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Pluto Walk, Lowell Observatory

pluto walk
Discoverer of the (Dwarf) Planet: Clyde Tombaugh

This photo was taken September 1990 in Flagstaff, Arizona during a chance meeting between Doug Hollis and myself (David Weir), and with Clyde Tombaugh and his wife Patricia. They happened to be visiting the observatory, from which Clyde discovered the ninth planet Pluto, to make their first stroll together down the newly constructed Pluto Walk. The photo was shared with Clyde and received his signature in May 1992.

 

 

 

 

 

 

 

Congratulations Clyde Tombaugh on your historic visit to Pluto!

Pluto: Dwarf Planet
Pluto’s Moon: Charon

NASA’s New Horizons spacecraft captured the above high-resolution enhanced color images of Pluto and Charon on July 14, 2015. The Pluto and Charon images resolve details as small as 0.8 miles and 1.8 miles, respectively. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.

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Denshal Dog Data: Is the Nakhla Dog Real?

Separating Myth from Fact: Is the Nakhla Dog Real?

A Personal Analysis By David Weir

standby for nakhla photo Although my skeptical nature leads me to scrutinize the impact dog event, I remain open-minded to new evidence supporting either side. Despite the absence of eyewitnesses and newspaper articles, I am of the mind that the probability of such a dog impact in Denshal can be further assessed through the scientific method, using the data and theoretical applications currently available.

While looking through the literature for any helpful data, I found a non-peer-reviewed paper published by Eugster et al. in LPSC 33 (2002), in which they describe research on ‘The Pre-Atmospheric Size Of Martian Meteorites’. The upper limit of the radii of martian ejecta translates to masses of 150–270 kg–too high to be a limiting factor when considering a Nakhla strewn field that might extend all the way to Denshal. However, in a diagram that compares the minimum pre-atmospheric weights of several Martian meteorites–including Nakhla, Zagami, Shergotty, QUE 94201, Chassigny, Los Angeles, and SaU 005–it is Nakhla that has the lowest, i.e., the smallest size. Therefore, one might reasonably expect Nakhla to also be at the low end of the range of weights of all martian meteorite falls, especially if a pattern is evident. The falls include the following four meteorites, listed in order from the smallest to the largest minimum calculated pre-atmospheric size, with the actual fall weights given in parentheses: Nakhla (10 kg), Zagami (18 kg), Shergotty (5 kg), and Chassigny (4 kg).

For those Martian meteorites that are finds, the two with the largest minimum pre-atmospheric masses, again with the actual fall weights given in parentheses, are SaU 005 (1.3 kg, but 10.6 kg with paired masses included) and then Los Angeles (0.7 kg), either of which may or may not be representive of their cumulative fall weights. In addition, having a minimum pre-atmospheric size similar to that of Chassigny, the Antarctic QUE 94201 (0.012 kg) likely does not represent its total fall weight. Although not included in this study, two other martians with large recovered weights can be mentioned for comparison–EET 79001 (7.9 kg) and the DaG 476 grouping (6.3 kg).

While I don’t observe a pattern, I would not expect the Nakhla fall to be much bigger than these. To my speculation, a greatly extended strewn field for Nakhla, with the usual pattern of larger masses falling further down range (into Denshal and the dog), would significantly increase the fall weight of Nakhla–a weight that presently seems to fit among the others quite comfortably, especially considering it was ascribed the lowest minimum pre-atmospheric weight.

While this is admittedly only a rudimentary stab at resolving the issue, I think there are other data out there, which taken together, could establish a preponderance of evidence and tip the scale one way or the other. For instance, in The Shergotty Consortium, published in Geochimica vol. 50, 1986, there are peer-reviewed papers concerning the pre-atmospheric and final fall sizes of certain shergottites. Following a determination of CRE ages from known profiles, cosmic ray track densities of specific samples were used to calculate the sample’s shielding depth and ablation characteristics on the pre-atmospheric meteoroid. This information was then used to calculate the size of the pre-atmospheric mass. From this calculated meteoroid size, the production rate of cosmogenic nuclides at different depths was used to better constrain the CRE age. For Shergotty, a pre-atmospheric size of ~12 cm was calculated. This is equal to a mass of 26 kg, of which only 5 kg was recovered, inferring an ablation rate of 80%. Ablation rates of 50–80% were determined for other shergottites.

This type of study could be done for Nakhla. Each piece of Nakhla studied would have cosmic ray track densities that were consistent with a specific shielding geometry, which should be consistent with the pre-atmospheric size as calculated from production rates of cosmogenic and radiogenic nuclides. An examination of a representative sampling of Nakhla fragments should be able to constrain its size and ablation characteristics, and perhaps determine if any anomalies in its fall weight are present. If not, it would be evidence tipping the scale in favor of a limited strewn field, thus ruling out an impact on a dog 33 km downrange in Denshal.


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Desert Varnish

DESERT VARNISH

This widespread desert phenomena has been considered by some to be a biogeochemical process that occurs in arid regions throughout the world (e.g., Grote and Krumbein, 1992). Desert varnish coatings on rocks might only be 0.01 mm thick, but they can turn entire desert mountain ranges black or reddish brown. Desert varnish is the result of a disequilibrium process incorporating oxides of manganese and iron, along with clays that form together on the surface of rocks exposed to the Sun for thousands of years. Desert varnish is considered by some to have formed by the actions of microscopic bacterial colonies living on the rock surface, but evidence for this process has not been documented. Trace amounts of manganese and iron are absorbed from the atmosphere and precipitated as a black layer of manganese oxide or reddish iron oxide on the rock surface. This thin layer also includes cemented clay particles. It has been estimated that up to 10,000 years are required for a complete varnish coating to form in extreme arid desert regions. A diagramatic representation of a possible biogeochemical process is shown below:

standby for desert varnish diagram

Perry et al. (2006) present their analysis of desert varnish in ‘Baking black opal in the desert sun: The importance of silica in desert varnish’. They revealed the presence of amorphous hydrated silica (opal) and the silica mineral moganite, similar to findings from siliceous hot-spring deposits. They conclude ‘… the slow dissolution of silica from anhydrous and hydrous minerals, and its subsequent gelling, condensation, and hardening, provides a simple explanation of a formation mechanism for desert varnish and silica glazes and the incorporation of organic material from local environments.’

In their paper ‘Nanometer-scale complexity, growth, and diagenesis in desert varnish’, Garvie et al. (2008) report on a high-resolution and spectroscopic study of desert varnish on a variety of rock samples from the Sonoran Desert of Arizona. They found that clay is the primary component of desert varnish incorporating nm-scale layers rich in Mn-bearing phases and Fe oxide (hematite), along with some secondary and trace elements proposed to be derived from atmospheric aerosols. Although C grains within the varnish possibly represent fungal and/or bacterial remnants, the formation of desert varnish is considered to be the result of mainly abiotic processes of diagenesis including hydration, evaporation, dissolution, freezing, baking, redox, and other forms of chemical and structural modification. They contend that opal may serve as a cementing material in some rocks. It is calculated that desert varnish is very slowly accumulated at rates of <1µm to perhaps tens of µm/t.y.


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COPYRIGHT


Many people think U.S. copyright law was created just to protect those who hold the rights to articles, books, music, software and other intellectual properties. However, the law’s purpose is mainly to encourage creativity in the arts, science and industry. It does this by offering financial incentive to creators.

1. What is intellectual property? Intellectual property is a legal concept under which we manage the protection and use of products of the human mind (as opposed to the human hand). The U.S. Constitution and the ‘Federalist Papers’ refer specifically to patents (which apply to ‘useful articles’, traditionally inventions) and copyright (which applies to ‘literary expressions’, traditionally books and articles) as comprising the scope of intellectual property. There have also been some more recent additions: Outside of patents and copyrights, there are such things as trademarks and service marks (like ‘Coca Cola’), ‘trade dress’ (a more amorphous concept involving the ‘look’ of a product, like Coca Cola’s red & white can with a script logo), ‘trade secrets’, and others. All of these separate areas of the law and commerce have been collected under the general term ‘intellectual property’. However, they are very different from each other and are meant to protect different things. 2. Is copyright law the same for words, pictures, movies, music and software? Yes, for the most part. Sure, it’s easy to download and reproduce materials that you might find on the Web, but that doesn’t make it lawful. Technically speaking, copyright law does deal differently with various media like music and software. However, these differences tend to be largely technical, and they are outweighed by the similarities in the law’s application. 3. Is it hard to get a copyright? No, it’s easy. Under U.S. law, anything original and creative, even your diary, memos, and personal correspondence, is protected by copyright. This protection is automatic, from the moment you create something, whether on paper or electronically. So, why bother to register your copyright with the federal government? Well, for one thing, it makes you eligible to receive ‘statutory damages’ which could reach as high as $100,000 per infringement. 4. Do I need a copyright notice to protect my work (writings, art, music, etc.)? Not at all. Copyright notices stopped being mandatory in this country in 1989 when the U.S. joined the Berne Convention. Still, using a notice is a good idea. That way, you put others on notice that you consider a work to be your property, and that nobody should use it without your permission. The correct form for a copyright notice is ‘Copyright [year of creation] by [author/owner]’. That’s it! Many people use the C-in-a-circle symbol instead of the word ‘Copyright’. Any copyright notice should be in the correct owner’s name. 5. If I see something and it does not have a copyright notice, does that automatically mean I can use it? No. A copyright notice is not required to have copyright protection. It is true that many things are not protected by copyright. However, it is a good practice to analyze any work that has no copyright notice, and determine whether it is likely to be protected by copyright. 6. If I use somebody’s work without permission but give credit to the author or publisher, am I still infringing on copyright? Probably. Giving credit is great, but nothing in the copyright law says that it somehow absolves you of infringement. If you are infringing, giving credit won’t help you! 7. Am I infringing on copyright even if I don’t make money from using somebody else’s material? Probably. Nothing in the copyright law says that not making money absolves you of infringement. In fact, Congress recently clarified the law on this point. On the other hand, not making money and not using the work for business purposes may help your argument that you were engaged in ‘fair use.’ 8. Is there anything I can use that I did not create myself? Yes. For example, works in the public domain are freely available to everyone. Public domain materials in the U.S. fall into two major groups: (1) works where the copyright has expired (generally materials created before 1923, plus some later works), and (2) works of the federal government. Both groups have exceptions, though. Do not automatically assume that if a work appears to fall into one of these groups, it is in the public domain. For example, Shakespeare’s original works are in the public domain, but recent movie versions of these plays are not. Similarly, while works by the federal government are in the public domain, works prepared for the federal government frequently are not. 9. How do I make ‘fair use’ of copyrighted works? This is a complicated concept and the subject of many lawsuits, learned articles and treatises. Some parts of fair use were written into the copyright statute in 1976. Fair use generally lets you use portions of copyrighted materials in face-to-face teaching, personal discussion, research, and news reporting. But how much you can use and what you can do with the material is by no means clear. Ultimately, it is up to a judge or jury whether you have ‘gone too far’ and how the law applies to your situation. 10. Can I reprint facts? Sure. Facts do not belong to anyone and they are not protected by copyright. However, there is a catch! The way a fact is expressed can be protected, if it is unique and creative. ‘The flag is flying’ is a fact not protectable by copyright. But ‘Oh, say, can you see, by the dawn’s early light, what so proudly we hailed at the twilight’s last gleaming?’ is an expression of the same fact that would be protected (except, since it was written in 1814, it is now in the public domain!). The quintessential example of unprotectable facts, as decided by the Supreme Court, is the telephone white pages. That’s because they contain no original or creative information. On the other hand, other courts have stated that certain aspects of the telephone yellow pages CAN be protected by copyright. That just goes to show how little originality or creativity is required for copyright protection! 11. Is copyright infringement always criminal? No. It can be a criminal violation with possible prison penalties, but it is most often a civil violation. That means the copyright holder needs to sue an infringer. If the infringement is proven, the rightsholder will get money either commensurate with the damage to the owner, or with the benefit gained by the infringer. There may possibly be statutory damages and an order (injunction) for the infringement to cease. In both civil and criminal cases, the statute of limitations for infringement is generally three years.

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Carbonado

standby for carbonado photo
Recognized 1840’s
Bahia Province, Brazil Terrestrial History

The name carbonado, meaning burnt or carbonized in Portuguese, was given to this material upon its discovery in Brazil in the 1840’s. This dark gray to black variant of diamond has been mined in the Bahia Province of Brazil since that time. Due to its much greater hardness than typical diamond, it is used industrially for drills and for edges in cutting implements. Carbonado was subsequently found to occur in the same sedimentary geological horizon on a separate continent—in the Ubangui region of the Central African Republic, and has also been reported to occur in Venezuela and the Soviet Union. Carbonado diamond is unique to these limited regions, and it has never been found during any conventional diamond mining and processing operations around the world. The largest recorded carbonado, weighing 3,167 carats (633.4 grams) and named ‘Sergio’, was found in Brazil in 1905.

In the ongoing debate to explain the circumstances surrounding the terrestrial occurrence of this unusual diamond, the theory which posits an arrival during a Precambrian (late Archaean) impact event has remained one of the primary contenders. The arrival occurred at a time when the present-day continents of South America and Africa formed a unified supercontinent known as Rodinia. A magnetic anomaly discovered in Central Africa, encompassing an area over 700,000 km², has also been dated to the Precambrian time. This impact feature, the largest known on Earth, might be associated with the delivery of the carbonado diamonds.

In a contrary opinion, S. Master (1998) proposed that the Precambrian feature known as the Kogo Structure in Equatorial Guinea (1° 11′ N., 10° 1′ E.), measuring 4.67 km in diameter, would have been situated exactly between the Brazilian and Central African carbonado source locations at the time of its occurrence. He determined that a direct relationship exists between the size of the carbonados and their distance from the Kogo Structure, and suggested that this is the probable impact point from which these diamonds were disseminated. The diagram below presented by Stephen E. Haggerty (2014) shows the only known site of carbonado as it appeared ~1.1 b.y. ago, on the Congo–São Francisco craton (age 3.3–3.7 b.y.; Barbosa and Sabate, 2004). This craton was either part of the Rodinia supercontinent or the pre-Rodinia supercontinent Nuna, the latter of which likely existed between ~1.78 b.y. and ~1.40 b.y. ago (Zhang et al., 2012). The Congo–São Francisco craton, at the time part of Gondwonaland, broke up ~180 m.y. ago into what is now Brazil and the Central African Republic. standby for carbonado locations photo
Image credit: Stephen E. Haggerty, Earth-Science Reviews, vol. 130, pp. 49–72 (March 2014, open access link)
‘Carbonado: Physical and chemical properties, a critical evaluation of proposed origins, and a revised genetic model’
(https://doi.org/10.1016/j.earscirev.2013.12.008)
Physical Characteristics

As described by Garai et al. (2006), carbonados are porous (5–15 vol%; Haggerty, 2017), polycrystalline aggregates of sub-µm- to µm-sized, mostly cuboid-shaped diamond crystallites in random orientation. The nodules have a polished surface rind reminiscent of a fusion crust, and it is considered likely that entry- and impact-related processes, including partial ablation at extremely high temperatures in Earth’s primordial oxygen-poor atmosphere, melted an initially porous texture. Thereafter, secondary mineralization filled the remaining surface pores with silica-based minerals. The interior of carbonado nodules is highly vesiculated, with some pores measuring up to 1 mm in size, and polycyclic aromatic hydrocarbons (PAHs) fill the pores (Kletetschka et al., 2000).

In their magnetization studies of carbonado, Kletetschka et al. (2000) found that magnetic carriers are only present at the smooth surface of carbonado nodules and that the nodules are completely non-magnetic throughout the interior. This suggests that the magnetic carriers were not present at the initial site of carbonado formation, but instead were added during the ablation process in Earth’s atmosphere and/or during secondary terrestrial weathering processes. This finding is contrary to what one would find given an origin within Earth’s crust or mantle.

While the C- and N-isotopic compositions and N abundances of carbonados recovered from Central Africa and Brazil are indistinguishable from each other, they are unlike any known terrestrial-sourced diamond varieties and are inconsistent with either a crustal or mantle origin (Shelkov et al., 1995; A. Pradenas, 2015). These unusual values, such as the isotopically light C content (δ13C ~ –27‰ compared to typical upper mantle values of δ13C ~ –5‰) and the low N abundances, are consistent with an extraterrestrial origin exemplified by Solar System material having high contents of organic matter (e.g., carbonaceous chondrites, comets). standby for carbonado c and n isotopic diagram
Image credit: Stephen E. Haggerty, Earth-Science Reviews, vol. 130, pp. 49–72 (March 2014, open access link)
‘Carbonado: Physical and chemical properties, a critical evaluation of proposed origins, and a revised genetic model’
(https://doi.org/10.1016/j.earscirev.2013.12.008)
Notably, P. Cartigny (2010) has described diamonds from Dachine komatiite (French Guyana) that exhibit high isotopic variability including some with isotopic similarities to carbonado. Therefore, and he suggests a possible formation for carbonado in the high-temperature transition zone at depths >300 km, as compared to depths of 150–300 km for typical diamonds. However, these findings of P. Cartigny (2010) are contrary to other studies which have found different isotopic values as well as a lack of isotopic variability in the transition zone (A. Pradenas, 2015). Moreover, his conclusion is at odds with the fact that carbonado has never been found associated with komatiites.

Spectroscopic analyses of mineral inclusions in carbonado diamond matrices from Brazilian and Central African source locations reveal the presence of highly reduced metals and metal alloys, including Fe, Si, Ti, Ni, Ag, FeNi-metal, FeCr-metal, and NiCr-metal, as well as the carbide SiC (De et al., 1998; Garai et al., 2006 and references therein); such highly reducing conditions occur within the deep mantle and are associated with certain solar system objects (S. Haggerty et al., 2014 and references therein). The presence of these exotic metals and alloys provides further evidence for an extraterrestrial origin for carbonado. The mineral osbornite (TiN) has also been identified in carbonado, a nitride previously found only in certain meteorites and recently acquired through NASA’s Stardust mission to comet Wild 2 (Jones et al., 2003). Theories of Origin

Over the years, various non-impact theories have been put forth to explain the formation of these enigmatic diamonds, including chemical vapor deposition (CVD), irradiation of carbonaceous material (e.g., kerogen, coal) over geologic timescales by highly energetic particles emitted from radiogenic U and Th, subduction of crustal organic matter into the mantle, and impact metamorphism of Archaean rock containing concentrated organic biomass. In their studies of carbonado, Yokochi et al. (2008) found that the cathodoluminescence spectra and the 40Ar values are inconsistent with an impact-generated formation for this diamond, and also that the relatively low concentration of Ar is inconsistent with a CVD origin of carbonado diamond.

Ozima and Zashu (1991) conducted noble gas isotopic studies in order to study the mechanism of diamond formation through irradiation by energetic particles. Their results do support the theory of micro-scale diamond formation through high-energy irradiation. They found that carbonado contains a high abundance of radiogenic 4He, nucleogenic 21Ne, and parentless 136Xe and 86Kr. This is consistent with implantation through an external radioactive decay process, most likely by U and Th in close contact with carbonado (e.g., Ozima and Zashu, 1991; Ozima and Tatsumoto, 1997). However, the exact nature of the metamorphic process (e.g., shock compression) by which micro-scale diamonds could have been aggregated into multi-carat-sized carbonado is only speculative at this time. Kletetschka et al. (2000) contend that a high-pressure crustal or upper mantle origin is inconsistent with the highly porous nature of carbonado as well as the indicated temperature of formation of <400°C. Based on the model of radiation-induced crystallization for micro-diamonds in carbonado, the crystallization age was constrained by the timescale of radiogenic Pb implantation from decay of U or Th—2.6 b.y. (instantaneous formation of micro-diamonds) to 3.8 b.y. (formation of micro-diamonds continued to the present) (Kaminsky, 1994; Ozima and Tatsumoto, 1997). This age range is in accord with that ascertained through Pb–Pb dating of quartz, rutile and clay mineral inclusions and matrix in Brazilian carbonado by Sano et al. (2002).

Robinson (1998) and Vicenzi and Heaney (2001) studied a formation theory which is based on the subduction of a slab containing organic sediments. They determined that the C and N isotopes and the N abundances have values that do not support such an origin for carbonado. Moreover, it is not understood how such diamonds could eventually end up in placer deposits, or why their sizes should only reach to µm-size. In addition, it is considered that subducted organic carbon would be too shallow for diamond formation, which is stable at ~150 km (A. Pradenas, 2015).

Based on examinations of carbonado by Smith and Dawson (1985), and the discovery of lonsdaleite in yakutite (a carbonado-like diamond from Yakutia (Soviet Union) which is significantly different from carbonado; F. Kaminsky, 1994), they favor the theory of impact metamorphism of Archaean crustal rock containing organic carbon or graphite. However, no evidence of high-pressure phases of silica such as coesite and stishovite have been identified in association with quartz. In addition, A. Pradenas (2015) recognized that the large sizes of some carbonado nodules are inconsistent with an impact origin, and also that the spectroscopic absorption band typically associated with impact-generated diamond is not present in carbonado.

An extraterrestrial origin for carbonado is supported by recent experiments utilizing Fourier transform infrared (FTIR) spectroscopy (Haggerty et al., 2006; Garai et al., 2006; Garai, 2012). By exposing carbonado to intense infrared light, they observed peaks primarily corresponding to C–H stretching of diamond hydride, spectra almost identical to that of presolar diamonds found in some meteorites. They assert that the hydrogen serves as the bonding agent (protonation) that sinters the microdiamonds together to form the carbonado. They determined that carbonado diamond is consistent with an origin in a hydrogen-rich environment similar to that of the solar nebula. Moreover, the presence of nitrogen mono-hydride substitution for C is more similar to that found in presolar diamonds than to terrestrial diamonds, providing a clear argument for an extraterrestrial origin. This substitution is inconsistent with the conditions under which conventional diamonds are formed, i.e., slow cooling over millions of years at high pressures.

As with the nanodiamonds present in some meteorites, carbonado diamonds may have also been produced in a supernova explosion. Over time, they would be accreted into a planetesimal or perhaps an iron core, as attested by their presence in the Canyon Diablo iron. On the other hand, perhaps the abundant carbonado that was produced broke up into asteroid-sized masses. The Florida International University and Case Western Reserve University research team has proposed that a carbonado-rich asteroid measuring ~1 km in diameter impacted the Earth billions of years ago when Africa and South America were part of a single supercontinent. They argue that the vesiculation present in carbonado was caused by gases escaping under conditions of low-pressure during formation, conditions which are inconsistent with the very high pressures existing at diamond formation depths of >150 km, but which do exist in space.

Other exotic mechanisms of carbonado formation have been proposed over the years. Scientists from Princeton University have postulated the existence of diamond layers within extrasolar carbon-rich planets. Haggerty (1996), supported by observations of astronomers from the Harvard–Smithsonian Astrophysical Observatory and other studies (e.g., Stroud et al., 2011), presumes that carbon was transformed into diamond by the intense shock waves generated during the explosive collapse of a red giant star (supernova), resulting in a white dwarf and its accompanying planetary nebula. White dwarf stars constitute ~6% of the stars in the solar neighborhood. Either of these mechanisms of diamond formation may have resulted in the injection of massive diamond asteroids into the protosolar cloud which become gravitationally attracted to Earth.

Closer to home, the ice-giant planets Uranus and Neptune are considered by some planetary scientists to potentially produce diamond from methane (CH4), which constitutes 10–15% of their dense atmospheres. It was theorized and experimentally verified that dissociation of CH4 will occur at high pressures (≈100 GPa) and temperatures >4000 K to form H2 and hydrocarbons, and possibly diamond (Richters and Kühne, 2013 and references therein). Extreme temperatures and pressures (0.6–1.1 TPa) are hypothesized to exist at great depth on Uranus and Neptune, possibly forming a liquid C metallic outer core which transitions to a solid diamond-rich layer at intermediate depths (Eggert et al., 2010). It was experimentally verified (e.g., Benedetti et al., 1999; M. Ross, Lawrence Livermore National Laboratory) that the conversion of methane to diamond did occur at the high-temperature (2000–3000 K) and high-pressure (10–50 GPa) conditions that exist on Uranus and Neptune (see Diamonds in the Sky, PBS–NOVA, P. Tyson). Under the ultra-high temperature and pressure conditions that exist in mid-layers on Uranus and Neptune, oceans of liquid diamond with solid chunks of diamond floating atop are thought to be plausible, in a manner similar to the unusual behavior of water and its less-dense form of ice (I. Silvera, 2010).

Notably, the Pb–Pb age of carbonado coincides with the period of Solar System history known as the Late Heavy Bombardment, 4.1–3.8 b.y. ago, during which time it is thought that the gas giant planets Jupiter and Saturn, and the ice giant planets Uranus and Neptune, underwent orbital migrations under the influence of mutual resonances (‘Nice model’). Among the effects of the resulting gravitational instabilities was the perturbation of the smaller planetesimals into eccentric orbits, eventually leading some to intersect with the terrestrial planets. Significant collisions with Uranus and Neptune would be likely to occur at this time, and it has been argued that the large obliquity of Uranus is the result of a severe tangential collision with an Earth-sized proto-planet early in its history (A. Brunini, 1995, 2006). It may be conjectured that this unique cataclysmic event might also be responsible for the delivery of carbonado into an Earth-crossing orbit at this time.

While the exact origin of carbonado remains a mystery, the accumulating evidence for an extraterrestrial origin, or even possibly an extrasolar origin, provokes much excitement; however, further research is necessary. The photo above shows a 1.07 carat (0.21 g) Brazilian carbonado nodule measuring 6.1 × 5.5 × 4.3 mm with a shiny, porous surface.


Information for this page was obtained through many published works, including the following (arranged by date):

  • The ice layer in Uranus and Neptune. Diamonds in the sky? M. Ross, Nature, vol. 292, pp. 435–436 (30 July 1981)
  • Carbonado: Diamond aggregates from early impacts of crystal rocks? Smith and Dawson, Geology, vol. 13, #5, pp. 342–343 (May 1985)
  • Constraints from noble-gas contents on the origin of carbonado diamonds. Ozima et al., Nature, vol. 351, #6326, pp. 472–474 (6 June 1991)
  • Radiation-induced diamond (carbonado): A possible mechanism for the origin of diamond in primitive meteorites. Ozima and Zashu, Meteoritics vol. 26, 54th MetSoc, p. 382 (1991)
  • Carbonado and Yakutite: Properties and possible genesis. F. Kaminsky, Proceedings of the 5th International Kimberlite Conference, vol. 2, pp. 136–143 (1991)
  • Do the Ubangui diamonds originate from a giant impact? D. Shelkov et al., Meteoritics vol. 29, 57th MetSoc, p. 532 (1994)
  • A possible constraint to Uranus’ great collision. A. Brunini, Planetary and Space Science, vol. 43, #8, pp. 1019–1021 (August 1995)
  • Carbonado: More clues to a common impact origin for samples from Brazil and the Central African Republic. Shelkov et al., 26th LPSC, pp. 1281–1282 (1995)
  • Radiation-induced diamond crystallization: Origin of carbonados and its implications on meteorite nano-diamonds. Ozima and Tatsumoto, Geochimica et Cosmochimica Acta, vol. 61, #2, pp. 369–376 (January 1997)
  • Microstructural observations of polycrystalline diamond: a contribution to the carbonado conundrum. De et al., Earth and Planetary Science Letters, vol. 164, #3–4, pp. 421–433 (30 December 1998)
  • The Kogo Structure (Equitorial Guinea) as a possible source crater for the origin of carbonado diamonds from Brazil and the Central African Republic. S. Master, Meteoritics & Planetary Science, vol. 33, 61st MetSoc, pp. 98–99 (1998)
  • Dissociation of CH4 at high pressures and temperatures: Diamond formation in giant planet interiors? Benedetti et al., Science, vol. 286, #5437, pp. 100–102 (1 Oct 1999)
  • Carbon isotope and nitrogen analysis of carbonado by secondary ion mass spectrometry (SIMS). Subarnarekha et al., Ninth Annual V. M. Goldschmidt Conference (1999)
  • Diamonds in the Sky. P. Tyson, NOVA, PBS Online—WGBH (1 February 2000)
  • Magnetic properties of aggregate polycrystalline diamond: implications for carbonado history. G. Kletetschka, Earth and Planetary Science Letters, vol. 181, #3, pp. 279–290 (15 September 2000)
  • The carbon and nitrogen isotopic composition of carnonado diamond: An in situ study. Vicenzi and Heaney, 11th Annual V. M. Goldschmidt Conference (2001)
  • Ion microprobe Pbï ¿ ½Pb dating of carbonado, polycrystalline diamond. Sano et al., Precambrian Research, vol. 113, #1-2, pp. 155–168 (2002)
  • A new nitride mineral in carbonado. Jones et al., Eighth International Kimberlite Conference Abstracts, Victoria, Canada, p. A95 (2003)
  • Archean and Paleoproterozoic crust of the São Francisco Craton, Bahia, Brazil: geodynamic features. Barbosa and Sabate, Precambrian Research, Vol. 133, #1-2, pp. 1–27 (2004)
  • Extrasolar Planets May Have Diamond Layers. M. Kuchner (Princeton University) and S. Seager (Carnegie Institute of Washington), press release from Princeton University (7 February 2005)
  • Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets. Gomes et al., Nature, vol. 435, pp. 466ï ¿ ½469 (26 May 2005)
  • Origin of the obliquities of the giant planets in mutual interactions in the early Solar System. A. Brunini, Nature, vol. 440, pp. 1163–1165 (27 April 2006)
  • Infrared absorption investigations confirm the extraterrestrial origin of carbonado diamonds. Garai et al., The Astrophysical Journal Letters, vol. 653, #2, pp. 153–156 (20 December 2006)
  • Intragrain Variation In δ13C and nitrogen concentration associated with textural heterogeneities of carbonado. Yokochi et al., The Canadian Mineralogist, vol. 46, #5, pp. 1283–1296 (2008)
  • Diamond: Molten under pressure. I. Silvera, Nature Physics, vol. 6, pp. 9–10 (1 January 2010)
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