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30-647: Hellas Planitia / ˈ h ɛ l ə s p l ə ˈ n ɪ ʃ i ə / is a plain located within the huge, roughly circular impact basin Hellas located in the southern hemisphere of the planet Mars . Hellas is the third- or fourth-largest known impact crater in the Solar System . The basin floor is about 7,152 m (23,465 ft) deep, 3,000 m (9,800 ft) deeper than the Moon's South Pole-Aitken basin , and extends about 2,300 km (1,400 mi) east to west. It

60-556: A 16 cm (6.3 in) refractor , produced "the first really truthful representation of the planet" (in the estimation of E. M. Antoniadi ). Radar images by the Mars Reconnaissance Orbiter (MRO) spacecraft's SHARAD radar sounder suggest that features called lobate debris aprons in three craters in the eastern region of Hellas Planitia are actually glaciers of water ice lying buried beneath layers of dirt and rock. The buried ice in these craters as measured by SHARAD

90-421: A combination of glacial action and explosive boiling may be responsible for gully features in the crater. Some of the low elevation outflow channels extend into Hellas from the volcanic Hadriacus Mons complex to the northeast, two of which Mars Orbiter Camera images show contain gullies: Dao Vallis and Reull Vallis . These gullies are also low enough for liquid water to be transient around Martian noon, if

120-535: A long series of popular treatises in rapid succession, amongst the more important of which are Light Science for Leisure Hours and The Sun (1871); The Orbs around Us and Essays on Astronomy (1872); The Expanse of Heaven , The Moon and The Borderland of Science (1873); The Universe and the Coming Transits and Transits of Venus (1874); Our Place among Infinities (1875); Myths and Marvels of Astronomy (1877) ; The Universe of Stars (1878); Flowers of

150-435: A monograph on Mars, when the failure of a New Zealand bank deprived him of an independence which would have enabled him to carry out his scheme without anxiety as to its commercial success or failure. Being thus obliged to depend upon his writings for the support of his family, and having learned by the fate of his Saturn and its System that the general public are not attracted by works requiring arduous study, he cultivated

180-580: A monthly in 1885), which had a considerable circulation. In it he wrote on a great variety of subjects, including chess and whist. Proctor was also the author of the articles on astronomy in the American Cyclopaedia and the ninth edition of the Encyclopædia Britannica , and was well known as a popular lecturer on astronomy in England, America and Australia. Proctor was elected a fellow of

210-414: A more popular style. He wrote for a number of periodicals; and although he has stated that he would at this time willingly have turned to stone-breaking on the roads, or any other form of hard and honest but unscientific labour, if a modest competence had been offered him in any such direction, he attained a high degree of popularity, and his numerous works had a wide influence in familiarising the public with

240-470: A time the position of mathematical coach for Woolwich and Sandhurst. Proctor's literary standing meantime improved, and he became a regular contributor to The Intellectual Observer , Chamber's Journal and the Popular Science Review . In 1870 appeared his Other Worlds Than Ours , in which he discussed the question of the plurality of worlds in the light of new facts. This was followed by

270-512: A valley, a plain is enclosed on two sides, but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains, or by cliffs . Where a geological region contains more than one plain, they may be connected by a pass (sometimes termed a gap ). Coastal plains mostly rise from sea level until they run into elevated features such as mountains or plateaus. Plains can be formed from flowing lava ; from deposition of sediment by water, ice, or wind; or formed by erosion by

300-408: Is a flat expanse of land with a layer of grass that generally does not change much in elevation , and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains , as coastal plains , and as plateaus or uplands . Plains are one of the major landforms on earth, where they are present on all continents, and cover more than one-third of the world's land area. In

330-405: Is about 250 m (820 ft) thick on the upper crater and about 300 m (980 ft) and 450 m (1,480 ft) on the middle and lower levels respectively. Scientists believe that snow and ice accumulated on higher topography, flowed downhill, and is now protected from sublimation by a layer of rock debris and dust. Furrows and ridges on the surface were caused by deforming ice. Also,

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360-496: Is centered at 42°24′S 70°30′E  /  42.4°S 70.5°E  / -42.4; 70.5 . It features the lowest point on Mars , serves as a known source of global dust storms, and may have contained lakes and glaciers. Hellas Planitia spans the boundary between the Hellas quadrangle and the Noachis quadrangle . With a diameter of about 2,300 km (1,400 mi), it

390-517: Is mere coincidence, is unknown. Due to its size and its light coloring, which contrasts with the rest of the planet, Hellas Planitia was one of the first Martian features discovered from Earth by telescope . Before Giovanni Schiaparelli gave it the name Hellas (which in Greek means Greece ), it was known as Lockyer Land , having been named by Richard Anthony Proctor in 1867 in honor of Sir  Joseph Norman Lockyer , an English astronomer who, using

420-457: Is named after him. Richard Proctor's father died in 1850 and his mother attended to his education. He was sent to King's College London and subsequently earned a scholarship at St John's College , Cambridge . He graduated in 1860 as 23rd wrangler. Proctor then read for the bar, but turned to astronomy and authorship instead, and in 1865 published an article on the Colours of Double Stars in

450-644: Is the largest unambiguous well-exposed impact structure on the planet; the obscured Utopia Planitia is slightly larger (the Borealis Basin , if it proves to be an impact crater, is considerably larger). Hellas Planitia is thought to have been formed during the Late Heavy Bombardment period of the Solar System , approximately 4.1 to 3.8 billion years ago, when a protoplanet or large asteroid, suggested to be around 370 kilometres (230 mi) in diameter, hit

480-492: The Cornhill Magazine . His first book Saturn and its System was published in the same year, at his own expense. This work contains an elaborate account of the phenomena presented by the planet; but although favourably received by astronomers, it had no great sale. He intended to follow it up with similar treatises on Mars , Jupiter , Sun , Moon , comets and meteors , stars , and nebulae , and had in fact commenced

510-510: The Royal Astronomical Society on 8 June 1866. He became honorary secretary in 1872, and contributed eighty-three separate papers to its Monthly Notices . Of these the more noteworthy dealt with the distribution of stars, star clusters and nebulae, and the construction of the sidereal universe . He was an expert in all that related to map-drawing, and published two star-atlases. A chart on an isographic projection , exhibiting all

540-535: The Earth. They are structurally depressed areas of the world that make up some of the most extensive natural lowlands on the Earth's surface. Richard Anthony Proctor Richard Anthony Proctor FRAS (23 March 1837 – 12 September 1888) was an English astronomer . He is best remembered for having produced one of the earliest maps of Mars in 1867 from 27 drawings by the English observer William Rutter Dawes . His map

570-513: The Sky (1879); The Poetry of Astronomy (1880); Easy Star Lessons and Familiar Science Studies (1882); Mysteries of Time and Space (1883) - Digital Copy ; "The Great Pyramid" (1883) - Digital Copy ; The Universe of Suns (1884); The Seasons (1885); Other Suns than Ours and Half-Hours with the Stars (1887). In 1881 Proctor founded Knowledge , a popular weekly magazine of science (converted into

600-404: The agents from hills or mountains. Biomes on plains include grassland ( temperate or subtropical ), steppe ( semi-arid ), savannah ( tropical ) or tundra ( polar ). In a few instances, deserts and rainforests may also be considered plains. Plains in many areas are important for agriculture because where the soils were deposited as sediments they may be deep and fertile , and

630-595: The flatness facilitates mechanization of crop production; or because they support grasslands which provide good grazing for livestock . The types of depositional plains include: Erosional plains have been leveled by various agents of denudation such as running water, rivers, wind and glacier which wear out the rugged surface and smoothens them. Plain resulting from the action of these agents of denudation are called peneplains (almost plain) while plains formed from wind action are called pediplains . Structural plains are relatively undisturbed horizontal surfaces of

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660-419: The ground in this region. The ice layer would have been between 100 m and 1 km thick. When one substance moves up through another denser substance, it is called a diapir . So, it seems that large masses of ice have pushed up layers of rock into domes that were subsequently eroded. After erosion removed the top of the layered domes, circular features remained. Planitia A plain or flatland

690-499: The main facts of astronomy. Proctor's earlier efforts were not always successful. His Handbook of the Stars (1866) was refused by Messrs Longmans and Messrs Macmillan, but being privately printed, it sold fairly well. For his Half-Hours with the Telescope (1868), which eventually reached a 20th edition, he received originally £25 from Messrs Hardwick. Although teaching was uncongenial to him he took pupils in mathematics, and held for

720-620: The official arrangements for observing the transits of Venus of 1874 and 1882. He was elected as a member to the American Philosophical Society in 1874. Proctor's largest and most ambitious work, Old and New Astronomy , left unfinished at his death, was completed by Arthur Cowper Ranyard and published in 1892 with a second edition in 1895. He settled in America some time after his second marriage in 1881, and died of yellow fever at New York City on 12 September 1888. A monument

750-581: The shapes of many features in Hellas Planitia and other parts of Mars are strongly suggestive of glaciers , as the surface looks as if movement has taken place. These relatively flat-lying "cells" appear to have concentric layers or bands, similar to a honeycomb. This honeycomb terrain was first discovered in the northwestern part of Hellas. The geologic process responsible for creating these features remains unresolved. Some calculations indicate that this formation may have been caused by ice moving up through

780-553: The stars contained in the Bonner Durchmusterung , was designed to show the laws according to which the stars down to the 9–10th magnitude are distributed over the northern heavens. His Theoretical Considerations respecting the Corona (Monthly Notices, xxxi. 184, 254) also deserve mention, as well as his discussions of the rotation of Mars, by which be deduced its period with a probable error of 0.005. He also vigorously criticised

810-437: The surface. The altitude difference between the rim and the bottom is over 9,000 m (30,000 ft). Despite being deeper than the Moon's South Pole-Aitken basin , Hellas' rim peaks are significantly less prominent. This may be because large Martian impacts such as Hellas induced global hot rainfall and meltwater flows that degraded crater rims, including their own. The crater's depth of 7,152 m (23,465 ft) below

840-512: The temperature were to rise above 0 Celsius. Hellas Planitia is antipodal to Alba Patera . It and the somewhat smaller Isidis Planitia together are roughly antipodal to the Tharsis Bulge , with its enormous shield volcanoes, while Argyre Planitia is roughly antipodal to Elysium , the other major uplifted region of shield volcanoes on Mars. Whether the shield volcanoes were caused by antipodal impacts like that which produced Hellas, or if it

870-498: The topographic datum of Mars explains the atmospheric pressure at the bottom: 12.4 mbar (1240 Pa or 0.18 psi) during winter, when the air is coldest and reaches its highest density. This is 103% higher than the pressure at the topographical datum (610 Pa, or 6.1 mbar, or 0.09 psi) and above the triple point of water , suggesting that the liquid phase could be present under certain conditions of temperature, pressure, and dissolved salt content. It has been theorized that

900-410: Was later superseded by those of Giovanni Schiaparelli and Eugène Antoniadi and his nomenclature was dropped (for instance, his "Kaiser Sea" became Syrtis Major Planum ). He used old drawings of Mars dating back to 1666 to try to determine the sidereal day of Mars. His final estimate, in 1873, was 24h 37m 22.713s, very close to the modern value of 24h 37m 22.663s. The crater Proctor on Mars

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