romans who named the planet Mars, for their god of war, often represented by the sword and shield of the planet's namesake. | https://en.wikipedia.org/wiki?curid=14640471 |
6,342 | In the fourth century BCE, Aristotle noted that Mars disappeared behind the Moon during an occultation, indicating that the planet was farther away. Ptolemy, a Greek living in Alexandria, attempted to address the problem of the orbital motion of Mars. Ptolemy's model and his collective work on astronomy was presented in the multi-volume collection later called the "Almagest" (from the Arabic for "greatest"), which became the authoritative treatise on Western astronomy for the next fourteen centuries. Literature from ancient China confirms that Mars was known by Chinese astronomers by no later than the fourth century BCE. In the East Asian cultures, Mars is traditionally referred to as the "fire star" (Chinese: ), based on the "Wuxing" system. | https://en.wikipedia.org/wiki?curid=14640471 |
6,343 | During the seventeenth century A.D., Tycho Brahe measured the diurnal parallax of Mars that Johannes Kepler used to make a preliminary calculation of the relative distance to the planet. From Brahe's observations of Mars, Kepler deduced that the planet orbited the Sun not in a circle, but in an ellipse. Moreover, Kepler showed that Mars sped up as it approached the Sun and slowed down as it moved farther away, in a manner that later physicists would explain as a consequence of the conservation of angular momentum. When the telescope became available, the diurnal parallax of Mars was again measured in an effort to determine the Sun-Earth distance. This was first performed by Giovanni Domenico Cassini in 1672. The early parallax measurements were hampered by the quality of the instruments. The only occultation of Mars by Venus observed was that of 13 October 1590, seen by Michael Maestlin at Heidelberg. In 1610, Mars was viewed by Italian astronomer Galileo Galilei, who was first to see it via telescope. The first person to draw a map of Mars that displayed any terrain features was the Dutch astronomer Christiaan Huygens. | https://en.wikipedia.org/wiki?curid=14640471 |
6,344 | By the 19th century, the resolution of telescopes reached a level sufficient for surface features to be identified. On 5 September 1877, a perihelic opposition of Mars occurred. The Italian astronomer Giovanni Schiaparelli used a telescope in Milan to help produce the first detailed map of Mars. These maps notably contained features he called "canali", which were later shown to be an optical illusion. These "canali" were supposedly long, straight lines on the surface of Mars, to which he gave names of famous rivers on Earth. His term, which means "channels" or "grooves", was popularly mistranslated in English as "canals". | https://en.wikipedia.org/wiki?curid=14640471 |
6,345 | Influenced by the observations, the orientalist Percival Lowell founded an observatory which had 30- and 45-centimetre (12- and 18-in) telescopes. The observatory was used for the exploration of Mars during the last good opportunity in 1894 and the following less favorable oppositions. He published several books on Mars and life on the planet, which had a great influence on the public. The "canali" were independently observed by other astronomers, like Henri Joseph Perrotin and Louis Thollon in Nice, using one of the largest telescopes of that time. | https://en.wikipedia.org/wiki?curid=14640471 |
6,346 | The seasonal changes (consisting of the diminishing of the polar caps and the dark areas formed during Martian summer) in combination with the canals led to speculation about life on Mars, and it was a long-held belief that Mars contained vast seas and vegetation. As bigger telescopes were used, fewer long, straight "canali" were observed. During observations in 1909 by Antoniadi with an telescope, irregular patterns were observed, but no "canali" were seen. | https://en.wikipedia.org/wiki?curid=14640471 |
6,347 | Mars is approximately half the diameter of Earth, with a surface area only slightly less than the total area of Earth's dry land. Mars is less dense than Earth, having about 15% of Earth's volume and 11% of Earth's mass, resulting in about 38% of Earth's surface gravity. The red-orange appearance of the Martian surface is caused by iron(III) oxide, or rust. It can look like butterscotch; other common surface colors include golden, brown, tan, and greenish, depending on the minerals present. | https://en.wikipedia.org/wiki?curid=14640471 |
6,348 | Like Earth, Mars has differentiated into a dense metallic core overlaid by less dense materials. Current models of its interior imply a core consisting primarily of iron and nickel with about 16–17% sulfur. This iron(II) sulfide core is thought to be twice as rich in lighter elements as Earth's. The core is surrounded by a silicate mantle that formed many of the tectonic and volcanic features on the planet, but it appears to be dormant. Besides silicon and oxygen, the most abundant elements in the Martian crust are iron, magnesium, aluminium, calcium, and potassium. The average thickness of the planet's crust is about , with a maximum thickness of . By comparison, Earth's crust averages in thickness. | https://en.wikipedia.org/wiki?curid=14640471 |
6,349 | Mars is seismically active. InSight has detected and recorded over 450 marsquakes and related events in 2019. In 2021 it was reported that based on eleven low-frequency Marsquakes detected by the "InSight" lander the core of Mars is indeed liquid and has a radius of about and a temperature around 1900–2000 K. The Martian core radius is more than half the radius of Mars and about half the size of the Earth's core. This is somewhat larger than models predicted, suggesting that the core contains some amount of lighter elements like oxygen and hydrogen in addition to the iron–nickel alloy and about 15% of sulfur. | https://en.wikipedia.org/wiki?curid=14640471 |
6,350 | The core of Mars is overlaid by the rocky mantle, which, however, does not seem to have a layer analogous to the Earth's lower mantle. The Martian mantle appears to be solid down to the depth of about 500 km, where the low-velocity zone (partially melted asthenosphere) begins. Below the asthenosphere the velocity of seismic waves starts to grow again and at the depth of about 1050 km there lies the boundary of the transition zone. At the surface of Mars there lies a crust with the average thickness of about 24–72 km. | https://en.wikipedia.org/wiki?curid=14640471 |
6,351 | Mars is a terrestrial planet with a surface that consists of minerals containing silicon and oxygen, metals, and other elements that typically make up rock. The Martian surface is primarily composed of tholeiitic basalt, although parts are more silica-rich than typical basalt and may be similar to andesitic rocks on Earth, or silica glass. Regions of low albedo suggest concentrations of plagioclase feldspar, with northern low albedo regions displaying higher than normal concentrations of sheet silicates and high-silicon glass. Parts of the southern highlands include detectable amounts of high-calcium pyroxenes. Localized concentrations of hematite and olivine have been found. Much of the surface is deeply covered by finely grained iron(III) oxide dust. | https://en.wikipedia.org/wiki?curid=14640471 |
6,352 | Although Mars has no evidence of a structured global magnetic field, observations show that parts of the planet's crust have been magnetized, suggesting that alternating polarity reversals of its dipole field have occurred in the past. This paleomagnetism of magnetically susceptible minerals is similar to the alternating bands found on Earth's ocean floors. One theory, published in 1999 and re-examined in October 2005 (with the help of the "Mars Global Surveyor"), is that these bands suggest plate tectonic activity on Mars four billion years ago, before the planetary dynamo ceased to function and the planet's magnetic field faded. | https://en.wikipedia.org/wiki?curid=14640471 |
6,353 | Scientists have theorized that during the Solar System's formation Mars was created as the result of a random process of run-away accretion of material from the protoplanetary disk that orbited the Sun. Mars has many distinctive chemical features caused by its position in the Solar System. Elements with comparatively low boiling points, such as chlorine, phosphorus, and sulfur, are much more common on Mars than Earth; these elements were probably pushed outward by the young Sun's energetic solar wind. | https://en.wikipedia.org/wiki?curid=14640471 |
6,354 | After the formation of the planets, all were subjected to the so-called "Late Heavy Bombardment". About 60% of the surface of Mars shows a record of impacts from that era, whereas much of the remaining surface is probably underlain by immense impact basins caused by those events. There is evidence of an enormous impact basin in the Northern Hemisphere of Mars, spanning , or roughly four times the size of the Moon's South Pole – Aitken basin, the largest impact basin yet discovered. This theory suggests that Mars was struck by a Pluto-sized body about four billion years ago. The event, thought to be the cause of the Martian hemispheric dichotomy, created the smooth Borealis basin that covers 40% of the planet. | https://en.wikipedia.org/wiki?curid=14640471 |
6,355 | The geological history of Mars can be split into many periods, but the following are the three primary periods: | https://en.wikipedia.org/wiki?curid=14640471 |
6,356 | Geological activity is still taking place on Mars. The Athabasca Valles is home to sheet-like lava flows created about 200 mya. Water flows in the grabens called the Cerberus Fossae occurred less than 20 Mya, indicating equally recent volcanic intrusions. The "Mars Reconnaissance Orbiter" has captured images of avalanches. | https://en.wikipedia.org/wiki?curid=14640471 |
6,357 | The "Phoenix" lander returned data showing Martian soil to be slightly alkaline and containing elements such as magnesium, sodium, potassium and chlorine. These nutrients are found in soils on Earth. They are necessary for growth of plants. Experiments performed by the lander showed that the Martian soil has a basic pH of 7.7, and contains 0.6% of the salt perchlorate, concentrations that are toxic to humans. | https://en.wikipedia.org/wiki?curid=14640471 |
6,358 | Streaks are common across Mars and new ones appear frequently on steep slopes of craters, troughs, and valleys. The streaks are dark at first and get lighter with age. The streaks can start in a tiny area, then spread out for hundreds of metres. They have been seen to follow the edges of boulders and other obstacles in their path. The commonly accepted theories include that they are dark underlying layers of soil revealed after avalanches of bright dust or dust devils. Several other explanations have been put forward, including those that involve water or even the growth of organisms. | https://en.wikipedia.org/wiki?curid=14640471 |
6,359 | Water in its liquid form cannot exist on the surface of Mars due to low atmospheric pressure, which is less than 1% that of Earth's, except at the lowest elevations for short periods. The two polar ice caps appear to be made largely of water. The volume of water ice in the south polar ice cap, if melted, would be enough to cover the entire surface of the planet with a depth of . Large quantities of ice are thought to be trapped within the thick cryosphere of Mars. Radar data from "Mars Express" and the "Mars Reconnaissance Orbiter" (MRO) show large quantities of ice at both poles, and at middle latitudes. The Phoenix lander directly sampled water ice in shallow Martian soil on 31 July 2008. | https://en.wikipedia.org/wiki?curid=14640471 |
6,360 | Landforms visible on Mars strongly suggest that liquid water has existed on the planet's surface. Huge linear swathes of scoured ground, known as outflow channels, cut across the surface in about 25 places. These are thought to be a record of erosion caused by the catastrophic release of water from subsurface aquifers, though some of these structures have been hypothesized to result from the action of glaciers or lava. One of the larger examples, Ma'adim Vallis, is long, much greater than the Grand Canyon, with a width of and a depth of in places. It is thought to have been carved by flowing water early in Mars's history. The youngest of these channels are thought to have formed only a few million years ago. Elsewhere, particularly on the oldest areas of the Martian surface, finer-scale, dendritic networks of valleys are spread across significant proportions of the landscape. Features of these valleys and their distribution strongly imply that they were carved by runoff resulting from precipitation in early Mars history. Subsurface water flow and groundwater sapping may play important subsidiary roles in some networks, but precipitation was probably the root cause of the incision in almost all cases. | https://en.wikipedia.org/wiki?curid=14640471 |
6,361 | Along crater and canyon walls, there are thousands of features that appear similar to terrestrial gullies. The gullies tend to be in the highlands of the Southern Hemisphere and to face the Equator; all are poleward of 30° latitude. A number of authors have suggested that their formation process involves liquid water, probably from melting ice, although others have argued for formation mechanisms involving carbon dioxide frost or the movement of dry dust. No partially degraded gullies have formed by weathering and no superimposed impact craters have been observed, indicating that these are young features, possibly still active. Other geological features, such as deltas and alluvial fans preserved in craters, are further evidence for warmer, wetter conditions at an interval or intervals in earlier Mars history. Such conditions necessarily require the widespread presence of crater lakes across a large proportion of the surface, for which there is independent mineralogical, sedimentological and geomorphological evidence. Further evidence that liquid water once existed on the surface of Mars comes from the detection of specific minerals such as hematite and goethite, both of which sometimes form in the presence of water. | https://en.wikipedia.org/wiki?curid=14640471 |
6,362 | In 2004, "Opportunity" detected the mineral jarosite. This forms only in the presence of acidic water, showing that water once existed on Mars. The "Spirit" rover found concentrated deposits of silica in 2007 that indicated wet conditions in the past, and in December 2011, the mineral gypsum, which also forms in the presence of water, was found on the surface by NASA's Mars rover Opportunity. It is estimated that the amount of water in the upper mantle of Mars, represented by hydroxyl ions contained within Martian minerals, is equal to or greater than that of Earth at 50–300 parts per million of water, which is enough to cover the entire planet to a depth of . | https://en.wikipedia.org/wiki?curid=14640471 |
6,363 | On 18 March 2013, NASA reported evidence from instruments on the "Curiosity" rover of mineral hydration, likely hydrated calcium sulfate, in several rock samples including the broken fragments of "Tintina" rock and "Sutton Inlier" rock as well as in veins and nodules in other rocks like "Knorr" rock and "Wernicke" rock. Analysis using the rover's DAN instrument provided evidence of subsurface water, amounting to as much as 4% water content, down to a depth of , during the rover's traverse from the "Bradbury Landing" site to the "Yellowknife Bay" area in the "Glenelg" terrain. In September 2015, NASA announced that they had found strong evidence of hydrated brine flows in recurring slope lineae, based on spectrometer readings of the darkened areas of slopes. These streaks flow downhill in Martian summer, when the temperature is above −23° Celsius, and freeze at lower temperatures. These observations supported earlier hypotheses, based on timing of formation and their rate of growth, that these dark streaks resulted from water flowing just below the surface. However, later work suggested that the lineae may be dry, granular flows instead, with at most a limited role for water in initiating the process. A definitive conclusion about the presence, extent, and role of liquid water on the Martian surface remains elusive. | https://en.wikipedia.org/wiki?curid=14640471 |
6,364 | Researchers suspect much of the low northern plains of the planet were covered with an ocean hundreds of meters deep, though this theory remains controversial. In March 2015, scientists stated that such an ocean might have been the size of Earth's Arctic Ocean. This finding was derived from the ratio of water to deuterium in the modern Martian atmosphere compared to that ratio on Earth. The amount of Martian deuterium is eight times the amount that exists on Earth, suggesting that ancient Mars had significantly higher levels of water. Results from the "Curiosity" rover had previously found a high ratio of deuterium in Gale Crater, though not significantly high enough to suggest the former presence of an ocean. Other scientists caution that these results have not been confirmed, and point out that Martian climate models have not yet shown that the planet was warm enough in the past to support bodies of liquid water. Near the northern polar cap is the wide Korolev Crater, which the Mars Express orbiter found to be filled with approximately of water ice. | https://en.wikipedia.org/wiki?curid=14640471 |
6,365 | In November 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region. The volume of water detected has been estimated to be equivalent to the volume of water in Lake Superior. During observations from 2018 through 2021, the ExoMars Trace Gas Orbiter spotted indications of water, probably subsurface ice, in the Valles Marineris canyon system. | https://en.wikipedia.org/wiki?curid=14640471 |
6,366 | Mars has two permanent polar ice caps. During a pole's winter, it lies in continuous darkness, chilling the surface and causing the deposition of 25–30% of the atmosphere into slabs of CO ice (dry ice). When the poles are again exposed to sunlight, the frozen CO sublimes. These seasonal actions transport large amounts of dust and water vapor, giving rise to Earth-like frost and large cirrus clouds. Clouds of water-ice were photographed by the "Opportunity" rover in 2004. | https://en.wikipedia.org/wiki?curid=14640471 |
6,367 | The caps at both poles consist primarily (70%) of water ice. Frozen carbon dioxide accumulates as a comparatively thin layer about one metre thick on the north cap in the northern winter only, whereas the south cap has a permanent dry ice cover about eight metres thick. This permanent dry ice cover at the south pole is peppered by flat floored, shallow, roughly circular pits, which repeat imaging shows are expanding by ?? meters per year; this suggests that the permanent CO cover over the south pole water ice is degrading over time. The northern polar cap has a diameter of about , and contains about of ice, which, if spread evenly on the cap, would be thick. (This compares to a volume of for the Greenland ice sheet.) The southern polar cap has a diameter of and a thickness of . The total volume of ice in the south polar cap plus the adjacent layered deposits has been estimated at 1.6 million cubic km. Both polar caps show spiral troughs, which recent analysis of SHARAD ice penetrating radar has shown are a result of katabatic winds that spiral due to the Coriolis effect. | https://en.wikipedia.org/wiki?curid=14640471 |
6,368 | The seasonal frosting of areas near the southern ice cap results in the formation of transparent 1-metre-thick slabs of dry ice above the ground. With the arrival of spring, sunlight warms the subsurface and pressure from subliming CO builds up under a slab, elevating and ultimately rupturing it. This leads to geyser-like eruptions of CO gas mixed with dark basaltic sand or dust. This process is rapid, observed happening in the space of a few days, weeks or months, a rate of change rather unusual in geology – especially for Mars. The gas rushing underneath a slab to the site of a geyser carves a spiderweb-like pattern of radial channels under the ice, the process being the inverted equivalent of an erosion network formed by water draining through a single plughole. | https://en.wikipedia.org/wiki?curid=14640471 |
6,369 | Although better remembered for mapping the Moon, Johann Heinrich Mädler and Wilhelm Beer were the first areographers. They began by establishing that most of Mars's surface features were permanent and by more precisely determining the planet's rotation period. In 1840, Mädler combined ten years of observations and drew the first map of Mars. | https://en.wikipedia.org/wiki?curid=14640471 |
6,370 | Features on Mars are named from a variety of sources. Albedo features are named for classical mythology. Craters larger than roughly 50 km are named for deceased scientists and writers and others who have contributed to the study of Mars. Smaller craters are named for towns and villages of the world with populations of less than 100,000. Large valleys are named for the word "Mars" or "star" in various languages; small valleys are named for rivers. | https://en.wikipedia.org/wiki?curid=14640471 |
6,371 | Large albedo features retain many of the older names but are often updated to reflect new knowledge of the nature of the features. For example, "Nix Olympica" (the snows of Olympus) has become "Olympus Mons" (Mount Olympus). The surface of Mars as seen from Earth is divided into two kinds of areas, with differing albedo. The paler plains covered with dust and sand rich in reddish iron oxides were once thought of as Martian "continents" and given names like Arabia Terra ("land of Arabia") or Amazonis Planitia ("Amazonian plain"). The dark features were thought to be seas, hence their names Mare Erythraeum, Mare Sirenum and Aurorae Sinus. The largest dark feature seen from Earth is Syrtis Major Planum. The permanent northern polar ice cap is named Planum Boreum. The southern cap is called Planum Australe. | https://en.wikipedia.org/wiki?curid=14640471 |
6,372 | Mars's equator is defined by its rotation, but the location of its Prime Meridian was specified, as was Earth's (at Greenwich), by choice of an arbitrary point; Mädler and Beer selected a line for their first maps of Mars in 1830. After the spacecraft "Mariner 9" provided extensive imagery of Mars in 1972, a small crater (later called Airy-0), located in the Sinus Meridiani ("Middle Bay" or "Meridian Bay"), was chosen by Merton Davies, Harold Masursky, and Gérard de Vaucouleurs for the definition of 0.0° longitude to coincide with the original selection. | https://en.wikipedia.org/wiki?curid=14640471 |
6,373 | Because Mars has no oceans and hence no "sea level", a zero-elevation surface had to be selected as a reference level; this is called the "areoid" of Mars, analogous to the terrestrial geoid. Zero altitude was defined by the height at which there is of atmospheric pressure. This pressure corresponds to the triple point of water, and it is about 0.6% of the sea level surface pressure on Earth (0.006 atm). | https://en.wikipedia.org/wiki?curid=14640471 |
6,374 | For mapping purposes, the United States Geological Survey divides the surface of Mars into thirty cartographic quadrangles, each named for a classical albedo feature it contains. | https://en.wikipedia.org/wiki?curid=14640471 |
6,375 | The shield volcano Olympus Mons ("Mount Olympus") is an extinct volcano in the vast upland region Tharsis, which contains several other large volcanoes. The edifice is over wide. Because the mountain is so large, with complex structure at its edges, allocating a height to it is difficult. Its local relief, from the foot of the cliffs which form its northwest margin to its peak, is over , a little over twice the height of Mauna Kea as measured from its base on the ocean floor. The total elevation change from the plains of Amazonis Planitia, over to the northwest, to the summit approaches , roughly three times the height of Mount Everest, which in comparison stands at just over . Consequently, Olympus Mons is either the tallest or second-tallest mountain in the Solar System; the only known mountain which might be taller is the Rheasilvia peak on the asteroid Vesta, at . | https://en.wikipedia.org/wiki?curid=14640471 |
6,376 | The dichotomy of Martian topography is striking: northern plains flattened by lava flows contrast with the southern highlands, pitted and cratered by ancient impacts. It is possible that, four billion years ago, the Northern Hemisphere of Mars was struck by an object one-tenth to two-thirds the size of Earth's Moon. If this is the case, the Northern Hemisphere of Mars would be the site of an impact crater in size, or roughly the area of Europe, Asia, and Australia combined, surpassing Utopia Planitia and the Moon's South Pole–Aitken basin as the largest impact crater in the Solar System. | https://en.wikipedia.org/wiki?curid=14640471 |
6,377 | Mars is scarred by a number of impact craters: a total of 43,000 craters with a diameter of or greater have been found. The largest exposed crater is Hellas, which is wide and deep, and is a light albedo feature clearly visible from Earth. There are other notable impact features, such as Argyre, which is around in diameter, and Isidis, which is around in diameter. Due to the smaller mass and size of Mars, the probability of an object colliding with the planet is about half that of Earth. Mars is located closer to the asteroid belt, so it has an increased chance of being struck by materials from that source. Mars is more likely to be struck by short-period comets, "i.e.", those that lie within the orbit of Jupiter. | https://en.wikipedia.org/wiki?curid=14640471 |
6,378 | The large canyon, Valles Marineris (Latin for "Mariner Valleys", also known as Agathodaemon in the old canal maps), has a length of and a depth of up to . The length of Valles Marineris is equivalent to the length of Europe and extends across one-fifth the circumference of Mars. By comparison, the Grand Canyon on Earth is only long and nearly deep. Valles Marineris was formed due to the swelling of the Tharsis area, which caused the crust in the area of Valles Marineris to collapse. In 2012, it was proposed that Valles Marineris is not just a graben, but a plate boundary where of transverse motion has occurred, making Mars a planet with possibly a two-tectonic plate arrangement. | https://en.wikipedia.org/wiki?curid=14640471 |
6,379 | Images from the Thermal Emission Imaging System (THEMIS) aboard NASA's Mars Odyssey orbiter have revealed seven possible cave entrances on the flanks of the volcano Arsia Mons. The caves, named after loved ones of their discoverers, are collectively known as the "seven sisters". Cave entrances measure from wide and they are estimated to be at least deep. Because light does not reach the floor of most of the caves, it is possible that they extend much deeper than these lower estimates and widen below the surface. "Dena" is the only exception; its floor is visible and was measured to be deep. The interiors of these caverns may be protected from micrometeoroids, UV radiation, solar flares and high energy particles that bombard the planet's surface. | https://en.wikipedia.org/wiki?curid=14640471 |
6,380 | Mars lost its magnetosphere 4 billion years ago, possibly because of numerous asteroid strikes, so the solar wind interacts directly with the Martian ionosphere, lowering the atmospheric density by stripping away atoms from the outer layer. Both "Mars Global Surveyor" and "Mars Express" have detected ionised atmospheric particles trailing off into space behind Mars, and this atmospheric loss is being studied by the MAVEN orbiter. Compared to Earth, the atmosphere of Mars is quite rarefied. Atmospheric pressure on the surface today ranges from a low of on Olympus Mons to over in Hellas Planitia, with a mean pressure at the surface level of . The highest atmospheric density on Mars is equal to that found above Earth's surface. The resulting mean surface pressure is only 0.6% of that of Earth . The scale height of the atmosphere is about , which is higher than Earth's , because the surface gravity of Mars is only about 38% of Earth's. | https://en.wikipedia.org/wiki?curid=14640471 |
6,381 | The atmosphere of Mars consists of about 96% carbon dioxide, 1.93% argon and 1.89% nitrogen along with traces of oxygen and water. The atmosphere is quite dusty, containing particulates about 1.5 µm in diameter which give the Martian sky a tawny color when seen from the surface. It may take on a pink hue due to iron oxide particles suspended in it. The concentration of methane in the Martian atmosphere fluctuates from about 0.24 ppb during the northern winter to about 0.65 ppb during the summer. Estimates of its lifetime range from 0.6 to 4 years, so its presence indicates that an active source of the gas must be present. Methane could be produced by non-biological process such as serpentinization involving water, carbon dioxide, and the mineral olivine, which is known to be common on Mars, or by Martian life. | https://en.wikipedia.org/wiki?curid=14640471 |
6,382 | Compared to Earth, its higher concentration of atmospheric CO and lower surface pressure may be why sound is attenuated more on Mars, where natural sources are rare apart from the wind. Using acoustic recordings collected by the "Perseverance" rover, researchers concluded that the speed of sound there is approximately 240 m/s for frequencies below 240 Hz, and 250 m/s for those above. | https://en.wikipedia.org/wiki?curid=14640471 |
6,383 | Auroras have been detected on Mars. Because Mars lacks a global magnetic field, the types and distribution of auroras there differ from those on Earth; rather than being mostly restricted to polar regions, a Martian aurora can encompass the planet. In September 2017, NASA reported radiation levels on the surface of the planet Mars were temporarily doubled, and were associated with an aurora 25 times brighter than any observed earlier, due to a massive, and unexpected, solar storm in the middle of the month. | https://en.wikipedia.org/wiki?curid=14640471 |
6,384 | Of all the planets in the Solar System, the seasons of Mars are the most Earth-like, due to the similar tilts of the two planets' rotational axes. The lengths of the Martian seasons are about twice those of Earth's because Mars's greater distance from the Sun leads to the Martian year being about two Earth years long. Martian surface temperatures vary from lows of about to highs of up to in equatorial summer. The wide range in temperatures is due to the thin atmosphere which cannot store much solar heat, the low atmospheric pressure, and the low thermal inertia of Martian soil. The planet is 1.52 times as far from the Sun as Earth, resulting in just 43% of the amount of sunlight. | https://en.wikipedia.org/wiki?curid=14640471 |
6,385 | If Mars had an Earth-like orbit, its seasons would be similar to Earth's because its axial tilt is similar to Earth's. The comparatively large eccentricity of the Martian orbit has a significant effect. Mars is near perihelion when it is summer in the Southern Hemisphere and winter in the north, and near aphelion when it is winter in the Southern Hemisphere and summer in the north. As a result, the seasons in the Southern Hemisphere are more extreme and the seasons in the northern are milder than would otherwise be the case. The summer temperatures in the south can be warmer than the equivalent summer temperatures in the north by up to . | https://en.wikipedia.org/wiki?curid=14640471 |
6,386 | Mars has the largest dust storms in the Solar System, reaching speeds of over . These can vary from a storm over a small area, to gigantic storms that cover the entire planet. They tend to occur when Mars is closest to the Sun, and have been shown to increase the global temperature. | https://en.wikipedia.org/wiki?curid=14640471 |
6,387 | Mars's average distance from the Sun is roughly , and its orbital period is 687 (Earth) days. The solar day (or sol) on Mars is only slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.8809 Earth years, or 1 year, 320 days, and 18.2 hours. | https://en.wikipedia.org/wiki?curid=14640471 |
6,388 | The axial tilt of Mars is 25.19° relative to its orbital plane, which is similar to the axial tilt of Earth. As a result, Mars has seasons like Earth, though on Mars they are nearly twice as long because its orbital period is that much longer. In the present day epoch, the orientation of the north pole of Mars is close to the star Deneb. | https://en.wikipedia.org/wiki?curid=14640471 |
6,389 | Mars has a relatively pronounced orbital eccentricity of about 0.09; of the seven other planets in the Solar System, only Mercury has a larger orbital eccentricity. It is known that in the past, Mars has had a much more circular orbit. At one point, 1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than that of Earth today. Mars's cycle of eccentricity is 96,000 Earth years compared to Earth's cycle of 100,000 years. | https://en.wikipedia.org/wiki?curid=14640471 |
6,390 | Mars approaches Earth in a synodic period of 779.94 days. Earth orbits the Sun the closest to Mars's orbit around the Sun, and Mars orbit is the second closest to Earth after the orbit of Venus. Therefore, their closest approaches, the inferior conjunctions, are the second closest for Earth after those with Venus, and the closest for Mars to any other planet. The gravitational potential difference, and thus the delta-v needed to transfer between Mars and Earth is the second lowest for Earth and the lowest for Mars to any other planet, while transfers can possibly be optimized with Venus flybys. | https://en.wikipedia.org/wiki?curid=14640471 |
6,391 | During the late nineteenth century, it was widely accepted in the astronomical community that Mars had life-supporting qualities, including the presence of oxygen and water. However, in 1894 W. W. Campbell at Lick Observatory observed the planet and found that "if water vapor or oxygen occur in the atmosphere of Mars it is in quantities too small to be detected by spectroscopes then available". That observation contradicted many of the measurements of the time and was not widely accepted. Campbell and V. M. Slipher repeated the study in 1909 using better instruments, but with the same results. It wasn't until the findings were confirmed by W. S. Adams in 1925 that the myth of the Earth-like habitability of Mars was finally broken. However, even in the 1960s, articles were published on Martian biology, putting aside explanations other than life for the seasonal changes on Mars. Detailed scenarios for the metabolism and chemical cycles for a functional ecosystem were being published as late as 1962. | https://en.wikipedia.org/wiki?curid=14640471 |
6,392 | The current understanding of planetary habitabilitythe ability of a world to develop environmental conditions favorable to the emergence of lifefavors planets that have liquid water on their surface. Most often this requires the orbit of a planet to lie within the habitable zone, which for the Sun is estimated to extend from within the orbit of Earth to about that of Mars. During perihelion, Mars dips inside this region, but Mars's thin (low-pressure) atmosphere prevents liquid water from existing over large regions for extended periods. The past flow of liquid water demonstrates the planet's potential for habitability. Recent evidence has suggested that any water on the Martian surface may have been too salty and acidic to support regular terrestrial life. | https://en.wikipedia.org/wiki?curid=14640471 |
6,393 | The environmental conditions on Mars are a challenge to sustaining organic life: the planet has little heat transfer across its surface, it has poor insulation against bombardment by the solar wind due to the absence of a magnetosphere and has insufficient atmospheric pressure to retain water in a liquid form (water instead sublimes to a gaseous state). Mars is nearly, or perhaps totally, geologically dead; the end of volcanic activity has apparently stopped the recycling of chemicals and minerals between the surface and interior of the planet. | https://en.wikipedia.org/wiki?curid=14640471 |
6,394 | "In situ" investigations have been performed on Mars by the "Viking" landers, "Spirit" and "Opportunity" rovers, "Phoenix" lander, and "Curiosity" rover. Evidence suggests that the planet was once significantly more habitable than it is today, but whether living organisms ever existed there remains unknown. The "Viking" probes of the mid-1970s carried experiments designed to detect microorganisms in Martian soil at their respective landing sites and had positive results, including a temporary increase of production on exposure to water and nutrients. This sign of life was later disputed by scientists, resulting in a continuing debate, with NASA scientist Gilbert Levin asserting that "Viking" may have found life. Tests conducted by the "Phoenix Mars" lander have shown that the soil has an alkaline pH and it contains magnesium, sodium, potassium and chloride. The soil nutrients may be able to support life, but life would still have to be shielded from the intense ultraviolet light. A 2014 analysis of Martian meteorite EETA79001 found chlorate, perchlorate, and nitrate ions in sufficiently high concentration to suggest that they are widespread on Mars. UV and X-ray radiation would turn chlorate and perchlorate ions into other, highly reactive oxychlorines, indicating that any organic molecules would have to be buried under the surface to survive. | https://en.wikipedia.org/wiki?curid=14640471 |
6,395 | Scientists have proposed that carbonate globules found in meteorite ALH84001, which is thought to have originated from Mars, could be fossilized microbes extant on Mars when the meteorite was blasted from the Martian surface by a meteor strike some 15 million years ago. This proposal has been met with skepticism, and an exclusively inorganic origin for the shapes has been proposed. Small quantities of methane and formaldehyde detected by Mars orbiters are both claimed to be possible evidence for life, as these chemical compounds would quickly break down in the Martian atmosphere. Alternatively, these compounds may instead be replenished by volcanic or other geological means, such as serpentinite. Impact glass, formed by the impact of meteors, which on Earth can preserve signs of life, has also been found on the surface of the impact craters on Mars. Likewise, the glass in impact craters on Mars could have preserved signs of life, if life existed at the site. | https://en.wikipedia.org/wiki?curid=14640471 |
6,396 | Mars has two relatively small (compared to Earth's) natural moons, Phobos (about in diameter) and Deimos (about in diameter), which orbit close to the planet. The origin of both moons is unclear, although a popular theory states that they were asteroids captured into Martian orbit. | https://en.wikipedia.org/wiki?curid=14640471 |
6,397 | Both satellites were discovered in 1877 by Asaph Hall and were named after the characters Phobos (the deity of panic and fear) and Deimos (the deity of terror and dread), twins from Greek mythology who accompanied their father Ares, god of war, into battle. Mars was the Roman equivalent to Ares. In modern Greek, the planet retains its ancient name "Ares" (Aris: "Άρης"). | https://en.wikipedia.org/wiki?curid=14640471 |
6,398 | From the surface of Mars, the motions of Phobos and Deimos appear different from that of the Earth's satellite, the Moon. Phobos rises in the west, sets in the east, and rises again in just 11 hours. Deimos, being only just outside synchronous orbitwhere the orbital period would match the planet's period of rotationrises as expected in the east, but slowly. Because the orbit of Phobos is below synchronous altitude, tidal forces from Mars are gradually lowering its orbit. In about 50 million years, it could either crash into Mars's surface or break up into a ring structure around the planet. | https://en.wikipedia.org/wiki?curid=14640471 |
6,399 | The origin of the two satellites is not well understood. Their low albedo and carbonaceous chondrite composition have been regarded as similar to asteroids, supporting a capture theory. The unstable orbit of Phobos would seem to point toward a relatively recent capture. But both have circular orbits, near the equator that is unusual for captured objects and the required capture dynamics are complex. Accretion early in the history of Mars is plausible, but would not account for a composition resembling asteroids rather than Mars itself, if that is confirmed. | https://en.wikipedia.org/wiki?curid=14640471 |
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