Siméon-Denis Poisson was a French mathematician known for his work on definite integrals, electromagnetic theory, and probability. Poisson’s family had intended him for a medical career, but he showed little interest or aptitude and in 1798 began studying mathematics at the École Polytechnique in

Poissy, town, Yvelines département, Île-de-France région, north-central France, on the Seine River. It contains the 12th-century collegiate church of Notre Dame, restored by the architect Eugène-Emmanuel Viollet-le-Duc, and the Savoye House (1929–31), a major work of the architect Le Corbusier. The

Poissy: …was the scene of the Colloquy of Poissy (September 1561), at which French Catholics and Huguenots (Protestants) tried unsuccessfully to reconcile their differences. An automobile assembly plant is located in Poissy, and the manufacture of automobile components is important. Pop. (1999) 35,841; (2014 est.) 36,994.

Eliza Jane Poitevent Holbrook Nicholson was an American poet and journalist, the first woman publisher of a daily newspaper in the Deep South. Eliza Jane Poitevent completed her schooling with three years at the Female Seminary of Amite, Mississippi. From her graduation in 1867 she began

Sidney Poitier was a Bahamian American actor, director, and producer who broke the color barrier in the U.S. motion-picture industry by becoming the first African American to win an Academy Award for best actor (for Lilies of the Field [1963]) and the first Black movie star. He also redefined roles

Poitiers, city, capital of Vienne département, Nouvelle-Aquitaine région, west-central France, southwest of Paris. Situated on high ground at the confluence of the Clain and Boivre rivers, the city commands the so-called Gate of Poitou, a gap 44 miles (71 km) wide between the mountains south of the

Battle of Tours, (October 732), victory won by Charles Martel, the de facto ruler of the Frankish kingdoms, over Muslim invaders from Spain. The battlefield cannot be exactly located, but it was fought somewhere between Tours and Poitiers, in what is now west-central France. The death of the

Battle of Poitiers, catastrophic defeat sustained by the French king John II on September 19, 1356, at the end of the first phase of the Hundred Years’ War between France and England. Many of the French nobility were killed, and King John was left a prisoner of the English. The battle is considered

Aquitaine: History: …Auvergne, of Toulouse, and of Poitiers each claimed this ducal title, but it was eventually secured by another William I, count of Poitiers (William III of Aquitaine). The powerful house of the counts of Poitiers retained Aquitaine during the 10th and 11th centuries, endeavouring from time to time to restore…

Poland: Emigration and revolt: …program was embodied in the Poitiers Manifesto of 1836, became the first democratically run, centralized, and disciplined political party of east-central Europe. Karl Marx regarded its concept of agrarian revolution as a major Polish contribution to European revolutionary thought.

University of Poitiers, coeducational, autonomous state institution of higher learning in Poitiers, Fr. Founded in 1970 under a law of 1968 reforming higher education, it replaced a university founded in 1431 by a Papal Bull of Eugene IV and confirmed by Charles VII in 1432. The university was

Poitou, historical and cultural region of west-central France, encompassing the départements of Vendée, Deux-Sèvres, and Vienne and coextensive with the former province of Poitou. Poitou derives its name from the Gallic tribe of Pictones, or Pictavi, whose civitas, or community, formed part of

Poitiers: …the city commands the so-called Gate of Poitou, a gap 44 miles (71 km) wide between the mountains south of the Loire River and the Massif Central that serves as the connecting link between northern and southern France.

Poitou-Charentes, former région of France. As a région, it encompassed the western départements of Vienne, Charente, Charente-Maritime, and Deux-Sèvres. In 2016 the Poitou-Charentes région was joined with the régions of Aquitaine and Limousin to form the new administrative entity of Nouvelle

Glenn Greenwald: …article he wrote on filmmaker Laura Poitras’s alleged persecution by the U.S. government brought him to the attention of Edward Snowden, who was looking for journalists he could trust to publish the classified documents he had collected as a subcontractor for the NSA. Snowden contacted Greenwald in December 2012, shortly…

Gustave Flaubert: Early life and works: …friendship with the young philosopher Alfred Le Poittevin, whose pessimistic outlook had a strong influence on him. No less strong was the impression made by the company of great surgeons and the environment of hospitals, operating theatres, and anatomy classes, with which his father’s profession brought him into contact.

Pierre Poivre was a French missionary-turned-entrepreneur whose enthusiasm for trade with Indochina stimulated French colonial expansion and whose many commercial schemes, had they been realized, might have established France securely in Indochina in the 18th instead of the 19th century. The son of

bivalve: Evolution and paleontology: …510 million years old), and Pojetaia runnegari from the Cambrian rocks of Australia. Fordilla is perhaps ancestral to the pteriomorph order Mytiloida, Pojetaia to the Palaeotazodonta order Nuculoida.

Masurian Lakeland, lake district, northeastern Poland. It is a 20,000-square-mile (52,000-square-km) area immediately to the south of the Baltic coastal plains and extends 180 miles (290 km) eastward from the lower Vistula River to the borders with Lithuania and Belarus. It lies within the

Pomeranian Lakeland, lake district, northwestern Poland. Located immediately south of the Baltic coastal plain, the 20,000-square-mile (52,000-square-km) lakeland is bounded by the lower Oder River on the west, the ancient river valley occupied by the modern Warta and Noteć rivers on the south, and

Great Poland Lakeland, lake district in west-central Poland that covers more than 20,000 square miles (55,000 square km). It crosses the provinces of Lubuskie, Wielkopolski, and, in part, Kujawsko-Pomorskie. The district is a north- to south-trending valley that lies between the middle Oder and

tlachtli: …the ritual ball game (ollama) played throughout pre-Columbian Mesoamerica. Possibly originating among the Olmecs (La Venta culture, c. 800–c. 400 bce) or even earlier, the game spread to subsequent cultures, among them those of Monte Albán and El Tajín; the Maya (as pok-ta-pok); and the Toltec, Mixtec, and Aztec.…

pokeweed, (Phytolacca americana), strong-smelling plant with a poisonous root resembling that of a horseradish. Pokeweed is native to wet or sandy areas of eastern North America. The berries contain a red dye used to colour wine, candies, cloth, and paper. Mature stalks, which are red or purplish

poke, dish of Hawaiian origin composed of small pieces of raw fish that are marinated and then served with vegetables, rice, and other ingredients. In the Polynesian language spoken in Hawaii, poke, which rhymes with okay, means “chunk” or “something cut away,” usually by crosscutting. In

poke bonnet, hood-shaped hat tied under the chin, with a small crown at the back and a wide projecting front brim that shaded the face. It became fashionable at the beginning of the 19th century and was worn by women and children of all ages. The size of the poke bonnet increased until, in 1830, a

pokeweed, (Phytolacca americana), strong-smelling plant with a poisonous root resembling that of a horseradish. Pokeweed is native to wet or sandy areas of eastern North America. The berries contain a red dye used to colour wine, candies, cloth, and paper. Mature stalks, which are red or purplish

Pokémon, electronic game series from Nintendo that debuted in Japan in February 1996 as Pokémon Green and Pokémon Red. The franchise later became wildly popular in the United States and around the world. The series, originally produced for the company’s Game Boy line of handheld consoles, was

Pokémon, 20th- and 21st-century Japanese fantasy-based cartoon creatures that spawned a video- and card-game franchise. What do you think? Explore the ProCon debate In the Pokémon—or “Pocket Monsters”—video-game series, players were able to explore the game’s fictional world by looking for wild

Ryan Reynolds: Hollywood career: >Pokémon Detective Pikachu (2019). Exhibiting his skill for self-mockery, he played himself in an episode of Seth MacFarlane’s series Family Guy (2011) and made memorable cameo appearances in MacFarlane’s feature comedies Ted (2012) and A Million Ways to Die in the West (2014).

Pokémon GO—the mobile app game, part of the massive Pokémon media franchise, that revolutionized augmented reality (AR) gaming—was downloaded more than 500 million times during its inaugural year of 2016, becoming the most popular mobile game ever. Within a month of its release, it had earned five

Pokémon: The mobile application Pokémon GO was a blockbuster success upon its release in 2016. Developed by Niantic Labs, a former division of Google, the game used GPS data and the mobile device’s camera to create an “augmented reality” that allowed users to capture Pokémon from real-life locations.

poker, card game, played in various forms throughout the world, in which a player must call (i.e., match) the bet, raise (i.e., increase) the bet, or concede (i.e., fold). Its popularity is greatest in North America, where it originated. It is played in private homes, in poker clubs, in casinos,

fireplace: The poker, designed to break burning coal into smaller pieces, did not become common until the 18th century. Coal scuttles appeared early in the 18th century and were later adapted into usually ornamental wood boxes or racks for fire logs. The fire screen was developed early…

poker dice, game involving five dice specially marked to simulate a playing-card deck’s top six cards (ace, king, queen, jack, 10, 9). The object is to throw a winning poker hand, with hands ranking as in poker except that five of a kind is high and there are no flushes. After a player’s first

Natasha Lyonne: Poker Face and His Three Daughters: …starred in the crime-thriller series Poker Face (2023– ), playing a wise-cracking casino worker who has the extraordinary gift of being able to tell if a person is lying. Lyonne also wrote and directed an episode. Her other credits from 2023 include the film His Three Daughters, in which she…

Lady Gaga: Success: The Fame and The Fame Monster: …other singles off The Fame—“Poker Face,” “LoveGame,” and “Paparazzi”—also reached number one on the radio chart, making Lady Gaga the first artist in the 17-year history of that chart to have four number ones from a debut album. The Fame was well received critically and proved enormously successful commercially,…

slot machine, gambling device operated by dropping one or more coins or tokens into a slot and pulling a handle or pushing a button to activate one to three or more reels marked into horizontal segments by varying symbols. The machine pays off by dropping into a cup or trough from two to all the

pokeweed, (Phytolacca americana), strong-smelling plant with a poisonous root resembling that of a horseradish. Pokeweed is native to wet or sandy areas of eastern North America. The berries contain a red dye used to colour wine, candies, cloth, and paper. Mature stalks, which are red or purplish

Phytolaccaceae, the pokeweed family of flowering plants, comprising 18 genera and 65 species of herbs, shrubs, and trees, mostly native to tropical and subtropical North America and Africa. Leaves are spiral, simple, and entire (i.e., smooth-edged). Flowers are typically arranged in branched or

Nepal: Drainage: …by the Seti River, the Pokharā Valley, 96 miles west of Kathmandu, is also a flat lacustrine basin. There are a few remnant lakes in the Pokharā basin, the largest being Phewa Lake, which is about two miles long and nearly a mile wide. North of the basin lies the…

nuclear weapon: India: …May 18, 1974, at the Pokhran test site on the Rajasthan Steppe, India, detonated a nuclear device with a yield later estimated to be less than 5 kilotons. (A figure of 12 kilotons was announced by India at the time.) India characterized the underground test as being for peaceful purposes,…

Andrzej Wajda: His debut feature, Pokolenie (1955; A Generation), together with Kanał (1957; “Canal”) and Popiół i diament (1958; Ashes and Diamonds), constituted a popular trilogy that is considered to have launched the Polish film school. The movies deal in symbolic imagery with sweeping social and political changes in Poland during the…

Vasily Aksyonov: Pokolenie zimy (1994; Generations of Winter) chronicles the fate of a family of intellectuals at the hands of the Soviet regime during the period of Joseph Stalin’s rule.

Pocomam, Mayan Indians of the highlands of eastern Guatemala. The Pocomam are primarily agriculturists; they cultivate corn (maize) and beans and manufacture pottery and charcoal. Houses are built of poles or adobe, with thatch, tile, or tin roofs. The houses are scattered over the countryside,

Julius Pokorny was a European linguist known for his work in Celtic studies and Indo-European etymological research. Pokorny was a professor at the University of Berlin from 1920 until 1935/36 and taught subsequently in Switzerland, holding lectureships at the University of Bern from 1944 to 1948

Kizhi Island: The Pokorovskaya (Intercession) Church (1764) has 10 cupolas, and its interior is decorated with icons made locally in the 17th and 18th centuries. St. Lazarus, the oldest church (built 1390) in the Karelian republic, was transported to the open-air museum from the Murom Monastery in the…

Africa Cup of Nations: …Nations (18), and Ivorian striker Laurent Pokou, who tallied five goals in a 6–1 victory over Ethiopia in 1970.

Lena River: Physiography: …(640 km), from Olyokminsk to Pokrovsk (60 miles [100 km] above Yakutsk), the Lena flows along the bottom of a narrow valley with sheer, broken slopes. The enormous limestone rock formations sometimes resemble the ruins of castles, or columns, or the figures of people and animals; and the area is…

Engels, city, Saratov oblast (province), western Russia. The city is situated on the left bank of the Volga River, opposite Saratov, to which it is connected by a highway bridge (completed 1965). Founded in 1747 as Pokrovskaya sloboda (military settlement), the city was the capital of the former

Saint Basil the Blessed, church constructed on Red Square in Moscow between 1554 and 1560 by Tsar Ivan IV (the Terrible), as a votive offering for his military victories over the khanates of Kazan and Astrakhan. The church was dedicated to the protection and intercession of the Virgin, but it came

Kharkiv: …the past are the 17th-century Pokrovsky Cathedral, the 19th-century Patriarchal Cathedral, and the belltower commemorating the victory over Napoleon I in 1812.

Saint Basil the Blessed, church constructed on Red Square in Moscow between 1554 and 1560 by Tsar Ivan IV (the Terrible), as a votive offering for his military victories over the khanates of Kazan and Astrakhan. The church was dedicated to the protection and intercession of the Virgin, but it came

Mikhail Nikolayevich Pokrovsky was a Soviet historian and government official, one of the most representative Russian Marxist historians. Pokrovsky joined the revolutionary movement as a young man, becoming a member of the Bolshevik Party in 1905. Forced to leave Russia following the revolutionary

Pol Pot was a Khmer political leader who led the Khmer Rouge totalitarian regime (1975–79) in Cambodia that imposed severe hardships on the Cambodian people. His radical communist government forced the mass evacuations of cities, killed up to three million people during the Cambodian genocide

Carpathian Mountains: Physiography of the Carpathian Mountains: …the largest among them is Pol’ana (4,784 feet).

graphic design: Graphic design in developing nations: …poster (1992) by Venezuelan designer Santiago Pol utilizes clear symbolic forms within a highly sophisticated spatial configuration, both elements of Modernist graphic design. In this work, dynamic shapes signify three peppers, symbols that are redolent with regional symbolism; the central pepper is formed by the white, or negative, space between…

Maharashtra: Recreation: During Pola in August, farmers bathe, decorate, and parade their bulls through the streets, signifying the start of the sowing season. The festival Ganesh Chaturthi, celebrating the birth of Hindu deity Ganesha, is held during the rainy season and is by far the most popular in…

Pula, major port and industrial centre in western Croatia. It lies at the southern tip of Istria (peninsula) at the head of the Bay of Pula and has a large, almost landlocked harbour in which there is a naval base and the Uljanik shipyards. Conquered by Rome in the 2nd century bce, Pula by the 2nd

Pola de Siero, town, north-central Asturias provincia (province) and comunidad autónoma (autonomous community), northwestern Spain. It lies on the Nora River, just northeast of Oveido city. Chartered in 1270 by Alfonso X of Castile, it is now a meatpacking centre, with brewing and tanning

Polab, member of the westernmost Slavs of Europe who dwelt in medieval times in the territory surrounded by the lower Elbe River in the west, the Baltic Sea in the north, the lower Oder River in the east, and Lusatia in the south. (This territory was situated in what later became Germany.) Their

Czech Republic: Relief: …roughly ovoid elevated basin (the Bohemian Plateau) encircled by mountains divided into six major groups. In the southwest are the Šumava Mountains, which include the Bohemian Forest (Böhmerwald). In the west are the Berounka River highlands. In the northwest, the Ore Mountains (Czech: Krušné hory; German: Erzgebirge) form the frontier…

Lekhitic languages: The extinct Polabian language, which bordered the Sorbian dialects in eastern Germany, was spoken by the Slavic population of the Elbe River region until the 17th or 18th century; a dictionary and some phrases written in the language exist.

technology of photography: The Polacolor process: Polaroid colour film has a larger number of active layers, including a blue-sensitive silver halide emulsion backed by a layer consisting of a yellow dye–developer compound, a green-sensitive layer backed by a layer of magenta dye–developer, and a red-sensitive layer backed by a…

Troy Polamalu is considered one of the best defensive backs of the early 21st century. Known for his speed, agility, and hard-hitting style, Polamalu played for the Pittsburgh Steelers of the National Football League (NFL) and was part of the teams that won the Super Bowl championships in 2006 and

Troy Polamalu is considered one of the best defensive backs of the early 21st century. Known for his speed, agility, and hard-hitting style, Polamalu played for the Pittsburgh Steelers of the National Football League (NFL) and was part of the teams that won the Super Bowl championships in 2006 and

Poland, country of central Europe. Poland is located at a geographic crossroads that links the forested lands of northwestern Europe and the sea lanes of the Atlantic Ocean to the fertile plains of the Eurasian frontier. Now bounded by seven nations, Poland has waxed and waned over the centuries,

Poland China, breed of pig developed between 1835 and 1870 in Butler and Warren counties, Ohio, U.S., by a fusion of Polish pigs and Big Chinas. The Poland China is black with a white face and feet and a white tip on the tail; the ears droop. Ranking among the largest modern breeds, it is a popular

World War II: The campaign in Poland, 1939: Against northern Poland, General Fedor von Bock commanded an army group comprising General Georg von Küchler’s 3rd Army, which struck southward from East Prussia, and General Günther von Kluge’s 4th Army, which struck eastward across the base of the Corridor. Much stronger in troops and in tanks,…

Megadeth: Formation and debut album: …were eventually joined by guitarist Chris Poland and drummer Gar Samuelson, two musicians from Dunkirk, New York. Megadeth quickly forged a sonically aggressive combination of intricate dual-guitar work and fast-thudding bass and drums with Mustaine growling angry lyrics laced with dark humor. In 1985 the band recorded its debut album,…

Congress Kingdom of Poland, Polish state created (May 3, 1815) by the Congress of Vienna as part of the political settlement at the end of the Napoleonic Wars. It was ruled by the tsars of Russia until its loss in World War I. The Kingdom of Poland comprised the bulk of the former Grand Duchy of

horizontally divided white-red national flag. It has a width-to-length ratio of 5 to 8.The first recorded use of the coat of arms of Poland, a white eagle on a red shield, dates from the 13th century. The reason for the choice of colours is not known, but it may simply have been a desire to make a

history of Poland, a survey of important events and people in the history of Poland from the time of its foundation as a state. Located at a geographic crossroads in central Europe, Poland has waxed and waned over the centuries, buffeted by the forces of regional history. In the mid-1500s united

Invasion of Poland, attack on Poland by Nazi Germany that marked the start of World War II. The invasion lasted from September 1 to October 5, 1939. As dawn broke on September 1, 1939, German forces launched a surprise attack on Poland. The attack was sounded with the predawn shelling, by the

Orthodox Church of Poland, ecclesiastically independent member of the Eastern Orthodox communion, established in 1924 to accommodate the four million Orthodox Christians residing in the vast Ukrainian and Byelorussian territories acquired by Poland after World War I. As the new political situation

Partitions of Poland, (1772, 1793, 1795), three territorial divisions of Poland, perpetrated by Russia, Prussia, and Austria, by which Poland’s size was progressively reduced until, after the final partition, the state of Poland ceased to exist. The First Partition occurred after Russia became

Poland: The early state: Two tribes, the Polanie—based around the fortified settlement (castrum) of Gniezno—and the Wiślanie—who lived near Kraków—expanded to bring other tribes under their control.

Tadeusz Kościuszko: Campaigns in Poland: …peasant masses, he issued the Manifesto of Połaniec, on May 7, suspending serfdom and reducing in half the existing villein service. This met with some resistance of the nobility. Defeats forced Kościuszko to retreat to his last stronghold, Warsaw. The defense of this city, besieged by Prussian and Russian armies…

clammyweed, (Polanisia trachysperma), North American herb of the Cleome genus of the family Cleomaceae, closely related to the mustard family, Brassicaceae. The plant is 60 cm (2 feet) tall and has leaves that give off a foul odour when bruised. The stems and three-parted leaves are hairy and

Paolo Sarpi was an Italian patriot, scholar, and state theologian during Venice’s struggle with Pope Paul V. Between 1610 and 1618 he wrote his History of the Council of Trent, an important work decrying papal absolutism. Among Italians, he was an early advocate of the separation of church and

Roman Polanski is a French Polish director, scriptwriter, and actor who, through a variety of film genres, explored themes of isolation, desire, and absurdity. (Read Martin Scorsese’s Britannica essay on film preservation.) Shortly after the young Polanski’s family settled in Kraków, Poland, his

Roman Polanski is a French Polish director, scriptwriter, and actor who, through a variety of film genres, explored themes of isolation, desire, and absurdity. (Read Martin Scorsese’s Britannica essay on film preservation.) Shortly after the young Polanski’s family settled in Kraków, Poland, his

Roman Polanski is a French Polish director, scriptwriter, and actor who, through a variety of film genres, explored themes of isolation, desire, and absurdity. (Read Martin Scorsese’s Britannica essay on film preservation.) Shortly after the young Polanski’s family settled in Kraków, Poland, his

John C. Polanyi is a chemist and educator who, with Dudley R. Herschbach and Yuan T. Lee, received the Nobel Prize for Chemistry in 1986 for his contribution to the field of chemical-reaction dynamics. Born to an expatriate Hungarian family, Polanyi was reared in England and attended Manchester

John C. Polanyi is a chemist and educator who, with Dudley R. Herschbach and Yuan T. Lee, received the Nobel Prize for Chemistry in 1986 for his contribution to the field of chemical-reaction dynamics. Born to an expatriate Hungarian family, Polanyi was reared in England and attended Manchester

Karl Polanyi was an economic anthropologist and former Hungarian political leader. In college in Budapest Polanyi founded the radical Club Galilei, which would have far-reaching effects on Hungarian intellectual life. He qualified as a lawyer in 1912 and served as a cavalry officer during World War

Karl Polanyi was an economic anthropologist and former Hungarian political leader. In college in Budapest Polanyi founded the radical Club Galilei, which would have far-reaching effects on Hungarian intellectual life. He qualified as a lawyer in 1912 and served as a cavalry officer during World War

emergence: …theory of personal knowledge of Michael Polanyi, a Hungarian scientist and philosopher, with its levels of being and of knowing, none of which are wholly intelligible to those they describe.

spitz, any of a group of northern dogs—such as the Akita, Pomeranian, and Samoyed—characterized by a wolflike or foxlike head; a dense, double coat in which the outer coat tends to stand off from the body; erect, pointed ears; and tails that curve over their backs. These traits were developed to

polar air mass, air mass that forms over land or water in the higher latitudes. See air mass;

polar anticyclone, wind system associated with a region in which high atmospheric pressure develops over or in the vicinity of the poles. The polar anticyclone is strongest in the cold season of the year. The Siberian anticyclone is an example of a polar anticyclone, as is the high-pressure area

telescope: Light gathering and resolution: In the equatorial mounting, the polar axis of the telescope is constructed parallel to Earth’s axis. The polar axis supports the declination axis of the instrument. Declination is measured on the celestial sky north or south from the celestial equator. The declination axis makes it possible for the telescope to…

polar ecosystem: …in polar regions such as polar barrens and tundra.

polar bear, (Ursus maritimus), great white northern bear (family Ursidae) found throughout the Arctic region. The polar bear travels long distances over vast desolate expanses, generally on drifting oceanic ice floes, searching for seals, its primary prey. The polar bear is the largest and most

Bathurst Island: Polar Bear Pass National Wildlife Area (1990), which extends through the centre of the island, has been the site of a wildlife research station since 1968. Discovered in 1819 by the British explorer Sir William Parry, the island was named for Henry Bathurst, the 3rd…

Polar Bear Provincial Park, wilderness park, northern Ontario, Canada, on Hudson and James bays. A huge undeveloped area of 9,300 square miles (24,087 square km), it is the largest of Ontario’s provincial parks; it was established in 1970. Polar Bear Provincial Park is accessible only by plane or

polar ecosystem, complex of living organisms in polar regions such as polar barrens and tundra. Polar barrens and tundra are found at high latitudes on land surfaces not covered by perpetual ice and snow. These areas lying beyond the tree line comprise more than 10 percent of the Earth’s land

oogenesis: …cell is known as a polar body. The secondary ovum grows in the ovary until it reaches maturation; it then breaks loose and is carried into the fallopian tubes. Once in the fallopian tubes, the secondary egg cell is suitable for fertilization by the male sperm cells. See also ovulation;…

ionic bond, type of linkage formed from the electrostatic attraction between oppositely charged ions in a chemical compound. Such a bond forms when the valence (outermost) electrons of one atom are transferred permanently to another atom. The atom that loses the electrons becomes a positively

Mars: Polar regions: For telescopic observers the most striking regular changes on Mars occur at the poles. With the onset of fall in a particular hemisphere, clouds develop over the relevant polar region, and the cap, made of frozen carbon dioxide, begins to grow. The smaller…

snow and ice climate, major climate type of the Köppen classification characterized by bitterly cold temperatures and scant precipitation. It occurs poleward of 65° N and S latitude over the ice caps of Greenland and Antarctica and over the permanently frozen portion of the Arctic Ocean. It is