[HN Gopher] 4.6B-year-old meteorite found
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4.6B-year-old meteorite found
Author : lambersley
Score : 83 points
Date : 2021-07-22 17:52 UTC (5 hours ago)
(HTM) web link (www.lboro.ac.uk)
(TXT) w3m dump (www.lboro.ac.uk)
| verytrivial wrote:
| Off-central-topic, but regarding where this was found, if you
| find yourself discussing this offline, "Loughborough" is
| pronounced "LUFF-burro" or "LUFF-burrah".
|
| Ref. https://www.youtube.com/watch?v=uYNzqgU7na4 for entertaining
| additions.
| [deleted]
| Yajirobe wrote:
| How was it dated?
| saltedonion wrote:
| Do we really expect these rocks to not undergo any sort of
| chemical reaction once they land on earth?
| verytrivial wrote:
| Depending on how heavy and dense, the crust can indeed melt but
| above a certain side the middle does not always get that hot,
| esp. if not very heat-conductive. This one looks rather porous
| and light, so likely slowed down very quickly. That's my
| understanding anyway.
| markus_zhang wrote:
| Was watching X-Files and wondering if Mulder ia going to Scotland
| yard to meet his girl friend!
| dheera wrote:
| What exactly does 4.6B-year-old mean?
|
| Landed on the Earth 4.6B years ago? That doesn't sound right, the
| Earth isn't that old.
|
| Flew off its former body 4.6B years ago? How do we measure that?
|
| Created 4.6B years ago? How does one define created, considering
| everything was ultimately created during the big bang?
| dredmorbius wrote:
| It's the time since the rock itself fused from molten or other
| non-fixed form.
|
| The age of formation of rock is typically determined
| unequivocably by radiometric dating. That "clock" uses the
| ratios of long-lived radioactive elements and their decay
| products (this is _not_ radio _carbon_ dating, which is similar
| but effective over a much shorter timespan of about 50,000
| years).
|
| The radiometric clock _starts_ when the materials in the sample
| solidify and initial proportions of mother and daughter
| elements are fixed, "neither the parent nuclide nor the
| daughter product can enter or leave the material after its
| formation" (Wikipedia). That point in time is the "age" of the
| rock.
|
| The specific decay chains used in geology are uranium-lead,
| samarium-neodymium, potassium-argon, rubidium-strontium, and
| uranium-thorium. These may rely on crystaline structures which
| _cannot form_ when the daughter elements (decay products) are
| present, therefor the amount of daughter element present gives
| the age. (I know this is the case for some methods, I 'm unsure
| it applies to all. The "this structure cannot form when the
| daughter products are present" feature is a compelling argument
| for age.)
|
| https://en.wikipedia.org/wiki/Radiometric_dating
|
| Newly-formed lava or other molten materials are "new" ---
| they've just been created _as rock_. The elements within them
| are older --- those date to whatever radiological apocalypse
| formed them (stellar fusion for elements up to iron, various
| novae and collisions between white dwarves and neutron stars
| for elements heavier than iron). And of course the protons and
| neutrons comprising them ... mostly ... date to the origin of
| the Universe in the Big Bang (there is some spontaneous
| creation of particles due to quantum energy and mass-energy
| fluctuations, though that 's minimal).
|
| The atomic transmutation of elements gives some interesting
| results. Virtually all of the helium in the Universe formed in
| stars from fusion of hydrogen. A very small percentage was
| formed in the Big Bang. But virtually all helium on Earth is
| the result of radioactive decay of _heavy_ elements, forming
| beta particles (two protons and two neutrons), that is, a
| helium nucleus. When that picks up electrons, it becomes
| helium. It 's generally trapped with natural gas and produced
| as a by-product of gas wells.
| ardit33 wrote:
| Created by clumped dust 4.6b years ago when the solar system
| was being formed.... but it hasn't been part of a larger body,
| so it is not that compressed, so it is not a chunk of another
| larger body that split off from collisions.
|
| It contains organic material, which means the dust that formed
| our solar system, contained plenty of it.
|
| If it arrived yesterday in earth, it still is 4.6b old.
|
| "Identifying organic compounds would support the idea that
| early meteorites carried amino acids - the building blocks of
| life - to supply the Earth's primordial soup where life first
| began.
|
| "Carbonaceous chondrites contain organic compounds including
| amino acids, which are found in all living things," said
| Director of Astrochemistry at EAARO Derek Robson who found the
| meteorite and who will soon join Loughborough University as an
| academic visitor for collaborative research.
|
| "Being able to identify and confirm the presence of such
| compounds from a material that existed before the Earth was
| born would be an important step towards understanding how life
| began.""
| ars wrote:
| > but it hasn't been part of a larger body, so it is not that
| compressed, so it is not a chunk of another larger body that
| split off from collisions.
|
| It's way too small to clump from its own gravity, it pretty
| much has to be a portion of something MUCH larger.
| dredmorbius wrote:
| _That_ assertion gets into questions of asteroid formation,
| which I find fascinating, though there 's very little
| information I've been able to find.
|
| Keep in mind that "gravitational accretion" simply kicks
| the can a bit further: the chunks that accrete
| gravitationally must themselves form and congeal somehow.
|
| What I understand of solar system formation is that all
| "metallic" solar systems (though with a substantial portion
| of elements other than hydrogen) from from the remains of
| earlier stars. So you have a nova, supernova, stellar
| collapse, collision (stars, white dwarves, neutron stars,
| ...). This ejects heavy materials (principally H, He, C, O,
| N, though others --- water is probably the most common non-
| elemental _molecule_ in the Universe), and _also_ creates
| pressure waves and imparts angular momentum. Both factors
| can draw material together. There 's also probably a lot of
| plasma in the mix, so that different portions of the cloud
| carry different charges. These may be attracted, repelled,
| and spark discharges (which might themselves melt and fuse
| material). There may also be surface-tension effects and
| other factors at play. Somehow, clumps form. Gravity is _a
| force_ at work, but not the _only_ force.
|
| Disclaimer: not an astronomer, just interested in far too
| many divers subjects. If anyone has anything authoritative
| to say on this I'm all ears. Most references I can find are
| either extremely basic, or address the formation of
| asteroid _belts_ but not the objects within them.
|
| There's some hypothesis on formation (condensation, shock
| waves, jet flows) here:
| http://www.psrd.hawaii.edu/Sept02/isotopicAges.html
| Koshkin wrote:
| I mean, probably in the same way as one would define, say, a
| person's age and the time of "creation". (Individual atoms are,
| of course, much older than any the object that is built from
| them, but that does not matter.)
| yongjik wrote:
| Not 100% sure but it seems clickbait - the title sounds like the
| meteorite was sitting on Earth for 4.6B years, but after reading
| the article, it sounds like the _rock_ was 4.6B years old - it
| likely fell to the Earth much more recently.
|
| In that case, it's not exactly remarkable - I think pretty much
| all the asteroids in the Solar System are 4.6B years old, because
| that's when they were all created.
| vardump wrote:
| I'm no geologist, but I'd guess _nothing_ can survive anywhere
| near 4.6B years on this planet with weather systems.
| Spare_account wrote:
| Rocks formed on earth have been dated as old as 4 billion
| years
|
| https://en.m.wikipedia.org/wiki/Oldest_dated_rocks
|
| It is unusual, though, you're right.
| throwaway894345 wrote:
| Is it unusual because of weather systems or because of
| plate tectonics (rocks get pushed into the mantle and
| melted down and new ones emerge later)?
| dredmorbius wrote:
| Both, though plate tectonics are the ultimate limit.
| There's extraordinarily little primaeval crust extant on
| Earth. The Canadian Shield / Laurentine Plain is one of
| the largest, and is dated to 3.96 billion years, though
| the oldest is in Australia (Jack Hills region), with
| dates to 4.39 billion years via zircon crystals. (I
| believe that may geologically related to a region in
| southern Africa, with which it was originally joined,
| though cannot find a reference.)
|
| The ocean floor is virtually completely newer material,
| little of it over a 200 million years old (about 5% of
| Earth's total age), due to subduction. Continental crust
| is lighter, floats on top of the heavier oceanic crust,
| and has at least a chance of survival.
|
| https://www.thoughtco.com/how-old-is-the-ocean-
| floor-3960755
|
| https://en.wikipedia.org/wiki/Canadian_Shield
|
| https://en.wikipedia.org/wiki/Jack_Hills
|
| https://www.geologyin.com/2015/11/44-billion-year-old-
| zircon...
|
| https://www.geologyin.com/2016/03/the-oldest-mountain-on-
| ear...
| mordnis wrote:
| Erosion?
| vardump wrote:
| I was also thinking about the presumed collision with the
| planet that gave birth to moon. Astoundingly there are
| apparently still ways for some of the rocks to survive all
| this maelstrom. Mind boggling.
| anonAndOn wrote:
| It's briefly mentioned the astronomer tracked its arrival and
| was able to recover it.
| _jal wrote:
| That is pretty great. I wonder how often that has happened.
|
| "It's a scientific fairy-tale. First your friend tracks a
| meteorite, then finds it and then gifts a bit of this extra-
| terrestrial material to you to analyse."
| mod wrote:
| " The material, which resembles loosely held-together concreted
| dust and particles, never underwent the violent cosmic
| collisions that most ancient space debris experienced as it
| smashed together to create the planets and moons of our solar
| system.
|
| It doesn't appear to have undergone thermal metamorphism, which
| means it's been sitting out there, past Mars, untouched, since
| before any of the planets were created meaning we have the rare
| opportunity to examine a piece of our primordial past."
|
| Basically, if the wording is correct, that's unusual even for
| meteorites.
| dredmorbius wrote:
| This meteorite is older than dirt. It's older than rock. It's
| older than the hellscape that was the early Earth.
|
| The age of the Earth is accepted as 4.54 +/- 0.05 billion years
| (determined to within 1%, that is, within 50 million years).
| That's based on samples of the oldest available Earth rocks, as
| well as lunar material (much returned by the Apollo missions),
| and other meteorite finds (Antarctica turns out to be highly
| effective at revealing meteorites as virtually all recent
| terrestrial rock is several kilometers under ice).
|
| But the article does indicate that the age and primordial
| nature of the specimin is the principle interest:
|
| _"It doesn't appear to have undergone thermal metamorphism,
| which means it's been sitting out there, past Mars, untouched,
| since before any of the planets were created meaning we have
| the rare opportunity to examine a piece of our primordial
| past._
|
| The one detail the article fails to provide is _how_ the
| specimin was dated, though at 4.6 billion years, it 's about
| 100 million years older than the highest accepted age of Earth
| itself. It would represent material from _before_ the era of
| planetary formation within the early dust cloud from which our
| Solar System was formed.
| tablespoon wrote:
| > "It doesn't appear to have undergone thermal metamorphism,
| which means it's been sitting out there, past Mars,
| untouched, since before any of the planets were created
| meaning we have the rare opportunity to examine a piece of
| our primordial past.
|
| It sounds like that's par for the course for this _type_ of
| meteorite. So it 's rare, but not unique:
| https://en.wikipedia.org/wiki/Carbonaceous_chondrite.
|
| > The carbonaceous chondrites were not exposed to higher
| temperatures, so that they are hardly changed by thermal
| processes. Some carbonaceous chondrites, such as the Allende
| meteorite, contain calcium-aluminum-rich inclusions (CAIs).
| These are compounds that emerged early from the primeval
| solar nebula, condensed out and represent the oldest minerals
| formed in the solar system .[3][4]
|
| > Some primitive carbonaceous chondrites, such as the CM
| chondrite Murchison, contain presolar minerals...
| dredmorbius wrote:
| The article is exceptionally vague on all the important
| bits. What you quote just goes to establishing a
| consequence of its age.
|
| It's not clear to me that this is the _oldest_ meteorite
| found, how it was dated, how it was tracked, etc., etc.
|
| For the technical deets on dating CCs:
|
| http://www.psrd.hawaii.edu/Sept02/isotopicAges.html
| mint2 wrote:
| I really wanted to know how they managed to find it, but aside
| from some offhand comments they didn't go there.
|
| Found in imprint of a horseshoe? What? Tracking it before it
| landed?
|
| Like in desert areas people will metal detect for meteors, but
| how did they find this one.
| chejazi wrote:
| I'm wondering the same thing. Maybe there is a path travelled
| by horseback often, and that's just where it was found
| anonAndOn wrote:
| It helps to have friends' assistance, but you can do it alone.
|
| https://ares.jsc.nasa.gov/meteorite-falls/how-to-find-meteor...
| pkdpic_y9k wrote:
| So do amino acids self-replicate on their own in some way
| independent of DNA / protective membranes etc? A little beyond my
| 8th-grade understanding of science but trying to get there...
| [deleted]
| MeteorMarc wrote:
| This link describes the find of the meteorite.
| https://www.nhm.ac.uk/discover/news/2021/march/uk-fireball-m...
| j_walter wrote:
| God put it there...
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