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Home , Devonian, Hangenberg event

arXiv:2007.01887v2 [astro-ph.HE] 25 Aug 2020 ihooedpein(e lo(),i ih feiec suc evidence of light in (6)), also (see depletion ozone with h aeDvna a rtatdpro flwseito r speciation low of period protracted a was Late The hsmnsrp a opldo uut2,2020 26, August on compiled was manuscript This ocnceuto n ag geu rvne(I)trigge (LIP) province igneous large a and eruption volcanic 0 y 1)b us fetntoso aypat includin many of extinctions of pulse a by (10) kyr 300 esuya lentv osbecuefrtepsuae oz postulated the for cause possible alternative an study we 244 https://doi.org/10.1073/pnas.2013774117 uenv rgesfrEdDvna Extinctions Fields D. Brian End-Devonian for Triggers Supernova taopei zn,psil u oagoa eprtr r temperature global a to due dramatic possibly a ozone, with coincided stratospheric have may event extinction indica final the evidence Recent eve extinction boundary. in Devonian- culminating decline, biodiversity in ing . . Liu a h re fmn huad fyas e.()age that argued (7) Ref. . of thousands many assemblages of palynological order in the persisting malformations as associate was event Hangenberg the that suggested recently (DCB) Devonian-Carboniferou the boundary around event) (Hangenberg tion fyas(,2,pntae ya xicinple(Kellwass pulse extinction an milli followed by over event) punctuated occurring 2), (1, rate years speciation of in decline protracted oso iest nsoe n olnfloe fe about after followed a and first However, was in there diversity that (9). of emerging remains loss be a to seems of consensus paucity general overall sett the terrestrial stratigra and and marine in between difficulties and within including correlation factors several any by cated whether and occurrence. (5), their for in test data could the evidence for additional astrophysica account whether consider could wel we sources Here as (8)), could damage. e.g., genetic that (see, rect of increase levels causes extinction UV-B elevated possible concomitant trigger be and to depletion known ozone are which radiation, ionizing episode an LIP. by to caused it not linked warming instead global (5) of whereas depletion, ozone ass arneK 64,USA; 66045, KS Lawrence Kansas, Extinction discussed. are hypothesis supernova possi of the Other of explosion nucleosythesis. supernova core-collapse probe the and star, to sive point origin, supernova a eie.Dtcigete fteln-ie radioisotopes long-lived the of either wher Detecting disk Galactic thin resides. the in m concentrated of are core-collapses these to stars; due likely are mass supernovae full nearby a Such precipitated have would that distance” “kill the tn omcry htcndlvrinzn aito o up for radiation ionizing acc deliver by can damage that inflict rays cosmic could ating that explosion supernova nearby a nvriyo lios raaI 10,USA; 61801, IL Urbana Illinois, of University ooaoSrns O880 USA; 80840, CO Springs, Colorado rgee ysproaepoin at extinction explosions end-Devonian supernova the by that triggered propose therefore We kyr. opttoa hsc,Ntoa nttt o hmclPh Chemical for Institute National Physics, Computational olg odn tad odnW2 L,UK; 2LS, WC2R London Strand, London, College liosCne o dacdSuiso h Universe; the of Studies Advanced for Center Illinois Pu h aeDvna idvriycii scaatrzdb a by characterized is crisis biodiversity Devonian late The h rcs atrspeaetdrn h C r compli- are DCB the during prevalent patterns precise The of sources astrophysical considered not has work Previous a,b es .Miller A. Jesse , noeo oeedDvna xicinsrt ol confirm would strata extinction end-Devonian more or one in | Supernova a,b,c,1 ∼ ∼ 0Mrltrb oemdrt extinc- moderate more a by later Myr 10 dinL Melott L. Adrian , | 5 y g 3 ) asale l (5) al. et Marshall 4). (3, ago Myr 359 a,b omcrays Cosmic n ra .Thomas C. Brian and , i k eateto clg,Uiest fKna,Lwec S66 KS Lawrence Kansas, of University , of Department eateto hsc n srnm,Wsbr University, Washburn Astronomy, and Physics of Department d | eateto hsc n srnm,Uiest fKansas, of University Astronomy, and Physics of Department Ozone ∼ f hoeia hsc eatet EN H11 eea2,S 23, Geneva CH-1211 CERN, Department, Physics Theoretical d 0pc 20 onEllis John , b | eateto srnm,Uiest fIlni,10 .Gr W. 1002 Illinois, of University Astronomy, of Department stp geology Isotope sc n ipyis äaa1,113Tlin Estonia; Tallinn, 10143 10, Rävala Biophysics, and ysics oehtbeyond somewhat , k e,f,g t erthe near nts extinction. 146 Sun the e n drop: one s.Here ise. dineF Ertel F. Adrienne , to l tests ble e that tes sdi- as l rpin drop were s mas- a assive Sm ∼ esult- phic ings eler- ons red 100 on er or d h g s l CO.TeCOte atcptsi nooedsryn cat ozone-destroying an in participates then ClO The (ClO). uhrcnrbtos D,J,adAMdsge h researc the designed ALM and JE, BDF, contributions: the Author to not but reduced, be would density column total The ao otiue oactltccceta ovrsinorga converts that cycle catalytic a to contributes vapor 1 interests. competing any of unaware are authors The acltos L,AE S,adBTaaye aa D,BJF BDF, data; analyzed BCT paper. and the BSL, AFE, ALM, calculations; hudb iie otelwrsrtshr ( stratosphere lower the to limited be should this. for cause reasons to several sufficient are be There would then change extinction. Until this an warranted. whether is unclear is study it detailed UV-B More ground-level (12). for exposure consequences have may and ex- depletion, of period the mechanism. of this a loss via that the layer to argues ozone lead protective (5) would warming Ref. observation sustained by and 13). ceptional verified (12, been wate modeling has of and stratosphere injection lower Cl convective Increased the following into contribut (12). extent ozone Br lesser involving decreased a cycles to and but of depletion, set ozone similar to A cycle. alytic xeto opeels ftepoetv zn layer. ozone protective the of affected. loss complete be a not of would the extent and of region bulk this the above stratosphere, depletion lies lower while layer the So, ozone in km. significant 20-30 be around concentrati may largest occurs the which with ozone, overlap of not does and altitude) rae ae ao ntelwrsrtshr asdb en- Wate by temperatures. caused surface stratosphere higher to lower due the convection in hanced in involving vapor mechanism depletion water ozone creased an proposes (5) Ref. Depletion Ozone for Mechanism Heating record. varia the their in study How- times to quiescent needed (11). during are layer tion data ozone quantitative the more with of UV- ever, destruction consistent and following features conditions, damage environmental walls, deteriorating pigmented severely dark malform including and morphologies spines distinct with episode years. this of tha thousands that least indicates fact at The beds over extended multiple toes. extinction over and the disappeared fingers b five , with these intact left largely and have to fish seems Hang this the Crisis; with conodon berg coeval possibly ammonites, acritarchs, , and fish, armored proto-, hoie(rmrl C n ClONO and HCl (primarily chlorine owo orsodnesol eadesd -al bdfield E-mail: addressed. be should correspondence whom To is,tevria xeto hsooedpeinmechanis depletion ozone this of extent vertical the First, ozone stratosphere lower for important is mechanism This es 5 ,1)as eottedsoeyo prsfrom spores of discovery the report also 11) 9, (5, Refs. a,b oeaK 62,USA 66621, KS Topeka 4,USA; 045, ra .Fry J. Brian , arneK 64,USA; 66045, KS Lawrence NS| PNAS j vltoayBooyadBoiest nttt,Univers Institute, Biodiversity and Biology Evolutionary e t,Ubn L681 USA; 61801, IL Urbana St., een h witzerland; hsc eatet ntdSae i oc Academy, Force Air States United Department, Physics h uut2,2020 26, August rc .Lieberman S. Bruce , g aoaoyo ihEeg and Energy High of Laboratory e eateto hsc,Kings Physics, of Department o.XX|n.X | XX no. | XXX vol. | 2 ofe aia form radical free to ) ;BF J,Z,adJMmade JAM and ZL, BJF, BDF, h; [email protected] E S,AM n C wrote BCT and ALM, BSL, JE, , c eateto Physics, of Department i,j Zhenghai , ∼ 12 − 8km 18 t of ity ony nic 1–3 en- on ed ts, m es O B r r t - - - , RE REPORT BRIEF Secondly, the duration of the effect should be relatively long-lived nuclear isotopes that could provide distinctive sig- short, . 1 week (12), since the injected water vapor is pho- natures, as we discuss later. tolyzed and ClO is converted back to HCl and ClONO2. Thus, There are two main types of SNe: (1) massive stars > unless convective transport of water vapor to the lower strato- (∼ 8M⊙) that explode as core-collapse SNe (CCSNe), and sphere, e.g., by storms, is continuous (on week timescales) the (2) white dwarfs that accrete from binary companions and ex- ozone reduction will be episodic, not sustained. The effect is plode as Type SNe. These SN types have similar explosion also seasonal, since strongly convective storms tend to be lim- energies, and both produce ionizing radiation able to dam- ited to the spring/summer. While this is likely detrimental age the biosphere. However, their different nucleosynthesis to surface life, most organisms have repair mechanisms that outputs lead to different radioisotope signatures. can cope with some short-duration UV-B exposure. Near-Earth CCSNe are more likely than Type Ia SNe. We Thirdly, the effect is likely to be limited geographically, estimate the nearby CCSN frequency using a Galactic rate −1 since strongly convective storms are not uniformly distributed RCCSN = (30 yr) and placing the Sun at a radius R⊙ = and the enhanced water vapor is likely only to spread over 8.7 kpc in a thin disk of scale radius 2.9 kpc and height 0.1 kpc ∼ −R⊙/R0 3 2 100 km horizontally (12). (23). This gives a CCSN rate RSN = e r /3R0h0 ∼ 3 −1 Finally, there is significant uncertainty as to the ozone de- 4 r20 Gyr within r20 = r/20 pc from Earth. Hence a CCSN pletion level needed to induce aberrations in pollen morphol- at a distance ∼ 2 times the “kill radius” of 10 pc is a plausible ogy and even more critically, large-scale extinction. While origin of the end-Devonian event(s). In contrast, the Type Ia the anthropogenic ozone “hole” over has led to SN rate is an order of magnitude smaller, as these events are increased UV-B exposure, no crash in the ecosystem has re- spread over the ∼ 8 times larger volume of the thick disk. sulted. This may partly be due to the seasonal of the Massive stars are usually born in clusters (OB associa- change, as would be the case here as well. Recent work (14) tions), and are usually in binaries with other massive stars. has shown that short-term exposure to significant increases Thus, if one CCSN occurred near the DCB, likely there were in UV-B does not result in large negative impacts on the pri- others. This could explain the Kellwasser and other enigmatic mary productivity of ocean phytoplankton, and other organ- Devonian events, in addition to the . isms show a wide range of sensitivity (15, 16). The amount of column depletion over a given location in those cases was Possible Radioisotope Signatures of Supernovae ∼ 50%. The depletion caused by the mechanism considered in (5) seems unlikely to be that large. Hence, the convective A CCSN close enough to cause a significant extinction would transport of water vapor to the lower stratosphere may not be also deliver SN debris to the Earth as dust grains–micron or sufficient to induce a substantial extinction. It is thus worth sub-micron sized particles created early after the explosion. considering other mechanisms for global . Grains in the explosion would decouple from the plasma (gas) and propagate in the magnetized SN remnant until they are stopped or destroyed by sputtering during collisions (24). Astrophysical Agents of Ozone Destruction and Bio- The portion that reaches the Earth would deposit in the sphere Damage atmosphere live (undecayed) radioactive isotopes. There is Astrophysical mechanisms for biosphere damage include very little pre-existing background for radioisotopes whose bolide impacts, solar proton events, supernova (SN) explo- lifetimes are much shorter than the age of the Earth. Those sions, gamma-ray bursts, and neutron star mergers (kilono- with lifetimes comparable to the time since the event would 60 vae). Bolide impacts, gamma-ray bursts and solar proton provide suitable signatures. The discoveries of live Fe in the events are essentially impulsive, and recovery of the ozone deep ocean, the lunar regolith and Antarctic snow provide one layer takes . 10 yr (17), which is likely to avert lasting bio- such signal, which is interpreted as due to at least one recent sphere destruction. Moreover, these events and kilonovae are nearby CCSN 2–3 Myr ago at a distance ∼ 50−100 pc, which unlikely to recur frequently. Accordingly, we focus on SNe. is compatible with the rate estimate given above (24). Supernovae (SNe) are prompt sources of ionizing photons: Possible relic SN radioisotopes from the end-Devonian pe- 146 extreme UV, X-rays, and gamma rays. Over longer timescales, riod with an age 360 Ma include Sm (half-life 103 Myr), 235 244 the blast collides with surrounding gas, forming a shock that U (half-life 704 Myr) and Pu (half-life 80.0 Myr). The 244 drives particle acceleration. In this way, SNe produce cosmic most promising signature may be provided by Pu, which rays, i.e., atomic nuclei accelerated to high energies. These has also been discovered in deep-ocean crust and sediment charged particles are magnetically confined inside the SN rem- samples deposited over the last 25 Myr (25). Moreover, it is nant, and are expected to bathe the Earth for ∼ 100 kyr. absorbed into bones and retained during life (26), whereas ura- 146 The cosmic-ray intensity would be high enough to deplete nium is absorbed during fossilization (27) and Sm is solu- 235 the ozone layer and induce UV-B damage for thousands of ble. There is a significant U background surviving from be- 235 238 years (18–21). In contrast to the episodic, seasonal, and ge- fore the formation of the Solar , with ( U/ U)⊕ = ographically limited ozone depletion expected from enhanced 0.721 ± 0.001%, so a significant detection above this back- 235 238 > convection, ozone depletion following a SN is long-lived and ground requires deposition attaining USN/ U⊕ ∼ 3 × global (see, e.g., (16, 20, 21)) and is therefore much more 10−5. U-Pb dating has been used to date the end-Devonian likely to lead to an , even given uncertainties extinction, but with an uncertainty in the 235U/238U ratio around the level of depletion necessary. (We note that, as well that is much larger than this target sensitivity, but even a as the induced UV-B damage, cosmic rays could also cause few atoms of non-anthropogenic 244Pu in end-Devonian fos- radiation damage via muons produced when they impact the sils would be unambiguous evidence for the r-process in SNe. atmosphere (22)). The SN blast itself is unlikely to wreak sig- We have estimated the terrestrial deposition of 146Sm, nificant damage on the biosphere, but may deposit detectable 235U and 244Pu by a nearby SN. 146Sm is a proton-rich

2 | https://doi.org/10.1073/pnas.2013774117 Fields et al. (“p-process”) nucleus that might be produced by CCSNe near the surface, they could be considered in end-Devonian or Type Ia SNe (28). Models for the p-process (28) give extinctions of living at depth. 146Sm/144Sm ∼ 0.01 − 2.5, with the predicted core-collapse Finally, if there was one CCSN at the DCB, there may abundance typically around 0.2. Assuming a CCSN that pro- have been more, which may have been responsible for the 144 duced a solar Sm/ø16 ratio, and ejected Mej(ø16) = 2M⊙, Kellwasser and additional events. These could show evidence we estimate a total yield of 146Sm in the ejecta of N (146Sm) ∼ for ozone depletion and the other signatures above. 1.6 × 1047 atoms. On the other hand, 244Pu and 235U are neutron-rich nuclei that are made by the rapid capture of ACKNOWLEDGMENTS. This work was partially supported by neutrons, the r-process, whose astrophysical sites are uncer- grants from the UK STFC and the Estonian Research Council. tain. There is evidence that kilonovae make at least some of 1. A Stigall, Speciation collapse and invasive species dynamics during the Late Devonian “Mass the lighter r-process nuclei (29), but it is uncertain whether Extinction". GSA Today 22, 272 (2012). 2. Jx Fan, et al., A high-resolution summary of to Early marine invertebrate these events make the heavier nuclei of interest here. Assum- biodiversity. Science 367, 272–277 (2020). ing that CCSNe are the dominant r-process sites, we estimate 3. S Kaiser, M Aretz, R Becker, The global Hangenberg Crisis (Devonian-Carboniferous tran- yields of N (235U, 244Pu) ∼ (3, 1.6)×1047 atoms per explosion. sition): review of a first-order mass extinction. Geol. Soc. London, Special Publ. 423, 387 (2015). The journey of SN-produced radioisotopes from explosion 4. 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Fields et al. PNAS | August 26, 2020 | vol.XXX | no.XX | 3