The geography of Pluto is mainly focused the distribution of physical features across Pluto. On 14 July 2015, the New Horizons spacecraft became the first spacecraft to fly by Pluto. [1] [2] During its brief flyby, New Horizons made detailed geographical measurements and observations of Pluto and its moons. [3]
Pluto may be defined as having retrograde rotation and an axial tilt of 60 degrees, or prograde rotation and a tilt of 120 degrees. Following the latter convention (the right-hand rule), the hemisphere currently in daylight is the northern one, with much of the southern hemisphere in darkness. This is the convention used by the International Astronomical Union (IAU) and the New Horizons team, and their maps put the sunlit hemisphere on top. However, older sources may define Pluto's rotation as retrograde and therefore the sunlit side as the southern hemisphere. East and West are also swapped between the two conventions. [4]
The prime meridian of Pluto is defined as the longitude facing Charon. [5]
The following names were originally proposed by the New Horizons discovery team. These names were variously taken from historical figures involved in the study of Pluto, notable space exploration missions, and a variety of chthonic deities or demons, some from ancient mythology and others from modern popular culture. While several of these names have been canonized by the IAU as of 2017, [6] most remain informal classifications that have yet to be considered.
Tombaugh Regio (nicknamed "The Heart") is a large, light-colored topographical region, formed in the shape of a heart, named after the modern discoverer of Pluto, Clyde Tombaugh. The two top lobes of the heart are distinct geological features, both having a bright and whiteish appearance, with the western lobe (called Sputnik Planitia --a vast plain of nitrogen and other ices) being smoother than the eastern lobe. [7] The heart is about 1,590 km (990 mi) across. The region contains two 3,400 m (11,000 ft) peaks composed of water-ice along its southwestern edge, Hillary Montes and Tenzing Montes . The lack of craters in the region suggests that its surface is less than 100 million years old, hence the speculation that Pluto is probably geologically active. [8] Subsequent data indicated that features near the western edges of the region (an area about the size of Texas) show evidence of "exotic ice flow", similar to melting glaciers, rich in methane, carbon monoxide, and nitrogen ices. Potentially recent glacial activity, near Cthulhu Macula, is suggested by the presence of lighter-hued material overlaid on top of darker, more ancient portions; according to Lillian Gipson at NASA, "...In the southernmost region of the heart, adjacent to the dark equatorial region, it appears that ancient, heavily-cratered terrain (informally named “Cthulhu Regio”) has been invaded by much newer icy deposits." [9]
A series of semi-regularly spaced dark spots with irregular boundaries are nicknamed the Brass Knuckles. They average about 480 km (300 mi) in diameter and are located along the equator between the Heart and the tail of the Whale. [10] [11] The brass knuckles are separated from one another by tall uplands. There are also many canyons running through them and through the surrounding mountains that are hundreds of miles long and several miles deep. [12] From west (south of Tombaugh Regio) to east (west of the Whale's tail), the Knuckles are: [13] [14]
Belton Regio (formerly called Cthulhu Macula or Cthulhu Regio), [16] nicknamed The Whale after its shape, is an elongated, dark region along Pluto's equator named in honor of astronomer Michael J. Belton, [17] and was informally named after the fictional deity from the works of H. P. Lovecraft. It is 2,990 km (1,860 mi) long and is the largest dark feature on Pluto. [18] It is the largest of the dark regions (Brass Knuckles) that span Pluto's equator. [16] The dark color of the area is speculated to be the result of a "tar" made of complex hydrocarbons called tholins covering the surface, formed from methane and nitrogen in the atmosphere interacting with ultraviolet light and cosmic rays. [19] [20] [21] The presence of a large number of craters within Cthulhu indicates that it is perhaps billions of years old, in contrast to the adjacent bright, craterless Sputnik Planitia, which may be as little as 100 million years old. [22]
A bright, ring-shaped feature about 350 km (220 mi) across located near the tail of the "Whale" in low-resolution images is nicknamed the "Donut". [23] It does not appear as a ring in higher-resolution images.
In the Western part of Sputnik Planitia near Al-Idrisi Montes, there are fields of transverse dunes formed by the winds, which blow from the center of Sputnik Planitia in the direction of surrounding mountings. The dune wavelengths are in the range of 0.4–1 km and they likely consist of methane ice particles 200–300 μm in size. The particles are lofted above the surface when the nitrogen ice sublimates under solar irradiation. After that, they are moved by gentle winds blowing with 1–10 m/s speeds despite generally low atmospheric pressure of about 15 μbar. [24]
The Working Group for Planetary System Nomenclature of the International Astronomical Union (IAU) is responsible for assigning official names to surface features on Pluto. On 7 September 2017, the first 14 names were officially approved by the IAU. [6]
As of August 2015, the New Horizons science team derives informal names from the following themes: explorers, space missions, spacecraft, scientists and engineers; fictional explorers, travellers, vessels, destinations, and origins; authors and artists who have envisioned exploration; and fictional underworlds, underworld beings, and travellers to the underworld. The New Horizons science team invited members of the public to propose names and vote on them before the spacecraft's arrival. [25]
Pluto is a dwarf planet in the Kuiper belt, a ring of bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest known trans-Neptunian object by volume, by a small margin, but is less massive than Eris. Like other Kuiper belt objects, Pluto is made primarily of ice and rock and is much smaller than the inner planets. Pluto has only one sixth the mass of Earth's moon, and one third its volume.
New Horizons is an interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with a team led by Alan Stern, the spacecraft was launched in 2006 with the primary mission to perform a flyby study of the Pluto system in 2015, and a secondary mission to fly by and study one or more other Kuiper belt objects (KBOs) in the decade to follow, which became a mission to 486958 Arrokoth. It is the fifth space probe to achieve the escape velocity needed to leave the Solar System.
The geology of Pluto consists of the characteristics of the surface, crust, and interior of Pluto. Because of Pluto's distance from Earth, in-depth study from Earth is difficult. Many details about Pluto remained unknown until 14 July 2015, when New Horizons flew through the Pluto system and began transmitting data back to Earth. When it did, Pluto was found to have remarkable geologic diversity, with New Horizons team member Jeff Moore saying that it "is every bit as complex as that of Mars". The final New Horizons Pluto data transmission was received on 25 October 2016. In June 2020, astronomers reported evidence that Pluto may have had a subsurface ocean, and consequently may have been habitable, when it was first formed.
Krun or Akrun is a Mandaean lord of the underworld. According to Mandaean cosmology, he dwells in the lowest depths of creation, supporting the entirety of the physical world.
The exploration of Pluto began with the arrival of the New Horizons probe in July 2015, though proposals for such a mission had been studied for many decades. There are no plans as yet for a follow-up mission, though follow-up concepts have been studied.
Tombaugh Regio, sometimes called "Pluto's heart" after its shape, is the largest bright surface feature of the dwarf planet Pluto. It is just north of the equator, to the northeast of Cthulhu Macula and to the northwest of Krun Macula, which are both dark features. Its western lobe, a 1,000 km (620 mi)-wide plain of nitrogen and other ices lying within a basin, is named Sputnik Planitia. The eastern lobe consists of high-albedo uplands thought to be coated by nitrogen transported through the atmosphere from Sputnik Planitia, and then deposited as ice. Some of this nitrogen ice then returns to Sputnik Planitia via glacial flow. The region is named after Clyde Tombaugh, the discoverer of Pluto.
Belton Regio is a prominent surface feature of the dwarf planet Pluto. It is an elongated dark region along Pluto's equator, 2,990 km (1,860 mi) long and one of the darkest features on its surface.
The Tenzing Montes are a range of icy mountains on Pluto, bordering the southwest region of Sputnik Planitia and the nearby Hillary Montes and Wright Mons. With peaks reaching 6.2 km in height, they are the highest mountain range on Pluto, and also the steepest, with a mean slope of 19.2 degrees.
Sputnik Planitia is a large basin on Pluto, about 1,050 by 800 km in size, partially submerged in large, bright glaciers of nitrogen ice. Named after Earth's first artificial satellite, Sputnik 1, it constitutes the western lobe of the heart-shaped Tombaugh Regio. Sputnik Planitia lies mostly in the northern hemisphere, but extends across the equator. Much of it has a surface of irregular polygons separated by troughs, interpreted as convection cells in the relatively soft nitrogen ice. The polygons average about 33 km (21 mi) across. In some cases troughs are populated by blocky mountains or hills, or contain darker material. There appear to be windstreaks on the surface with evidence of sublimation. The dark streaks are a few kilometers long and all aligned in the same direction. The planitia also contains pits apparently formed by sublimation. No craters were detectable by New Horizons, implying a surface less than 10 million years old. Modeling sublimation pit formation yields a surface age estimate of 180000+90000
−40000 years. Near the northwest margin is a field of transverse dunes, spaced about 0.4 to 1 km apart, that are thought to be composed of 200-300 μm diameter particles of methane ice derived from the nearby Al-Idrisi Montes.
Krun is the westernmost of the "Brass Knuckles", a series of equatorial dark regions on Pluto. It is named after Krun, the greatest of the five Mandaean lords of the underworld.
Ala is the smallest of the "Brass Knuckles", a series of equatorial dark regions on Pluto. It is named after Ala "earth", the chthonic and most important deity of the Igbo people.
Balrog Macula is the largest of the "Brass Knuckles", a series of equatorial dark regions on Pluto.
Vucub-Came is one of the "Brass Knuckles", a series of equatorial dark regions on Pluto. It is named after Wuquub' Kameh "Seven Death", one of the Quiché death gods in the Popol Vuh.
Meng-pʻo is the easternmost of the "Brass Knuckles", a series of equatorial dark regions on Pluto. Meng-pʻo straddles the zero meridian, directly under Pluto's tidally locked moon Charon and just west of the tail of the "Whale", Belton Regio. It is named after Meng Po, the Chinese underworld deity of forgetfulness.
The Hillary Montes or are a mountain range that reach 3.5 km above the surface of the dwarf planet Pluto. They are located northwest of Tenzing Montes in the southwest border area of Sputnik Planitia in the south of Tombaugh Regio. The Hillary Montes were first viewed by the New Horizons spacecraft on 14 July 2015, and announced by NASA on 24 July 2015.
Morgoth Macula is the informal name for a small dark region on the surface of Pluto, southwest of the Norgay Montes and adjacent to Sputnik Planitia. It was discovered in 2015 by the spacecraft New Horizons and named after Morgoth, the primary antagonist in J.R.R. Tolkien's legendarium.
Voyager Terra is a region on the dwarf planet Pluto, north of Viking Terra and Tombaugh Regio and west of Pioneer Terra, which was discovered in July 2015 by the New Horizons spacecraft. It is named for the Voyager program and Voyager 2, the first spacecraft to explore Uranus and Neptune and to cross into interstellar space. On 7 September 2017, the name Voyager Terra was officially approved together with the names of Tombaugh Regio and twelve other nearby surface features.
Cadejo is a small dark surface feature on Pluto near Voyager Terra. It is unofficially named after El Cadejo, a hellish spirit from Central American folklore which appears in the form of a large dog-like creature with burning red eyes. The feature was photographed by the New Horizons probe during the July 2015 flyby of the dwarf planet.
Baret Montes is a chain of mountains on the surface of the dwarf planet Pluto. It is located near the western border of Sputnik Planitia in Tombaugh Regio. These mountains were first viewed by the New Horizons spacecraft. It features large ridges that are formed by the compression of methane and water ice.
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