User:Marshallsumter/Rocks/Rocky objects/Astronomy

A division of astronomical objects between rocky objects, liquid objects, gaseous objects (including gas giants and stars), and plasma objects may be natural and informative.

This division allows moons like Io to be viewed as rocky objects like Earth, rather than as a satellite around Jupiter.

The astronomy of such objects may be called rocky-object astronomy.

Def. a natural object in the sky especially at night is called an astronomical object.

Def. a rocky, natural object in the sky especially at night is called an astronomical rocky object, or a rocky object.

Rocky objects are astronomical objects with solid surfaces.

Def. a natural object in the sky especially at night is called an astronomical object.

Astronomical objects that radiate, reflect, or fluoresce may range in size from individual atoms or subatomic particles to rocky objects. A rocky object may be radiation, radiated, or irradiated.

A division of astronomical objects between rocky objects and gaseous objects (including gas giants and stars) may be natural and informative. This division allows moons like Io to be viewed as rocky objects like Earth as part of rocky object science rather than as a natural satellite around a gaseous object like Jupiter, or a plasma object like a coronal cloud.

A rock is a naturally occurring solid aggregate of one or more minerals or mineraloids.

Def. any natural material with a distinctive composition of minerals is called a rock.

Def. a solid, homogeneous, crystalline chemical element or compound that results from natural inorganic processes is called a mineral.

Def. a naturally occurring, glimmering glass-like allotrope of carbon in which each atom is surrounded by four others in the form of a tetrahedron is called a diamond.

Def. a solid, homogeneous, monoclinic (space group P2/c, no. 13, or P2₁/c, no. 14), naturally occurring, chemical compound with the formula C₂₄H₁₂ that results from natural inorganic processes is called a carpathite.

Def. a continuous framework tectosilicate of SiO₄ silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of silicon dioxide SiO₂ of trigonal trapezohedral class 3 2, usually with some substitutional or interstitial impurities, is called α-quartz.

When the concentration of interstitial or substitutional impurities becomes sufficient to change the space group of a mineral such as α-quartz, the result is another mineral. When the physical conditions are sufficient to change the solid space group of α-quartz without changing the chemical composition or formula, another mineral results.

Alpha-quartz (space group P3₁21, no. 152, or P3₂21, no. 154) under a high pressure of 2-3 gigapascals and a moderately high temperature of 700°C changes space group to monoclinic C2/c, no. 15, and becomes the mineral coesite. It is "found in extreme conditions such as the impact craters of meteorites>.

Def. a high-temperature (above 1470°C) polymorph of α-quartz with cubic, Fd3m, space group no. 227, and a tetragonal form (P4₁2₁2, space group no. 92) is called cristobalite.

Def. a polymorph of α-quartz formed by pressures > 100 kbar or 10 GPa and temperatures > 1200 °C is called stishovite.

Def. a polymorph of α-quartz formed at an estimated minimum pressure of 35 GPa up to pressures above 40 GPa with a orthorhombic space group Pmmm no. 47 is called seifertite.

Def. a polymorph of α-quartz formed at temperatures from 22-460°C with at least seven space groups for its forms with tabular crystals is called tridymite.

Def. any of a group of olive green magnesium-iron orthosilicates "that crystallize in the orthorhombic system> is called an olivine.

Def. any group of silicates that have structurally isolated double tetrahedra is called a sorosilicate.

Def. any group of silicates that have a ring of linked tetrahedra is called a cyclosilicate.

Def. a group of monoclinic or orthorhombic, single chain inosilicates with the general formula of X Y(Si,Al)₂O₆, where

X is calcium, sodium, ferrous iron (Fe²⁺), magnesium, zinc, manganese and lithium;

Y is chromium, aluminum, ferric iron (Fe³⁺), magnesium, manganese, scandium, titanium, vanadium, and ferrous iron (Fe²⁺)

is called a pyroxene.

Def. a group of monoclinic or orthorhombic double chain inosilicates with the general formula of

X₂Y₅Z₈O₂₂(OH)₂ where

X is magnesium, ferrous iron (Fe²⁺), calcium, lithium, sodium, and ferric iron (Fe³⁺)

Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.

Z is chiefly Si or Al

is called an amphibole.

Def. a group of monoclinic phyllosilicates with the general formula^[1]

X₂Y_4–6Z₈O₂₀(OH,F)₄

in which X is K, Na, or Ca or less commonly Ba, Rb, or Cs;

Y is Al, Mg, or Fe or less commonly Mn, Cr, Ti, Li, etc.;

Z is chiefly Si or Al, but also may include Fe³⁺ or Ti;

dioctahedral (Y = 4) and trioctahedral (Y = 6)

is called a mica.

Def. any of a large group of aluminum tectosilicates of the alkali metals sodium, potassium, calcium and barium is called feldspar.

Def. any of a group of aluminum silicate feldspathic minerals ranging in their ratio of calcium to sodium is called plagioclase.

Def. a substance that resembles a mineral but does not exhibit crystallinity is called a mineraloid.

Def. a small, round, dark glassy object, composed of silicates is called a tektite.

Def. a naturally occurring, silvery-colored, metallic liquid, composed primarily of the chemical element mercury, is called mercury, or native mercury.

Def. a hard, generally yellow to brown translucent fossil resin is called an amber.

Def. a flammable liquid ranging in color from clear to very dark brown and black, consisting mainly of hydrocarbons is called petroleum.

Def. a naturally occurring black glass is called an obsidian.

Def. a naturally occurring, hydrous, amorphous form of silica, where 3% to 21% of the total weight is water is called an opal.

Def. full of, or abounding in, rocks; consisting of rocks is called rocky.

Top right is an image of an olivine rock.

Top left is the mineral mica in a rock.

Second on the right is an image of Cristobalite spheres within obsidian.

Second on the left is an image of a specimen that consists of "porcelainite" - a semivitrified chert- or jasper-like rock composed of cordierite, mullite and tridymite, admixture of corundum, and subordinate K-feldspar.

Third on the right is a feldspar rock.

Last on the left is an image of a rock, a diabase with an aphanitic groundmass and plagioclase phenocrysts.

Shocked quartz is associated with two high pressure polymorphs of silicon dioxide: coesite and stishovite. These polymorphs have a crystal structure different from α-quartz that can only be formed by intense pressure and moderate temperatures. High temperatures would anneal the quartz back to its standard form. Stishovite may be formed by an instantaneous over pressure such as by an impact or nuclear explosion type event.

So far several of the polymorphs of α-quartz formed at high temperature and pressure occur with rock types away from meteorite impact craters.

Astrogeology is the study of naturally occurring astronomical rocky objects, their physical structure and substance, history and origin, and the processes that act on them, especially by examination of their rocks.

A crater may be any large, roughly circular, depression or hole in or beneath the rocky surface of a rocky object.

Crater astronomy applies the techniques of astronomy to the apparent craters observed on rocky objects in an effort to understand what they are, when they occurred, and their importance to rocky objects.

A caldera is a cauldron-like volcanic feature usually formed by the collapse of land following a volcanic eruption. They are sometimes confused with volcanic craters. The word comes from Spanish caldera, and this from Latin CALDARIA, meaning "cooking pot". In some texts the English term cauldron is also used.

Elements usually emit a gamma-ray during nuclear decay or fission. The gamma-ray spectrum at right shows typical peaks for ²²⁶Ra, ²¹⁴Pb, and ²¹⁴Bi. These isotopes are part of the uranium-radium decay line. As ²³⁸U is an alpha-ray emitter, it is not shown. The peak at 40 keV is not from the mineral. From the color of the rock shown the yellowish mineral is likely to be autunite.

Autunite occurs as an oxidizing product of uranium minerals in granite pegmatites and hydrothermal deposits. Uraninite is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO₂, but also contains UO₃ and oxides of lead, thorium, and rare earth elements. It is most commonly known as pitchblende (from pitch, because of its black color). All uraninite minerals contain a small amount of radium as a radioactive decay product of uranium. Uraninite also always contains small amounts of the lead isotopes ²⁰⁶Pb and ²⁰⁷Pb, the end products of the decay series of the uranium isotopes ²³⁸U and ²³⁵U respectively. The extremely rare element technetium can be found in uraninite in very small quantities (about 0.2 ng/kg), produced by the spontaneous fission of uranium-238.

The image at left shows well-formed crystals of uraninite. The image at right shows botryoidal unraninite. Because of the uranium decay products, both sources are gamma-ray emitters.

Thorianite is a rare thorium oxide mineral, ThO₂.^[2] It has a high percentage of thorium; it also contains the oxides of uranium, lanthanum, cerium, praseodymium and neodymium. The mineral is slightly less radioactive than pitchblende, but is harder to shield due to its high energy gamma rays. It is common in the alluvial gem-gravels of Sri Lanka, where it occurs mostly as water worn, small, heavy, black, cubic crystals.

Torbernite is a radioactive, hydrated green copper uranyl phosphate mineral, found in granites and other uranium-bearing deposits as a secondary mineral. Torbernite is isostructural with the related uranium mineral, autunite. The chemical formula of torbenite is similar to that of autunite in which a Cu²⁺ cation replaces a Ca²⁺. The number of water hydration molecules can vary between 12 and 8, giving rise to the variety of metatorbernite when torbernite spontaneously dehydrates.

Uranophane Ca(UO₂)₂(SiO₃OH)₂·5H₂O is a rare calcium uranium [nesosilicate] hydrate mineral that forms from the oxidation of uranium bearing minerals. Uranophane is also known as uranotile. It has a yellow color and is radioactive.

On September 20, the X-Ray Laboratory at the Faculty of Geological Sciences, Mayor de San Andres University, La Paz, Bolivia, published a report of their analysis of a small sample of material recovered from the impact site. They detected iron, nickel, cobalt, and traces of iridium — elements characteristic of the elemental composition of meteorites. The quantitative proportions of silicon, aluminum, potassium, calcium, magnesium, and phosphorus are incompatible with rocks that are normally found at the surface of the Earth.^[3]

In X-ray wavelengths, many scientists are investigating the scattering of X-rays by interstellar dust, and some have suggested that astronomical X-ray sources would possess diffuse haloes, due to the dust.^[4]

File:6 Hebe from NASA.jpg

6 Hebe is a siliceous asteroid of subtype IV [S(IV)].^[5]

The image on the right is a photograph of 6 Hebe (the brightest spot) in 2004.

"Compositional analysis of 2007 LE reveal Fs₁₇ and Fa₁₉ values, which are consistent with the Fa and Fs values for the H-type ordinary chondrites (Fs_14.5–18 and Fa_16–20) and of Asteroid (6) Hebe (Fs₁₇ and Fa₁₅)."^[6]

"It is probable that the H-chondrites and IIE irons came from (6) Hebe (Gaffey and Gilbert, 1998), though caveats exist (e.g., Rubin and Bottke, 2009)."^[6]

Ultraviolet lamps are also used in analyzing minerals and gems. Materials may look the same under visible light, but fluoresce to different degrees under ultraviolet light, or may fluoresce differently under short wave ultraviolet versus long wave ultraviolet.

Ultraviolet lamps may cause certain minerals to fluoresce, and is a key tool in prospecting for tungsten mineralisation.

"Many samples of fluorite exhibit fluorescence under ultraviolet light, a property that takes its name from fluorite.^[7] Many minerals, as well as other substances, fluoresce. Fluorescence involves the elevation of electron energy levels by quanta of ultraviolet light, followed by the progressive falling back of the electrons into their previous energy state, releasing quanta of visible light in the process. In fluorite, the visible light emitted is most commonly blue, but red, purple, yellow, green and white also occur. The fluorescence of fluorite may be due to mineral impurities such as yttrium, ytterbium, or organic matter in the crystal lattice. In particular, the blue fluorescence seen in fluorites from certain parts of Great Britain responsible for the naming of the phenomenon of fluorescence itself, has been attributed to the presence of inclusions of divalent europium in the crystal.^[8]

Between 190 and 1700 nm, the ordinary refractive index [of calcite] varies roughly between 1.9 and 1.5, while the extraordinary refractive index varies between 1.6 and 1.4.^[9]

Under longwave (365 nm) ultraviolet light, diamond may fluoresce a blue, yellow, green, mauve, or red of varying intensity. The most common fluorescence is blue, and such stones may also phosphoresce yellow—this is thought to be a unique combination among gemstones. There is usually little if any response to shortwave ultraviolet.

Beryl of various colors is found most commonly in granitic pegmatites, but also occurs in mica schists.. Goshenite [a beryl clear to white cyclosilicate]] is found to some extent in almost all beryl localities.

Quartzite (from German Quarzit^[10]) is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone.^[11][12] Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to gray, though quartzites often occur in various shades of pink and red due to varying amounts of iron oxide (Fe₂O₃). Other colors, such as yellow and orange, are due to other mineral impurities.

The great majority of silicates are oxides which comprise the majority of the earth's crust, as well as the other terrestrial planets, rocky moons, and asteroids. Sand, Portland cement, and thousands of minerals are examples of silicates.

Mineralogically, silicate minerals are divided according to structure of their silicate anion into the following groups:^[13][14]

• Nesosilicates (lone tetrahedron) - [SiO₄]⁴⁻, e.g. olivine, tephroite.
• Sorosilicates (double tetrahedra) - [Si₂O₇]⁶⁻, e.g. epidote, melilite group, leucophanite.
• Cyclosilicates (rings) - [Si_nO_3n]²ⁿ⁻, e.g. tourmaline group.
• Inosilicates (single chain) - [Si_nO_3n]²ⁿ⁻, e.g. pyroxene group.
• Inosilicates(double chain) - [Si_4nO_11n]⁶ⁿ⁻, e.g. amphibole group.
• Phyllosilicates (sheets) - [Si_2nO_5n]²ⁿ⁻, e.g. micas and clays like Kaolin.
• Tectosilicates (3D framework) - [Al_xSi_yO_2(x+y)]^x−, e.g. quartz, feldspars, zeolites.

White is the color of fresh milk and snow.^[15]; "of the colour of fresh milk or snow."^[15]See also , (1988): "Having the color of pure snow or milk."^[16]

The white cliffs shown in the image at right are made of chalk, or calcium carbonate.

Crystal boundaries and imperfections can also make otherwise transparent materials white, as in the milky quartz or the microcrystalline structure of a seashell.

Black is the color of coal. As in the image at left basalt may also be black.

Axinite-(Mg) or magnesioaxinite, Ca₂MgAl₂BOSi₄O₁₅(OH) magnesium rich, [can be] pale blue to pale violet^[17]

Fluorapatite, a sample of which is shown at right, is a mineral with the formula Ca₅(PO₄)₃F (calcium fluorophosphate). Fluorapatite as a mineral is the most common phosphate mineral. It occurs widely as an accessory mineral in igneous rocks and in calcium rich metamorphic rocks. It commonly occurs as a detrital or diagenic mineral in sedimentary rocks and is an essential component of phosphorite ore deposits. It occurs as a residual mineral in lateritic soils.^[18]

At lower left is another fluorapatite example that is violet in color on quartz crystals.

Lower right shows both a rough stone and a cut stone of tanzanite. Tanzanite is the blue/purple variety of the mineral zoisite (a calcium aluminium hydroxy silicate) with the formula (Ca₂Al₃(SiO₄)(Si₂O₇)O(OH))]. Tanzanite is noted for its remarkably strong trichroism, appearing alternately sapphire blue, violet and burgundy depending on crystal orientation.^[19] Tanzanite can also appear differently when viewed under alternate lighting conditions. The blues appear more evident when subjected to fluorescent light and the violet hues can be seen readily when viewed under incandescent illumination. A rough violet sample of tanzanite is third down at left.

Tanzanite in its rough state is usually a reddish brown color. It requires artificial heat treatment to 600 °C in a gemological oven to bring out the blue violet of the stone.^[20]

Tanzanite is found only in the foothills of Mount Kilimanjaro.

Tanzanite is universally heat treated in a furnace, with a temperature between 550 and 700 degrees Celsius, to produce a range of hues between bluish-violet to violetish-blue. Some stones found close to the surface in the early days of the discovery were gem-quality blue without the need for heat treatment.

Perhaps the most common violet mineral is sapphire. A sample of uncut natural sapphire is at lowest right. Sapphires may be found naturally, by searching through certain sediments (due to their resistance to being eroded compared to softer stones) or rock formations.

Lepidolite (KLi₂Al(Al,Si)₃O₁₀(F,OH)₂ is a lilac-gray or rose-colored member of the mica group that is a secondary source of lithium. It is a phyllosilicate mineral^[14] and a member of the polylithionite-trilithionite series.^[21]

It is associated with other lithium-bearing minerals like spodumene in pegmatite bodies. It is one of the major sources of the rare alkali metals rubidium and caesium.^[22]

It occurs in granite pegmatites, in some high-temperature quartz veins, greisens and granites. Associated minerals include quartz, feldspar, spodumene, amblygonite, tourmaline, columbite, cassiterite, topaz and beryl.^[18]

Often a mineral appears blue due to the presence of copper or sulfur. Glaucophane is a blue silicate that owes its color to its characteristic formation.

Covellite has been found in veins at depths of 1,150 meters, as the primary mineral. Covellite formed as clusters in these veins reaching one meter across.

Glaucophane is a mineral belonging to the amphibole group, chemical formula Na₂Mg₃Al₂Si₈O₂₂(OH)₂. The blue color is very diagnostic for this species. It, along with the closely related mineral riebeckite are the only common amphibole minerals that are typically blue. Glaucophane forms in metamorphic rocks that are either particularly rich in sodium or that have experienced low temperature-high pressure metamorphism such as would occur along a subduction zone. This material has undergone intense pressure and moderate heat as it was subducted downward toward the mantle. It is glaucophane's color that gives the blueschist facies its name. Glaucophane is also found in eclogites that have undergone retrograde metamorphism.^[23]

Hauyne, haüyne or hauynite occurs in Vesuvian lavas in Monte Somma, Italy.^[24] It is a tectosilicate mineral with sulfate, with endmember formula Na₃Ca(Si₃Al₃)O₁₂(SO₄).^[25] It is a feldspathoid and a member of the sodalite group.^[26][27] Haüyne occurs in phonolites and related leucite- or nepheline-rich, silica-poor, igneous rocks; less commonly in nepheline-free extrusives^{[28][26][27][29]} and metamorphic rocks (marble).^[26]

Usually, Hibonite ((Ca,Ce)(Al,Ti,Mg)₁₂O₁₉) as shown at right is a brownish black mineral. It is rare, but is found in high-grade metamorphic rocks on Madagascar. Some presolar grains in primitive meteorites consist of hibonite. Hibonite also is a common mineral in the Ca-Al-rich inclusions (CAIs) found in some chondritic meteorites. Hibonite is closely related to hibonite-Fe (IMA 2009-027, ((Fe,Mg)Al₁₂O₁₉)) an alteration mineral from the Allende meteorite.^[25] Hibonite is blue perhaps like the image at left in meteorite occurrence.

Lazurite is a tectosilicate mineral with sulfate, sulfur and chloride with formula: (Na,Ca)₈[(S,Cl,SO₄,OH)₂|(Al₆Si₆O₂₄)]. It is a feldspathoid and a member of the sodalite group. The colour is due to the presence of S^3- anions. Lazurite is a product of contact metamorphism of limestone.

Sodalite is a rich royal blue mineral. Massive sodalite samples are opaque, crystals are usually transparent to translucent. Occurring typically in massive form, sodalite is found as vein fillings in plutonic igneous rocks such as nepheline syenites.

Eclogite Blueschist Greenschist Prehnite- Pumpellyite Zeolite Granulite Amphibolite Hornfels Sanidinite P (kbar) T (°C) 0 100 200 300 400 500 600 700 800 900 1000 0 2 4 6 8 10 12 14 16 18 20

Diagram showing metamorphic facies in pressure-temperature space. The domain of the graph corresponds to circumstances within the Earth's crust and upper mantle.

A metamorphic facies is a set of metamorphic mineral assemblages that were formed under similar pressures and temperatures.^[30] The assemblage is typical of what is formed in conditions corresponding to an area on the two dimensional graph of temperature vs. pressure (See diagram at right).^[30] Rocks which contain certain minerals can therefore be linked to certain tectonic settings, times and places in geological history of the area.^[30] The boundaries between facies (and corresponding areas on the temperature v. pressure graph), are wide, because they are gradational and approximate.^[30] The area on the graph corresponding to rock formation at the lowest values of temperature and pressure, is the range of formation of sedimentary rocks, as opposed to metamorphic rocks, in a process called diagenesis.^[30]

Blueschist is a metavolcanic rock that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures, approximately corresponding to a depth of 15 to 30 kilometers and 200 to ~500 degrees Celsius. The blue color of the rock comes from the presence of the mineral glaucophane. Blueschists are typically found within orogenic belts as terranes of lithology in faulted contact with greenschist or rarely eclogite facies rocks. Blueschist, as a rock type, is defined by the presence of the minerals glaucophane + ( lawsonite or epidote ) +/- jadeite +/- albite or chlorite +/- garnet +/- muscovite in a rock of roughly basaltic composition. Blueschist often has a lepidoblastic, nematoblastic or schistose rock microstructure defined primarily by chlorite, phengitic white mica, glaucophane, and other minerals with an elongate or platy shape. Grain size is rarely coarse, as mineral growth is retarded by the swiftness of the rock's metamorphic trajectory and perhaps more importantly, the low temperatures of metamorphism and in many cases the anhydrous state of the basalts. However, coarse varieties do occur. Blueschists may appear blue, black, gray, or blue-green in outcrop.

Blue ice occurs when snow falls on a glacier, is compressed, and becomes part of a glacier blue ice was observed in Tasman Glacier, New Zealand in January 2011.^[31] Ice is blue for the same reason water is blue: it is a result of an overtone of an oxygen-hydrogen (O-H) bond stretch in water which absorbs light at the red end of the visible spectrum.^[32]

Sin-Kamen (Синь-Камень, in Russian literally – Blue Stone, or Blue Rock) is a type of pagan sacred stones, widespread in Russia, in areas historically inhabited by both Eastern Slavic (Russian), and Uralic tribes (Merya, Muroma^[33]).

While in the majority of cases, the stones belonging to the Blue Stones type, have a black, or dark gray color, this particular stone [in the image] does indeed look dark blue, when wet.^[34]

"Several types of rock surface materials can be recognized at the two sites [Viking Lander 1 and Viking Lander 2]; dark, relatively 'blue' rock surfaces are probably minimally weathered igneous rock, whereas bright rock surfaces, with a green/(blue + red) ratio higher than that of any other surface material, are interpreted as a weathering product formed in situ on the rock."^[35]

At second right is an approximately natural color image of the asteroid 243 Ida. "There are brighter areas, appearing bluish in the picture, around craters on the upper left end of Ida, around the small bright crater near the center of the asteroid, and near the upper right-hand edge (the limb). This is a combination of more reflected blue light and greater absorption of near infrared light, suggesting a difference in the abundance or composition of iron-bearing minerals in these areas."^[36]

"The [Sloan Digital Sky Survey] SDSS “blue” asteroids are related to the C-type (carbonaceous) asteroids, but not all of them are C-type. They are a mixture of C-, E-, M-, and P-types."^[37]

Malachite is a green mineral occurring on Earth. It gets its green color from the presence of copper as copper(II) carbonate.

Green earth is a natural pigment It s composed of clay colored by iron oxide, magnesium, aluminum silicate, or potassium. Large deposits were found in the South of France near Nice, and in Italy around Verona, on Cyprus, and in Bohemia. The clay was crushed, washed to remove impurities, then powdered. It was sometimes called Green of Verona.^[39]

At right is a visual close up of green sand which is actually olivine crystals that have been eroded from lava rocks. Some olivine crystals are still inside the lava rock.

Forsterite (Mg₂SiO₄) is the magnesium rich end-member of the olivine solid solution series.

Forsterite is associated with igneous and metamorphic rocks and has also been found in meteorites. In 2005 it was also found in cometary dust returned by the Stardust probe.^[40] In 2011 it was observed as tiny crystals in the dusty clouds of gas around a forming star.^[41]

Two polymorphs of forsterite are known: wadsleyite (also orthorhombic) and ringwoodite (isometric). Both are mainly known from meteorites.

At lower right is an image of a small volcanic bomb of (black) basanite with (green) dunite.

Dunite is an igneous, plutonic rock, of ultramafic composition, with coarse-grained or phaneritic texture. The mineral assemblage is greater than 90% olivine, with minor amounts of other minerals such as pyroxene, chromite and pyrope. Dunite is the olivine-rich end-member of the peridotite group of mantle-derived rocks. Dunite and other peridotite rocks are considered the major constituents of the Earth's mantle above a depth of about 400 kilometers. Dunite is rarely found within continental rocks, but where it is found, it typically occurs at the base of ophiolite sequences where slabs of mantle rock from a subduction zone have been thrust onto continental crust by obduction during continental or island arc collisions (orogeny). It is also found in alpine peridotite massifs that represent slivers of sub-continental mantle exposed during collisional orogeny. Dunite typically undergoes retrograde metamorphism in near-surface environments and is altered to serpentinite and soapstone.

Greenstone belts are zones of variably metamorphosed mafic to ultramafic volcanic sequences with associated sedimentary rocks that occur within Archaean and Proterozoic cratons between granite and gneiss bodies.

The name comes from the green hue imparted by the colour of the metamorphic minerals within the mafic rocks. Chlorite, actinolite and other green amphiboles are the typical green minerals.

A greenstone belt is typically several dozens to several thousand kilometres long and although composed of a great variety of individual rock units, is considered a 'stratigraphic grouping' in its own right, at least on continental scales.

"Greenstone belts" are distributed throughout geological history from the Phanerozoic Franciscan belts of California where blueschist, whiteschist and greenschist facies are recognised, through to the Palaeozoic greenstone belts of the Lachlan Fold Belt, Eastern Australia, and a multitude of Proterozoic and Archaean examples.

Archaean greenstones are found in the Slave craton, northern Canada, Pilbara craton and Yilgarn Craton, Western Australia, Gawler Craton in South Australia, and in the Wyoming Craton in the US. Examples are found in South and Eastern Africa, namely the Kaapvaal craton and also in the cratonic core of Madagascar, as well as West Africa and Brazil, northern Scandinavia and the Kola Peninsula (see Baltic Shield).

Phanerozoic ophiolite belts and greenstone belts occur in the Franciscan Complex of south-western North America, within the Lachlan Fold Belt, the Gympie Terrane of Eastern Australia, the ophiolite belts of Oman and around the Guiana Shield.

Moldavite is an olive-green or dull greenish vitreous substance possibly formed by a meteorite impact. It is one kind of tektite.

Because of their difficult fusibility, extremely low water content, and its chemical composition, the current overwhelming consensus among Earth scientists is that moldavites were formed 15 million years ago during the impact of a giant meteorite in present-day Nördlinger Ries. Splatters of material that was melted by the impact cooled while they were actually airborne and most fell in central Bohemia—traversed by the Vltava river. Currently, moldavites have been found in [an] area that includes southern Bohemia, western Moravia, the Cheb Basin (northwest Bohemia), Lusatia (Germany), and Waldviertel (Austria).^[42] Isotope analysis of samples of moldavites have shown a beryllium-10 isotope composition similar to the composition of Australasian tektites (Australites)and Ivory Coast tektites (Ivorites). Their similarity in beryllium-10 isotope composition indicates that moldavites, Australites, and Ivorites consist of near surface and loosely consolidated terrestrial sediments melted by hypervelocity impacts.^[43]

At right is an image of a piece of native gold discovered as part of a placer deposit, a gold nugget.

Sulfur occurs naturally as the pure element (native sulfur) and as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient times, mentioned for its uses in ancient India, ancient Greece, China and Egypt. Octasulfur is a soft, bright-yellow solid with only a faint odor, similar to that of matches.

Carnotite is a potassium uranium vanadate radioactive mineral with chemical formula: K₂(UO₂)₂(VO₄)₂·3H₂O. The water content can vary and small amounts of calcium, barium, magnesium, iron, and sodium are often present. Carnotite is a bright to greenish yellow mineral that occurs typically as crusts and flakes in sandstones. Amounts as low as one percent will color the sandstone a bright yellow. The high uranium content makes carnotite an important uranium ore and also radioactive. It is a secondary vanadium and uranium mineral usually found in sedimentary rocks in arid climates. It is an important ore of uranium in the Colorado Plateau region of the United States where it occurs as disseminations in sandstone and concentrations around petrified logs.

Cubanite is a yellow mineral of copper, iron, and sulfur, CuFe₂S₃.^[44] Cubanite occurs in high temperature hydrothermal deposits with pyrrhotite and pentlandite as intergrowths with chalcopyrite. It results from exsolution from chalcopyrite at temperatures below 200 to 210 °C.^[45] It has also been reported from carbonaceous chondrite meteorites.^[45]

Microlite is composed of sodium calcium tantalum oxide with a small amount of fluorine (Na,Ca)₂Ta₂O₆(O,OH,F). Microlite is a mineral in the pyrochlore group that occurs in pegmatites and constitutes an ore of tantalum. It has a Mohs hardness of 5.5 and a variable specific gravity of 4.2 to 6.4. It occurs as disseminated microscopic subtranslucent to opaque octahedral crystals with a refractive index of 2.0 to 2.2. Microlite is also called djalmaite. Microlite occurs as a primary mineral in lithium-bearing granite pegmatites, and in miarolitic cavities in granites.

Orpiment, As₂S₃, is a common monoclinic arsenic sulfide mineral. Orpiment is an orange to yellow mineral that is found worldwide [on Earth], and occurs as a sublimation product in volcanic fumaroles, low temperature hydrothermal veins, hot springs and as a byproduct of the decay of another arsenic mineral, realgar.

The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS₂. This mineral's metallic luster and pale brass-yellow hue have earned it the nickname fool's gold because of its superficial resemblance to gold. Pyrite is the most common of the sulfide minerals on Earth. Pyrite is usually found associated with other sulfides or oxides in quartz veins, sedimentary rock, and metamorphic rock, as well as in coal beds, and as a replacement mineral in fossils. Despite being nicknamed fool's gold, pyrite is sometimes found in association with small quantities of gold. Gold and arsenic occur as a coupled substitution in the pyrite structure. In the Carlin–type gold deposits, arsenian pyrite contains up to 0.37 wt% gold.^[46]

Satterlyite is a hydroxyl bearing iron phosphate mineral. The mineral can be found in phosphetic shales. Satterlyite is part of the phosphate mineral group. Satterlyite is a transparent, light brown to light yellow mineral Satterlyite has a formula of (Fe²⁺,Mg,Fe³⁺)₂(PO₄)(OH). Satterlyite occurs in nodules in shale in the Big Fish River (Mandarino, 1978). These nodules were about 10 cm in diameter, some would consist of satterlyite only and others would show satterlyite with quartz, pyrite, wolfeite or maricite.

Holtedahlite, a mineral that was found in Tingelstadtjern quarry in Norway, with the formula (Mg₁₂PO₄)₅(PO₃OH,CO₃)(OH,O)₆ is isostructural with satterlyite (Raade, 1979). Infrared absorption powder spectra show that satterlyite is different than natural haltedahlite in that there is no carbonate for phosphate substitution (Kolitsch, 2002). Satterlyite is also structurally related to phosphoellenbergerite, a mineral that was discovered in Modum, Norway; near San Giocomo Vallone Di Gilba, in Western Alps of Italy (Palache, 1951); the minerals formula is Mg₁₄(PO₄)₅(PO₃OH)₂(OH)₆ (Kolitsch, 2002).

Spurrite is a nesosilicate that can occur naturally as a yellow mineral. Its chemical formula is Ca₅(SiO₄)₂CO₃.^[47] Spurrite is generally formed in contact metamorphism zones as mafic magmas are intruded into carbonate rocks.^[48]

Tarapacaite is a natural mineral pigment composed of potassium chromate which is a likely source of yellow.

Limonite is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·nH₂O, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the two principle iron ores, the other being hematite, and has been mined for the production of iron since at least 2500 BCE.^[49][50] Although originally defined as a single mineral, limonite is now recognized as a mixture of related hydrated iron oxide minerals, among them goethite, akaganeite, lepidocrocite, and jarosite. Individual minerals in limonite may form crystals, but limonite does not, although specimens may show a fibrous or microcrystalline structure,^[51] and limonite often occurs in concretionary forms or in compact and earthy masses; sometimes mammillary, botryoidal, reniform or stalactitic. Because of its amorphous nature, and occurrence in hydrated areas limonite often presents as a clay or mudstone. However there are limonite pseudomorphs after other minerals such as pyrite.^[52] This means that chemical weathering transforms the crystals of pyrite into limonite by hydrating the molecules, but the external shape of the pyrite crystal remains. Limonite pseudomorphs have also been formed from other iron oxides, hematite and magnetite; from the carbonate siderite and from iron rich silicates such as almandine garnets. Limonite usually forms from the hydration of hematite and magnetite, from the oxidation and hydration of iron rich sulfide minerals, and chemical weathering of other iron rich minerals such as olivine, pyroxene, amphibole, and biotite. It is often the major iron component in lateritic soils. One of the first uses was as a pigment. The yellow form produced yellow ochre for which Cyprus was famous.^[53]

"U-Pb ages of zircon from the Firehole and Analcite ash beds in the Eocene Green River Formation (Wyoming, United States) are indistinguishable from ⁴⁰Ar/³⁹Ar ages of sanidine after adjusting the latter to the astronomically calibrated age of 28.201 Ma for the Fish Canyon sanidine standard."^[54]

"Calibrating Green River Formation ⁴⁰Ar/³⁹Ar ages to the 28.201 Ma age for Fish Canyon sanidine permits the first direct comparison of specific Green River Formation strata to the astronomical solution for Early Eocene insolation. This comparison supports the hypothesis that periods of fluvial deposition coincided with minima in long and short eccentricity, and that periods of lake expansion and evaporite deposition correspond to eccentricity maxima."^[54]

"Euhedral, pale yellow zircons were isolated from the Analcite and Firehole ash beds by hand-crushing and heavy liquid concentration."^[54]

"Euhedral crystals [from the Lodran meteorite AMNH 314] of olivine and clear pale yellow fragments of orthopyroxene (Opx) and two green grains were examined by precession camera."^[55]

The earliest brasses may have been natural alloys made by smelting zinc-rich copper ores.^[56]

Rhodolite is a varietal name for rose-pink to red mineral pyrope, a species in the garnet group.

Chemically, rhodolite is an iron-magnesium-aluminium silicate, [(Mg,Fe)₃Al₂(SiO₄)₃,] part of the pyrope-almandine solid-solution series, with an approximate garnet composition of Py₇₀Al₃₀.

Breithauptite is a nickel antimonide mineral with the simple formula NiSb. Breithauptite is a metallic opaque copper-red mineral crystallizing in the hexagonal - dihexagonal dipyramidal crystal system. It is typically massive to reniform in habit, but is observed as tabular crystals. It has a Mohs hardness of 3.5 to 4 and a specific gravity of 8.23.

It occurs in hydrothermal calcite veins associated with cobalt–nickel–silver ores.

Cinnabar or cinnabarite (red mercury(II) sulfide (HgS), native vermilion), is the common ore of mercury. Its color is cochineal-red, towards brownish red and lead-gray. Cinnabar may be found in a massive, granular or earthy form and is bright scarlet to brick-red in color.^[57] Generally cinnabar occurs as a vein-filling mineral associated with recent volcanic activity and alkaline hot springs. Cinnabar is deposited by epithermal ascending aqueous solutions (those near surface and not too hot) far removed from their igneous source.

Crocoite is a mineral consisting of lead chromate, PbCrO₄. Crystals are of a bright hyacinth-red color. Relative rarity of crocoite is connected with specific conditions required for its formation: an oxidation zone of lead ore bed and presence of ultramafic rocks serving as the source of chromium (in chromite).

Eudialyte is a somewhat rare, red silicate mineral, which forms in alkaline igneous rocks, such as nepheline syenites.

Hematite is the mineral form of iron(III) oxide (Fe₂O₃), one of several iron oxides. Hematite is colored black to steel or silver-gray, brown to reddish brown, or red. Huge deposits of hematite are found in banded iron formations.

A variant of ochre containing a large amount of hematite, or dehydrated iron oxide, has a reddish tint known as "red ochre". Red ochre, Fe₂O₃, takes its reddish color from the mineral hematite, which is a dehydrated iron oxide.>

"The rocky objects have rather smooth, red spectra (the Mars spectrum has some incompletely-removed terrestrial features)."^[58]

"The complex terrain of Ariel is viewed in [the image at right], the best Voyager 2 color picture of the Uranian moon. The individual photos used to construct this composite were taken Jan. 24, 1986, from a distance of 170,000 kilometers (105,000 miles. Voyager captured this view of Ariel's southern hemisphere through the green, blue and violet filters of the narrow-angle camera; the resolution is about 3 km (2 mi). Most of the visible surface consists of relatively intensely cratered terrain transected by fault scarps and fault-bounded valleys (graben). Some of the largest valleys, which can be seen near the terminator (at right), are partly filled with younger deposits that are less heavily cratered. Bright spots near the limb and toward the left are chiefly the rims of small craters. Most of the brightly rimmed craters are too small to be resolved here, although one about 30 km (20 mi) in diameter can be easily distinguished near the center. These bright-rim craters, though the youngest features on Ariel, probably have formed over a long span of geological time. Although Ariel has a diameter of only about 1,200 km (750 mi), it has clearly experienced a great deal of geological activity in the past."^[59]

"Asteroids in particularly large classes tend to be broken into subgroups with the first letter denoting the dominant group and the succeeding letters denoting less prominent spectral affinities or subgroups."^[60]

"The recent investigation of the orbital distribution of Centaurs (Emel’yanenko et al., 2005) showed that there are two dynamically distinct classes of Centaurs, a dominant group with semimajor axes a > 60 AU and a minority group with a < 60 AU."^[61] "[T]he intrinsic number of such objects is roughly an order of magnitude greater than that for a<60 AU".^[61]

"From the dominant group, the asteroids evolve to intersect the Earth's orbit on a median time scale of about 60 Myr."^[62] "The MB group is the most numerous group of MCs. 50 % of the MB Mars-crossers [MCs] become ECs within 59.9 Myr and [this] contribution dominates the production of ECs"^[62]. MB denotes the main belt of asteroids.^[62] EC denotes Earth-crossing.^[62]

"Spectrally blue (B-type) asteroids are rare, with the second discovered asteroid, Pallas, being the largest and most famous example."^[63]

"[T]he negative optical spectral slope of some B-type asteroids is due to the presence of a broad absorption band centered near 1.0 μm. The 1 μm band can be matched in position and shape using magnetite (Fe₃O₄), which is an important indicator of past aqueous alteration in the parent body. ... Observations of B-type asteroid (335) Roberta in the 3 μm region reveal an absorption feature centered at 2.9 μm, which is consistent with the absorption due to phyllosilicates (another hydration product) observed in CI chondrites. ... at least some B-type asteroids are likely to have incorporated significant amounts of water ice and to have experienced intensive aqueous alteration."^[63]

C-type asteroids are carbonaceous asteroids. They are the most common variety, forming around 75% of known asteroids,^[64] and an even higher percentage in the outer part of the asteroid belt beyond 2.7 AU, which is dominated by this asteroid type. The proportion of C-types may actually be greater than this, because C-types are much darker than most other asteroid types except D-types and others common only at the extreme outer edge of the asteroid belt. Their spectra contain moderately strong ultraviolet absorption at wavelengths below about 0.4 μm to 0.5 μm, while at longer wavelengths they are largely featureless but slightly reddish. The so-called "water" absorption feature around 3 μm, which can be an indication of water content in minerals is also present.

F-type asteroids have spectra generally similar to those of the B-type asteroids, but lack the "water" absorption feature around 3 μm indicative of hydrated minerals, and differ in the low wavelength part of the ultraviolet spectrum below 0.4 μm.

G-type asteroids are a relatively uncommon type of carbonaceous asteroid. The most notable asteroid in this class is 1 Ceres. Generally similar to the C-type objects, but containing a strong ultraviolet absorption feature below 0.5 μm.

At right is a complete global color image of Callisto. Bright scars on a darker surface testify to a long history of impacts on Jupiter's moon Callisto. The picture, taken in May 2001, is the only complete global color image of Callisto obtained by Galileo, which has been orbiting Jupiter since December 1995. Of Jupiter's four largest moons, Callisto orbits farthest from the giant planet. Callisto's surface is uniformly cratered but is not uniform in color or brightness. Scientists believe the brighter areas are mainly ice and the darker areas are highly eroded, ice-poor material.

Callisto's ionosphere was first detected during Galileo flybys;^[65] its high electron density of 7–17 x 10⁴ cm⁻³ cannot be explained by the photoionization of the atmospheric carbon dioxide alone.

High-resolution ultraviolet Hubble Space Telescope images taken in 1995 showed a dark spot on its surface which was nicknamed "Piazzi" in honour of the discoverer of Ceres.^[66] This was thought to be a crater. Later near-infrared images with a higher resolution taken over a whole rotation with the Keck telescope using adaptive optics showed several bright and dark features moving with the dwarf planet's rotation.^[67][68]

The image at the right is an optical astronomy image of the comet 67P/Churyumov-Gerasimenko. Rosetta's OSIRIS narrow-angle camera made the image on 3 August 2014 from a distance of 285 km. The image resolution is 5.3 metres/pixel.

The left image is rotated 90° from the right. The location of the right image is the front view of the left side just out of view in the left image. The object rotates by the right hand rule from the left image to the right.

Note that due to the evaporation of volatiles, the surface of the rocky object appears pitted or cratered.

This at right is an "[e]nhanced color composite of Saturn's moon Dione, based on infrared, green, ultraviolet, and clear-filter images [is] taken by the Cassini spacecraft December 14, 2004."^[69]

It shows "the darker, fractured terrain of the trailing hemisphere. The Padua Chasmata trace an arc on the left, interrupted near the top by central peak crater Ascanius. The Janiculum Dorsa extend along the upper right terminator. Near the lower left limb is the small crater Cassandra with its prominent ray system."^[69]

At left is another image of Dione partially rotated from the one at right and showing a violet cast on the apparent higher elevation portion toward the terminator. This image is from Cassini "taken 1 August 2005 from 243,000 km away."^[70]

"The south polar terrain is marked by a striking set of 'blue' fractures and encircled by a conspicuous and continuous chain of folds and ridges, testament to the forces within Enceladus that have yet to be silenced."^[71]

"The mosaic was created from 21 false-color frames taken during the Cassini spacecraft's close approaches to Enceladus on March 9 and July 14, 2005. Images taken using filters sensitive to ultraviolet, visible and infrared light (spanning wavelengths from 338 to 930 nanometers) were combined to create the individual frames."^[71]

"The mosaic is an orthographic projection centered at 46.8 degrees south latitude, 188 degrees west longitude, and has an image scale of 67 meters (220 feet) per pixel. The original images ranged in resolution from 67 meters per pixel to 350 meters (1,150 feet) per pixel and were taken at distances ranging from 11,100 to 61,300 kilometers (6,900 to miles) from Enceladus."^[71]

"Reddish spots and shallow pits pepper the enigmatic ridged surface of Europa in this view [at right] combining information from images taken by NASA's Galileo spacecraft during two different orbits around Jupiter."^[72]

"The image combines higher-resolution information obtained when Galileo flew near Europa on May 31, 1998, during the spacecraft's 15th orbit of Jupiter, with lower-resolution color information obtained on June 28, 1996, during Galileo's first orbit."^[72]

"In this global view of Ganymede's trailing side, the colors are enhanced to emphasize color differences. The enhancement reveals frosty polar caps in addition to the two predominant terrains on Ganymede, bright, grooved terrain and older, dark furrowed areas. Many craters with diameters up to several dozen kilometers are visible. The violet hues at the poles may be the result of small particles of frost which would scatter more light at shorter wavelengths (the violet end of the spectrum). Ganymede's magnetic field, which was detected by the magnetometer on NASA's Galileo spacecraft in 1996, may be partly responsible for the appearance of the polar terrain. Compared to Earth's polar caps, Ganymede's polar terrain is relatively vast. The frost on Ganymede reaches latitudes as low as 40 degrees on average and 25 degrees at some locations. For comparison with Earth, Miami, Florida lies at 26 degrees north latitude, and Berlin, Germany is located at 52 degrees north."^[73]

"North is to the top of the picture. The composite, which combines images taken with green, violet, and 1 micrometer filters, is centered at 306 degrees west longitude. The resolution is 9 kilometers (6 miles) per picture element. The images were taken on 29 March 1998 at a range of 918000 kilometers (570,000 miles) by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft."^[73]

"Although it is no longer uncharted land, the origin of the dark territory of Cassini Regio on Iapetus remains a mystery. Also puzzling is the equatorial ridge that bisects this terrain, and how it fits into the story of the moon's strange brightness dichotomy. The ridge is seen here, curving along the lower left edge of Iapetus. The view looks down onto the northern hemisphere of Iapetus (1,468 kilometers, or 912 miles across), and shows terrain on the moon's leading hemisphere."^[74]

"The image was taken in polarized green light with the Cassini spacecraft narrow-angle camera on Nov. 12, 2005 at a distance of approximately 417,000 kilometers (259,000 miles) from Iapetus and at a Sun-Iapetus-spacecraft, or phase, angle of 95 degrees. Image scale is about 2 kilometers (1 mile) per pixel."^[74]

In the second image are three "different false-color views of Saturn's moon Iapetus show the boundary of the global "color dichotomy" on the hemisphere of this moon facing away from Saturn. The "color dichotomy," which has been detected in images from the Cassini imaging team, is a second global pattern found on Iapetus besides the well-known global brightness dichotomy."^[75]

"This image consists of three panels, each of which was contrast-enhanced in different ways to bring out surface features. Minimal enhancement was applied to the image on the left panel while those on the middle and right panels were enhanced more (with contrast increased by factors of two and four, respectively), making them appear brighter and overexposed."^[75]

"In the case of the color dichotomy seen here, its boundary is quite well correlated with the boundary between the moon's leading and the trailing hemispheres. At near-infrared wavelengths, the bright terrain on the leading side is redder than on the trailing side. This pattern is visible in the panel on the left, which uses normal contrast enhancement. The characteristic reddish distribution also appears on the dark material, as seen in the middle and right-hand panels that have been adjusted with even higher contrast. Indeed, the otherwise uniformly dark material shows different color hues, depending on whether the viewer looks at the leading vs. the trailing side."^[75]

"This is the first full picture showing both asteroid 243 Ida and its newly discovered moon to be transmitted to Earth from the National Aeronautics and Space Administration's (NASA's) Galileo spacecraft--the first conclusive evidence that natural satellites of asteroids exist. Ida, the large object, is about 56 kilometers (35 miles) long. Ida's natural satellite is the small object to the right. This portrait was taken by Galileo's charge-coupled device (CCD) camera on August 28, 1993, about 14 minutes before the Jupiter-bound spacecraft's closest approach to the asteroid, from a range of 10,870 kilometers (6,755 miles). Ida is a heavily cratered, irregularly shaped asteroid in the main asteroid belt between Mars and Jupiter--the 243rd asteroid to be discovered since the first was found at the beginning of the 19th century. Ida is a member of a group of asteroids called the Koronis family. The small satellite, which is about 1.5 kilometers (1 mile) across in this view, has yet to be given a name by astronomers. It has been provisionally designated '1993 (243) 1' by the International Astronomical Union. ('1993' denotes the year the picture was taken, '243' the asteroid number and '1' the fact that it is the first moon of Ida to be found.) Although appearing to be 'next' to Ida, the satellite is actually in the foreground, slightly closer to the spacecraft than Ida is. Combining this image with data from Galileo's near-infrared mapping spectrometer, the science team estimates that the satellite is about 100 kilometers (60 miles) away from the center of Ida. This image, which was taken through a green filter, is one of a six-frame series using different color filters. The spatial resolution in this image is about 100 meters (330 feet) per pixel."^[76]

"With over 400 active volcanoes, Io is the most geologically active object in the Solar System.^[77][78] Most of Io's surface is characterized by extensive plains coated with sulfur and sulfur dioxide frost. Io's volcanism is responsible for many of the satellite's unique features. Its volcanic plumes and lava flows produce large surface changes and paint the surface in various shades of yellow, red, white, black, and green, largely due to allotropes and compounds of sulfur.

In the image at right, the smallest features that can be discerned are 2.5 kilometers in size. There are rugged mountains several kilometers high, layered materials forming plateaus, and many irregular depressions called volcanic calderas. Several of the dark, flow-like features correspond to hot spots, and may be active lava flows. There are no landforms resembling impact craters, as the volcanism covers the surface with new deposits much more rapidly than the flux of comets and asteroids can create large impact craters. The picture is centered on the side of Io that always faces away from Jupiter; north is to the top.

Mars is the fourth planet from the Sun in the Solar System. Named after the Roman god of war, Mars, it is often described as the "Red Planet" as the iron oxide prevalent on its surface gives it a reddish appearance.^[79] The red-orange appearance of the Martian surface is caused by iron(III) oxide, more commonly known as hematite, or rust.^[80] Much of the surface is deeply covered by finely grained iron(III) oxide dust.^[81][82]

"A higher-reflectance, relatively red material occurs as a distinct class of smooth plains that were likely emplaced volcanically; a lower-reflectance material with a lesser spectral slope may represent a distinct crustal component enriched in opaque minerals, possibly more common at depth."^[83]

"The distinctively red smooth plains (HRP) appear to be large-scale volcanic deposits stratigraphically equivalent to the lunar maria (20), and their spectral properties (steeper spectral slope) are consistent with magma depleted in opaque materials. The large areal extent (>10⁶ km²) of the Caloris HRP is inconsistent with the hypothesis that volcanism was probably shallow and local (10); rather, such volcanism was likely a product of extensive partial melting of the upper mantle."^[83]

"Despite the dearth of ferrous iron in silicates, Mercury's surface nonetheless darkens and reddens with time like that of the Moon. This darkening and reddening has been interpreted to be the result of production of nanophase iron (e.g., Pieters et al., 2000; Hapke, 2001), which could be derived from an opaque phase in the crustal material or from delivery by micrometeorite impacts (Noble and Pieters, 2003). On the Moon, deposits that are brighter and redder than the average Moon spectrum appear to be lower in iron (e.g., highland material); deposits that are darker and redder than average are higher in iron (e.g., low-Ti mare material) (Lucey et al., 1995)."^[84]

"This color composite [at lower right] of the Uranian satellite Miranda was taken by Voyager 2 on Jan. 24, 1986, from a distance of 147,000 kilometers (91,000 miles). This picture was constructed from images taken through the narrow-angle camera's green, violet and ultraviolet filters. It is the best color view of Miranda returned by Voyager."^[85]

"Miranda, just 480 km (300 mi) across, is the smallest of Uranus' five major satellites. Miranda's regional geologic provinces show very well in this view of the southern hemisphere, imaged at a resolution of 2.7 km (1.7 mi). The dark- and bright-banded region with its curvilinear traces covers about half of the image. Higher-resolution pictures taken later show many fault valleys and ridges parallel to these bands. Near the terminator (at right), another system of ridges and valleys abuts the banded terrain; many impact craters pockmark the surface in this region. The largest of these are about 30 km (20 mi) in diameter; many more lie in the range of 5 to 10 km (3 to 6 mi) in diameter."^[85]

"During its flight, the Galileo spacecraft returned images of the Moon. The Galileo spacecraft took these images on December 7, 1992 on its way to explore the Jupiter system in 1995-97. The distinct bright ray crater at the bottom of the image is the Tycho impact basin. The dark areas are lava rock filled impact basins: Oceanus Procellarum (on the left), Mare Imbrium (center left), Mare Serenitatis and Mare Tranquillitatis (center), and Mare Crisium (near the right edge). This picture contains images through the Violet, 756 nm, 968 nm filters. The color is 'enhanced' in the sense that the CCD camera is sensitive to near infrared wavelengths of light beyond human vision."^[86]

The Moon has been detected using gamma-ray astronomy. These gamma-rays are produced by cosmic ray bombardment of its rocky surface.

Four radiometers aboard Luna 13 recorded infrared radiation from the Moon's surface.

"Nine out of 10 well-characterized Apollo 17 breccia matrices fall into Group 2, and this includes both the blue-grey breccias which are the dominant rock type at this site".^[87]

"Pallas, minor-planet designation 2 Pallas, is the second asteroid to have been discovered (after Ceres), and one of the largest in the Solar System. It is estimated to comprise 7% of the mass of the asteroid belt,^[88] and its diameter of 544 kilometres (338 mi) is slightly larger than that of 4 Vesta. It is however 10–30% less massive than Vesta,^[89] placing it third among the asteroids.

Rocky objects have been used to approximate a location for the Sun based on Kepler's laws. No rocky objects are known to have been emitted, reflected, or deflected by the Sun. Nor, have any rocky objects impacted the surface of the Sun.

"Sun-grazing comets almost never re-emerge, but their sublimative destruction near the sun has only recently been observed directly, while chromospheric impacts have not yet been seen, nor impact theory developed."^[90] "[N]uclei are ... destroyed by ablation or explosion ... in the chromosphere, producing flare-like events with cometary abundance spectra."^[90]

"The death of a comet at r ~ R_ʘ has been seen directly only very recently (Schrijver et al 2011) using the SDO AIA XUV instrument. This recorded sublimative destruction of Comet C/2011 N3 as it crossed the solar disk very near periheloin q = 1.139R_ʘ."^[90]

At right is the first global high-resolution color image of Tethys.

"The color map shows the prominent dusky bluish band along the equator, first seen by Voyager in 1980, and shown ... to be due to the bombardment and alteration of the surface by high energy electrons traveling slower than the satellite's revolution period."^[91]

"This false color image of Triton is a composite of images taken through the violet, green and ultraviolet filters. The image was taken early on Aug. 25, 1989 when Voyager 2 was about 190,000 kilometers (118,000 miles) from Triton's surface. The smallest visible features are about 4 kilometers (2.5 miles) across. The image shows a geologic boundary between completely dark materials and patchy light/dark materials. A layer of pinkish material stretches across the center of the image. The pinkish layer must be thin because underlying albedo patterns show through. Several features appear to be affected by the thin atmosphere; the elongated dark streaks may represent particulate materials blown in the same direction by prevailing winds, and the white material may be frost deposits. Other features appear to be volcanic deposits including the smooth, dark materials alongside the long, narrow canyons. The streaks themselves appear to originate from very small circular sources, some of which are white, like the source of the prominent streak near the center of the image. The sources may be small volcanic vents with fumarolic-like activity. The colors may be due to irradiated methane, which is pink to red, and nitrogen, which is white."^[92]

The object at left is detected to be a rocky object beneath extensive clouds using radar astronomy. It is a false color image of Venus produced from a global radar view of the surface by the Magellan probe while radar imaging between 1990-1994.

"The [NASA's Dawn spacecraft] Framing Camera (FC) discovered enigmatic orange material on Vesta. FC images revealed diffuse orange ejecta around two impact craters, 34-km diameter Oppis, and 30-km diameter Octavia, as well as numerous sharp-edge orange units in the equatorial region."^[93] The spacecraft "entered orbit around asteroid (4) Vesta in July 2011 for a year-long mapping orbit."^[93]

"Using Dawn’s Gamma Ray and Neutron Detector, ... Global Fe/O and Fe/Si ratios are consistent with [howardite, eucrite, and diogenite] HED [meteorite] compositions."^[94]

"The presence of elements heavier than helium in white dwarf atmospheres is often a signpost for the existence of rocky objects that currently or previously orbited these stars."^[95]

"Al can be quite abundant in rocky objects formed at high temperatures".^[95]

1. Radar astronomy is especially beneficial on rocky objects.

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