Can GRB cause mass-extinctions?

[Entropy]

This afternoon there will be a colloquium at my university on the topic of GRBs causing mass extinctions. It sounds like a pretty interesting topic and so I want to know what you guys think about it. Here is the offical email that was sent to my FSU account:

Dr. Adrian Melott
University of Kansas
(Host: Dr. J. Owens)

"Did a Gamma-ray Burst Initiate the Late Ordovician Extinction?


Gamma-ray bursts are the most powerful explosions known in the Universe.
A GRB within our galaxy could have catastrophic consequences for the
Earth. Extrapolations from the global rate suggest an average interval
of a few hundred million years for events in which the Earth is
irradiated from an event on our side of the Galaxy. The atmosphere
would become heavily ionized, resulting in major destruction of the
ozone layer, darkened skies and nitric acid
rain.

Both the prompt UV and the solar UV resulting from long-term loss of the
ozone layer are destructive to living organisms. The attenuation length
of UV in water is tens of meters. There is a strong candidate for a GRB
based mass extinction in the late Ordovician, 440 My ago. Planktonic
organisms and those animals living in shallow water seem to have been
particularly hard hit during this mass extinction.

Adrian Melott

There are two main theories about the sources GRBs. One, which I favor is the hypernovae hypothesis. The other, which this guy probably believes in, is the collision of neutron stars with other neutron stars, or neutron stars with black holes.

 

[selfAdjoint]

I believe there are now thought to be two populations of GRB, short burst below 10 seconds and long ones over that limit. The long bursts have been observed both at the gamma frequency and visually, and the hypernova explanation seems well attested. The short bursts have just been spotted at visual frequencies, and their cause is more speculative.

 

[SpaceTiger]

If either type of GRB occurred in our galaxy (and was directed toward us), I think there's little doubt that it would be extremely destructive. I would think it would be hard to determine whether or not it causes mass extinctions, since systems like that are extremely difficult to model the associated remnant would have long since faded. I certainly find it plausible, but wouldn't venture to speculate on whether or not it actually occurred.

 

[Mike2]

If either type of GRB occurred in our galaxy (and was directed toward us), I think there's little doubt that it would be extremely destructive. I would think it would be hard to determine whether or not it causes mass extinctions, since systems like that are extremely difficult to model the associated remnant would have long since faded. I certainly find it plausible, but wouldn't venture to speculate on whether or not it actually occurred.

From what I've heard on documentaries, the burst is directed in the direction of the angular momentum of the collapsing star(s), in other words, along the "z" axis. If that is so, then perhaps the fact that we live in a sprial galaxy would make the probabilities greater for star formation with angular moment vectors perpedicular to the galactic plane.

 

[Entropy]

since systems like that are extremely difficult to model the associated remnant would have long since faded.

Not really, an event like a near by GRB, or even an extremely close supernovae, will cause alterations in Earth's isotops via cosmic rays. If a significate alteration in isotops in Earth's crust coincides with a mass extinction then it would support that a GRB or supernovae might have caused it.

 

[SpaceTiger]

Not really, an event like a near by GRB, or even an extremely close supernovae, will cause alterations in Earth's isotops via cosmic rays. If a significate alteration in isotops in Earth's crust coincides with a mass extinction then it would support that a GRB or supernovae might have caused it.

I was actually referring to the supernova/GRB remnant, but I hadn't thought of that means of verification. Did they say in the talk how easy it would be to distinguish such changes from geological processes? Are the initial isotopic alterations primarily in the atmosphere or crust? Which isotopes in particular are they looking for?

 

[Garth]

A problem would be that another major candidate for mass extinctions is an asteroid/comet impact. The signature for those is also anomalous isotope abundancy along the mass extinction line, caused in a similar way by material irradiated by cosmic rays - this time while the impact object was in space.

It might be difficult to distinguish between the two candidates.

Garth

 

[Math Is Hard]

I'm glad someone posted this. I am working on a biology paper about what high-energy blasts could do to the Earth's atmosphere, and the possibility that one might have caused the late Ordovician extinction. I am reading an article about this in this month's Astronomy magazine, "Do we live in a cosmic shooting gallery?".
What I don't understand is how it could have been a GRB, since I always thought of them as happening really, really far away (but I am not sure how I got this idea). How probable is it that one could have occurred in our galaxy? I apologize if this is a dumb question.

 

[russ_watters]

What I don't understand is how it could have been a GRB, since I always thought of them as happening really, really far away (but I am not sure how I got this idea). How probable is it that one could have occurred in our galaxy?

It is a matter of probability: if there are 10 billion galaxies in our observable universe close enough to notice a GRB and we see 10 of these bursts a year (I think that's about the frequency), the probability of seeing one in any given galaxy (including ours) is 1 in 1 billion per year. So odds would be decent that we'd see one in our galaxy every billion years or so (rough, rough numbers...). Perhaps someone else can help firm up those numbers for your paper...

 

[Andre]

Would the statistical highly relevant http://www.lbl.gov/Science-Articles/Archive/Phys-fossil-biodiversity.html have anyting to do with gamma ray bursts? Would it happen about every 62 million years or would the traditional causes (meteorite impacts and trap volcanism) have that typical cycle?

 

[Math Is Hard]

It is a matter of probability: if there are 10 billion galaxies in our observable universe close enough to notice a GRB and we see 10 of these bursts a year (I think that's about the frequency), the probability of seeing one in any given galaxy (including ours) is 1 in 1 billion per year. So odds would be decent that we'd see one in our galaxy every billion years or so (rough, rough numbers...). Perhaps someone else can help firm up those numbers for your paper...

Thanks, Russ. I found one source that says we are detecting them at the rate of about one per day.

In the article I am reading they say that they think GRBs were much more frequent in the early history of our galaxy "when star formation was in full bloom". So I guess the odds of us not getting blasted are a little better than they were? If there's a chance of life forming on planets of other star systems in the Milky Way, the longer interval between the blasts should give them a better shot at it now. I think that's what this article is driving at anyway - that we've missed something in Drake Equation that is pretty influential.

 

[Astronuc]

There was a recent gamma ray burst - 27 December 2004 - http://www.everything-science.com/index.php?option=com_content&task=view&id=111&Itemid=2

The burst came from SGR 1806-20, a neutron star in Sagittarius about 50,000 light years from Earth.

http://www.nature.com/nature/journal/v434/n7037/full/nature03519.html

"The next biggest flare ever seen from any soft gamma repeater was peanuts compared to this incredible December 27 event, said Dr. Bryan Gaensler of the Harvard-Smithsonian Center for Astrophysics, lead author on the Nature paper. Had this happened within 10 light years of us, it would have severely damaged our atmosphere and possibly have triggered a mass extinction. Fortunately there are no magnetars anywhere near us."

http://en.wikipedia.org/wiki/SGR_1806-20

A similar blast within 100 petametres (10 light years) of Earth would destroy the ozone layer and would be similar to a 12 kt of TNT (50 TJ) nuclear blast at 7.5 km. Fortunately, the nearest known magnetar to Earth is 1E 2259+586, 120 exametres (13,000 light years) away.

from Wikipedia Other sources suggest that 1E 2259+586 is 18,000 ly from Earth.

 

[Chronos]

A gamma burst strong enough to trigger mass extinctions would be strong enough to leave a radiation signature in geological formations. Impact events [aka asteroid collisions] would of course pollute these signatures.

 

[Garth]

But they may be nearer than we think! (Short GRBs that is)
Is there a galactic component for the ultra high energy cosmic rays?

Under the hypothesis that Gamma Ray Burst (GRB) might be responsible for the origin of Ultra High Energy Cosmic Ray (UHECR), we propose a two component (galactic and extra-galactic) model for the UHECR origin. The model is based on two facts. The first is the anisotropies found in the angular distribution of GRBs from BATSE catalog. Second is that, of all the located long-GRBs, only approximately 15 percent of them have their spectroscopic redshift determined, and some 38 percent of them have a X-ray, optical, or radio afterglow. So far, in short-GRBs, no afterglow and no red shift have been detected, suggesting that these GRB sources are inside or close to our Galaxy. This two component model for the UHECR is further supported by the experimental evidences of an UHECR excess around 10¹⁸ eV from the direction of the galactic central region. The model offers in a natural way an explanation for the presence of cosmic rays with energies beyond the Greisen-Zatsepin-Kuz'min (GZK) cutoff.

Note: because of the significant energy loss by the GZK (Greisen-Zatsepin-Kuzmin 1966) mechanism, the present universe is not transparent to the highest energy cosmic rays (10²⁰ eV), http://prola.aps.org/abstract/PRL/v73/i26/p3491_1.

Therefore any sources contributing to the bulk of these cosmic rays should be within 500 Mpc of Earth for 10¹⁹ eV CR particles and a few ten's of Mpc for 10²⁰ eV CR particles.

A prevalence of 'near-by' merging BHs and Neutron stars?

Garth

 

[Entropy]

Are the initial isotopic alterations primarily in the atmosphere or crust? Which isotopes in particular are they looking for?

I asked the guy giving the colloquium and he told me that it's unlikely that you could look for isotopic anomolies because they would primarily have been in the atmosphere and impossible to desiguish. So I was wrong in saying it would be easy.And he also said GRBs don't necissarily give off lots of cosmic rays, they is one model where they do give off lots of cosmic rays and one model where they don't.

What would really be the smoking gun would be to find a unusual amount of nitrates in the soil around the time of the mass extinction. Most of the energy from the gamma rays from the GRB would go into turning ozone, molecular oxygen and nitrogen into nitrates. The depletion of ozone would be what would start the extinction. According to his model UVB rays would increase by up to 200% for a decade because of the atmospheric changes. As little as 20% increase in UVB rays will kill plankton.

It is a matter of probability: if there are 10 billion galaxies in our observable universe close enough to notice a GRB and we see 10 of these bursts a year (I think that's about the frequency), the probability of seeing one in any given galaxy (including ours) is 1 in 1 billion per year. So odds would be decent that we'd see one in our galaxy every billion years or so (rough, rough numbers...). Perhaps someone else can help firm up those numbers for your paper...

That is way off. We see about one burst EVERY DAY. According to his research a "long" GRB would have to be with a few kpc (~6000 light years) to threaten Earth. And according to his estimates there sould have been an average of three GRB in the last billion years this close to Earth. Sorry I can't post the source, I don't think he has a web site.

 

[Garth]

. We see about one burst EVERY DAY.

I am being lazy - do you have a breakdown on the frequency of long and short duration GRBs?

Garth

 

[Nereid]

Several things:

- the 'per galaxy' rate for GRBs (of either type) is still pretty much unknown. The association of long/soft GRBs with (one? type of) supernova is now reasonably well established; however, the frequency of these supernovae is not so well established, nor is the extent to which the 'G's are beamed

- the association of short/hard GRBs with compact object mergers (NS-NS, NS-BH, BH-BH?) is much more recent (and less secure); that these do 'beam' is, however, reasonably well established

- whether there are just these two causes of GRBs, of either kind (or, esp, of the 'ones in the middle') is an open question

- 'starquakes' on magnetars can also produce massive amounts of gammas, though not nearly the flux of even the short/hard GRBs

- the existence of populations of 'sub-luminous' GRBs is uncertain; if there are significant populations, making estimates of the likelihood of an extinction event on Earth, due to a 'GRB', will be very tough (today)

- most of the major 'mass extinctions' seem to have more prosaic causes (to do with geophysics rather than astrophysics); the exception is the KT one (a comet/asteroid is clearly implicated); the Cambrian one - who knows? I rather doubt the geological record is good enough (given our present capabilities) to reliably detect a GRB trigger, so attributing a mass extinction to a GRB (or SN or nearby magnetar, or ..) may come down 'finding the shadow' (eliminate all other possible causes, only GRB is left). Here's a good book for those interested: Tony Hallam, Catastrophes And Lesser Calamities: The Causes of Mass Extinctions.

- and what if mass extinctions are like earthquakes (they follow a power law)?