APOD: The Brightest Spot on Ceres (2015 Dec 11)

[APOD Robot]

The Brightest Spot on Ceres

Explanation: Dwarf planet Ceres is the largest object in the Solar System's main asteroid belt with a diameter of about 950 kilometers. Exploring Ceres from orbit since March, the Dawn spacecraft's camera has revealed about 130 or so mysterious bright spots, mostly associated with impact craters scattered around the small world's otherwise dark surface. The brightest one is near the center of the 90 kilometer wide Occator Crater, seen in this dramatic false color view combining near-infrared and visible light image data. A study now finds the bright spot's reflected light properties are probably most consistent with a type of magnesium sulfate called hexahydrite. Of course, magnesium sulfate is also known to Earth dwellers as epsom salt. Haze reported inside Occator also suggests the salty material could be left over as a mix of salt and water-ice sublimates on the surface. Since impacts would have exposed the material, Ceres' numerous and widely scattered bright spots may indicate the presence of a subsurface shell of ice-salt mix. In mid-December, Dawn will begin taking observations from its closest Ceres mapping orbit.

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[/b]

[neufer]

[b][size=150][color=#0000FF]Epsom salt (MgSO[sub]4[/sub]·7H[sub]2[/sub]O)[/color][/size][/b]

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<<Magnesium sulfate (or magnesium sulphate) is an inorganic salt containing magnesium, sulfur and oxygen, with the formula MgSO4. It is often encountered as the heptahydrate sulfate mineral epsomite (MgSO₄·7H₂O), commonly called Epsom salt, taking its name from a bitter saline spring in Epsom in Surrey, England, where the salt was produced from the springs that arise where the porous chalk of the North Downs meets non-porous London clay. It is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system. The use of Epsom salt may help "draw out" splinters.>>

[Boomer12k]

Wow....OK...HOT SPRINGS AND FOOT BATHS!!!!!!!!!!! Well, ok, we heat up the water when we get there.

Glad they solved that one...

:---[===] *

[neufer]

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Wow....OK...HOT SPRINGS AND FOOT BATHS!!!!!!!!!!! Well, ok, we heat up the water when we get there.

Glad they solved that one...

It was only a matter of time before they found a solution.

Solution, n. [OE. solucion, fr. solvere, solutum, to loosen, dissolve. See Solve.] The act or process by which a body (whether solid, liquid, or gaseous) is absorbed into a liquid, and, remaining or becoming fluid, is diffused throughout the solvent.

<<The commercial spacecraft Nos-Bromo is on a return trip to Earth hauling 20 million tons of Epsom Salts mined from the salt mines of Ceres. Detecting a mysterious transmission, possibly a distress signal, from a nearby planetoid, the ship's computer, MOTHER, awakens the crew...>>

[Rules For]

Quick question about Ceres' density - anyone know how it was measured before Dawn's arrival? Can't imagine how without any moons. Thanks for any insight...

[neufer]

Quick question about Ceres' density - anyone know how it was measured before Dawn's arrival? Can't imagine how without any moons. Thanks for any insight...

As the most massive asteroid, Ceres produces noticeable perturbations on its neighboring asteroids.

<<Ceres is in a near-1:1 mean-motion orbital resonance with Pallas (their proper orbital periods differ by 0.2%). However, a true resonance between the two would be unlikely; due to their small masses relative to their large separations, such relationships among asteroids are very rare. Nevertheless, Ceres is able to capture other asteroids into temporary 1:1 resonant orbital relationships (for periods up to 2 million years or more); fifty such objects have been identified. Several temporary trojans of Ceres are known.>>

[b][color=#FF00FF]An ultraviolet image of Pallas showing its flattened shape, taken by the Hubble Space Telescope in 2007[/color][/b]

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<<In 1801, the astronomer Giuseppe Piazzi discovered an object which he initially believed to be a comet. Shortly thereafter he announced his observations of this object, noting that the slow, uniform motion was uncharacteristic of a comet, suggesting it was a different type of object. This was lost from sight for several months, but was recovered later that year by the Baron von Zach and Heinrich W. M. Olbers after a preliminary orbit was computed by Friedrich Gauss. This object came to be named Ceres, and was the first asteroid to be discovered.

A few months later, Olbers was again attempting to locate Ceres when he noticed another moving object in the vicinity. This was the asteroid Pallas, coincidentally passing near Ceres at the time. The orbit of Pallas was determined by Gauss, who found the period of 4.6 years was similar to the period for Ceres. Pallas has a relatively high orbital inclination to the plane of the ecliptic.>>

[Patrick60]

I think there was a typo. Should be hexahydrate, not hexahydrite.

[Patrick60]

PS. The largest object New Horizons passed was Jupiter. Pluto is small potatoes compared to a gas giant.

[bystander]

I think there was a typo. Should be hexahydrate, not hexahydrite.

Hexahydrite is a specific hexahydrate of magnesium sulfate (MgSO₄ • 6H₂O).

[Chris Peterson]

I think there was a typo. Should be hexahydrate, not hexahydrite.

No, I don't think so. "Hydrite" and "hydrate" tend to be used interchangeably in mineral names (despite the fact that chemically, they are called "hydrates").

[starsurfer]

Is it possible that some asteroids are remnants of previous comets?

[neufer]

I think there was a typo. Should be hexahydrate, not hexahydrite.

No, I don't think so. "Hydrite" and "hydrate" tend to be used interchangeably in mineral names (despite the fact that chemically, they are called "hydrates").

Hexahydrite is a specific hexahydrate of magnesium sulfate (MgSO₄ • 6H₂O).

Hydrites appear to be drier versions of better known Hydrates:

<<Anhydrite is a mineral—anhydrous calcium sulfate, CaSO₄. The name anhydrite was given by A. G. Werner in 1804, because of the absence of water of crystallization, as contrasted with the presence of water in gypsum. When exposed to water, anhydrite readily transforms to the more commonly occurring gypsum, (CaSO₄ • 2H₂O) by the absorption of water. This transformation is reversible, with gypsum or calcium sulfate hemihydrate forming anhydrite by heating to ~200°C under normal atmospheric conditions.>>

anhydrite (CaSO₄) <=> calcium sulfate hemihydrate [gypsum], (CaSO₄ • 2H₂O)

magnesium sulfate hexahydrite (MgSO₄ • 6H₂O) <=>

• magnesium sulfate heptahydrate (MgSO₄ • 7H₂O) epsomite (Epsom salt)

[neufer]

Is it possible that some asteroids are remnants of previous comets?

• Yes.

<<When found, asteroids were seen as a class of objects distinct from comets. The main difference between an asteroid and a comet is that a comet shows a coma due to sublimation of near surface ices by solar radiation. A few objects have ended up being dual-listed because they were first classified as minor planets but later showed evidence of cometary activity. Conversely, some (perhaps all) comets are eventually depleted of their surface volatile ices and become asteroids. A further distinction is that comets typically have more eccentric orbits than most asteroids; most "asteroids" with notably eccentric orbits are probably dormant or extinct comets.

On 22 January 2014, ESA scientists reported the detection, for the first definitive time, of water vapor on Ceres, the largest object in the asteroid belt. The detection was made by using the far-infrared abilities of the Herschel Space Observatory. According to one of the scientists, "The lines are becoming more and more blurred between comets and asteroids.">>

[Tekija]

Europa also has magnesium sulfate salt. Magnesium is thought to detive from Europa's ocean and sulfur from Io.

http://asterisk.apod.com/viewtopic.php?t=35456

Where did Ceres get its magnesium and sulfur?

[Chris Peterson]

Where did Ceres get its magnesium and sulfur?

These materials were certainly present in the pre-solar mix, and concentrated by differentiation.

[neufer]

Where did Ceres get its magnesium and sulfur?

These materials were certainly present in the pre-solar mix, and concentrated by differentiation.

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<<Periodic table showing the cosmogenic origin of each element. Elements from carbon up to sulfur may be made in small stars by the alpha process. Elements beyond iron are made in large stars with slow neutron capture (s-process), followed by expulsion to space in gas ejections (see planetary nebulae). Elements heavier than iron may be made in supernovae after the r-process, involving a dense burst of neutrons and rapid capture by the element.>>

[geckzilla]

PS. The largest object New Horizons passed was Jupiter. Pluto is small potatoes compared to a gas giant.

Thanks for mentioning that... I modified the question. I really just wanted the answer to be something the spam bots won't get instantly and don't care much about it otherwise.

[neufer]

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[neufer]

Quick question about Ceres' density - anyone know how it was measured before Dawn's arrival? Can't imagine how without any moons. Thanks for any insight...

As the most massive asteroid, Ceres produces noticeable perturbations on its neighboring asteroids.

<<Ceres is in a near-1:1 mean-motion orbital resonance with Pallas (their proper orbital periods differ by 0.2%). However, a true resonance between the two would be unlikely; due to their small masses relative to their large separations, such relationships among asteroids are very rare. Nevertheless, Ceres is able to capture other asteroids into temporary 1:1 resonant orbital relationships (for periods up to 2 million years or more); fifty such objects have been identified. Several temporary trojans of Ceres are known.>>

2 Pallas taken by the Hubble Space Telescope in 2007

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<<In 1801, the astronomer Giuseppe Piazzi discovered an object which he initially believed to be a comet. Shortly thereafter he announced his observations of this object, noting that the slow, uniform motion was uncharacteristic of a comet, suggesting it was a different type of object. This was lost from sight for several months, but was recovered later that year by the Baron von Zach and Heinrich W. M. Olbers after a preliminary orbit was computed by Friedrich Gauss. This object came to be named Ceres, and was the first asteroid to be discovered.

A few months later, Olbers was again attempting to locate Ceres when he noticed another moving object in the vicinity. This was the asteroid Pallas, coincidentally passing near Ceres at the time. The orbit of Pallas was determined by Gauss, who found the period of 4.6 years was similar to the period for Ceres. Pallas has a relatively high orbital inclination to the plane of the ecliptic.>>

Clockwise from top left: 29 Amphitrite, 324 Bamberga, 2 Pallas, and 89 Julia. These images were taken by ESO's SPHERE (Spectro-Polarimetric High-Contrast Exoplanet Research) instrument, installed on the Very Large Telescope at the Paranal Observatory, Chile. Credit: ESO/Vernazza et al.

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<<Pallas, minor-planet designation 2 Pallas, is the second asteroid to have been discovered (after Ceres), and is one of the largest asteroids in the Solar System. At 512±3 km in diameter, Pallas is slightly smaller than Vesta (525.4±0.2 km). The mass of Pallas is ~84% that of Vesta, 22% that of Ceres and about 0.3% that of the Moon.

Pallas's surface is most likely composed of a silicate material; its spectrum and estimated density resemble carbonaceous chondrite meteorites. With an orbital inclination of 34.8°, Pallas's orbit is unusually highly inclined to the plane of the asteroid belt, and its orbital eccentricity is nearly as large as that of Pluto, making Pallas relatively inaccessible to spacecraft.

Pallas has a very high axial tilt of 84°. This means that every Palladian summer and winter, large parts of the surface are in constant sunlight or constant darkness for a time on the order of an Earth year, with areas near the poles experiencing continuous sunlight for as long as two years.

Pallas is farther from Earth and has a much lower albedo than Vesta, and hence is dimmer as seen from Earth. Pallas's mean opposition magnitude is +8.0, which is well within the range of 10×50 binoculars, but, unlike Ceres and Vesta, it will require more-powerful optical aid to view at small elongations, when its magnitude can drop as low as +10.6. During rare perihelic oppositions, Pallas can reach a magnitude of +6.4, right on the edge of naked-eye visibility.

Pallas is thought to have undergone at least some degree of thermal alteration and partial differentiation, which suggests that it is a remnant protoplanet. During the planetary formation stage of the Solar System, objects grew in size through an accretion process to approximately this size. Many of these objects were incorporated into larger bodies, which became the planets, whereas others were destroyed in collisions with other protoplanets. Pallas and Vesta are likely survivors from this early stage of planetary formation.>>

[bystander]

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