The Tombo region, also known as the "heart of Pluto", is home to Sputnik Plain
Sputnik Planitia appeared due to a combination of atmospheric processes on Pluto and its topographical features, scientists report in an article published in the journal Nature. In addition, researchers believe that methane ice deposits in the middle and high latitudes of the dwarf planet's northern hemisphere should disappear in the next decade.
Last year, the New Horizons probe discovered an unusual relief feature on Pluto. His camera captured images of a plateau that was significantly lighter than the surrounding area. The area located in the “heart of Pluto” was called “Sputnik Planitia.” Studies have shown that it is covered with ice, consisting of a mixture of nitrogen, methane and carbon monoxide, and formed over the past 100 million years. The plain has a complex structure - its surface is divided into “cells” 20 to 30 kilometers wide, which are the result of convection. It also revealed ice hills drifting on frozen nitrogen, which are fragments of hills located at the edges of the “heart of Pluto.”
Scientists still did not know what exactly led to the formation of the Sputnik Plain. To find out, they created a computer simulation of the distribution of matter on the surface of Pluto over the past 50 thousand years (during which time it would have made 200 revolutions around the Sun). The researchers assumed that the dwarf planet was entirely covered with a small layer of ice, and its atmosphere contained gaseous nitrogen, methane and carbon monoxide. When creating the model, the authors of the work took into account many parameters, such as the inclination of the planetoid’s rotation axis, seasonal thermal inertia and albedo.
The simulation showed that if Pluto's surface were smooth, it would have either a permanent band of nitrogen ice at its equator or seasonal snow caps at its poles. These results were not consistent with observational data. Then the researchers added realistic terrain by placing three large craters on the dwarf planet, one of which is supposedly located under Sputnik Planitia and has a depth of four kilometers. In this case, due to the high pressure, and, as a consequence, the higher condensation temperature, nitrogen, most of the methane and carbon monoxide began to accumulate in the lowlands.
Ice distribution on the surface of Pluto. The dwarf planet was originally covered in ice made of nitrogen, methane and carbon monoxide. Over time, ice consisting only of methane begins to dominate on the planet, and by 2030 all the ice is concentrated only in the Sputnik Plain region.
Tanguy Bertrand and François Forget / Nature, 2016
The computer model also suggests that as Pluto moves away from the Sun, the average pressure on the dwarf planet will fall. According to the authors of the work, this will lead to the fact that methane ice in the northern hemisphere of the planetoid will disappear by 2030. If observations confirm this hypothesis, then the authors’ model can be considered reliable.
The New Horizons spacecraft, which transmitted photographs of the Sputnik plain, was launched in 2006 by the NASA aerospace agency. Its mission is to study the formation of the Pluto-Charon system, as well as other moons and Kuiper Belt objects. The probe's closest approach to Pluto occurred in July 2015; New Horizons is now at a distance of 3.5 AU from the dwarf planet and is moving towards the asteroid 2014 MU 69.
Until last year, there were no high-quality photographs of Pluto, a dwarf planet of ice and rock located in the Kuiper belt. Until 1992, it was considered the ninth planet in the solar system, but after several similar objects were discovered, Pluto was classified as a dwarf planet and the largest object in the Kuiper belt. This review contains interesting photographs and facts about this planet.
Because Pluto was the most distant planet from Earth (it is between 4.3 and 7.5 billion km from Earth, depending on its current orbital position), it remains one of the least studied and understood objects in the solar system. In July 2015, New Horizons became the first spacecraft to fly past Pluto, taking a ton of unique images during that time.
1. Pluto in high resolution
One of the latest high-resolution images of Pluto. The photo was taken by NASA's New Horizons spacecraft.
2. Sunset 06/14/2015
Just 15 minutes after the craft made its closest approach to Pluto on July 14, 2015, the spacecraft's cameras looked back at the Sun. At the same time, it was possible to capture unique shots of the sunset over the icy mountains and flat icy plains stretching to the horizon of Pluto.
3. Landforms
This image illustrates the incredible variety of geological landforms on the surface of the dwarf planet.
4. The atmosphere of a dwarf planet
Pluto's atmosphere glows against the background of the Sun, surrounding the dwarf planet. In this image taken by the New Horizons spacecraft on July 15, the atmosphere appears to be a halo.
5. Shadows of the Hills
The setting sun illuminates the fog or near-surface haze. At the same time, parallel shadows of many local hills and small mountains are visible in the haze.
6. Charon
One of the clearest and most detailed images of Charon, Pluto's largest moon.
7. Pluto and Charon
Pluto and its satellite Charon. Photo taken by New Horizons in color and at the highest possible resolution.
8. Ice Mountain Range
New Horizons has discovered a new, apparently less elevated mountain range on the lower left edge of Pluto's most famous feature: the ice mountains.
9. Nikta and Hydra
While Pluto's largest moon, Charon, is fairly well-known among astronomy enthusiasts, the dwarf planet's smaller and lesser-known moons are usually overlooked. The New Horizons spacecraft photographed 2 of these satellites - Nix and Hydra.
10. Dual system
New photo of Pluto and Charon. The dwarf planet and its satellite were sometimes even considered a binary system, since the barycenter of their orbits is not located on either of these cosmic bodies.
11. “Heart” of the planet
The bright, mysterious “heart” of Pluto in close proximity. New Horizons took this image on July 12 from a distance of 2.5 million kilometers.
12. Carbon monoxide and crystalline nitrogen
In the western half of the planet, scientists have discovered what scientists have informally dubbed the "Heart of Pluto" due to the similarity of this bright area to the shape of a heart. New Horizons revealed that this bright spot is composed of frozen carbon monoxide and crystalline nitrogen.
13. Haze in the atmosphere
The bright haze in Pluto's atmosphere produces a soft twilight that illuminates the surface before sunrise and after sunset.
14. Satellite Nikta
A close-up shot of Pluto's small moon Nix. The size of Nikta is only 54 × 41 × 36 kilometers.
15. Hydra satellite
Hydra, Pluto's outer moon, was discovered in 2005. The dimensions of the ice-covered satellite are 43 × 33 km.
And in continuation of the space theme, we have collected.
In the solar system, disastrous events do not usually result in the destruction of worlds. A planet or moon can be hit by an asteroid or comet, and, having strayed from the previous trajectory, hesitate for some time and change the tilt of its axis, experiencing a change in the landscape. But everything will eventually stabilize.
It is precisely these titanic changes that are now taking place on Pluto, and their main reason is the famous heart on its surface. The dwarf planet's orientation in space is controlled by the heavy ice at its heart, as well as the massive global sea that astronomers believe lies beneath it.
When New Horizons captured detailed images of Pluto last year, the small world—originally the ninth planet, demoted to dwarf status a decade ago—appeared as a rocky ball wrapped in a shell of sand-colored ice and surrounded by a nitrogen atmosphere. Astronomers believe that between the rocky bottom and the icy crust there is an ocean of water that washes wrinkled mountains sprinkled with methane snow. Much of the dwarf planet's surface appears like snakeskin, rippling with gray and red-brown folds and pits. However, Pluto's defining feature is its huge heart, called Tombaugh's Region. Its left side is a 1000 km wide basin called Sputnik Planitia. Many astronomers think that this teardrop-shaped spot is a scar left by a giant cosmic body that collided with Pluto thousands of years ago.
Pluto and its moon, Charon, always face the same way towards each other - just like our Moon faces the Earth. The bright Tombaugh Region always faces away from Charon. The alignment is so precise that it appears as if Charon is floating over the area that is directly opposite Satellite Planitia. This suggests that there is additional mass in this area that causes Pluto to rotate to maintain balance between its mass and its sister Moon. Astronomers have figured out how such a reorganization occurred; several publications published yesterday in the journal Nature are devoted to this.
« The problem is that Sputnik Planitia is a hole in the surface, and accordingly there should be less mass there than everywhere else, not more" - says Francis Nimmo, planetary scientist at the University of California, Santa Cruz - " if this is true, then we will have to figure out a way to find the hidden mass«.
This mass could be in the form of a dirty part of the ocean, Nimmo says. When the huge body hit Pluto, it opened up part of the planet's ice sheet. The ocean below the surface rose up to fill the void. The density of water is higher than the density of ice, so Pluto's mass then began to be distributed unevenly. After this, the entire planet turned out to be unbalanced, seeming to become heavier on one side (we know that something similar happened to our Moon). Over time, this will reorient Pluto's rotation until it balances itself again. This would be what brought Satellite Planitia to its current location, directly opposite Charon.
According to Nimmo's co-author, MIT planetary scientist Richard Binzel, the temperatures and pressures inside Pluto suggest the existence of a viscous, dirty ocean. This body of water may also contain ammonium, a known antifreeze. Pluto is 40 times farther from the sun than Earth, but it can warm itself with radioactive elements in its round core. This internal reactor will heat the reservoir for another billion years or so. Charon may also have had its own ocean of water, but it was so small and the emission of radioactive elements so weak that it must have frozen two billion years ago.
Research suggests that many other distant worlds in the Kuiper Belt may also have internal oceans of water and other liquids.
Ice and the movement of that ice across the planet's surface controls almost all of the geology we see.
“The only place where you won’t find a lot of water is the inner solar system,” Nimmo says, “the outer part is quite rich in it.”
Above this dirty sea lies Pluto's frozen heart, which is filled with nitrogen snow that may also have played a role in changing the dwarf planet's orientation in the millennia after the collision. Pluto lies on its side, so the poles receive more sunlight than the equator. As the planet moves slowly around the sun—one orbit takes 248 Earth years—nitrogen and other gases freeze in the permanently darkened regions, then return to gaseous form and then become solid again. This nitrogen snow can accumulate over billions of years, and eventually the heavy nitrogen glacier in the Sputnik Planitia region could change the shape of the planet, says James Keene, a scientist at the University of Arizona.
Whether due to groundwater or snow on the surface, the result is the same: Pluto is reorienting.
This phenomenon is called true polar wander, and is common on rocky worlds: scientists have studied it on Earth, the moon and Mars. True polar wander is different from the 23 degrees tilt on Earth's axis that gives our planet its seasons. When this phenomenon occurs, the planet's axis of rotation does not tilt; instead, its crust shifts. It's as if the Earth's tilt remained the same, but the continents slid so that New York was moving towards the North Pole. You can also draw an analogy with a peach in your hand, when you peel its skin, but do not touch the pulp.
True polar wander occurs when something very catastrophic happens, causing changes in the distribution of the planet's mass. In a rotating world, extra mass moves towards the equator, and zones with less mass move towards the poles. This happened on the Moon when lava erupted billions of years ago, forming the characteristic appearance of our satellite. On Mars, a similar process occurred when Mount Tharsis, which erupted lava between 4.1 and 3.7 billion years ago, deformed the planet.
Pluto's polar wander began with the influence of Sputnik Planitia and is still happening today, according to Keene, who also studied the dwarf planet's cracked surface. The pattern of damage matches what would be seen during a true polar wander, he says. The faults also support the idea of a sea beneath the surface.
The reorientation shows that the long-term seasonal migration of ice—in a sense, weather patterns—dictates Pluto's fate.
“Ice and the movement of that ice across the surface controls almost all of the geology that we see,” Keane says. This interaction between climate and orbital evolution may also occur on other icy worlds, the scientist believes.
New Horizons is now far from Pluto and is moving towards its next target - 2014 MU69, preparing to arrive on January 1, 2019. Last month, scientists received the latest Pluto transmission, which contains more than 50 gigabits of data. They will study it for years to come, but some are already dreaming about what we could do next. If people could ever send a probe there, they could equip it with a radar instrument that would allow them to look under Pluto's crust and into its ocean.
In the distant future, we may be able to send an orbiter or even a pair into orbit around Pluto. Such a device will be able to study the layers of nitrogen ice on Sputnik Planitia and the ice that forms the crust. It will be possible to observe the dwarf planet's seasons slowly changing. It will be possible to see what is actually hidden under the ice and how, over the course of millennia, a world thrown to the edge of the solar system can change itself.
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Thanks to a climate model, French scientists have figured out how glaciers formed on the so-called “heart of Pluto.” The study was published in the journal Nature.
Pluto is a dwarf planet in the solar system. Compared to the orbits of other planets, Pluto's orbit is more eccentric (that is, it is slightly "stretched") and inclined to the ecliptic plane. Thanks to this orbit, the dwarf planet sometimes crosses the orbit of Neptune and becomes closer to the Sun than Neptune. The maximum distance at which Pluto approaches the Sun is 4.4 billion km. One revolution of the dwarf planet around the Sun takes 248 Earth years.
In July 2015, the world saw the highest quality image of Pluto to date, taken using the LORRI (Long Range Reconnaissance Imager) instrument, when the New Horizons station was at a distance of 768 thousand km from the surface of the dwarf planet.
However, the greatest interest among researchers was aroused by the so-called “heart of Pluto” (otherwise known as the Tombaugh region, in honor of Clyde Tombaugh, who discovered the planet) - an area on the planet about 1,600 km wide, the outlines of which resemble a heart. The region is divided into two geologically separate sections - western and eastern.
This area is currently known to contain the icy Sputnik Planitia, named after Earth's first artificial satellite. The depth of the plain is four kilometers, the length is about a thousand kilometers, and the width is about eight hundred. Sputnik Planitia is home to a massive glacier made mostly of frozen nitrogen, carbon monoxide and methane.
Previously it was believed that the area of glacier formation was associated with the depths of the Tombo region. According to another hypothesis, the glacier was caused by depressions in which volatile substances collected from the entire surface of the planet. However, thin deposits of frozen nitrogen were found not only in the Sputnik Planitia region, but also in the mid-northern latitudes of the planet. It was also discovered that, with the exception of the darker equatorial unglaciated regions, most of the planet is covered in methane ice.
To understand how the glacier formed on Sputnik Planitia, French scientists from Pierre and Marie Curie University Tanguy Bertrand and Francois Forget modeled the chemical processes that occurred in icy deposits on Pluto over 50 thousand Earth years. Experts also studied the amount of gases in the planet's atmosphere, climate changes and examined topographic data using images obtained from the New Horizons space probe and the Hubble telescope.
During the initial phase of the simulation, the scientists completely covered the model of Pluto with an equal amount of each type of ice. Then the planet was “allowed” to change over 50 thousand Earth years. The appearance of ice, which occurred each year, depended on a number of key parameters: topography, albedo (the reflectance of any surface) and emissivity of ice, the total volume of its reserves, as well as the thermal conductivity of near-surface and deep-lying horizons, which determines the daily and seasonal thermal inertia (the ability to resist temperature changes over a certain time).
Modeling results also revealed that the surface of Pluto's middle and high latitudes is covered by frozen methane and, in some cases, nitrogen, depending on the season. This explains why there are bright areas in the northern polar region of the planet.
Scientists have found that geological activity in the Sputnik Planitia region does not stop, and seasonal thermal inertia plays an important role in it. Due to high thermal inertia, thick layers of nitrogen glacier form on the plain, and surface pressure tripled during observations from 1988 to 2015. This can be explained by the fact that during the period under review, the point of the planet closest to the Sun, where the Sun’s rays fall exactly perpendicular to the surface of Pluto, was located at the latitudes of Sputnik Plain, and the insolation of icy nitrogen—irradiation by sunlight—was almost maximum.
According to the simulation results, icy nitrogen was “captured” by Sputnik Planitia when thermal inertia, albedo and emissivity reached their highest values. During the cold part of the Plutonian year, due to the decrease in thermal inertia, the temperature on the planet's surface dropped to the point of nitrogen condensation, so ice accumulated there. Scientists have concluded that the lower the level of thermal inertia, albedo and emissivity of ice, the more mobile the ice becomes. This leads to longer and more widespread seasonal frosts.
It also turned out that frozen nitrogen does not form a permanent ice “belt.” The fact is that depressions on the plain contribute to a higher surface pressure, and thus influence a higher condensation temperature, as a result of which ice accumulates in them. This phenomenon can also be observed on Mars, where frozen carbon dioxide usually forms in lowlands, such as the Hellas Planitia. On this plain, a fairly deep lowland, there are also different forms of relief, and the thickness of the atmosphere above it is significantly greater than above the neighboring areas.
The atmospheric pressure at its lowest point is 1240 Pa or 12.4 millibars, which is twice as high as the average on the surface of the planet. In winter on Mars, this plain is covered with an ice crust and is visible from Earth as a large bright spot. It is believed that since the pressure at the bottom of the Hellas Plain is higher than the pressure corresponding to the triple point of water (certain values of temperature and pressure at which water exists in three forms: solid, liquid and gaseous), the existence of liquid water is possible there.
According to the modeling results, after 2015 the average pressure decreased as insolation on the plain decreased. This happened because first the subsolar point (the point on a body belonging to the solar system from which observers would see the Sun at its zenith) was at higher latitudes, and later because Pluto moved further from the Sun. Under such conditions, as well as moderate and high levels of thermal inertia, carbon monoxide accumulates along with icy nitrogen precisely on the Sputnik plain, which also agrees with the data of the New Horizons apparatus.
As for methane, unlike nitrogen, it is less volatile. After 50 thousand years, a seasonal ice crust of methane is formed, which is obtained from atmospheric methane as a result of the interaction of compression and evaporation processes. According to the model, this crust forms in both hemispheres of the planet in autumn, winter and spring, but is absent in the equator region, where ice never exists. On the Sputnik Plain, methane settles slowly and evaporates with difficulty.
According to experts, frozen methane may actually be thawing, for example when the perihelion or inclination of Pluto's orbit changes. The scientists hypothesize that persistent methane deposits form locally due to processes that were not included in the study model, such as reduced insolation on local slopes or adiabatic cooling that causes methane precipitation in the mountains.
It turned out that the relief also influences the formation of the glacier: deep depressions intensify the formation of ice. At the same time, the seasonal ice crust is determined by the climate cycles of the planet. According to the results, over the next ten years, most of it in the middle and high latitudes of the planet will disappear. As the authors of the study note, the decrease in pressure and amount of methane in the atmosphere they predicted in the future can be tracked using telescopes.
According to NASA representatives, Pluto has a subsurface ocean.which, firstly, may indicate that other dwarf planets are capable of hiding liquid oceans, and secondly, makes us think about the possibility of life existing in this oceanic environment.
According to William MacKinnon, a professor of planetary sciences at Washington University in St. Louis and co-author on two of the four new studies on Pluto, the heart-shaped region of Pluto's surface hides an ocean of ammonia. This suggests that the existence of any forms of life in this environment is hardly possible.
It is the presence of this caustic, colorless liquid that he believes helps explain not only Pluto's orientation in space, but also the persistence of a massive, icy ocean cap that other researchers call "wet" but MacKinnon prefers to define as "thick."
Using computer models, along with topographic and compositional data obtained from the New Horizons spacecraft's July 2015 flyby of Pluto, MacKinnon made a comprehensive analysis of the ocean beneath the surface of Sputnik Planitia's region. This allowed him to write an incredibly interesting article about the gravity and orientation of Pluto and the primary role of the subglacial ocean in this. The analysis showed that the subsurface ocean is about 1000 km wide and more than 80 km deep. The research was published in the journal Nature.
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Under the “heart” of Pluto (Tombaugh Regio is a huge icy region of a characteristic shape) hides a viscous liquid ocean, reports the American space agency NASA, citing data from the New Horizons spacecraft. Data about this were published in an article in the journal Nature.
Scientists believe the presence of a subsurface ocean may solve a long-standing mystery: why for many decades the Tombaugh Regio, that bright region of Pluto, has been locked in a position almost directly opposite the dwarf planet's largest moon, Charon.
According to researchers, the deep ocean may serve as a kind of “gravitational anomaly”, which is the tether connecting Pluto to its satellite. Over millions of years, the planet rotated to align its subsurface ocean and the heart-shaped region above it almost exactly opposite the line connecting Pluto and Charon.
"Pluto has proven difficult to study," said co-investigator Richard Binzel, professor of terrestrial, atmospheric and planetary sciences at the Massachusetts Institute of Technology. “Previously, there were only assumptions that a near-surface layer of water could be found somewhere on Pluto. We were able to confirm this information through a flyby of Pluto and data analysis, thanks to which we received convincing arguments in favor of the existence of a subsurface ocean. Pluto continues to surprise us."
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Scientists have long wondered about the origin of the large heart-shaped frozen plain that was discovered on Pluto in 2015 by the New Horizons spacecraft. Two researchers from the laboratory of metrology (CNRS/Ecole Polytechnique/UPMC/ENS) in Paris were able to come closer than ever to solving this phenomenon.
A new model by scientists has shown that the peculiar insolation of Pluto’s atmosphere creates nitrogen condensations near the equator, in the lower regions of the atmosphere. In addition, the model explains why there is an abundance of other types of volatiles observed on Pluto on the surface and in the atmosphere. The results of the study were published in the journal Nature on September 19, 2016.
Pluto is a glaciologist's paradise. Of the types of ice that cover its surface, nitrogen is the most unstable: when it sublimes (at -235°C), it forms a thin atmosphere in equilibrium with a reservoir of ice on the surface. One of the most surprising observations from New Horizons, which flew past Pluto in July 2015, was that this reservoir of solid nitrogen turned out to be extremely massive, most of it concentrated on the so-called Sputnik Plateau. Methane can also be observed throughout the northern hemisphere of the dwarf planet, with the exception of the equator, but carbon monoxide ices in small quantities were found only within the Sputnik Plateau.
Until now, the issue of the distribution of ice on Pluto remained unclear. To better understand the physical processes occurring on Pluto, researchers have developed a numerical thermal model of the dwarf planet's surface that can simulate the cycles of nitrogen, methane and carbon monoxide over thousands of years. After which, they compared the results with observations made by the New Horizons spacecraft.
The simulations showed that nitrogen ice would inevitably accumulate on the plateau, thereby forming a permanent nitrogen reservoir, as noted by New Horizons. Numerical simulations also describe the carbon monoxide and methane cycles. Because of its volatility similar to nitrogen, carbon monoxide is completely absorbed by nitrogen in this plain, again consistent with New Horizons measurements. As for methane, its low volatility at temperatures prevailing on Pluto allows it to exist in other places, not just on the Sputnik Plateau. The model shows that pure methane ice covers both hemispheres seasonally.
