Astronomy

Diamonds in Neptune?

Diamonds in Neptune?

In this publication from 1981, was shown that Neptune is raining diamonds:

Many of the current models of Uranus and Neptune postulate a three-layer structure, consisting of an inner rocky core, a middle 'ice' layer of fluid, $ m H_2 m O$, $ m{CH}_4$, $ m{NH}_3$ and an outer hydrogen-helium layer of solar composition. The estimated pressures and temperatures of the ice layer range from about 6Mbar and 7,000K at the inner core-ice boundary to $approx$ 0.2 Mbar and 2,200K at the outer ice/hydrogen-helium boundary. I point out here, that shockwave experiments on these liquids, as well as theoretical studies, imply that the $ m H_2 m O$ and $ m{NH}_3$ in the ice layer are almost totally ionized, and the $ m{CH}_4$ has been pyrolysed to carbon, possibly in the metallic or diamond form.

Question: In the decades since this work was published in 1981 have these predictions been addressed further, or even proven or disproven?

If this turns out to be true, would these diamonds have different physical properties than those on Earth because of the different formation mechanism?


People have demonstrated high-pressure diamond formation using laser-driven shocks, much in line with the original idea. The diamond rain idea seems to be doing well (popular science article about it, with references).

However, it is quite likely that the diamonds could have different properties because of formation mechanisms. There are a lot of unusual allotropes of carbon, and local conditions of formation (not to mention impurities) may cause the carbon to turn into these forms rather than the standard diamond lattice.

Simulations show that beyond 1000 GPa diamond has a BC8 structure. However, this is a pressure unlikely to occur inside Neptune's atmosphere: it occurs deep in the mantle, so sinking diamonds may shift crystal form.


There are probably a variety of factors. How fast they form, how fast they sink through the atmosphere. Like rain, there's likely a part in the atmosphere where they form and grow, and a part, deeper in the atmosphere where the temperature gets too high and the diamonds dissolve again into plasma, perhaps releasing some free/charged carbon to return upwards and be part of the cycle all over again.

If I was to guess, I would guess that the diamonds formed in gas giant atmospheres would be much more impure. The interior of the Earth is relatively slow moving and consistent in temperature, often cooling very slowly. It's the same process which helps form veins of metals form, which are followed in mining. This very gradual cooling in Earth's core probably plays a role in the purity of diamonds. Earth's core also has very little nitrogen, Diamonds formed in Earth are about 99.95% carbon atoms on average, with nitrogen, often the primary impurity.

https://www.gia.edu/diamond-description

http://www.dianerdiamonds.com/diamond_info/nitrogen_in_diamonds

The relative abundance of nitrogen available in gas giant planets suggests to me that on average, gas giant diamonds would be more impure. Less consistency in temperature during formation and an availability of nitrogen suggests to me that 99.95% pure carbon diamonds are unlikely. There's also the problem of how large they'd be. If diamonds form slowly, which seems likely and as they grow larger, they would have a density problem, likely slowly falling deeper into the gas giant's atmosphere, where they would get too hot and likely become plasma and dissipate.

If I was to guess, I'd guess that the diamonds that form inside the 4 gas giant planets in our solar-system are more along the grain of sand to perhaps raindrop size and probably quite impure. But I'm mostly guessing. There might be a planet out there somewhere, (perhaps a mini Neptune) with just the right mix of lower gravity and possible suspension and temperature where it forms grapefruit or basketball sized diamonds of high purity. It's certainly possible, but my guess is that diamonds inside our solar-systems 4 gas giants would be pretty uninteresting, though the chemical and gas-giant geological processes that form them would still be interesting, but I don't think the diamonds would stand out as gem quality or worth harvesting.


Diamonds in Neptune? - Astronomy




Oceans of diamond possible on Uranus and Neptune
DR EMILY BALDWIN
ASTRONOMY NOW
Posted: 21 January 2010

High pressure experiments that mimic conditions on the icy gas giants show that chunks of diamond can float on a sea of liquid carbon.

The research provides the first detailed measurements of the melting point of diamond, the hardest natural material known, and the finding that could also help explain the strange orientation of Uranus and Neptune's magnetic fields.

Uranus (left) and Neptune (right), as seen by the Voyager 2 spacecraft. Image: NASA/JPL.

The existence of pure carbon in the interiors of these giant planets has gained both experimental and theoretical support in recent years, and understanding the high pressure and temperature behaviour of carbon is essential to predicting their evolution and structure. Current theories speculate that Neptune and Uranus have solid cores surrounded by an icy mantle of water, ammonia and methane ices.

In the new experiment, led by Jon Eggert of the Lawrence Livermore National Laboratory, scientists blasted diamonds just two millimetres in diameter and 0.5 millimetres thick with a powerful laser – the Omega laser at the University of Rochester, New York – to reach temperatures and pressures of 110,000 Kelvin and 4,000 giga Pascals respectively. The pressure, which is equivalent to 40 mega bars, is 40 million times greater than what a person feels when standing at sea level on the Earth.

As the scientists watched the pressure decay they saw that the temperature increased. "This implied a large energy sink which we interpret to be melting of diamond," Eggert tells Astronomy Now.  "What is really neat is that we could measure the temperature and pressure of the diamond-melt mixture over a large pressure range from about 6 to 11 million atmospheres." Over this pressure range the diamond showed behaviour much like water in the sense that the solid component was less dense than the liquid – the scientists saw tiny chunks of diamond floating in a sea of liquid carbon, just as ice floats on water.

Time-integrated photograph of an OMEGA laser shot to measure high-pressure diamond melt. The diamond target is at centre right, bright white light is ablated plasma, and radial yellow lines are tracks of hot target fragments very late in time. Image: Eugene Kowaluk, LLE.

While providing new understanding of the behaviour of diamond at high pressures, the results can also be applied to the conditions that prevail inside ice giants Neptune and Uranus. Could we expect great seas of diamonds in the outer reaches of our Solar System? "This is a very speculative scenario," says Eggert. "I think it could be more like a liquid carbon core surrounded by floating diamond or possibly 'diamond-bergs'. Whether the diamond would break up into chunks or bergs is pure speculation at this point. It should also be remembered that there would be a whole planet of hydrogen and helium on top of this carbon ocean, but if there was diamond it would be the first solid found in these planets." 

A swirling internal ocean of diamond could explain the long-standing mystery as to why the ice giants' magnetic poles are offset from the geographic poles by up to 60 degrees. Planetary magnetic fields are generated by complex fluid motions in electrically conducting regions of the planet and the diamond could deflect or tilt the field to match the observed orientation of these planets' magnetic fields.

However, there are still many pieces to fill in before fully understanding the internal structure of these outer Solar System planets and what is driving their magnetic fields. "It is very likely that at the temperatures and pressures near the centre of Neptune/Uranus the molecules are unstable and break up, so that the water, ammonia, methane mixtures in the upper planet dissociate into hydrogen, carbon, nitrogen, oxygen and helium at depth," says Eggert. "These elements may then mix or separate. This has had little or no experimental testing because it is only very recently that we could obtain these pressures and temperatures in the laboratory to do these experiments, but these types of mixtures are definitely on our list of experiments to do in the future!"


Knowing How Neptune Rains With Diamonds

The researchers conducted a new experiment using the SLAC National Accelerator Laboratory's Linac Coherent Light Source (LCLS) X-ray laser. This is to get the most precise measurement yet of how Neptune came to have a diamond rain and find out carbon transitions directly into a crystalline diamond.

Plasma physicist Mike Dunne, the director of the LCLS, who is not part of the paper, explained that this new experiment provides information on a phenomenon that is very difficult to model computationally, which is the miscibility of the two elements.

Neptune and Uranus are the most poorly understood planets in the Solar System since they are located very far with only a single space probe, Voyager 2, has even been close to them.

But according to NASA, ice giants are fairly common in the Milky Way, with Neptune-like exoplanets are ten times more widespread than Jupiter-like exoplanets.

Calculations and experiments done decades ago to understand what happens in the atmospheres of Uranus and Neptune have shown that sufficient pressure and temperature, methane can be broken down into diamonds.

Physicist Dominik Kraus at the Helmholtz-Zentrum Dresden-Rossendorf in Germany led an experiment before which used X-ray diffraction to demonstrate this process. Presently, he and his team are taking it a step further, hopeful that their new approach based on X-ray scattering will become more relevant the more exoplanets are discovered.

It is difficult to replicate the atmospheric conditions of the giant planets here on Earth because it will need intense equipment. Through LCLS and a material that replicates the things inside the giant planet-which they used the hydrocarbon polystyrene (C8H8) in place of methane (CH4) - the researchers were able to create a model that somehow replicates the giant planets.


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Many of these impact-spawned diamonds bear the cubic structure of ordinary, Earth-grown diamonds. But analysts studying the Canyon Diablo diamonds found that up to a third of them bore a hexagonal atomic structure never before seen in diamond. Mineralogists named the new hexagonal variant of diamond lonsdaleite after the British mineralogist Dame Kathleen Lonsdale, who helped advance the study of natural diamond crystals.

Origins unclear

Today, more than 30 years after the discovery of the Canyon Diablo diamonds, scientists still debate how such mini-diamonds form. Some suspect they were wrought in the vacuum of space by vapor deposition, a process that specialists can use to make synthetic diamond here on Earth. Others maintain that, within the hurtling meteorite itself, carbon atoms (or, in a minority opinion, grains of meteoritic black graphite) transformed instantly into diamond during the extraordinary heat and shock of impact.

Whatever the origin of meteorite diamonds, some scientists believe they have found evidence that the colossal cloud of dust thought to be thrown up into the atmosphere in the wake of such impacts may spread newly formed diamond dust all around the world. In 1991, Canadian geologists David B. Carlisle and Dennis R. Braman reported finding Lilliputian diamonds embedded in a layer of sediment 65 million years old—right at the time when many scientists believe a giant meteor slammed into Earth and precipitated the extinction of the dinosaurs.

Can these miniature diamonds, which are so fine-grained that the researchers deem them the result of a collision, serve as an indicator of this ancient catastrophe, much as the famous iridium layer has done? Scientists won't be able to say without further study, but the idea holds promise. (In the 1998 book The Nature of Diamonds, the geologist George Harlow and two Russian colleagues wrote simply, "This subject is very new, and many exciting discoveries have yet to be announced.")

For scientists, the allure of carbonados, otherwise known as black diamonds, lies not in their look but in their age and origin.

Black diamonds

Outer space may also be the birthplace of the mysterious black diamonds known as carbonados. From the Portuguese word for burned or carbonized, carbonados were first found in Brazil in the 1800s and have since turned up elsewhere, most notably in central Africa. Unlike the clear diamonds of engagement rings, which are single crystals, black diamond consists of aggregations of individual crystals, which lend the gem its dark color. The largest diamond ever found was a carbonado from Brazil. Named Sergio, the stone weighed 3,167 carats. (One carat equals one-fifth of a gram.)

The origins of carbonados have long baffled scientists. Black diamonds don't adhere to the rules of diamond mineralogy, and they don't occur in the usual places where clear diamonds turn up. Even so, scientists initially believed they must have been fashioned in the same conditions under which clear diamonds are thought to form. That is, they were crafted deep within the Earth, 100 to 300 miles down, when intense heat and pressure transformed carbon into diamonds, which volcanic eruptions then lofted to the surface.

But that theory suffered a blow when scientists examined the carbon isotopes of black diamonds. (Isotopes are species of a chemical element that reside in the same place on the periodic table but have different atomic weights and physical properties.) Unlike clear diamonds, black diamonds feature ratios of the two most common carbon isotopes in the Earth's crust, carbon-12 and carbon-13. These isotopes characterize surface carbons rather than those found in the Earth's depths.

Did carbonados form in the unimaginably explosive shock waves emitted by dying stars, such as the one whose death throes created the Eskimo nebula (seen here)?

Wherefrom?

This finding helped lead to a new theory of carbonado formation. In 1985, Joseph Smith of the University of Chicago and J. Barry Dawson of the University of Sheffield in England suggested in an article published in the journal Geology that large meteor impacts in the Precambrian Era (570 million years ago back to Earth's beginning some 4.5 billion years ago) formed the black diamonds we find today. Scientists had long deemed carbonados quite old, because the streams where they are typically uncovered cut through geologic strata dated from one to more than two billion years old. In fact, recent atomic measurements of black diamonds have placed their origins at nearly four billion years ago, a time when a constant barrage of giant meteors battered the Earth.

In the 1990s, other scientists showed that Brazilian and African carbonados bear similar isotopes of carbon and nitrogen, suggesting a common origin, while still others provided theoretical and physical evidence that black diamonds could have arisen during the extreme shock and heat of a meteor impact. But why, some scientists wondered, had no unambiguous evidence ever been shown for craters associated with carbonados?

Geologist Stephen Haggerty of the University of Massachusetts at Amherst had an idea why, and he shared it with a dumbfounded audience at a 1996 American Geophysical Union meeting in Baltimore. Carbonados were born not on Earth, either the way regular diamonds are or by meteor impact, he said. Rather, they originated in dying stars, when shock waves from exploding red giants crushed carbon into dense aggregations of black diamond and sent them hurtling into deep space. Eons later, the sun's gravity lured some of this material into our solar system, where blocks of it slammed into our atmosphere, shattering into the fragments we find strewn over select areas today, perhaps billions of years after they formed.

Neptune, seen here in a composite image from the Voyager 2 mission, may be a veritable diamond factory.

Lucid in the sky with diamonds

Even nearby planets may be churning out diamonds. In fact, planetary scientists say that Uranus and Neptune, the seventh and eighth planets from the sun, may rain diamonds, which then pile up miles-thick at the planets' cores.

Uranus and Neptune are each nearly four times the size of Earth. Scientists believe that, beneath an outer layer of hydrogen and helium, the gaseous atmospheres of both planets contain 10 to 15 percent methane, a hydrocarbon. Deep within the extremely dense atmospheres, above a rocky core, these planets are also thought to bear temperatures ranging from 3,000 to 12,000°F and pressures varying from 200,000 to 6,000,000 times the pressure of our own atmosphere.

In other words, possibly ideal conditions for producing diamonds.

With this in mind, a team at Lawrence Livermore National Laboratory tested in the early 1980s what would happen to methane under intense pressure. One of the team's leaders, Marvin Ross, had calculated that the gas would separate into hydrogen and carbon at temperatures above 3,000°F and pressures exceeding 200,000 Earth atmospheres. The carbon atoms would be squeezed so tightly together that they would become diamonds, he theorized.

To find out if he was right, Ross and his team used a gas cannon to severely compress and shock methane samples. Resulting data, they later reported, indicated the fleeting formation of diamonds in the instant before the target material evaporated, and recent experiments at several labs support the predictions.

For the foreseeable future, the greatest benefit we'll see from diamonds in the sky will be increased scientific knowledge.

Reaping the benefits

As for tapping the riches of any diamonds from space, don't hold your breath. Earth-hitting meteorites that either bear or engender diamonds are few and far between, and unlike diamonds you're likely used to, their associated diamonds often cannot be seen, much less admired, with the naked eye. Black diamonds, for their part, are rare and are primarily used for industrial purposes. And the challenges of harvesting any diamonds on Uranus and Neptune, which are roughly 1,700 and 2,720 million miles away from Earth, respectively, are as clear as the Koh-i-Noor diamond. Alas, scientific understanding is the primary beneficiary of diamonds from the heavens.


Contents

Discovery

Some of the earliest recorded observations ever made through a telescope, Galileo's drawings on 28 December 1612 and 27 January 1613 contain plotted points that match up with what is now known to be the position of Neptune. On both occasions, Galileo seems to have mistaken Neptune for a fixed star when it appeared close—in conjunction—to Jupiter in the night sky. [27] Hence, he is not credited with Neptune's discovery. At his first observation in December 1612, Neptune was almost stationary in the sky because it had just turned retrograde that day. This apparent backward motion is created when Earth's orbit takes it past an outer planet. Because Neptune was only beginning its yearly retrograde cycle, the motion of the planet was far too slight to be detected with Galileo's small telescope. [28] In 2009, a study suggested that Galileo was at least aware that the "star" he had observed had moved relative to the fixed stars. [29]

In 1821, Alexis Bouvard published astronomical tables of the orbit of Neptune's neighbour Uranus. [30] Subsequent observations revealed substantial deviations from the tables, leading Bouvard to hypothesise that an unknown body was perturbing the orbit through gravitational interaction. [31] In 1843, John Couch Adams began work on the orbit of Uranus using the data he had. He requested extra data from Sir George Airy, the Astronomer Royal, who supplied it in February 1844. Adams continued to work in 1845–46 and produced several different estimates of a new planet. [32] [33]

In 1845–46, Urbain Le Verrier, independently of Adams, developed his own calculations but aroused no enthusiasm in his compatriots. In June 1846, upon seeing Le Verrier's first published estimate of the planet's longitude and its similarity to Adams's estimate, Airy persuaded James Challis to search for the planet. Challis vainly scoured the sky throughout August and September. [31] [34]

Meanwhile, Le Verrier sent a letter and urged Berlin Observatory astronomer Johann Gottfried Galle to search with the observatory's refractor. Heinrich d'Arrest, a student at the observatory, suggested to Galle that they could compare a recently drawn chart of the sky in the region of Le Verrier's predicted location with the current sky to seek the displacement characteristic of a planet, as opposed to a fixed star. On the evening of 23 September 1846, the day Galle received the letter, he discovered Neptune just northeast of Iota Aquarii, 1° from the "five degrees east of Delta Capricorn" position Le Verrier had predicted it to be, [35] [36] about 12° from Adams's prediction, and on the border of Aquarius and Capricornus according to the modern IAU constellation boundaries. Challis later realised that he had observed the planet twice, on 4 and 12 August, but did not recognise it as a planet because he lacked an up-to-date star map and was distracted by his concurrent work on comet observations. [31] [37]

In the wake of the discovery, there was a heated nationalistic rivalry between the French and the British over who deserved credit for the discovery. Eventually, an international consensus emerged that Le Verrier and Adams deserved joint credit. Since 1966, Dennis Rawlins has questioned the credibility of Adams's claim to co-discovery, and the issue was re-evaluated by historians with the return in 1998 of the "Neptune papers" (historical documents) to the Royal Observatory, Greenwich. [38] [39]

Naming

Shortly after its discovery, Neptune was referred to simply as "the planet exterior to Uranus" or as "Le Verrier's planet". The first suggestion for a name came from Galle, who proposed the name Janus. In England, Challis put forward the name Oceanus. [40]

Claiming the right to name his discovery, Le Verrier quickly proposed the name Neptune for this new planet, though falsely stating that this had been officially approved by the French Bureau des Longitudes. [41] In October, he sought to name the planet Le Verrier, after himself, and he had loyal support in this from the observatory director, François Arago. This suggestion met with stiff resistance outside France. [42] French almanacs quickly reintroduced the name Herschel for Uranus, after that planet's discoverer Sir William Herschel, and Leverrier for the new planet. [43]

Struve came out in favour of the name Neptune on 29 December 1846, to the Saint Petersburg Academy of Sciences. [44] Soon, Neptune became the internationally accepted name. In Roman mythology, Neptune was the god of the sea, identified with the Greek Poseidon. The demand for a mythological name seemed to be in keeping with the nomenclature of the other planets, all of which, except for Earth, were named for deities in Greek and Roman mythology. [45]

Most languages today use some variant of the name "Neptune" for the planet indeed, in Chinese, Vietnamese, Japanese, and Korean, the planet's name was translated as "sea king star" ( 海王星 ). [46] [47] In Mongolian, Neptune is called Dalain van ( Далайн ван ), reflecting its namesake god's role as the ruler of the sea. In modern Greek the planet is called Poseidon ( Ποσειδώνας , Poseidonas), the Greek counterpart of Neptune. [48] In Hebrew, Rahab ( רהב ), from a Biblical sea monster mentioned in the Book of Psalms, was selected in a vote managed by the Academy of the Hebrew Language in 2009 as the official name for the planet, even though the existing Latin term Neptun ( נפטון ) is commonly used. [49] [50] In Māori, the planet is called Tangaroa, named after the Māori god of the sea. [51] In Nahuatl, the planet is called Tlāloccītlalli, named after the rain god Tlāloc. [51] In Thai, Neptune is referred both by its Westernised name Dao Nepjun ( ดาวเนปจูน ), and is also named Dao Ketu ( ดาวเกตุ , lit. 'star of Ketu'), after Ketu ( केतु ), the descending lunar node, who plays a role in Hindu astrology. In Malay, the name Waruna, after the Hindu god of seas, was attested as far as the 1970s [52] until it was eventually superseded by the Latinate equivalent either as Neptun (in Malaysian [53] ) or Neptunus (in Indonesian [54] ).

The usual adjectival form is Neptunian. The nonce form Poseidean ( / p ə ˈ s aɪ d i ən / ), from Poseidon, has also been used, [4] though the usual adjectival form of Poseidon is Poseidonian ( / p oʊ s aɪ ˈ d oʊ n i ən / ). [55]

Status

From its discovery in 1846 until the discovery of Pluto in 1930, Neptune was the farthest-known planet. When Pluto was discovered, it was considered a planet, and Neptune thus became the second-farthest-known planet, except for a 20-year period between 1979 and 1999 when Pluto's elliptical orbit brought it closer than Neptune to the Sun. [56] The discovery of the Kuiper belt in 1992 led many astronomers to debate whether Pluto should be considered a planet or as part of the Kuiper belt. [57] [58] In 2006, the International Astronomical Union defined the word "planet" for the first time, reclassifying Pluto as a "dwarf planet" and making Neptune once again the outermost-known planet in the Solar System. [59]

Neptune's mass of 1.0243 × 10 26 kg [6] is intermediate between Earth and the larger gas giants: it is 17 times that of Earth but just 1/19th that of Jupiter. [d] Its gravity at 1 bar is 11.15 m/s 2 , 1.14 times the surface gravity of Earth, [60] and surpassed only by Jupiter. [61] Neptune's equatorial radius of 24,764 km [10] is nearly four times that of Earth. Neptune, like Uranus, is an ice giant, a subclass of giant planet, because they are smaller and have higher concentrations of volatiles than Jupiter and Saturn. [62] In the search for extrasolar planets, Neptune has been used as a metonym: discovered bodies of similar mass are often referred to as "Neptunes", [63] just as scientists refer to various extrasolar bodies as "Jupiters".

Internal structure

Neptune's internal structure resembles that of Uranus. Its atmosphere forms about 5% to 10% of its mass and extends perhaps 10% to 20% of the way towards the core, where it reaches pressures of about 10 GPa, or about 100,000 times that of Earth's atmosphere. Increasing concentrations of methane, ammonia and water are found in the lower regions of the atmosphere. [24]

  1. Upper atmosphere, top clouds
  2. Atmosphere consisting of hydrogen, helium and methane gas
  3. Mantle consisting of water, ammonia and methane ices
  4. Core consisting of rock (silicates and nickel–iron)

The mantle is equivalent to 10 to 15 Earth masses and is rich in water, ammonia and methane. [1] As is customary in planetary science, this mixture is referred to as icy even though it is a hot, dense fluid. This fluid, which has a high electrical conductivity, is sometimes called a water–ammonia ocean. [64] The mantle may consist of a layer of ionic water in which the water molecules break down into a soup of hydrogen and oxygen ions, and deeper down superionic water in which the oxygen crystallises but the hydrogen ions float around freely within the oxygen lattice. [65] At a depth of 7,000 km, the conditions may be such that methane decomposes into diamond crystals that rain downwards like hailstones. [66] [67] [68] Scientists also believe that this kind of diamond rain occurs on Jupiter, Saturn, and Uranus. [69] [67] Very-high-pressure experiments at the Lawrence Livermore National Laboratory suggest that the top of the mantle may be an ocean of liquid carbon with floating solid 'diamonds'. [70] [71] [72]

The core of Neptune is likely composed of iron, nickel and silicates, with an interior model giving a mass about 1.2 times that of Earth. [73] The pressure at the centre is 7 Mbar (700 GPa), about twice as high as that at the centre of Earth, and the temperature may be 5,400 K. [24] [25]

Atmosphere

At high altitudes, Neptune's atmosphere is 80% hydrogen and 19% helium. [24] A trace amount of methane is also present. Prominent absorption bands of methane exist at wavelengths above 600 nm, in the red and infrared portion of the spectrum. As with Uranus, this absorption of red light by the atmospheric methane is part of what gives Neptune its blue hue, [74] although Neptune's vivid azure differs from Uranus's milder cyan. Because Neptune's atmospheric methane content is similar to that of Uranus, some unknown atmospheric constituent is thought to contribute to Neptune's colour. [21]

Neptune's atmosphere is subdivided into two main regions: the lower troposphere, where temperature decreases with altitude, and the stratosphere, where temperature increases with altitude. The boundary between the two, the tropopause, lies at a pressure of 0.1 bars (10 kPa). [20] The stratosphere then gives way to the thermosphere at a pressure lower than 10 −5 to 10 −4 bars (1 to 10 Pa). [20] The thermosphere gradually transitions to the exosphere.

Models suggest that Neptune's troposphere is banded by clouds of varying compositions depending on altitude. The upper-level clouds lie at pressures below one bar, where the temperature is suitable for methane to condense. For pressures between one and five bars (100 and 500 kPa), clouds of ammonia and hydrogen sulfide are thought to form. Above a pressure of five bars, the clouds may consist of ammonia, ammonium sulfide, hydrogen sulfide and water. Deeper clouds of water ice should be found at pressures of about 50 bars (5.0 MPa), where the temperature reaches 273 K (0 °C). Underneath, clouds of ammonia and hydrogen sulfide may be found. [75]

High-altitude clouds on Neptune have been observed casting shadows on the opaque cloud deck below. There are also high-altitude cloud bands that wrap around the planet at constant latitude. These circumferential bands have widths of 50–150 km and lie about 50–110 km above the cloud deck. [76] These altitudes are in the layer where weather occurs, the troposphere. Weather does not occur in the higher stratosphere or thermosphere.

Neptune's spectra suggest that its lower stratosphere is hazy due to condensation of products of ultraviolet photolysis of methane, such as ethane and ethyne. [20] [24] The stratosphere is also home to trace amounts of carbon monoxide and hydrogen cyanide. [20] [77] The stratosphere of Neptune is warmer than that of Uranus due to the elevated concentration of hydrocarbons. [20]

For reasons that remain obscure, the planet's thermosphere is at an anomalously high temperature of about 750 K. [78] [79] The planet is too far from the Sun for this heat to be generated by ultraviolet radiation. One candidate for a heating mechanism is atmospheric interaction with ions in the planet's magnetic field. Other candidates are gravity waves from the interior that dissipate in the atmosphere. The thermosphere contains traces of carbon dioxide and water, which may have been deposited from external sources such as meteorites and dust. [75] [77]

Magnetosphere

Neptune resembles Uranus in its magnetosphere, with a magnetic field strongly tilted relative to its rotational axis at 47° and offset at least 0.55 radii, or about 13,500 km from the planet's physical centre. Before Voyager 2 's arrival at Neptune, it was hypothesised that Uranus's tilted magnetosphere was the result of its sideways rotation. In comparing the magnetic fields of the two planets, scientists now think the extreme orientation may be characteristic of flows in the planets' interiors. This field may be generated by convective fluid motions in a thin spherical shell of electrically conducting liquids (probably a combination of ammonia, methane and water) [75] resulting in a dynamo action. [80]

The dipole component of the magnetic field at the magnetic equator of Neptune is about 14 microteslas (0.14 G). [81] The dipole magnetic moment of Neptune is about 2.2 × 10 17 T·m 3 (14 μT·RN 3 , where RN is the radius of Neptune). Neptune's magnetic field has a complex geometry that includes relatively large contributions from non-dipolar components, including a strong quadrupole moment that may exceed the dipole moment in strength. By contrast, Earth, Jupiter and Saturn have only relatively small quadrupole moments, and their fields are less tilted from the polar axis. The large quadrupole moment of Neptune may be the result of offset from the planet's centre and geometrical constraints of the field's dynamo generator. [82] [83]

Neptune's bow shock, where the magnetosphere begins to slow the solar wind, occurs at a distance of 34.9 times the radius of the planet. The magnetopause, where the pressure of the magnetosphere counterbalances the solar wind, lies at a distance of 23–26.5 times the radius of Neptune. The tail of the magnetosphere extends out to at least 72 times the radius of Neptune, and likely much farther. [82]

Neptune's weather is characterised by extremely dynamic storm systems, with winds reaching speeds of almost 600 m/s (2,200 km/h 1,300 mph)—nearly reaching supersonic flow. [23] More typically, by tracking the motion of persistent clouds, wind speeds have been shown to vary from 20 m/s in the easterly direction to 325 m/s westward. [85] At the cloud tops, the prevailing winds range in speed from 400 m/s along the equator to 250 m/s at the poles. [75] Most of the winds on Neptune move in a direction opposite the planet's rotation. [86] The general pattern of winds showed prograde rotation at high latitudes vs. retrograde rotation at lower latitudes. The difference in flow direction is thought to be a "skin effect" and not due to any deeper atmospheric processes. [20] At 70° S latitude, a high-speed jet travels at a speed of 300 m/s. [20]

Neptune differs from Uranus in its typical level of meteorological activity. Voyager 2 observed weather phenomena on Neptune during its 1989 flyby, [87] but no comparable phenomena on Uranus during its 1986 fly-by.

The abundance of methane, ethane and acetylene at Neptune's equator is 10–100 times greater than at the poles. This is interpreted as evidence for upwelling at the equator and subsidence near the poles because photochemistry cannot account for the distribution without meridional circulation. [20]

In 2007, it was discovered that the upper troposphere of Neptune's south pole was about 10 K warmer than the rest of its atmosphere, which averages approximately 73 K (−200 °C). The temperature differential is enough to let methane, which elsewhere is frozen in the troposphere, escape into the stratosphere near the pole. [88] The relative "hot spot" is due to Neptune's axial tilt, which has exposed the south pole to the Sun for the last quarter of Neptune's year, or roughly 40 Earth years. As Neptune slowly moves towards the opposite side of the Sun, the south pole will be darkened and the north pole illuminated, causing the methane release to shift to the north pole. [89]

Because of seasonal changes, the cloud bands in the southern hemisphere of Neptune have been observed to increase in size and albedo. This trend was first seen in 1980 and is expected to last until about 2020. The long orbital period of Neptune results in seasons lasting forty years. [90]

Storms

In 1989, the Great Dark Spot, an anticyclonic storm system spanning 13,000 km × 6,600 km (8,100 mi × 4,100 mi) [87] was discovered by NASA's Voyager 2 spacecraft. The storm resembled the Great Red Spot of Jupiter. Some five years later, on 2 November 1994, the Hubble Space Telescope did not see the Great Dark Spot on the planet. Instead, a new storm similar to the Great Dark Spot was found in Neptune's northern hemisphere. [91]

The Scooter is another storm, a white cloud group farther south than the Great Dark Spot. This nickname first arose during the months leading up to the Voyager 2 encounter in 1989, when they were observed moving at speeds faster than the Great Dark Spot (and images acquired later would subsequently reveal the presence of clouds moving even faster than those that had initially been detected by Voyager 2). [86] The Small Dark Spot is a southern cyclonic storm, the second-most-intense storm observed during the 1989 encounter. It was initially completely dark, but as Voyager 2 approached the planet, a bright core developed and can be seen in most of the highest-resolution images. [92] More recently, in 2018, a newer main dark spot and smaller dark spot were identified and studied. [22]

Neptune's dark spots are thought to occur in the troposphere at lower altitudes than the brighter cloud features, [93] so they appear as holes in the upper cloud decks. As they are stable features that can persist for several months, they are thought to be vortex structures. [76] Often associated with dark spots are brighter, persistent methane clouds that form around the tropopause layer. [94] The persistence of companion clouds shows that some former dark spots may continue to exist as cyclones even though they are no longer visible as a dark feature. Dark spots may dissipate when they migrate too close to the equator or possibly through some other unknown mechanism. [95]

The appearance of a Northern Great Dark Spot in 2018 is evidence of a huge storm brewing [96]

The Northern Great Dark Spot and a smaller companion storm imaged by Hubble in 2020 [97]

The Great Dark Spot, as imaged by Voyager 2

Neptune's shrinking vortex [98]

Internal heating

Neptune's more varied weather when compared to Uranus is due in part to its higher internal heating. The upper regions of Neptune's troposphere reach a low temperature of 51.8 K (−221.3 °C). At a depth where the atmospheric pressure equals 1 bar (100 kPa), the temperature is 72.00 K (−201.15 °C). [100] Deeper inside the layers of gas, the temperature rises steadily. As with Uranus, the source of this heating is unknown, but the discrepancy is larger: Uranus only radiates 1.1 times as much energy as it receives from the Sun [101] whereas Neptune radiates about 2.61 times as much energy as it receives from the Sun. [102] Neptune is the farthest planet from the Sun, and lies over 50% farther from the Sun than Uranus, and receives only 40% its amount of sunlight, [20] yet its internal energy is sufficient to drive the fastest planetary winds seen in the Solar System. Depending on the thermal properties of its interior, the heat left over from Neptune's formation may be sufficient to explain its current heat flow, though it is more difficult to simultaneously explain Uranus's lack of internal heat while preserving the apparent similarity between the two planets. [103]

The average distance between Neptune and the Sun is 4.5 billion km (about 30.1 astronomical units (AU)), and it completes an orbit on average every 164.79 years, subject to a variability of around ±0.1 years. The perihelion distance is 29.81 AU the aphelion distance is 30.33 AU. [104]

On 11 July 2011, Neptune completed its first full barycentric orbit since its discovery in 1846, [105] [106] although it did not appear at its exact discovery position in the sky, because Earth was in a different location in its 365.26-day orbit. Because of the motion of the Sun in relation to the barycentre of the Solar System, on 11 July Neptune was also not at its exact discovery position in relation to the Sun if the more common heliocentric coordinate system is used, the discovery longitude was reached on 12 July 2011. [11] [107] [108]

The elliptical orbit of Neptune is inclined 1.77° compared to that of Earth.

The axial tilt of Neptune is 28.32°, [109] which is similar to the tilts of Earth (23°) and Mars (25°). As a result, Neptune experiences similar seasonal changes to Earth. The long orbital period of Neptune means that the seasons last for forty Earth years. [90] Its sidereal rotation period (day) is roughly 16.11 hours. [11] Because its axial tilt is comparable to Earth's, the variation in the length of its day over the course of its long year is not any more extreme.

Because Neptune is not a solid body, its atmosphere undergoes differential rotation. The wide equatorial zone rotates with a period of about 18 hours, which is slower than the 16.1-hour rotation of the planet's magnetic field. By contrast, the reverse is true for the polar regions where the rotation period is 12 hours. This differential rotation is the most pronounced of any planet in the Solar System, [110] and it results in strong latitudinal wind shear. [76]

Orbital resonances

Neptune's orbit has a profound impact on the region directly beyond it, known as the Kuiper belt. The Kuiper belt is a ring of small icy worlds, similar to the asteroid belt but far larger, extending from Neptune's orbit at 30 AU out to about 55 AU from the Sun. [111] Much in the same way that Jupiter's gravity dominates the asteroid belt, shaping its structure, so Neptune's gravity dominates the Kuiper belt. Over the age of the Solar System, certain regions of the Kuiper belt became destabilised by Neptune's gravity, creating gaps in the Kuiper belt's structure. The region between 40 and 42 AU is an example. [112]

There do exist orbits within these empty regions where objects can survive for the age of the Solar System. These resonances occur when Neptune's orbital period is a precise fraction of that of the object, such as 1:2, or 3:4. If, say, an object orbits the Sun once for every two Neptune orbits, it will only complete half an orbit by the time Neptune returns to its original position. The most heavily populated resonance in the Kuiper belt, with over 200 known objects, [113] is the 2:3 resonance. Objects in this resonance complete 2 orbits for every 3 of Neptune, and are known as plutinos because the largest of the known Kuiper belt objects, Pluto, is among them. [114] Although Pluto crosses Neptune's orbit regularly, the 2:3 resonance ensures they can never collide. [115] The 3:4, 3:5, 4:7 and 2:5 resonances are less populated. [116]

Neptune has a number of known trojan objects occupying both the Sun–Neptune L4 and L5 Lagrangian points—gravitationally stable regions leading and trailing Neptune in its orbit, respectively. [117] Neptune trojans can be viewed as being in a 1:1 resonance with Neptune. Some Neptune trojans are remarkably stable in their orbits, and are likely to have formed alongside Neptune rather than being captured. The first object identified as associated with Neptune's trailing L5 Lagrangian point was 2008 LC 18 . [118] Neptune also has a temporary quasi-satellite, (309239) 2007 RW 10 . [119] The object has been a quasi-satellite of Neptune for about 12,500 years and it will remain in that dynamical state for another 12,500 years. [119]

The formation of the ice giants, Neptune and Uranus, has proven difficult to model precisely. Current models suggest that the matter density in the outer regions of the Solar System was too low to account for the formation of such large bodies from the traditionally accepted method of core accretion, and various hypotheses have been advanced to explain their formation. One is that the ice giants were not formed by core accretion but from instabilities within the original protoplanetary disc and later had their atmospheres blasted away by radiation from a nearby massive OB star. [62]

An alternative concept is that they formed closer to the Sun, where the matter density was higher, and then subsequently migrated to their current orbits after the removal of the gaseous protoplanetary disc. [120] This hypothesis of migration after formation is favoured, due to its ability to better explain the occupancy of the populations of small objects observed in the trans-Neptunian region. [121] The current most widely accepted [122] [123] [124] explanation of the details of this hypothesis is known as the Nice model, which explores the effect of a migrating Neptune and the other giant planets on the structure of the Kuiper belt.

Neptune has 14 known moons. [6] [125] Triton is the largest Neptunian moon, comprising more than 99.5% of the mass in orbit around Neptune, [e] and it is the only one massive enough to be spheroidal. Triton was discovered by William Lassell just 17 days after the discovery of Neptune itself. Unlike all other large planetary moons in the Solar System, Triton has a retrograde orbit, indicating that it was captured rather than forming in place it was probably once a dwarf planet in the Kuiper belt. [126] It is close enough to Neptune to be locked into a synchronous rotation, and it is slowly spiralling inward because of tidal acceleration. It will eventually be torn apart, in about 3.6 billion years, when it reaches the Roche limit. [127] In 1989, Triton was the coldest object that had yet been measured in the Solar System, [128] with estimated temperatures of 38 K (−235 °C). [129]

Neptune's second-known satellite (by order of discovery), the irregular moon Nereid, has one of the most eccentric orbits of any satellite in the Solar System. The eccentricity of 0.7512 gives it an apoapsis that is seven times its periapsis distance from Neptune. [f]

From July to September 1989, Voyager 2 discovered six moons of Neptune. [130] Of these, the irregularly shaped Proteus is notable for being as large as a body of its density can be without being pulled into a spherical shape by its own gravity. [131] Although the second-most-massive Neptunian moon, it is only 0.25% the mass of Triton. Neptune's innermost four moons—Naiad, Thalassa, Despina and Galatea—orbit close enough to be within Neptune's rings. The next-farthest out, Larissa, was originally discovered in 1981 when it had occulted a star. This occultation had been attributed to ring arcs, but when Voyager 2 observed Neptune in 1989, Larissa was found to have caused it. Five new irregular moons discovered between 2002 and 2003 were announced in 2004. [132] [133] A new moon and the smallest yet, Hippocamp, was found in 2013 by combining multiple Hubble images. [134] Because Neptune was the Roman god of the sea, Neptune's moons have been named after lesser sea gods. [45]

Planetary rings

Neptune has a planetary ring system, though one much less substantial than that of Saturn. The rings may consist of ice particles coated with silicates or carbon-based material, which most likely gives them a reddish hue. [135] The three main rings are the narrow Adams Ring, 63,000 km from the centre of Neptune, the Le Verrier Ring, at 53,000 km, and the broader, fainter Galle Ring, at 42,000 km. A faint outward extension to the Le Verrier Ring has been named Lassell it is bounded at its outer edge by the Arago Ring at 57,000 km. [136]

The first of these planetary rings was detected in 1968 by a team led by Edward Guinan. [26] [137] In the early 1980s, analysis of this data along with newer observations led to the hypothesis that this ring might be incomplete. [138] Evidence that the rings might have gaps first arose during a stellar occultation in 1984 when the rings obscured a star on immersion but not on emersion. [139] Images from Voyager 2 in 1989 settled the issue by showing several faint rings.

The outermost ring, Adams, contains five prominent arcs now named Courage, Liberté, Egalité 1, Egalité 2 and Fraternité (Courage, Liberty, Equality and Fraternity). [140] The existence of arcs was difficult to explain because the laws of motion would predict that arcs would spread out into a uniform ring over short timescales. Astronomers now estimate that the arcs are corralled into their current form by the gravitational effects of Galatea, a moon just inward from the ring. [141] [142]

Earth-based observations announced in 2005 appeared to show that Neptune's rings are much more unstable than previously thought. Images taken from the W. M. Keck Observatory in 2002 and 2003 show considerable decay in the rings when compared to images by Voyager 2. In particular, it seems that the Liberté arc might disappear in as little as one century. [143]

Neptune brightened significantly between 1980 and 2000. [144] The apparent magnitude currently ranges from 7.67 to 7.89 with a mean of 7.78 and a standard deviation of 0.06. [15] Prior to 1980 the planet was as faint as magnitude 8.0. [15] Neptune is too faint to be visible to the naked eye and can be outshone by Jupiter's Galilean moons, the dwarf planet Ceres and the asteroids 4 Vesta, 2 Pallas, 7 Iris, 3 Juno, and 6 Hebe. [145] A telescope or strong binoculars will resolve Neptune as a small blue disk, similar in appearance to Uranus. [146]

Because of the distance of Neptune from Earth, its angular diameter only ranges from 2.2 to 2.4 arcseconds, [6] [16] the smallest of the Solar System planets. Its small apparent size makes it challenging to study visually. Most telescopic data was fairly limited until the advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics (AO). [147] [148] [149] The first scientifically useful observation of Neptune from ground-based telescopes using adaptive optics was commenced in 1997 from Hawaii. [150] Neptune is currently entering its spring and summer season and has been shown to be heating up, with increased atmospheric activity and brightness as a consequence. Combined with technological advancements, ground-based telescopes with adaptive optics are recording increasingly more detailed images of it. Both Hubble and the adaptive-optics telescopes on Earth have made many new discoveries within the Solar System since the mid-1990s, with a large increase in the number of known satellites and moons around the outer planet, among others. In 2004 and 2005, five new small satellites of Neptune with diameters between 38 and 61 kilometres were discovered. [151]

From Earth, Neptune goes through apparent retrograde motion every 367 days, resulting in a looping motion against the background stars during each opposition. These loops carried it close to the 1846 discovery coordinates in April and July 2010 and again in October and November 2011. [108]

Neptune's 164 year orbital period means that the planet takes an average of 13 years to move through each constellation of the zodiac. In 2011, it completed its first full orbit of the Sun since being discovered and returned to where it was first spotted northeast of Iota Aquarii. [35]

Observation of Neptune in the radio-frequency band shows that it is a source of both continuous emission and irregular bursts. Both sources are thought to originate from its rotating magnetic field. [75] In the infrared part of the spectrum, Neptune's storms appear bright against the cooler background, allowing the size and shape of these features to be readily tracked. [152]

Voyager 2 is the only spacecraft that has visited Neptune. The spacecraft 's closest approach to the planet occurred on 25 August 1989. Because this was the last major planet the spacecraft could visit, it was decided to make a close flyby of the moon Triton, regardless of the consequences to the trajectory, similarly to what was done for Voyager 1 ' s encounter with Saturn and its moon Titan. The images relayed back to Earth from Voyager 2 became the basis of a 1989 PBS all-night program, Neptune All Night. [153]

During the encounter, signals from the spacecraft required 246 minutes to reach Earth. Hence, for the most part, Voyager 2 's mission relied on preloaded commands for the Neptune encounter. The spacecraft performed a near-encounter with the moon Nereid before it came within 4,400 km of Neptune's atmosphere on 25 August, then passed close to the planet's largest moon Triton later the same day. [154]

The spacecraft verified the existence of a magnetic field surrounding the planet and discovered that the field was offset from the centre and tilted in a manner similar to the field around Uranus. Neptune's rotation period was determined using measurements of radio emissions and Voyager 2 also showed that Neptune had a surprisingly active weather system. Six new moons were discovered, and the planet was shown to have more than one ring. [130] [154]

The flyby also provided the first accurate measurement of Neptune's mass which was found to be 0.5 percent less than previously calculated. The new figure disproved the hypothesis that an undiscovered Planet X acted upon the orbits of Neptune and Uranus. [155] [156]

After the Voyager 2 flyby mission, the next step in scientific exploration of the Neptunian system, is considered to be a Flagship orbital mission. [157] Such a hypothetical mission is envisioned to be possible in the late 2020s or early 2030s. [157] However, there have been discussions to launch Neptune missions sooner. In 2003, there was a proposal in NASA's "Vision Missions Studies" for a "Neptune Orbiter with Probes" mission that does Cassini-level science. [158] Another, more recent proposal was for Argo, a flyby spacecraft to be launched in 2019, that would visit Jupiter, Saturn, Neptune, and a Kuiper belt object. The focus would be on Neptune and its largest moon Triton to be investigated around 2029. [159] The proposed New Horizons 2 mission (which was later scrapped) might also have done a close flyby of the Neptunian system. Currently a pending proposal for the Discovery program, the Trident would conduct a flyby of Neptune and Triton. [160] Neptune Odyssey is the current mission concept for a Neptune orbiter and atmospheric probe being studied as a possible large strategic science mission by NASA that would launch in 2033 and arrive at Neptune in 2049. [161]


VerifiED: Is It Really Raining Diamonds In Neptune And Uranus?

Have you ever woken up from a very strange dream? A dream involving diamonds pouring from the sky? Falling on your roof on to the ground? But what if I tell you it’s not just a dream. This is real.

Yes, you read it right! It rains diamonds. But not on earth, unfortunately (or fortunately!). The diamond shower is an actual phenomenon in Neptune and Uranus!

Neptune and Uranus are huge “ice giants”. For many years, scientists have tried to research intensively about these planets. Being very distant, they are the most unexplored and inadequately studied major planets in our solar system. Voyager 2 is the only successful space mission that has managed to have approached these isolated celestial-bodies yet.

Published in the journal Nature , an experiment conducted by scientists has proven that the special atmospheres of Neptune and Uranus are ideal for the diamond shower.

Neptune and Uranus are called ice giants, but “ice” refers to hot slush-like materials, like water, ammonia and methane, over an Earth-sized rock core and lighter gases like hydrogen and helium below it.

Read More: Is It True That NASA Found Evidence Of A Parallel Universe Where Time Flows Backwards?

The experiment

The new experiment was conducted using the Stanford Linear Accelerator Center (SLAC) and the National Accelerator Laboratory’s Linac Coherent Light Source (LCLS) X-ray laser for precise measurements to demonstrate how the ‘diamond rain’ process should occur. They found that carbon transitions directly into the crystalline diamond.

The team exposed polystyrene, a type of plastic composed of carbon and hydrogen, to high-powered shock waves produced by an optical laser and X-rays. The shock waves highly compressed the plastic at pressures of 150 gigapascals and temperatures over 9,000 degrees Fahrenheit.

“We produce about 1.5 million bars, that is equivalent to the pressure exerted by the weight of some 250 African elephants on the surface of a thumbnail,”said Dr. Dominik Kraus, a scientist at Helmholtz-Zentrum Dresden-Rossendorf who led the study.

This enormous reaction broke the bonds between the hydrogen and carbon molecules and compressed carbon atoms into microscopic diamonds.

In the new study, scientists used a unique technique called “X-ray Thomson scattering” that allowed them to accurately replicate diffraction results whilst observing how the elements of non-crystal samples are mixed together.

This scattering technique helped the experimenters to reproduce the exact diffractions from hydrocarbons that split into carbon and hydrogen just like they would inside Neptune and Uranus. This resulted in crystalization of the carbon because of extreme pressure and heat. This leads to a downpour of diamonds 6,200 miles underground, gradually plummeting inside the planets’ cores.

“In the case of the ice giants we now know that the carbon almost exclusively forms diamonds when it separates and does not take on a fluid transitional form,”said Dr. Dominik Kraus.

He also added that “This technique will allow us to measure interesting processes that are otherwise difficult to recreate,” “For example, we’ll be able to see how hydrogen and helium, elements found in the interior of gas giants like Jupiter and Saturn, mix and separate under these extreme conditions.”

“It’s a new way to study the evolutionary history of planets and planetary systems, as well as supporting experiments towards potential future forms of energy from fusion.”

This newly discovered knowledge about the various processes on ice giants is anticipated to promote the search for planets that can endure life and help us to understand the solar system.

Image Source: Google Images

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This post is tagged under: science, astronomy, planets, Neptune, Uranus, Diamond, Diamond rain, Raining, ice giants, Solar System, space, Voyager 2, NASA, experiment, celestial bodies, physics, Earth


It rains solid diamonds on Uranus and Neptune

Consider this your daily reminder that the solar system is even more awesomely bonkers than you realized: On Uranus and Neptune, scientists forecast rain storms of solid diamonds.

The gems form in the hydrocarbon-rich oceans of slush that swath the gas giants' solid cores. Scientists have long speculated that the extreme pressures in this region might split those molecules into atoms of hydrogen and carbon, the latter of which then crystallize to form diamonds. These diamonds were thought to sink like rain through the ocean until they hit the solid core.

But no one could prove that this would really work — until now. In a study published this week in the journal Nature Astrophysics, researchers say they were able to produce this "diamond rain" using fancy plastic and high-powered lasers.


Icy Planets' Diamond Rain Created in Laser Laboratory

For the first time, the kind of diamond rain that scientists think falls within the icy giant planets of the solar system has been generated in the lab, a new study finds.

Thousands of miles below the surfaces of icy giant planets such as Neptune and Uranus, carbon and hydrogen are thought to compress under extreme heat and pressure to form diamonds, according to previous research going back 30 years. These diamonds are then thought to sink through the layers of the gas giant planets, creating a "diamond rain" that eventually settles around the planetary cores.

However, until now, scientists could not confirm whether, when and how such diamond rain could actually form in the chemistry, temperatures and pressures found deep within ice giants. [Our Solar System: A Photo Tour of the Planets]

Researchers simulated the interior of ice giants by creating shock waves in polystyrene (a kind of plastic) with an intense laser at SLAC National Accelerator Laboratory in Menlo Park, California. The polystyrene simulated molecules known as hydrocarbons that are derived from methane, the compound that gives Neptune its blue tint. These hydrocarbons are what diamonds are thought to form from in the high pressures and temperatures in the intermediate layers of ice giants.

The scientists used the laser to generate pairs of shock waves, with the first member of each pair overtaken by its stronger partner. When the shock waves overlapped, diamonds formed at temperatures of about 8,540 degrees Fahrenheit (4,725 degrees Celsius) and pressures about 1.48 million times greater than Earth's atmospheric pressure at sea level. Such conditions resemble the environments about 6,200 miles (10,000 kilometers) below the surfaces of Neptune and Uranus, the researchers said.

"It was very surprising that we got such a clear diamond signature and that the diamonds formed so quickly," said study lead author Dominik Kraus, an experimental laser-plasma physicist at the Helmholtz-Zentrum Dresden-Rossendorf research laboratory in Germany, told Space.com. "I was expecting to look for very tiny hints in the data, and our theorist co-workers actually predicted that it might be impossible to observe diamond formation in our experiment. I already prepared my team for a very difficult experiment and data analysis. But then, the data was just incredibly clear from the first moments in the experiment."

As the diamonds were born, the scientists analyzed them using intense, fast pulses of X-rays only 50 femtoseconds long &mdash essentially, the "shutter speed" of this laser camera is 50 millionths of a billionth of a second, and can thus capture very-fast-moving chemical reactions. These X-ray snapshots helped capture the exact chemical composition and molecular structures of the diamonds as they formed.

In the experiments, the researchers saw that nearly every carbon atom of the plastic targets got incorporated into diamonds up to a few nanometers (billionths of a meter) wide. They predicted that if similar reactions happened within Neptune and Uranus, diamonds could become much larger, perhaps millions of carats large. (One carat is 200 milligrams, or 0.007 ounces.)

But don't expect these findings to generate a rush of diamond miners to Neptune or Uranus.

"The diamonds created in ice giants and our experiment are certainly not gem-quality cut and polished brilliants," Kraus told Space.com. Instead, they are probably spherical diamonds loaded with impurities, he said.

The researchers suggested that over thousands of years, these diamonds would slowly sink through the icy layers within ice giants, assembling into a thick layer around the cores of these planets.

"Some models predict that the temperature around the core may be high enough that diamond would melt, forming underground seas of liquid metallic carbon, maybe with some diamond 'icebergs' swimming on top," Kraus said. "This could help to explain the unusual magnetic fields of Uranus and Neptune. However, most models suggest that diamond would remain solid around the cores of Neptune and Uranus."

As these diamonds rain downward, they are expected to generate heat, much as meteors burn as they plummet through Earth's atmosphere. This heat could help explain why Neptune is hotter than expected, Kraus said.

Moreover, these new findings could help shed light on the inner workings of distant planets outside the solar system and, in turn, help researchers better model and classify such exoplanets, Kraus said.

The researchers added that one day, the microscopic "nanodiamonds" they created could be harvested for commercial purposes, such as medicine and electronics. Currently, nanodiamonds are commercially produced using explosives, and "high-energy lasers may be able to provide a more elegant and controllable method," Kraus said. However, the lasers they use currently accelerate the diamonds they create to very high speeds of about 11,185 mph (18,000 km/h), "and we need to gently stop them," he said.

Furthermore, these findings could help researchers understand and improve experiments that seek to generate energy from nuclear fusion. In some of these experiments, hydrogen fuel is surrounded by a layer of plastic and is then blasted with lasers, and these new findings suggest "that considering chemical processes may be important for modeling some types of fusion implosions," Kraus said.

Future research can investigate the roles that other elements &mdash such as oxygen, nitrogen and helium &mdash might play in ice giants, Kraus said. He and his colleagues detailed their findings online Aug. 21 in the journal Nature Astronomy.


What causes Diamond Rain on Neptune?

It rains solid diamonds on Uranus and Neptune. Scientists have long speculated that the extreme pressures in this region might split those molecules into atoms of hydrogen and carbon, the latter of which then crystallize to form diamonds.

Likewise, which planet has Rain of Diamonds? 'Diamond rain' falls on Saturn and Jupiter. Diamonds big enough to be worn by Hollywood film stars could be raining down on Saturn and Jupiter, US scientists have calculated. New atmospheric data for the gas giants indicates that carbon is abundant in its dazzling crystal form, they say.

Correspondingly, what type of rain falls on Neptune?

Sparkling diamond rain which was theorised to fall on Neptune and Uranus has been created in the laboratory for the first time by scientists. A team from the US, the UK and Germany recreated the conditions found deep inside the icy giant planets of the Solar System and watched as tiny diamonds formed.

Does it rain diamonds on Jupiter yes or no?

Lightning storms make it rain diamonds on Saturn and Jupiter It sounds like a wacky fantasy, but scientists believe that it rains diamonds in the clouds of Saturn and Jupiter. Diamonds are made from highly compressed and heated carbon. On Earth, diamonds form about 100 miles underground.


Why Neptune and Uranus Rain Diamonds

Something weird is happening on the ice giants. Again.

  • Scientists have recreated conditions on Neptune and Uranus in a lab at Stanford's SLAC National Accelerator Laboratory.
  • The team explored how sheets of diamond rain form on the ice giants using lasers.
  • The phenomenon may explain why Neptune's core is strangely hot.

Scientists don't know much about the ice giants on the other end of our solar system. They're a constant source of mystery and intrigue.

Take the conundrum, for example, of how the chemical reactions inside of Neptune and Uranus may cause diamonds to rain down on the planets' cores. Under immense pressure deep below the planets' surfaces, carbon and hydrogen atoms are smushed together, forming the crystals.

Scientists first conducted an experiment to explore this phenomenon in 2017, but now they've finally narrowed down exactly how these diamonds likely formed, publishing their results today in the journal Nature Communication.

"Our experiments are delivering important model parameters where, before, we only had massive uncertainty," physicist Dominic Kraus, of the Helmholtz-Zentrum Dresden-Rossendorf research institute in Germany, said in a press statement. "This will become ever more relevant the more exoplanets we discover." Kraus and his team conducted the experiments at the SLAC National Accelerator Laboratory at Stanford University.

To better understand how this molecular magic happens, the researchers recreated the diamond rain within Neptune's core in the lab. Instead of using methane, which would be found inside the ice giants, as their sample, the scientists used the hydrocarbon polystyrene (C8H8), known colloquially as Styrofoam.

Kraus and his colleagues applied heat and pressure to the polystyrene and then used an optical laser to generate shockwaves that rippled through the material. When those shockwaves met, temperatures soared to 8,540 degrees Fahrenheit. (Earth's core, for reference, is about 10,800 degrees Fahrenheit.) Pressure within the material also skyrocketed.

"We produce about 1.5 million bars, that is equivalent to the pressure exerted by the weight of some 250 African elephants on the surface of a thumbnail," Kraus said.

The scientists then used SLAC's Linac Coherent Light Source (LCLS) instrument to direct X-rays at the sample and measure how light bounced off of electrons inside it. For the first time, they watched the chemical reaction inside the non-crystalline substance unfold. The hydrocarbons split apart the carbon rapidly converted to diamond and sank while the hydrogen escaped.

Kraus says the experiment may explain why Neptune's core produces a perplexing amount of energy&mdashmore than twice the amount it absorbs from the sun. These sheets of diamonds, the researchers suspect, could generate gravitational energy and subsequently heat energy as they rain down on the planets.

Ultimately, the experiment will help scientists solve mysteries here in our own solar system and in distant star systems.


Photo Simulate diamond rain on Neptune and Thien Vuong

Diamonds form inside the core of planets like Neptune and Uranus.(Photo: NASA).

"Previously, researchers could only assume the diamond was created," said Dominik Kraus, the study's lead author at the Helmholtz Zentrum Dresden-Rossendorf laboratory. "When I saw the results of this latest experiment, it was one of the best moments in my scientific career."

The team used the Linac Coherent Light Source device at the SLAC National Accelerator Laboratory to transmit shock waves to polystyrene specimens . Polystyrene is the perfect replica of elements that exist in the ice core of planets because it is made up of many carbon and hydrogen chains.

Under shock waves, almost all atoms in the specimen turn into nanoscale diamonds. This is just a small scale experiment compared to the process that happens on planets. Researchers believe that diamonds form inside Neptune and Uranus is much larger in size. Based on the mass and composition of the two planets, they can produce diamonds weighing over 200kg.

The study marks the first time scientists can observe diamonds in real time. Previous research also simulated diamond formation under similar conditions but could not observe the process. The laser-fired electron-free laser shot in the laboratory allows researchers to record what happens in the specimen over time to a millionth of a second.


Watch the video: So LANGE kann man auf diesen 6 PLANETEN überleben! (January 2022).