First ever evidence of a comet striking Earth

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The first ever evidence of a comet entering Earth’s atmosphere and exploding, raining down a shock wave of fire which obliterated every life form in its path, has been discovered by a team of South African scientists and international collaborators, and will be presented at a public lecture on Thursday.

The discovery has not only provided the first definitive proof of a comet striking Earth, millions of years ago, but it could also help us to unlock, in the future, the secrets of the formation of our solar system.

“Comets always visit our skies – they’re these dirty snowballs of ice mixed with dust – but never before in history has material from a comet ever been found on Earth,” says Professor David Block of Wits University.

The comet entered Earth’s atmosphere above Egypt about 28 million years ago. As it entered the atmosphere, it exploded, heating up the sand beneath it to a temperature of about 2 000 degrees Celsius, and resulting in the formation of a huge amount of yellow silica glass which lies scattered over a 6 000 square kilometer area in the Sahara. A magnificent specimen of the glass, polished by ancient jewellers, is found in Tutankhamun's brooch with its striking yellow-brown scarab.

Written By: University of the Witwatersrand
continue to source article at wits.ac.za

27 COMMENTS

  1. The fact that this planet was seeded by material from outer space is beyond doubt ,I can understand theology denying this if all new the truth they would have no control over the people.
    my father drummed evolution into me for this I am grateful I have seen Dr Dawkins at London zoo where I am a scientific fellow and find his logic amazing

    • In reply to #1 by davidashbyash:

      The fact that this planet was seeded by material from outer space is beyond doubt ,I can understand theology denying this if all new the truth they would have no control over the people.
      my father drummed evolution into me for this I am grateful I have seen Dr Dawkins at London zoo where I am a scie…

      Thank you for your remark, which I value, but I found it quite difficult to read without punctuation. As a scientific fellow, you surely must be accustomed to more precise writing.

    • In reply to #2 by ApexDisorder:

      …oh yeah lightening.

      Actually, that is the process which makes you “white and delightsome”. I think you mean “lightning”.

      (Gets kite, key, Leyden jar and leaves…)

      Steve

      • In reply to #3 by Agrajag:

        In reply to #2 by ApexDisorder:

        …oh yeah lightening.

        Actually, that is the process which makes you “white and. Music and bitche delightsome”. I think you mean “lightning”.

        (Gets kite, key, Leyden jar and leaves…)

        Steve

        Spelling id not an option for me. I try to think. It ain’t s always an option for a musician/amateur scientists..lol.

        • In reply to #4 by ApexDisorder:

          In reply to #3 by Agrajag:

          In reply to #2 by ApexDisorder:

          …oh yeah lightening.

          Actually, that is the process which makes you “white and. Music and bitche delightsome”. I think you mean “lightning”.

          (Gets kite, key, Leyden jar and leaves…)

          Steve

          Spelling id not an option for me. I try to t…

          Good idea to turn on spell checker, Steve. Saves me on many occasions!

          Apologies if I’m stating the obvious but SO many folks on the net seem unaware…

          • In reply to #6 by Billy Joe:

            In reply to #4 by ApexDisorder:

            In reply to #3 by Agrajag:

            In reply to #2 by ApexDisorder:

            …oh yeah lightening.

            Actually, that is the process which makes you “white and. Music and bitche delightsome”. I think you mean “lightning”.

            (Gets kite, key, Leyden jar and leaves…)

            Steve

            Spelling id…

            I aints got times fo spell checks….I got a sets ta do..peace babies…luvs y’all……….wait.. im done with my set. Stay off druggs kids.

      • In reply to #3 by Agrajag:

        In reply to #2 by ApexDisorder:

        …oh yeah lightening.

        Actually, that is the process which makes you “white and delightsome”. I think you mean “lightning”.

        (Gets kite, key, Leyden jar and leaves…)

        Steve

        Eats roots shoots and leaves, Steve?. Naughty!

  2. never before in history has material from a comet ever been found on Earth

    So where did all the oceans come from? I thought that was pretty well established to have been delivered as comets.

    Also, apart from the dirty-snowball comets, there are the rocky meteors – the deposits of heavy metals available for our convenience. Any that had been here from the start would have sunk to the core, so they too must be late arrivals.

    Or is there some other explanation?

      • In reply to #14 by Alan4discussion:

        In reply to #5 by OHooligan:

        Or is there some other explanation?

        Some heavy elements are carried up to the crust in mantle convection currents and volcanic eruptions.

        I’m curious – is there a known value (or ratio) for “some” – convected from deep vs impacted on surface. From an amateur viewpoint, it would seem difficult for Uranium or any other very dense element to be raised from the depths via convection. Unless I suppose there are stable compounds of lesser density that would carry them. Not much of a geochemist, am I?

        • In reply to #19 by OHooligan:

          I’m curious – is there a known value (or ratio) for “some” – convected from deep vs impacted on surface.

          There is certainly a greater percentage of lighter elements on the “floating” continental crust, than in the volcanic sea-floor crust.

          From an amateur viewpoint, it would seem difficult for Uranium or any other very dense element to be raised from the depths via convection. Unless I suppose there are stable compounds of lesser density that would carry them. Not much of a geochemist, am I?

          The convection of dense rocks in the mantle produces forces which move continents. There are certainly traces of heavy elements like Uranium in granite with these tending to concentrate in patches or veins during the cooling processes. The changes in the chemistry of Earth’s reducing/oxidising atmosphere affects its solubility.

          Uranium in a Nutshell
          As large bodies of granite solidify, the trace amounts of uranium become concentrated in the last bits of fluid left. Especially at shallow levels, these may fracture and invade surrounding rocks with metal-bearing fluids, leaving veins of ore. More episodes of tectonic activity can concentrate these further, and the world’s largest uranium deposit is one of these, a hematite breccia complex at Olympic Dam in South Australia.

      • In response to #14 by Alan4discussion:

        Asteroid 100955 Bennu 1999 RQ36 is an excellent asteroid for NASA to explore. It is in the Apollo group of asteroids, an “earth-crosser” with perihelion of 0.897 AU, rather small at about 0.28 km radius, but with a high(ish) density of about 3.1 grams per cubic centimetre, which suggests heavy elements. It weighs some 2.84E+11 kgs, so I wish NASA the best of luck, for if only a small percentage of Bennu is silver, gold and platinum, it might wipe out the US debt of 17 trillion dollars, make the Fed give the Germans back their gold which seems to have vanished, slow down the rampant quantative easing, and who knows? perhaps NASA might get a few dollars for a manned mission to Mars. But if it turns out to be mostly iron, then back to the drawing board :)

        • In reply to #22 by ZedBee:

          In response to #14 by Alan4discussion:

          Asteroid 100955 Bennu 1999 RQ36 is an excellent asteroid for NASA to explore. It is in the Apollo group of asteroids, an “earth-crosser” with perihelion of 0.897 AU, rather small at about 0.28 km radius, but with a high(ish) density of about 3.1 grams per cubic centimetre, which suggests heavy elements.

          There are initially 12 promising candidate asteroids according to this report.

          http://gizmodo.com/researchers-discover-12-asteroids-close-enough-for-spac-1110020692

          It weighs some 2.84E+11 kgs, so I wish NASA the best of luck, for if only a small percentage of Bennu is silver, gold and platinum, it might wipe out the US debt of 17 trillion dollars, make the Fed give the Germans back their gold which seems to have vanished, slow down the rampant quantative easing, and who knows? perhaps NASA might get a few dollars for a manned mission to Mars.

          While there could be a market for precious minerals returned to Earth, the greatest potential is for resources such a water, which can be used for life support or fuel/propellant in space. There is of course effectively unlimited solar energy available in Earth or Lunar orbit for processing.

          But if it turns out to be mostly iron, then back to the drawing board.

          Not necessarily. There are plans to mine metals, and plans for construction of metal and ceramic components in orbit using 3D printers. They have just shipped a 3D printer to the ISS to experiment.

          These would initially be very good for making replacement parts for satellites and later for constructing parts for spacecraft, space stations, robot machines, or space mining colonies.

          http://news.discovery.com/space/asteroids-meteors-meteorites/could-asteroid-mining-drive-21st-century-space-industry-130204.htm

          Planetary Resources have the long term goal of being able to alter the orbital trajectories of asteroids, and return entire asteroids into lunar orbit for mining. Meanwhile, DSI’s plans involve a 3D printer, dubbed the “Microgravity Foundry”, which will be able to create high quality metal components in orbit. Between them, we could be looking at the beginnings of true orbital industry.

          This link on deflection ideas could also be interesting!
          http://news.discovery.com/space/asteroids-meteors-meteorites/top-10-asteroid-deflection-130130.htm

          • In reply to #24 by Alan4discussion:

            There are plenty of asteroids in close proximity to the earth’s orbit which are potentially water-ice bearing, and many more with carbon or heavy metals. The advancement in science and engineering is a constant wonder; the question remaining is when the lead players in this game would rather allocate resources for suitable facilities to be built, transported, and used to advance space exploration, than frittering their wealth away on weapons and other fruitless activities. I can only speculate that private enterprise is more interested in bringing back precious metals, while national authorities might be more interested in scientific exploration, but who knows, both may surprise us.

          • In reply to #25 by ZedBee:

            I can only speculate that private enterprise is more interested in bringing back precious metals, while national authorities might be more interested in scientific exploration, but who knows, both may surprise us.

            They have said they are interested in precious metals, which can be packaged with a heat shield and dropped out of orbit, but they have also identified a market for producing fuel/propellant from water (ice), and 3D printed spares, and then using these to recondition and refuel old satellites at a fraction of the cost of new launches.

            The service robots to facilitate this are already being developed.

            http://www.space.com/15681-satellite-repair-robot-spacecraft-technology.html

            Unfortunately many NASA websites are down at present, so some links are not available.

  3. @OP – First ever evidence of a comet striking Earth

    I think this title is misleading. It should read:

    “Early cometary metamorphic effects and material from Earth cometary impact found in the Sahara”.

    The Earth and its planetesimal precursors formed from cometary material, but it (like the Moon) was later shot with craters during the “Late Heavy Bombardment” – about 3.9 billion years ago! http://astroclock2010.wordpress.com/cosmic-timeline-17/

  4. Moderators’ message

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    • In reply to #11 by Moderator:

      Moderators’ message

      Point taken. However, it was meant to be slightly humorous and slightly pedantic, and would have been considered derogatory only by the thinnest-skinned among us.

      Back on topic, I find it astounding that the radiant energy from the fireball could melt the sand on the surface from an altitude which must have been thousands of feet!

      Steve

  5. Such an impact (even an “air blast”) might be expected to coincide with a mass extinction event, is there any evidence of a mass extinction 28 mgo?

    Comets are nowadays granted an almost mystic place in planetary evolution with the suggestion that they may not have been created within the planetary nebula that was the womb of the solar system. Were they or were they not created 4 1/2 billion years ago with the rest of the solar system or not? Or both?

    • In reply to #15 by Philoctetes:

      Such an impact (even an “air blast”) might be expected to coincide with a mass extinction event, is there any evidence of a mass extinction 28 mgo?

      Air blasts can be much more local than major surface impacts, – as was the recent meteor which crashed in Russia. http://www.dailymail.co.uk/sciencetech/article-2387639/Meteor-crashed-Russia-656-foot-wide-asteroid-broke-orbit-Earth.html

      Comets are nowadays granted an almost mystic place in planetary evolution with the suggestion that they may not have been created within the planetary nebula that was the womb of the solar system. Were they or were they not created 4 1/2 billion years ago with the rest of the solar system or not? Or both?

      Have a look at the link @10 or this one here. After the initial accretion process starting about 4½ billion years ago, there was a major reorganisation of the outer Solar System around 3.9 billion years ago, which according to the “Nice model” theory, caused the “Late Heavy Bombardment” of Earth, and set up the present Asteroid belt, Kuiper Belt, and the Oort Cloud.

    • In reply to #15 by Philoctetes:

      The direct answer to your question is that the latest extinctions of species and/or geological upheavals and Alpine, Andean, and Himalayan orogenies occurred at 39.3, 26.2 and 13 million years ago, but no such major event recorded at 28 mya. Perhaps this date needs finer tuning. I don’t know whether it is significant or not, but this date occurs during the Chattian Division of 28.4 to 23.03 mya.

  6. Now a repeat of such an event that eliminates about 6G of our population could save our planet and just maybe our species. Lets just hope its the scientifically literate one that survive and the religious nut cases end up with their imaginary gods. (perhaps we need some kind of god for this to happen)

  7. It is difficult commenting on the topic without knowing exactly what Professor David Block said about “comets”, “dirty snowballs”, “Tutankhamun” and the “shock wave of fire which obliterated every life form” over the Sahara Desert, “28 million years ago”, but there are some clues which indicate that the topic is perhaps a tad more sensational that it needs to be. For example:

    1) During the Oligocene Epoch (about 23 to 34 million years ago) there was no “Sahara Desert”. That area, during the Oligocene was covered with forests and vegetation. The sandy desert in Libya, Egypt and Arabia did not form until about the Middle Miocene Epoch (11 to 16 million years ago).

    2) Some, but not all, comets (and asteroids) are “dirty snowballs”. Of the 34.111 named and numbered comets and asteroids that I have of these objects, larger than about 10 meters across, less than about 15% have high(ish) albedo (above 0.2) and densities between 1 and 2 grams per cubic centimetre, which suggests the presence of water-ice. The rest are rocky, carbonaceous, or metallic objects, with low albedo (less than 0.1) and densities well above 2 grams per cubic centimetre.

    3) The expression “THE extinction of the dinosaurs, 65 million years ago” keeps cropping up, yet there have been numerous extinctions of life-forms (including 5 major ones) since there was life on earth, which, according to my main sources (“Dinosauria” and “The Phanerzoic Time Scale” of the Geological Society of London) seem to be repeated at intervals of just over 13 million years. The reason for these periodic bombardments could well be the subject of another topic, but not this one.

    4) I don’t want to worry you, but there are about 2,500 asteroids which orbit close enough to the earth, or intercept the earth’s orbit, which are classified by NASA as being hazardous. The one which exploded over Chelyabinsk wasn’t even one of them, being too small to be observed before it arrived.

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