swansont Posted 8 hours ago Posted 8 hours ago “Something extraordinary happened on Earth around 10 million years ago, and whatever it was, it left behind a “signature” of radioactive beryllium-10. This finding, which is based on studies of rocks located deep beneath the ocean, could be evidence for a previously-unknown cosmic event or major changes in ocean circulation. With further study, the newly-discovered beryllium anomaly could also become an independent time marker for the geological record.” https://physicsworld.com/a/radioactive-anomaly-appears-in-the-deep-ocean/ A couple of nits, though “Because beryllium-10 has a half-life of 1.4 million years, it is possible to use its abundance to pin down the dates of geological samples that are more than 10 million years old.” 10 million would be ~7 half-lives. Much longer than that would be increasingly tough to pin down since you are decreasing signal/noise. So while you could get results a bit beyond 10 mya, it’s not good for arbitrarily long ages. It also says B-10and Be-10 have the same mass, but they differ slightly which is my their mass spectrometer could distinguish them. 2
John Cuthber Posted 7 hours ago Posted 7 hours ago 1 hour ago, swansont said: It also says B-10and Be-10 have the same mass, but they differ slightly which is my their mass spectrometer could distinguish them. If they had said "mass number" would you have been content? 1 hour ago, swansont said: it’s not good for arbitrarily long ages. They didn't say it was. If I say my car can go over 100 MPH, I'm not claiming 200 In any event, the discovery (assuming it doesn't turn out to be a glitch in teh sampling or whatever) is interesting.
studiot Posted 6 hours ago Posted 6 hours ago Just now, swansont said: “Something extraordinary happened on Earth around 10 million years ago, and whatever it was, it left behind a “signature” of radioactive beryllium-10. This finding, which is based on studies of rocks located deep beneath the ocean, could be evidence for a previously-unknown cosmic event or major changes in ocean circulation. With further study, the newly-discovered beryllium anomaly could also become an independent time marker for the geological record.” https://physicsworld.com/a/radioactive-anomaly-appears-in-the-deep-ocean/ Interesting, thanks. +1 I note that this is very early days for this and the first step is to determine whether this is a local or earth-global event. Quote To distinguish between these competing hypotheses, the researchers now plan to analyse additional samples from different locations on Earth. “If the anomaly were found everywhere, then the astrophysics hypothesis would be supported,” Koll says. “But if it were detected only in specific regions, the explanation involving altered ocean currents would be more plausible.”
TheVat Posted 6 hours ago Posted 6 hours ago “If the anomaly were found everywhere, then the astrophysics hypothesis would be supported,” Koll says. “But if it were detected only in specific regions, the explanation involving altered ocean currents would be more plausible.” How easily is bottom rock/sediment moved long distances by ocean currents? Going just on that article, the cosmic radiation hypothesis seems more likely, but maybe currents can move more material than initially seems possible. (or maybe tectonic effects are also in play?)
Sensei Posted 6 hours ago Posted 6 hours ago (edited) 1 hour ago, swansont said: It also says B-10and Be-10 have the same mass, but they differ slightly which is my their mass spectrometer could distinguish them. The difference is 0.556 MeV/c2 = 556 keV/c2 https://en.wikipedia.org/wiki/Beryllium-10 (on the right properties panel) (slightly more than one electron mass ) https://en.wikipedia.org/wiki/Isotopes_of_beryllium https://en.wikipedia.org/wiki/Isotopes_of_boron 10.01353469 u - 10.012936862 u = 0.000597828 u * 931.494 MeV/u = 0.556 MeV The mass spectrometer does not distinguish by the difference in mass, but by the difference in mass-to-charge ratio. https://en.wikipedia.org/wiki/Mass-to-charge_ratio "This differential equation is the classic equation of motion for charged particles. Together with the particle's initial conditions, it completely determines the particle's motion in space and time in terms of m/Q. Thus mass spectrometers could be thought of as "mass-to-charge spectrometers". When presenting data in a mass spectrum, it is common to use the dimensionless m/z, which denotes the dimensionless quantity formed by dividing the mass number of the ion by its charge number.[1]" 10.01353469 / 4 = 2.5 10.012936862 / 5 = 2 For this reason, a beam of fully ionized particles in a strong magnetic field deflects differently and hits the detector at a different location. Edited 6 hours ago by Sensei
studiot Posted 6 hours ago Posted 6 hours ago (edited) Interestingly Beryllium is more plentiful in both lunar rocks and meteorites than terrestrial rocks. In terrestrial rocks it is usually par of the minereral composition of igneous rccks, particularly weathered ones. Quite a few Beryllium compounds are soluble; Notable insoluble ones are beryllium hydroxide - which supports the accumulation in marine nodules and other sediments theory. https://adsabs.harvard.edu/full/1972LPI.....3..699S Edited 6 hours ago by studiot
swansont Posted 6 hours ago Author Posted 6 hours ago 1 hour ago, John Cuthber said: They didn't say it was. If I say my car can go over 100 MPH, I'm not claiming 200 No but they didn’t say it wasn’t. It also suggests maybe it didn’t work for shorter time periods. It’s a bit ambiguous and imprecise, like the mass comment. They could have stated what the actual limit is (like how radiocarbon is limited to 50k-60k years)
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