Tech trials to find Antarctica’s ‘missing’ iron meteorites

The project to find Antarctica’s “missing meteorites” is making excellent progress, say scientists.

A group led from Manchester University is developing detection equipment it believes will discover a bounty of iron space objects buried in the polar ice.

This survey gear has just come through a week of successful trials.

Presently, 10 times fewer iron meteorites are found in Antarctica compared with other parts of the globe.

The scientists say this discrepancy has nothing to do with differing fall rates; rather, it can be explained simply by the tendency of metal objects to sit just under the ice surface out of the view of collectors.

The team’s equipment, adapted from mine-detection technology, was dragged behind a snowmobile across a simulation field set up at the Ny-Ålesund research base on Svalbard in the Arctic.

Dummy meteorites were hidden in a glacier at varying depths and then the system driven over them to locate their positions.

“It’s gone really well,” said Dr Geoff Evatt. “We’ve got the mechanics of the detector pretty nailed down in terms of the towing, the data-logging, the GPS coordinates – the way we use the system.

“There’s the inevitable teething problems, of course, in making sure the equipment all works with the environment in the cold, but the only way to sort out those problems is to get out here and start using the detector, he told BBC News”

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    Of the more-than-35,000 meteorites catalogued in collections worldwide, something like two-thirds have been retrieved from Antarctica.

    Not only does the colour contrast make for easier prospecting, but hunters also get a helping hand from the way the ice sheet moves. Meteorites that crash in Antarctica’s high interior are buried and transported towards the coast, ultimately to be dumped in the ocean.

    But if this conveyor happens to run into a barrier on the way – such as a range of mountains – the ice will be forced upwards and scoured by winds to reveal its cargo.

    Meteorite hunters on the continent concentrate their searches in these special “stranding zones”.

    What they have noticed, however, is a bias towards stony-type space rocks.

    The iron ones are underrepresented compared with the global distribution. Modelling work by Dr Evatt and his team suggests the metal meteorites are still there; they just do not come back to the surface in the same way.

    It is thought that as they start to rise through the ice, their iron absorbs energy from the Sun and efficiently warms the meteorites’ undersides, enabling them to sink back down.

    Manchester team-member, Dr Katherine Joy will be heading out to Antarctica later this year on an initial survey to assess the stranding zones.

    Places with the highest density of stony-type meteorites sitting on the surface should also be the locations with the greatest number of iron meteorites hidden in the ice below.

    “A reconnaissance trip will help the team investigate which blue icefields that have not been visited before are productive for meteorite collection,” she said.

    “The outcomes of this initial search will help us to target where to take the full detector setup to test for buried meteorites.”

    This is likely to happen in the austral summer of 2019/2020. But working in these remote locations will be extremely challenging and will require the assistance and expertise of the British Antarctic Survey.

    Equipment failure is an ever-present hazard and the team knows it has to go with a detector that is robust and simple to use.

    “Ny-Ålesund has been reasonably comfortable so if we’ve needed to pop up a lid on the equipment and get our hands dirty with the electronics, we can,” said Dr Evatt.

    “We’ve also been able to come back to the base in the evening and make fine adjustments. However, when we use this system in anger in Antarctica, we won’t have those luxuries. The aim therefore is to develop a system with minimal switches and user interface, and one that is robust not just to the environment but to human error.”

    The hope is that iron meteorites “numbering in the low tens” can be recovered on the 2019/2020 expedition.

    These will be brought back to Manchester to be curated and studied.

    Iron meteorites are interesting because they represent the smashed up innards of bodies that almost became planets at the start of the Solar System.

    They therefore provide clues about events that occurred some 4.6 billion years ago when the Earth was forming.

    Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos

Antarctica ‘gives ground to the ocean’

Scientists now have their best view yet of where Antarctica is giving up ground to the ocean as some of its biggest glaciers are eaten away from below by warm water.

Researchers using Europe’s Cryosat radar spacecraft have traced the movement of grounding lines around the continent.

These are the places where the fronts of glaciers that flow from the land into the ocean start to lift and float.

The new study reveals an area of seafloor the size of Greater London that was previously in contact with ice is now free of it.

The report, which covers the period from 2010 to 2016, is published in the journal Nature Geoscience.

“What we’re able to do now with Cryosat is put the behaviour of retreating glaciers in a much wider context,” said Dr Hannes Konrad from the University of Leeds, UK.

“Our method for monitoring grounding lines requires a lot of data but it means you could now basically build a permanent service to monitor the state of the edges of the continent,” he told BBC News.

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    Although the end product is quite simple, the process of getting to it is quite a complex one.

    Viewed from above, the position of grounding lines is not always obvious.

    The glaciers themselves are hundreds of metres thick, and where they begin to float as they come off the continent can be hard to discern in simple satellite images.

    But there are radar techniques that can find their location by spotting the up and down tidal movement of a glacier’s floating ice. This, however, is just a snapshot in time.

    What Dr Konrad and colleagues have done is use these known positions and then combine the data with knowledge about the shape of the underlying rock bed and changes in the height of the glaciers’ surface to track the evolving status of the grounding lines through time.

    The new study triples the coverage of previous surveys.

    On the face of it, the results are pretty much as expected.

    Of the 1,463km² of grounded ice that has been given up, most of it is in well documented areas of West Antarctica where warm ocean water is known to be infiltrating the undersides of glaciers to melt them.

    Dr Konrad explained: “If you take 25m per year as a threshold, which is sort of the average since the end of the last ice age, and you say anything below this threshold is normal behaviour and anything above it is faster than normal – then in West Antarctica, almost 22% of grounding lines are retreating more rapidly than 25m/yr.

    “That’s a statement we can only make now because we have this wider context.”

    The new data-set confirms other observations that show the mighty Pine Island Glacier, one of the biggest and fast-flowing glaciers on Earth, and whose grounding line had been in major retreat since the 1940s, appears now to have stabilised somewhat.

    The line is currently going backwards by only 40m/yr compared with the roughly 1,000m/yr seen in previous studies. This could suggest that ocean melting at the PIG’s base is pausing.

    Its next-door neighbour, Thwaites Glacier, on the other hand, is seeing an acceleration in the reversal of its grounding line – from 340m/yr to 420m/yr.

    Thwaites is now the glacier of concern because of its potential large contribution to global sea-level rise. And the UK and American authorities will shortly announce a major joint campaign to go and study this ice stream in detail.

    Elsewhere on the continent, 10% of marine-terminating glaciers around the Antarctic Peninsula are above the 25m/yr threshold; whereas in East Antarctic, only 3% are.

    The significant stand-out in the East is Totten Glacier, whose grounding line is retreating at a rate of 154m/yr.

    Overall, for the entire continent, 10.7% of the grounding line retreated faster than 25m/yr, while 1.9% advanced faster than the threshold.

    One fascinating number to come out of the study is that grounding lines in general are seen to retreat 110m for every metre of thinning on the fastest flowing glaciers. This relationship will constrain computer models that try to simulate future change on the continent.

    Leeds co-author Dr Anna Hogg said: “The big improvement here is Cryosat, which gives us continuous, continent-wide coverage, which we simply didn’t have with previous radar missions.

    “Its capabilities have allowed us to build up a picture of retreat rates, especially at the steeply sloping margins of the continent, which is where these changes are taking place. We have eight years of coverage now and it’s guaranteed in the future for as long as Cryosat keeps working,” she told BBC News.

    Since conducting the study at Leeds, Dr Konrad has now moved to the Alfred Wegener Institute in Bremerhaven, Germany.

    Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos