Photogrammetry and non-destructive determination of properties of Antarctic meteorites

Tom Harvey writes:

Throughout ejection from their parent body, transportation through space and subsequent arrival on Earth, meteorites undergo extreme pressures and temperatures. Some meteorites, despite having survived entry to Earth, can be extremely fragile. Some of the analytical techniques that provide a wealth of information about meteorite geochemistry and physical properties can be damaging to a meteorite sample, either exposing it to some forms of contamination, or destroying it entirely. Given the opportunity to analyse relatively pristine samples from Antarctica, we opted to develop a procedure for understanding some of the fundamental properties of the returned meteorites that was entirely non-destructive.

Density (the mass per unit volume of a material) is a useful property to understand because it can allow us to make inferences about parent body composition, in addition to being an important metric in understanding thermal evolution models, as well as the survivability of materials in impacts, and during atmospheric entry to Earth. Non-destructive, high-precision measurement of the mass of a meteorite is straightforward to undertake using lab scales (i.e., weighing balances).

However, the determination of sample volume is not so straightforward. Traditional “Archimedean” methods for the determination of volume involve measurement of the displacement of a well-characterised medium (for example water, ceramic beads or inert gases) when the sample is emplaced into (see this previous study Consolmagno et al. 2008). Depending on the medium that the meteorite might come into contact with, it is possible that the sample might be chemically altered or mechanically damaged. Volume determination has also been performed by laser scanning of meteorite samples, to produce a three-dimensional (3-D) computer model of the sample surface topography (for example, see McCausland et al. 2011).  A potential barrier to performing this sort of study is the requirement for expensive and highly specialised laser and camera technology.

An alternative to these methods that we have chosen to develop is the production of 3-D computer models of the samples returned by the Lost Meteorites of Antarctica project. This method involves the use of a suite of photographs of an object to computationally generate a three-dimensional colour model of that object. The method is non-contaminating, scalable, and the only necessary hardware was a DSLR camera, some small portable lights, and a computer with the appropriate software installed.  Furthermore, the production of an accurate computer model of the samples’ surface topography and colour makes an excellent curatorial record which can be used in lab decision making, and to understand the orientation relationship between sub-splits in the future.

Tom Harvey in the curation lab imaging one of the meteorite samples. Photo: KJoy

First, the meteorites were placed into a controlled light environment. This meant that we could control the amount of reflection and shadow on the sample surface, which is important for producing a good model. By using the appropriate sterile tools and portable lights, this method did not expose the samples to any alteration or contamination. Photographs were taken using a high-resolution camera at 5º rotational intervals around the sample (and in multiple orientations to capture) to ensure that we had captured all the details of the sample surface.

These photographs were then loaded into Agisoft Metashape, a professional software for photogrammetry applications, which were used to produce the models. This process is broken into several key steps which involve a pixel matching algorithm, and alignment of the various orientations of the sample to generate a shape file for the sample, followed by the production of a mosaic derived from the sample photographs to map over the shape file to bring it to life in colour.

In order to determine the volume of these models, the shape files were imported into a computer-aided design (CAD) software, 3DS Max, and scaled according to known external sample dimensions, measured in the lab with a Vernier calliper. In order to understand how well this method determined the true volume of the sample, we produced models of wooden cuboid blocks of known size and found that the computed volumes of these blocks were within 2% of their true, measured volume.

Final model of Antarctic Meteorite OUT 18010, images of which are shown in the above slideshow. Video: Tom Harvey

Using the data from this method, we will be able to compare our computed volumes with measurements derived from other methods such as computed tomography scans of the sample. The photogrammetry derived volume measurements and the sample masses measured in the lab allowed us to compute a density value for each meteorite in the study. Once all of the meteorites are formally classified, we will also be able to compare the densities derived from our photogrammetry-based method, with literature density values for meteorites of the same type as the ones recovered by the Lost Meteorites of Antarctica team to assess the usefulness of the method.

One of the potential drawbacks of our method is that it can be fairly time consuming, taking several days to carefully photograph, and computationally process a meteorite from start to finish. Furthermore, the method may be challenging to undertake on highly reflective metallic samples – the software relies on identifying matching features in different pictures, and so a sample that predominantly reflects light might cause issues.

However, it is possible to make high fidelity models of meteorites of a range of a size, shape and colours. These can be useful curational tools and should also provide a dataset of information about the samples that would otherwise be difficult to attain whilst maintaining the pristine nature of the samples.

This study was the topic of a 2021 LPSC abstract which you can find here. You can find the various models we’ve made dotted about the individual meteorite information pages from the first season, or you can find a selection of them below!


Three more meteorites classified

Three more meteorites have been classified from the first search season in 2018-2019. If you want to find out more about how we have classified these samples take a look at this blog post.

This time we announce the collection and classification of two samples that are achondrites – meaning they are from parent asteroids that have been differentiated (see here for more details). These two samples are classified as mesosiderites – called OUT 18014 (made up of two separate stones found about 5 m apart from each other) and OUT 18018 (one stone) found ~1.7 km away from the other two samples.

Mesosiderites are an unusual type of meteorite – they are stony-iron, meaning that they are made up of roughly equal parts silicate minerals and iron metal. As of May 2021 there are only 280 meteorites that have been classified as being a mesosiderite, with only 61 of the group having been found in Antarctica. In terms of the Lost Meteorite of Antarctica project goals, finding this sample is very interesting – as it is a stony-iron type of meteorite we would have perhaps expected to find meteorites like this sitting below the ice, rather than on the top ice surface. We are looking into this question as we classify more of the samples we found.

We also report another L-chondrite sample (adding to the list that we previously reported – see below. This one is called OUT 18004 and it looks like this:

These newly classified stones join the first nine chondrite samples we announced early in May 2021: see below for a gallery of the previous meteorites classified from the project.

A list of all the meteorites classified so far can be found here.

UK Antarctic Meteorite Classification – the process

The first of the UK Antarctic meteorites have been classified! Nine rocks retrieved from the Hutchison (HUT) and Outer Recovery (OUT) icefields have been approved and published by the Meteoritical Bulletin. For details of these, please see this table and follow the links.

How were they classified?
The rocks collected in Antarctica were shipped frozen to the UK and kept in temperature monitored freezers. Each rock was thawed in an exisccator chamber to minimise any chemical reaction with residual ice; any ice present should sublimate straight to gas from the solid phase. After thawing, the rocks were all individually weighed and photographed. Measurements were taken of the rock’s magnetic susceptibility and electrical conductivity (see this previous blog post by Tom Harvey, as these properties can give a provisional indication of their possible classification.

Some of the meteorites were chosen to undergo computerised tomography (CT) scanning and photogrammetry. CT-scanning gives a 3D image of the interior of the rock. This provided compositional information and helped us to choose where to attempt to break or cut the rock. Photogrammetry allows a full 3D surface rendering of the meteorite to be made. For more details of this work, please see Tom’s LPSC conference presentation.

20200130_103524
Tom Harvey in the curation lab imaging one of the meteorite samples. Photo: KJoy

Where there were no natural crumbs or fragments of material for further analysis, each rock was split with rock splitters, keeping them inside their sterile bag so that the only contact was with the stainless steel blade. A few meteorites and some of the fragments from the rock splitters were cut with a low speed saw to ensure the material does not get hot enough to cause any alteration.

Fragments were weighed, photographed and then made into epoxy blocks. These have to be polished to a very flat surface, in order to be able to examine the chemical composition using a scanning electron microscope (imaging system) and electron microprobe (used to determine mineral chemistry).

The scanning electron microprobe provides greyscale images (see left below), where the brightness corresponds to the differences in atomic number (number of protons) of the different elements. For example, iron, with an atomic number of 26, will be much brighter compared to sodium, with an atomic number of 11. It can also be used to quantify the difference in this brightness to get an idea of the relative abundance of each element and likely mineral. We use the scanning electron microscope first to get an image and element maps of the whole section (see right image below).

Following this, around 30-40 spots (points) are selected for measurement with the electron microprobe as this allows for more precise and accurate quantification of the mineral composition. In the element map above, the silicate minerals shown in green are usually olivine, and the minerals in light blue are usually pyroxene. The iron content of olivine and pyroxene varies and this is used to distinguish ordinary chondrites between the “H”, “L”, and “LL” classifications (check out where these meteorites sit within the family tree here).  “H” chondrites have the highest iron metal content, but lower iron oxide in pyroxene and olivine. “L” chondrites have lower iron and less metal but higher iron oxide in pyroxene and olivine, whereas “LL” have the lowest total iron but the highest iron oxide in pyroxene and olivine.

Graph showing the iron oxide abundance in pyroxene (Fs) against the iron oxide abundance in olivine (Fa). Yellow crosses show the data collected for five UK Antarctic meteorites, superimposed on a graph of values recommended as distinguishing the H, L and LL ordinary chondrite groups for the Nomenclature committee (Grossman & Rubin, 2006).

Meteorites classified!

We have news…. its a big day for the project as we have our first batch of meteorites that have been formally classified by the Meteoritical Society Nomenclature committee and have now been published in the Meteoritical Bulletin Database!

A list of the newly classified meteorites can be found here https://ukantarcticmeteorites.wordpress.com/meteorite-discoveries/ , and you can click on each meteorite name to learn more and see some pictures of the samples. So far all of those classified from our 1st field season come from parent bodies in the asteroid belt: all are undifferentiated ordinary chondrite types. This means that they come from some from asteroids that represent some of the earliest Solar System building block rocky material that never got big enough to completely melt (hence they are undifferentiated), but they are all are from quite a common type of meteorite group (the ordinary chondrites). So far all the types classified are stony and not metal types – meaning that they are dominantly made up of silicate minerals rather than metal. In case you get lost with all the terms used – an overview of the different types of meteorites can be found at https://ukantarcticmeteorites.wordpress.com/meteorite-classification/

The first classified batch include nine meteorites: two were recovered from from the Hutchison Icefield area (these ones are called HUT), and seven from the Outer Recovery icefield area (these ones are called OUT). The number after the acronym name specifies the particular sample type. If you want to read more about the names of icefields we visited you can read here https://ukantarcticmeteorites.wordpress.com/2021/04/15/new-meteorites-new-names/

This has been the cumulation of a lot of hard work from the field search teams from the 1st 2018-2019 field season (Julie Baum and Katie Joy) and logistics support personnel, the BAS cargo transfer team, the local meteorite lab and classification team – lead by Jane MacArthur with help from Thomas Harvey, Rhian Jones and Katie Joy. A huge thanks to the local analytical lab leads who have kept the instruments we use to image the samples and determine their chemistry (Lewis Hughes and Jon Fellowes), those who support the labs we use to prepare our samples (John Cowpe and Lydia Fawcett) and appreciate key advice from Andrew Smedley, Romain Tartese and Geoff Evatt. Thanks also to all the external help we have had from the Natural History Museum staff in helping these efforts, and to the Meteoritical Society Nomenclature team and Meteorite Bulletin teams for reviewing, approving and sharing the samples’ new names.

You can also read a blog from Jane on the lab curation approach where she will talk about how we go from picking up a sample in the field to working out what type of meteorite it represents.

We also have more samples under review by the nomenclature team so will announce what else we have found in the near future… stay tuned for more meteorites to come…

Photo of the largest sample found in season 1 – now called OUT 18021 (or still affectionately referred to as the melon on account of its large size). the scale cube is 1 cm in size. Image: Lost Meteorites of Antarctica / The University of Manchester

New meteorites need new names…

To be able to give the meteorites we have recovered a formal name we have to go through some procedures…

Dense meteorite stranding zones (areas where lots of meteorites are found) are awarded a name by the Meteoritical Society Nomenclature committee. The meteorites recovered from these areas are then named after these sites – for example the first recognised lunar meteorite Allan Hills (ALHA for short) 81005 is named after the Allan Hills icefield A in Antarctica. Thus, to be given a name we need the place that the meteorites are found to be called something!

Our issue is that the regions we visited in Antarctica had not been formally allocated names by the countries who administrate these areas. So we have gone through two different routes to formally assign names to the field sites we visited so that we can use the names of these geographical features in future research publications and use them to name the meteorites we recovered.

We are happy to announce that our two main field areas have been approved as the Outer Recovery Icefields in Dronning Maud Land by the Norwegian Polar Institute and Hutchison Icefield in Coats Land (British Antarctic Territory ) by the UK Antarctic Place-names Committee. Both of these field sites contain nunataks (mountain tops emerging from the ice), which have also been named after meteorite and meteor scientists (see below for details). The UK site names are included in the UK Antarctic Gazetteer (https://apc.antarctica.ac.uk/) and are available for use on all maps and charts and in all publications. They are also included in the Scientific Committee on Antarctic Research (SCAR) Composite Gazetteer of Antarctica (https://data.aad.gov.au/aadc/gaz/scar/ ).

These names have now also been approved by the Meteoritical Society as dense meteorite collection areas and we will be able to call the meteorites either OUT (for those collected at the Outer Recovery Icefields) and HUT for those collected from the Hutchison Icefield.

Regional context of the fieldsites for the Lost Meteorites of Antarctica project. See below for details of the two areas highlighted with black boaxes. Base map is Landsat Image Mosaic of Antarctica. Image: Katherine Joy.

Outer Recover Icefields Area

Outer Recovery Icefields. named because of its proximity to the Recovery Glacier found adjacent to the northern extent of the area. Link to online Norwegian record.

Halliday Nunatak (81°24’32.97″S, 18° 1’59.88″W): Located in the Outer Recovery Icefields. named after Canadian astronomer Dr Ian Halliday (1928-2018) who was a Canadian astronomer with expertise in meteor (asteroid and comet) delivery rates to the Earth. Link to online Norwegian record

Outer Recovery Icefield area showing locations of the nunatak and four separate blue ice fields. Base map is Landsat Image Mosaic of Antarctica overlain with high resolution Sentinel 2 image. Map scale is 1:250,000 Image: Katherine Joy.

Hutchison Icefield Area

Hutchison Icefield (81°30′ 30″S, 26°10’W): Named after British meteorite scientist Dr Robert Hutchison (1938-2007) who was the Curator of Meteorites at the Natural History Museum, London. He was Head of the Cosmic Mineralogy Research Programme at the NHM, and responsible for the national meteorite collection, one of the most significant meteorite collections in the world. Awarded the Gold Medal of the Royal Astronomical Society in 2002; asteroid 5308 named Hutchison by the International Astronomical Union. Named in association with names of pioneering meteoriticists grouped in this area. Link to online SCAR record.

Turner Nunatak (81°27′ 50.42″S, 26°24’48.88″W): Located in the Hutchison Icefield. Named after Professor Grenville Turner FRS (b. 1936) pioneering lunar and meteorite scientist, Emeritus Professor at the University of Manchester. He established the University of Manchester Isotope Cosmochemistry group and his pioneering work on rare gases in meteorites led him to develop the argon–argon dating technique that demonstrated the great age of meteorites and provided a precise chronology of rocks brought back by the Apollo missions. He was one of the few UK scientists to be a Principal Investigator of the Apollo samples during the time of the US manned Moon missions. Link to online SCAR record.

Pillinger Nunatak (81°34’40″S, 26°24’15″W): Located in the Hutchison Icefield. Named after Professor Colin Pillinger FRS (1943-2014), English planetary scientist who was a founding member of the Planetary and Space Sciences Research Institute at Open University in Milton Keynes, and through his career studied stable isotopes in Apollo Moon samples, martian meteorites and asteroidal meteorites. He was also the Principal Investigator for the British Beagle 2 Mars lander project. Link to online SCAR record.

Map showing Hutchison Icefield area with Turner nunatak to the north and Pillinger nunatak to the south. Karpenko massif is a region of disturbed ice named after a Russian Engineer Aleksei Illaryonovich Karpenko (1940-82). Base map is Sentinel 2 image. Image: Dr Adrian Fox (UK Antarctic Place-names Committee)

With many thanks to Dr Adrian Fox (UK Antarctic Place-names Committee), Dr Oddveig Øien Ørvoll of the Norwegian Polar Institute for all of their help with the naming of these regions and advice from Laura Gerrish at the British Antarctic Survey.

New paper: The spatial flux of Earth’s meteorite falls found via Antarctic data

By Geoff Evatt:

So, how many new meteorites are landing from space each? How much total mass of them are we gaining? And where about’s on Earth are we most likely to be hit? (especially timely this week given the news story about a 1 km asteroid passing within 4 million km of the Earth! ) This are just some of the questions answered in our latest publication, as published by the journal Geology this week.

In this study, we combined glaciology, mathematics and physics, and sprinkled it all with meteorite collection data, to produce an accturate estimate of these quantities. The headline figure being we estimate over 17,000 falls each year weighing over 50 gr (that is to say, some 17,000 objects fall from space and hit the earth every year, where each component fragment is known as a meteorite, and the summed mass of these meteorites are over 50 gr), and this equates to over 16,000 kg per year landing on the Earth. As for the regions most likely to be impacted, then this, it turns out, appears to be at the equator, where the poles receive about 60% of the equatorial flux.

The first part of the study was to work out the flux of extraterrestrial material in Antarctica. With it having the most documented meteorites on earth, and collected in a very systematic fashion, this meant we were able to harness the data from thousands of samples. However the nature of meteorites in Antarctica means that working out the area they originally landed on is not simple (because the ice is flowing). Combining mathematics with glaciology, we were able to invert for the effective surface area of ice which feeds into Meteorite Stranding Zones (the areas from which they are collected). And since we know flow speeds of the ice, and the number of meteorites collected from them, we were then able to solve for the flux of meteorites falling on a typical square kilometre of ice. Such a figure is useful, but beggars the question: how does that relates to elsewhere on Earth?

Schematic of meteorite stranding zone ice flow and loss used to help build our model of Antarctic meteorite stranding zone data. Image Andrew Smedley (as published in the supplementary materials of Evatt et al., 2020)

Solving for the places most likely to be impacted (the latitudinal variation) was a lovely problem, as the answer was not obvious because competing effects pulled the result to either the poles or the equator. Why the poles? Well, because material orbiting the sun might do so above/below the Earth, yet when in the vicinity of the Earth gravitational attraction, the  objects would be deviated towards the polar regions. Conversely, the equatorial regions face head-on into the asteroid belt, and thus more surface area is available for receiving the material. As it turns out (after much old-school orbital mechanics) the equator still dominate for earth, but with the polar region receiving a decent whack – about 60% of the equatorial flux. This computed variation ties in very neatly with observations of the spatial distribution of fireballs across the globe – which was extremely reassuring.  With us knowing a good estimate for the flux at the poles, is was then straight forward to use the derived latitudinal variation curve to estimate it for everywhere else.

Now, despite the equator being more likely to be hit, in regards being hit by anything dangerously big, this is not anything to worry about for many many years. This is because such events are extremely rare. And since the whole planet is receiving so many non-dangerous falls each year (17,000+), and each event creating a glorious fireball (much brighter than the shooting stars we see which are formed from dust-sized grains) it really tells us to head outside and look up: there is a good chance of seeing such a fireball event if you give it just a few nights. 

Stay safe and look up!

Read the article (open access): G.W. Evatt, A.R.D. Smedley, K.H. Joy, L. Hunter, W.H. Tey,I.D. Abrahams, and L. Gerrish (2020) The spatial flux of Earth’s meteorite falls found via Antarctic data Geology https://doi.org/10.1130/G46733.1

Read a BBC Science online news story about the study

New paper

Andy Smedley | 23 March 2020

A little over two weeks ago the latest paper from the project was published. Given what’s happening in the world right now (it’s late March 2020), that seems a long time ago, but perhaps this short blogpost will provide some useful distraction whilst we all practise social distancing.

Occasionally meteorites will be found partly encased in the translucent ice, the ice underneath having melted and then refrozen [Credit: Katie Joy]

So our new study looks at how sunlight interacts with the blue ice where the vast majority of Antarctica’s meteorites are found. In the original paper that kicked off the project we used a simple mathematical model of how sunlight penetrates into the ice and how much is absorbed by the meteorite. How much sunlight is absorbed by a meteorite trapped in the ice determines how much it will heat up, and if it reaches the melting point of ice, how much the meteorite will then sink dow. In the original paper we used a fairly simple model of how sunlight is attenuated by blue ice and treated the system as one dimensional. In reality though it’s a 3D system and things are more complicated. One of the major ways in that it’s more complicated is that sunlight is made up of many different wavelengths (think the colours you see when it passes through a prism, or when a rainbow is visible, but extending beyond the range your eyes can see). Each of these wavelengths is affected by the ice properties slightly differently which means that the total attenuation is more subtle that we first assumed. When sunlight at infrared wavelengths hits the surface of the ice and passes into it, it’s rapidly absorbed by the ice. In contrast the part of sunlight corresponding to blue wavelengths is absorbed much less readily, and so is repeatedly scattered by the tiny bubbles within the ice. (These bubbles are actually tiny pockets of air trapped when snowflakes fell many thousands of years ago and their chemistry can help us understand how climate has changed on geological timescales.) As it so difficult for light at these blue wavelengths to be absorbed by the ice they continue to be scattered around inside the ice enhancing the amount of energy available to be absorbed by any dark meteorites present. As a result a meteorite sitting within the ice can act as a sink for nearby solar radiation, but, as well as absorbing more, because we now treat them 3-dimensionally, more energy is dissipated. To figure out how these different contributions balance out, we took the results of our sunlight modelling and added in the other things that might cause heating or cooling of the meteorite: the temperature of the air above the ice, the wind blowing over the surface, the motion of the ice, whether the meteorite gets warm enough to melt the ice and how far it then sinks and how these factors might vary over several years, plus the 3D nature of the problem.

It’s hard enough to find meteorites in Antarctica without them sinking into the ice. [Credit: Katie Joy]

All in, rather than iron meteorites being predicted to lie ~30 cm below the surface of the ice whilst their stony counterparts rise to the surface, this study suggests that the difference is much less, with iron meteorites being only 5-10 cm deeper than the stony ones. This isn’t a huge distance of course, and the blue ice is slightly translucent, but when you’re scanning from your skidoo for a speck of dark rock surrounded by the immensity of Antarctica, it’s enough to make spotting them virtually impossible. Interestingly though this new modelling shows the meteorite sinking mechanism is more nuanced than we first thought, with iron meteorites reaching the surface over the winter (when it is dark) before sinking into the ice early in the summer period after the sun rises. Though some questions remain, this seems more in line with what has been found in Antarctica as it gives the potential to find some iron meteorites if the conditions are right, and if the field expedition is during the early part of the summer.

If you fancy reading some of the technicalities of the paper, it can be found here.

Sledge Victor Over and Out

Katie Joy | 21 Jan 2020

The last few days have been somewhat manic to say the least. A final search on the 17th Jan didn’t yield any more meteorites, though we finished off the southern ice field and could put the doos (skidoos) to bed.

End of season thumbs up selfie from the two remaining Sledge Victor field party members (Katie in the stormtrooper mask at left, Taff in his duck beak mask at right). [Credit: Katie Joy]

A weather window then opened up across the Ronne Ice Shelf meaning that a plane was quickly dispatched from Rothera to come out to our field site at Outer Recovery to collect fieldguide Taff and I. We had a busy day of packing up camp, building and finalising the depots to be left over the Antarctic winter, sorting out all the kit to be brought back to Rothera.

Evening sun at our field site just before we broke camp. [Credit: Katie Joy]
Kelvin-Helmholtz clouds forming in the area, indicative shearing winds. [Credit: Katie Joy]

The weather was quite changeable in the day, with at one point snow blowing across the ice surface under 25 knot winds (not ideal for landing a plane when you need to see the skiway contrast). However, the Otter landed at about 10 pm on the 18th Jan with pilot Ian and co-pilot Callam, uplifting us back west, where we had a late night camping out in a mountain tent on Berkner Island. The air was still, but cold with our hair freezing up turning us grey, and the surface was snowy and looking like a million sugar lumps. The next morning on the 19th we departed for Rothera via Fossil Bluff, landing around 7 pm.

Flying back over the Peninsula – mountain ranges emerge out of the ice. [Credit: Katie Joy]
Melt ponds forming as the sea ice melts near Fossil Bluff. [Credit: Katie Joy]

Everything was rapidly unloaded from the aircraft and shifted to various parts of the base to be organised — the meteorites to the freezer, the rubbish to the rubbish centre, our science cargo to its storage area be sorted, all the field gear to the Fuchs building (sorry guys for making it a mess). Utterly overwhelming to see so many people after the relative quietness and tranquillity of the field. Finding our rooms, quick shower, making it to the dining hall (just) for the end of service (lamb roast – amazing). I was scheduled on the Dash 7 flight north to Chile for 9 am the next morning on the 20th…  so had to run around to organise all of my personal kit separating it from the BAS borrowed field kit and making sure things were washed (sorry to my roommate Sarah who’s bedroom was suddenly inundated with stinking clothes and four bags of stuff tipped out on the floor – I hope the smell of kerosene and field grime is not lingering) and the science cargo to be shipped back north later this month, to be ready to leave. Ahhhhh… finally got a beer at the end of a long day. Then the next morning saying goodbye to people, heading north on the Dash, dinner in Punta, an early night and collection at 4 am today for the next flights back to the UK via Santiago and Sau Paulo.

Flying over the Andes on route out of Santiago airport. [Credit: Katie Joy]

So yes, its been a bit mad for the last few days and I am missing life of being at Outer Recovery whizzing around the ice spotting meteorites. Antarctica grabs you (well it has certainly has got to me) and doesn’t let you go — hopefully I will get a chance to come back someday to continue the search for more space rocks on the ice.

It has been amazing that in just two field seasons with such small teams we have collected over 100 surface stones for future scientific study by the cosmochemistry community and I am very proud of what we have achieved and look forward very much to finding out what types of meteorites we have collected. Over to the laboratory and curation team now for the next phase of the science story, and hopefully we can continue to source more funding and the support of BAS to get back out to the ice in the next few years to continue our scientific success.

Saying goodbye to our fieldsite. [Credit: Katie Joy]

More blogs posts to come when we have results in from the last season’s meteorite haul, and to update everyone on our science research paper outcomes.

Some thanks and shout outs from me at this stage:

  • The rest of the Sledge Victor Manchester fieldteam — Geoff, Wouter, and Romain who fought a determined fight with the metal detector panels, and found some great meteorites during surface search days. To the story of 118-218-119-119alpha.
  • Andy Smedley, our Man back in Manchester, who has been receiving our emails from the field to post the blog. [BTW – we named the 3rd blue detector panel sledge Sledge Smedley (mentioned in this previous blog) in his honour at not having him with us in Antarctica]. Whilst Sledge Smedley only had a few days out and about, he lived his life to the full bouncing around and at least still has an intact bottom.
  • The Twin Otter flight teams (Mark, Ian, Dutch, and Dave) and co-pilots from Rothera and Halley who have come out to visit us this season and help get us and plane fuel across the enormity of the continent. The Rothera field operations managers who work 3-d chess to try and get everyone in the right place on the right day working around the ever changeable weather. The Rothera science coordinator Maz who has been so brilliant in helping out with requests for boxes, getting our cargo together for shipment, and just being completely fab. Everyone at Rothera and Halley who works hard to just get stuff done.
  • And a special thanks to our wonderful team of field guides Julie, Taff and Rob who have kept us safe, organised camp, provided great chats and moral, and have helped us to find the meteorites we have collected. Thanks guys for putting up with us all for the different parts of the project you have worked on this year and last, its been a privilege to spend time with you.

A productive few days out and about

Katie Joy | 16 Jan 2020

Although most of the team are now heading north back to the UK, Taff and I are still working hard at our field site and it’s been a productive and busy few days out in the field as we wrap up the season with some surface meteorite searching on two of the ice fields that we visited last year. Revisiting sites is interesting as some of our old tracks are still preserved as imprints in the snow patches like fossilised tracks, indicating past exploration. Both areas are much clearer of fresh snow now than last year (though they still have some thicker patches of older snow), and as there has been less wind it has been pleasant getting out and about and systematically covering the ground to try and find as many samples as possible.

Meteorite sample encased within ice. Just the top portion was poking out and we had to dig the rest of the sample out. [Credit: Katie Joy]

We managed to collect seven samples on the 14th (including a nice big one spotted from about 100 m away), two samples yesterday (rewards for a lot of driving around getting frustrated that we weren’t finding much), and four more today on the 16th (including a nearly completely ice submerged sample), bringing the total number of meteorite stones collected to 82 from this area in total from this year. Several meteorites found over the last few days have been stunning — really nice flight shaped stones preserving evidence of the orientation they travelled through Earth’s atmosphere. A couple others have very fresh fusion crusts suggesting they might be recent falls, and some have hints of pale coloured interiors which look different from the normal chondrite type (primitive asteroid) of samples that we most commonly collect.

We are not sure how many more days we will have in the field as we now await a break in the weather for a plane to travel over from Rothera to collect us — but tea supplies and moral levels are high, and we will keep getting out searching until before our skidoo petrol runs down. Then we will drink some more tea and reflect on a great end to the season.

Cracking ice – as the ice field extends and the ice speeds up it cracks and twists into small faults a few cms wide. We don’t typically find meteorites in areas like this, but sometimes have to drive past and it is like a structural geology lecture in action. [Credit: Katie Joy]
Taff pointing the way to the stunning meteorite (a whole stone) we found today with a rollover lip. [Credit: Katie Joy]

PS Thanks to our Sledge Victor teammates Romain, Geoff and Wouter, and quizmaster K for the amazing sausage roll song rendition over skeds. We didn’t think you would deliver, but you didn’t fail us. Quite magnificent. Who knew there were so many verses to get through. We hope that your travel back to the UK goes well, and see you back Manchester way. 119 is a lot cleaner without you. 🙂

(Still) Chasing Meteorites

Katie Joy | 13 Jan 2020

The remaining team of Taff and Katie are still in the field at Outer Recovery and after two tent days (one because the winds were blowing at 30 knots all day, and yesterday due to bad contrast as it was cloudy) we made it out and about for some more meteorite searching. The high winds of a couple of days ago has blown away all the pretty hoar frost which was covering the area, but also more importantly has shifted the snow off our local ice field meaning that we could get back there to search the final southerly section which had previously been hidden from us under a couple of centimetres of covering.

We headed out in strong cold winds, today was the first day I have had to put on the big yellow down jacket over all the other layers I have been wearing. Pretty much as soon as we started out we were off the mark with a large 15 cm stone, and despite the cold, the day continued to prove fruitful with seven more meteorites collected and bagged*. These included a very nice hand sized complete fusion crusted stone which are pretty uncommon and a tiny pea sized perfect small rounded stone. By the time we headed back to camp the winds had dropped off, making for a pleasant returning home commute.

Katie_Meteorite
A lovely fusion crusted stone sitting on a small crack on the blue ice field. [Credit: Katie Joy].

We are not sure yet of our field retrieval date – but it feels really good to get a few more meteorites collected before we have to return to Rothera.


* Well a small one nearly wasn’t bagged when a gust of wind whipped the meteorite encased in its plastic collection bag away across the ice field — I jumped on the skidoo and whizzed off chasing after it, and upon catching up jumped off the skidoo on a snow patch to make a dive… Well, I missed and fell on my butt (you try running on ice when dressed like the Michelin man), and the bag and stone flew on past me at what I can only assume must be the quickest pace it has experienced since landing on Earth. Back on the skidoo I shot off again, overtook the flying bag again and this time aligned both me and the skidoo to make the interception. Bagged meteorite retrieved and safely stored despite its best attempts to get away. I was feeling pretty cold before this chase episode, but the rapid retrieval and adrenaline shot seemed to have done the trick to warm me up.