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#1 2017-12-12 10:28:49

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,854

Natural nuclear explosion on Mars...for real?

I've just learnt about how uranium fields can become natural reactors and in some circumstances could become explosive. This was news to me!

Apparently such an event is thought to have occurred on Earth near Oklo in Gabon.   Self-sustaining nuclear fission reactions took place at the site approximately 1.7 billion years ago, and ran for a few hundred thousand years.  Some scientists have speculated the Moon might have been created through a runaway nuclear reaction on Earth.

https://en.wikipedia.org/wiki/Natural_n … on_reactor

So to Mars...

There are claims that Mars in similar fashion suffered a nuclear explosive catastrophe...a huge explosive event of 1000 megatons...1000 billion tonnes...knowing what a couple of tonnes of explosive can do in central London (back in the 1990s) I can see something of that sort of output would destroy all life, and all structures, if they existed. It has been suggeseted the site of the explosion was Mare Acidalium.

Here is an interesting article on the subject.

http://www.foxnews.com/tech/2011/04/01/ … -mars.html

Any thoughts?


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#2 2017-12-12 12:56:08

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 6,025
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Re: Natural nuclear explosion on Mars...for real?

Getting a nuclear device to explode is very difficult. An implosive has to focus on the physics package just perfectly. If it isn't perfect, it'll break the core apart rather than triggering an explosion. And critical mass has to be brought together very quickly. Too slow results in a "fizzle". A natural reactor would come together closely, resulting in heat but no explosion. Chernobyl was a chemical explosion driven by heat from the reactor.

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#3 2017-12-12 17:23:51

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,854

Re: Natural nuclear explosion on Mars...for real?

Yes...but don't the chances of a runaway nuclear reaction increase over one billion years (1,000,000,000 years). Either you are saying it is impossible or you are saying it is possible...which is it?


RobertDyck wrote:

Getting a nuclear device to explode is very difficult. An implosive has to focus on the physics package just perfectly. If it isn't perfect, it'll break the core apart rather than triggering an explosion. And critical mass has to be brought together very quickly. Too slow results in a "fizzle". A natural reactor would come together closely, resulting in heat but no explosion. Chernobyl was a chemical explosion driven by heat from the reactor.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#4 2017-12-12 23:44:24

RobertDyck
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From: Winnipeg, Canada
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Re: Natural nuclear explosion on Mars...for real?

Chance of what? It sounds like you're trying to box me into something. Rhetoric games won't change reality. And reality is there is no way a natural nuclear explosion is possible. Ever. Period. Yes, there are natural nuclear reactors. There's one in Canada right now, a mine that has the highest concentration of uranium ever discovered. No one has figured out how to mine it, because it's naturally reacting. It produces heat and neutron radiation. It's so radioactive that any miner would be killed. But it's still there, no explosion, no crater.

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#5 2017-12-13 00:30:33

IanM
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From: Chicago
Registered: 2015-12-14
Posts: 276

Re: Natural nuclear explosion on Mars...for real?

RobertDyck wrote:

Yes, there are natural nuclear reactors. There's one in Canada right now, a mine that has the highest concentration of uranium ever discovered. No one has figured out how to mine it, because it's naturally reacting. It produces heat and neutron radiation. It's so radioactive that any miner would be killed. But it's still there, no explosion, no crater.

I thought Oklo was the only one known to have ever existed in Earth's history, but in any case the reactors are rare enough to preclude an explosion from having happened in the 4.5 billion years of Mars's existence. And even if there was an explosion, there would very likely be radiogenic glass from such explosion on the Martian surface, which has yet to be found (although in all fairness the rovers can only look for so much).


The Earth is the cradle of the mind, but one cannot live in a cradle forever. -Paraphrased from Tsiolkovsky

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#6 2017-12-13 01:47:54

Spaniard
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From: Spain
Registered: 2008-04-18
Posts: 69

Re: Natural nuclear explosion on Mars...for real?

IanM wrote:
RobertDyck wrote:

Yes, there are natural nuclear reactors. There's one in Canada right now, a mine that has the highest concentration of uranium ever discovered. No one has figured out how to mine it, because it's naturally reacting. It produces heat and neutron radiation. It's so radioactive that any miner would be killed. But it's still there, no explosion, no crater.

I thought Oklo was the only one known to have ever existed in Earth's history, but in any case the reactors are rare enough to preclude an explosion from having happened in the 4.5 billion years of Mars's existence. And even if there was an explosion, there would very likely be radiogenic glass from such explosion on the Martian surface, which has yet to be found (although in all fairness the rovers can only look for so much).

As RobertDyck I think that natural nuclear detonation is impossible, at least with stable matter. Perhaps a natural reactor in a huge asteroid that though a huge impact could detonate... I'm not sure... But not spontanously.

It's different that a nuclear reactor generate a "gas explosion". Because a nuclear reactor could stop or start simply by ground movements or moderator movements (like water), a fast raise of heat could evaporate some substance and turn some solid or liquid into a gas generating a big explosion. Or other reactions that accumulate some chemical that could be later generate fast oxidation and a explosion. Just like hydrogen explosion in Fukushima.
It's not a nuclear explosion but a chemical explosion driving by a compound generated by a natural nuclear reactor. It's not the same. Or a fast phase change to gas of some substante too, like in a volcano, but with a different source of heat.

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#7 2017-12-13 06:45:45

louis
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From: UK
Registered: 2008-03-24
Posts: 5,854

Re: Natural nuclear explosion on Mars...for real?

You just clarified - you don't think it's possible.  I wasn't sure whether you were saying it was impossible or highly unlikely. However, a number of scientists disagree with you.  I found this reference to the spontaneous criticality in the Core-Mantle Boundary (CMB):

"The calculations above show that without additional concentration factors, U, Th and Pu concentrations in the CMB are insufficient to reach criticality. Additional concentrations can be achieved by a combination of two processes: growth of the relative concentration of the fissile materials by a transient pressure wave, induced by an impact at the Earth’s surface (Anisichkin, 1997; Voronin and Anisichkin, 2001), and/or the development of compositional heterogeneities (de Meijer and Van Westrenen, 2008).

As shown by Voronin (2011) for fissile material at the CMB, an impact of a 100km- diameter asteroid can create a transient pressure increase of several TPa at the CMB, sufficient to concentrate fissile material from a subcritical to a supercritical condition followed by a nuclear explosion. Regarding the development of compositional heterogeneities, it should be noted that small-scale heterogeneities exist in the core-mantle boundary region even today (e.g., van der Hilst et al., 2007): volumes exhibiting both higher-than-average and lower-than-average wave propagation speeds, with diameters as small as 30 km, are now resolvable. Some studies suggest that the bottom of the mantle is partially molten today, forming a so-called ‘basal magma ocean’ (e.g. Williams and Garnero, 1996; Labrosse et al., 2007; Lee et al., 2010)."

I found that on this forum:

https://earthscience.stackexchange.com/ … explosions

Mars would of course be a good candidate for a huge asteroid strike.


RobertDyck wrote:

Chance of what? It sounds like you're trying to box me into something. Rhetoric games won't change reality. And reality is there is no way a natural nuclear explosion is possible. Ever. Period. Yes, there are natural nuclear reactors. There's one in Canada right now, a mine that has the highest concentration of uranium ever discovered. No one has figured out how to mine it, because it's naturally reacting. It produces heat and neutron radiation. It's so radioactive that any miner would be killed. But it's still there, no explosion, no crater.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#8 2017-12-13 15:07:14

Rusakov
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Registered: 2012-12-19
Posts: 34

Re: Natural nuclear explosion on Mars...for real?

U235 (which is the uranium isotope that is able to undergo the kind of fission necessary) is really rare. That's why it takes a lot of effort to produce nuclear fuel, you have to get tons of naturally occurring uranium ore then separate out the tiny fraction of it that consists of U235 isotopes.

I'm pretty skeptical to be honest.


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#9 2017-12-13 18:33:30

louis
Member
From: UK
Registered: 2008-03-24
Posts: 5,854

Re: Natural nuclear explosion on Mars...for real?

Presumably you need to isolate it for a bomb because you then have to subject it to a pressure wave from a conventional explosion and that would be impossible if it was in its natural state.  But I guess those who say it is possible are arguing it would be such a catastrophic and chaotic pressure event  that it could cause a runaway reaction in some heated up uranium at the CMB.


Rusakov wrote:

U235 (which is the uranium isotope that is able to undergo the kind of fission necessary) is really rare. That's why it takes a lot of effort to produce nuclear fuel, you have to get tons of naturally occurring uranium ore then separate out the tiny fraction of it that consists of U235 isotopes.

I'm pretty skeptical to be honest.


Let's Go to Mars...Google on: Fast Track to Mars blogspot.com

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#10 2017-12-14 12:38:57

Antius
Member
From: Cumbria, UK
Registered: 2007-05-22
Posts: 1,003

Re: Natural nuclear explosion on Mars...for real?

It is possible, though it is probably impossible for the ore body to go super prompt critical.

If water flowed into an enriched ore body and the ore went critical (i.e. achieved self-sustaining fission) the result would be steam generation.  This could accumulate under a layer of impermeable rock (or an ice barrier?) until pressure rises enough to cause the impermeable layer to fail catastrophically.  If the ice layer and ore body underneath extended for several kilometres in either direction, a blast equivalent to megatons of TNT is possible.

Today, uranium enrichment is down to 0.7% and this sort of thing would be impossible.  But on young Mars, enrichment could have been 3% - which is close to the enrichment level for light water reactors.  It could not have happened 180million years ago.  Though it might have happened 4billion years ago.

Last edited by Antius (2017-12-14 12:40:03)

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