Iron meteorites 'buried in Antarctica' by the Sun

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Iron meteorites 'buried in Antarctica' by the Sun

Postby David Entwistle » Wed Feb 17, 2016 7:51 am

BBC report on paper suggesting why iron meteorites are underrepresented in samples collected in Antarctica.

The churning of glaciers spews many space rocks out on to the surface in Antarctica, but compared to elsewhere on Earth, few of them are made of iron.

Based on modelling and lab experiments, scientists say the missing metallic rocks might be burying themselves, by melting the ice as sunlight heats them.

To prove their idea, the team now wants to look for the rocks themselves.

"The study is proposing a hypothesis - these samples should be there. We just have to go and locate them," said Dr Katherine Joy from the University of Manchester, a co-author of the paper published in Nature Communications.


The paper is available here.

A potential hidden layer of meteorites below the ice surface of Antarctica by G. W. Evatt, M. J. Coughlan, K. H. Joy, A. R. D. Smedley, P. J. Connolly & I. D. Abrahams.

Antarctica contains some of the most productive regions on Earth for collecting meteorites. These small areas of glacial ice are known as meteorite stranding zones, where upward-flowing ice combines with high ablation rates to concentrate large numbers of englacially transported meteorites onto their surface. However, meteorite collection data shows that iron and stony-iron meteorites are significantly under-represented from these regions as compared with all other sites on Earth. Here we explain how this discrepancy may be due to englacial solar warming, whereby meteorites a few tens of centimetres below the ice surface can be warmed up enough to cause melting of their surrounding ice and sink downwards. We show that meteorites with a high-enough thermal conductivity (for example, iron meteorites) can sink at a rate sufficient to offset the total annual upward ice transport, which may therefore permanently trap them below the ice surface and explain their absence from collection data.
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Re: Iron meteorites 'buried in Antarctica' by the Sun

Postby Barwellian » Wed Feb 17, 2016 11:44 am

Interesting....perhaps another change for Katie to get back meteorite hunting in Antarctica.

G
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Re: Iron meteorites 'buried in Antarctica' by the Sun

Postby David Entwistle » Sun Feb 21, 2016 12:13 pm

Barwellian wrote:Interesting....perhaps another change for Katie to get back meteorite hunting in Antarctica.

G


It's an interesting idea. I've only just got round to scanning the paper, which is freely available (which is great).

To me the lab experiment seems a little aggressive, in terms of solar flux and ambient temperature, to draw too great a conclusion from.

Our experiments centred around subjecting a meteorite encased in a block of ice (400 × 400 × 50 mm) to the radiation from an Oriel Solar Simulator arc lamp (irradiance 1,440 W m−2) that was held at a constant 10 mm above the ice surface and focused onto the englacial meteorite. This was conducted in a (otherwise dark, non-reflecting) temperature-controlled room, with ambient temperature −1 °C.


Image

I assume it would be easy to repeat the lab experiment with more representative values, but would need to run for a representative period of time.

I guess the next step could be to drop some meteorite samples (or analogues) on the ice in a meteorite stranding zone and leave them for one year to see if they disappear below the ice surface.
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Re: Iron meteorites 'buried in Antarctica' by the Sun

Postby Barwellian » Sun Feb 21, 2016 9:34 pm

Good idea Dave...I'll lend them one if they take me along for the ride ;-)

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