Sunday, July 31, 2022

3638 - METEORITES - bringing the materials for life?

  -  3638  -     METEORITES  -    bringing the materials for life?  The Japanese spacecraft Hayabusa2 recently brought the asteroid Ryugu down to Earth.   NASA's OSIRIS-REx probe is due to touch down with samples of the near-Earth asteroid Bennu in 2023.  These will be analyzed to learn if they contain the ingredients for life.


-----------------  3638  -     METEORITES  -    bringing the materials for life? 

-  While studying diamonds inside an ancient meteorite, scientists have found a strange, interwoven microscopic structure that has never been seen before.   The structure, an interlocking form of graphite and diamond, has unique properties that could one day be used to develop superfast charging or new types of electronics. 

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-  The diamond structures were locked inside the “Canyon Diablo meteorite“, which slammed into Earth 50,000 years ago and was first discovered in Arizona in 1891. The diamonds in this meteorite aren't the kind most people are familiar with. 

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-  Most known diamonds were formed around 90 miles beneath Earth's surface, where temperatures rise to more than 2,000 degrees Fahrenheit. The carbon atoms within these diamonds are arranged in cubic shapes.

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-  The diamonds inside the Canyon Diablo meteorite are known as “lonsdaleite” and have a hexagonal crystal structure. These diamonds form only under extremely high pressures and temperatures. Scientists have successfully made lonsdaleite in a lab using gunpowder and compressed air to propel graphite disks 15,000 mph at a wall.  Lonsdaleite is otherwise formed only when asteroids strike Earth at enormously high speeds. 

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-   Instead of the pure hexagonal structures they were expecting, the researchers found growths of another carbon-based material called “graphene” interlocking with the diamond. These growths are known as “diaphites“, and inside the meteorite, they form in a particularly intriguing layered pattern. In between these layers are "stacking faults," which mean the layers don't line up perfectly.  

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-  Finding diaphites in the meteoritic lonsdaleite suggests that this material can be found in other carbonaceous material,.  Graphene is made of a one-atom-thick sheet of carbon, arranged in hexagons. 

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-   Because it is both as light as a feather and as strong as a diamond; both transparent and highly conductive; and 1 million times thinner than a human hair, it could one day be used for more targeted medicines, tinier electronics with lighting-fast charging speeds, or faster and bendier technology.

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-  Through the controlled layer growth of structures, it should be possible to design materials that are both ultra-hard and also ductile, as well as have adjustable electronic properties from a conductor to an insulator.  What we can learn from old meteors.  Amazing!

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-  Three other meteorites have been found that contain the molecular building blocks of DNA and its cousin RNA.  

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-  The new discovery supports the idea that, some four billion years ago, a barrage of meteorites may have delivered the molecular ingredients needed to jump-start the emergence of the earliest life on Earth. 

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-  However, not everyone is convinced that all of the newfound DNA components are extraterrestrial in origin; rather, some may have ended up in the meteorites after the rocks touched down on Earth.  Additional studies are needed to rule out this possibility.

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-  Assuming that all of the compounds did originate in space, one subset of building blocks, a class of compounds known as “pyrimidines“, appeared in extremely low concentrations in the meteorites. This finding hints that the world's first genetic molecules emerged not due to an influx of DNA components from space but rather as a result of the geochemical processes unfolding on early Earth.

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-   These nucleobases might be lurking, undetected, in the space rocks that slammed into Earth.   In lab settings, scientists have recreated the chemical conditions of interstellar space where immense clouds of gas and dust measure about 10 kelvins (minus 263.15 degrees Celsius) and the parent asteroids of meteorites can be found. 

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-   Researchers synthesized thymine, cytosine and the other primary nucleobases, suggesting that all of these compounds could theoretically be detectable in meteorites.

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-    Hydrocarbons and the building blocks of proteins (amino acids) have been identified in the three meteorites.   High-performance liquid chromatography is involved using pressurized water to separate the meteorite samples into their component parts. This extracted the nucleobases from each sample which was analyzed using mass spectrometry. 

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-    To check that the nucleobases were extraterrestrial in origin rather than the result of Earthly contamination, the team repeated the experimental procedures without any meteorite material in the test chambers. No nucleobases were detected during these blank experiments. 

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-  The team also had access to soil samples from the site where the Murchison meteorite first plummeted to Earth. They detected some nucleobases in the soil, but their distribution and concentrations are clearly different from those found in meteorites.

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-   Earth matter contains different ratios of carbon isotopes and nitrogen isotopes than matter from space,  analyses could help discriminate the terrestrial nucleobases from extraterrestrial ones.

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-  If these results are representative of typical “pyramiding” concentrations in meteorites, then geochemical synthesis on early Earth would likely have been responsible for the emergence of genetic material, rather than inputs from extraterrestrial delivery.

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July 29, 2022      -     METEORITES  -    bringing the materials for life?         3638                                                                                                                                        

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