October 2021 Issue Table of Contents
Meteorite hunting is a lot like football (soccer) … just run with us on this. Success requires skill, a cracking team, a whole lot of luck … and, historically, England (and the UK) are not very good at it … we were just unlucky … the (fire)ball always seems to miss the goal! Meanwhile, around the world, meteorite fall recoveries are becoming more and more frequent; but in the UK, to put it in the style of the famous English football anthem by the band the Lightning Seeds, it’s been “30 years of hurt” since our last meteorite fall. The Glatton meteorite of 1991 that landed in Arthur Pettifor’s back garden, as he was tending to his onions, was the last time the UK has tasted the success of recovering a meteorite fall (Meteoritical Bulletin Database – Glatton). However, based on data from the France-based Fireball Recovery and InterPlanetary Observation Network (FRIPON), calculations suggest that approximately three meteorites of over 100 g should fall on the UK each year (Colas et al. 2020), so right now the UK is batting way below its average (yes, we know that’s cricket not soccer).
Recovering meteorites that have been seen to fall is incredibly important for planetary science as we seek to understand how our Solar System formed and evolved. Even better is when the fireball (the bright light trail left behind as the rock passes through Earth’s atmosphere) is caught on camera. This has two important results: firstly, these images allow us to triangulate where the meteorite landed and quickly get boots on the ground to search for any visiting space rocks before they get contaminated by Earth’s environment; secondly, it provides key geological context to our meteorite collection by enabling us to link these special rocks back to their source region in space and, potentially, their parent asteroid (Devillepoix et al. 2020; Jenniskens 2020). The more images of the fireball we get, from as many locations as possible, the better our triangulation will be.
Thus, over the last few decades, and from around the world, researchers and amateur astronomers have been developing automated camera networks to image meteors and fireballs alongside sophisticated models to figure out if a meteorite survived, where it may have landed and where it came from in space. The UK has, over the last five years, become a melting pot of fireball camera networks, all using a variety of equipment from narrow angle closed circuit television (CCTV) cameras to digital single lens reflex (DSLRs) and industrial cameras equipped with 360° ‘all sky’ lenses. There are no less than six active meteor and fireball networks: Network for Meteor Triangulation and Orbit Determination (NEMETODE); the UK Meteor Observation Network (UKMON); the UK Fireball Network (UKFN) (Devillepoix et al. 2020); System for Capture of Asteroid and Meteorite Paths/Fireball Recovery and InterPlanetary Observation Network (SCAMP/FRIPON) (Colas et al. 2020); the Global Meteor Network; and AllSky7. Even better, since 2018, all these camera networks work together and share data in a standardized way to aid in meteorite recovery under the umbrella of the UK Fireball Alliance or UKFAll (Fig. 1) (https://www.ukfall.org.uk/).
Since the inception of UKFAll, we have had a fair few near misses. Some promising fireballs have been obscured by clouds across most of the country (which is pretty typical for the UK!), meaning we couldn’t get a good lock on the fireball. And even when we were blessed with clear skies and saw a meteorite dropper burn bright above the UK, as happened on the 16 February 2020, the surviving fragment ended up in the North Sea (deep sea dive search anybody?). All these teaser trailer fireballs have allowed us to prepare for the real deal and develop better and faster data-sharing methods, iron out some of the kinks in our data pipeline, and test run getting the word out. UKFAll was ready for the big one … we just needed something to fall out of the sky on top of us. Enter spring 2021 and the amazing story of the Winchcombe fall event in Gloucestershire County, England (Rowe 2021).
On the 28 February 2021 at 21:54 we got exactly what we had waited so long for. A bright seven second fireball was observed across the UK and Northern Europe. The UKFAll cameras typically ping us if they see anything, but that message doesn’t normally arrive until the cameras have processed the data the next day. Thankfully, social media feeds started alerting us with messages about the fireball. We checked the cameras and fired off a quick message to our international colleagues at the Global Fireball Observatory (GFO) in Australia and the FRIPON camera network in France, asking them if our cameras had seen anything, before turning in for the night.
Early the next day, we woke up to a barrage of the best kind of e-mails you’d ever want to receive. Yes, three of our (UKFN) cameras had caught the fireball, along with 13/16 other separate observatories in the UKFAll network (Fig. 2). Additionally, ~1,000 members of the public reported seeing it and hearing a sonic boom through the UKMON/American Meteor Society portal. Video footage showing fragmentation of the meteor suggested a good chance that meteorites survived, with the initial calculations hinting at a possible cometary orbit (!). Further number crunching with multi-network data showed that the object originated in the asteroid belt and further increased our confidence in finding meteorites on the ground. The game was afoot.
Now, under normal circumstances we’d already be in cars rushing to the fall site, as well as lighting the beacons to tell UKFAll’s army of citizen science volunteers to mobilise. However, these are not normal times, and we faced two problems. The first was COVID. The UK was under a national lockdown, so getting people to the area was not going to be easy, especially for members of the public because travel outside of home areas wasn’t permitted apart from for work purposes. The second problem was that we didn’t have a well-constrained dark flight model yet, i.e., the meteorite’s journey from when the light of the fireball goes out (sending the rock into freefall where it is blown about by the wind) to it landing on the ground. This meant that our initial estimate of where the rock had landed was a 280 km2 area (Fig. 3), a bit too big to search by foot, too big to start a goldrush of people flocking to the area if we released this information to the media, and a far cry from our usual search areas that are typically no bigger than 10 km2.
While we were waiting for a more refined search area, we decided to alert the media with an approximate fall location to see if any lucky locals had come across any new rocks that looked black and shiny (black and shiny because this is the typical appearance of a freshly fallen meteorite that has had its surface melted as it passed through the atmosphere). The UKFAll network had a set of pre-prepared press releases for just this occasion. So, we populated them with the specific details of the fall and had the story out the door by 8 a.m. on Monday morning. Our press release was picked up and next thing we knew various members of UKFAll were on national television and radio talking about what to do if you think you have found a meteorite and who to contact (Amos 2021).
Simultaneous to our media efforts, but unbeknownst to us, most of the meteorite was already sitting in a clean plastic bag in the Wilcock family home in the small town of Winchcombe. The daughter of the family, Hannah, had heard a loud cracking sound outside their home at about 22:00 the previous evening, but didn’t see anything unusual when she looked out of the window that night. The next morning, however, the whole family had found a splatter of dust and black rocky fragments on their driveway. Their initial thought was, “Has someone been lobbing lumps of coal into peoples’ gardens?” Fortunately, their son Daniel had seen the news and told them about the possible meteorite fall in the area. Realizing its potential importance, they bagged the debris and sent in a photo of what they had found to the UKMON (Fig. 4). The speedy action of the Wilcock family was amazing and meant that around 300 g of the meteorite had spent less than 12 hours on the ground before it was collected, with no rain having fallen (see, it does stop sometimes!). This meteorite is about as fresh as you can get and is comparable to the material brought back by asteroid sample-return missions, such as Hayabusa2 and OSIRIS-REx, especially with the fireball data telling us its orbit. But we’re getting ahead of ourselves.
We were inundated by a rogue’s gallery of images of unusual-looking rocks that had been sent in to both the UKMON and the Natural History Museum (NHM). Most were sadly ‘meteorwrongs’, but there were a couple that looked promising. However, we must admit that several of us were not initially convinced by the unassuming image of a pile of black dust from a driveway in Winchcombe (Fig. 4): it was more likely to be the residue from a barbecue than a space rock! Luckily, science is a team effort and lots of eyes were looking at these images, including those of Dr Richard Greenwood (Open University, UK) who immediately recognized it for what it was: a meteorite! Not only that, he also recognized that it was likely a rare meteorite type known as a carbonaceous chondrite.
Living locally to Winchcombe, Dr Greenwood managed to visit the Wilcock family and confirm that it really was what we’d been hoping for – a freshly fallen UK meteorite!
We now had a confirmed meteorite recovered from a driveway in Winchcombe, plus several other promising-looking images that had been sent in by the public. At the same time, our colleagues at the GFO had run the darkflight model and sent us a much smaller, more searchable, area where the meteorite could have landed, which is known as a strewn field. The fragmentation of the fireball also suggested that more pieces should be nearby. Now was the time to get boots on the ground to try to find the rest of it. There was just that small problem of the national COVID-19 lockdown. After a literal mountain of paperwork and risk assessments, we received institutional sign off to get a team of around 15 planetary scientists from academic institutions across the UK (including Glasgow, Manchester, Plymouth, Imperial College, the NHM, and the Open University) into the field. We’re going on a meteorite hunt! We hope to find a big one!
The search team was assembled near Winchcombe in the beautiful countryside of the Cotswolds on an overcast, but thankfully rain-free, spring morning. We had a short briefing, where most of us got our first glimpse of the Winchcombe meteorite to help get our eye in for the coming search, before it got whisked away to the NHM for curation and preliminary analysis. Those of us who had been meteorite searching before in Antarctica or Australia gave a crash course in meteorite hunting techniques, and we set off. Meteorite hunting, it turns out, is the ideal socially distanced activity: using many tried-and-tested search-and-rescue techniques, the group lined up ~2 m apart and slowly walked across the landscape scanning the ground in front for shiny black objects (Fig. 5). We mark our slow progress with GPS, slowly filling in the search area either side of the fall line.
We had ideal searching conditions, overcast meant no long shadows from the sun, no rain was good for both not contaminating any meteorites that were in the fields waiting for us (and also morale), while the season meant the grass was short and there were fewer places for little black rocks to hide. We also received a really warm reception from the local landowners who very graciously allowed us onto their property to search, for which we were extremely grateful. The underlying bedrock of the Cotswolds is oolitic limestone, a bright white rock and about as different from a meteorite as you can be; therefore, it was our hope that almost any solid shiny black thing would be what we were after. However, you would not believe how many things lying about in the UK countryside look like the fusion crust of a meteorite, from sheep poop to dewy cobwebs in the morning sun, making the search slow going. We checked every … single … one.
We don’t think anyone actually expected anything to come of the search, but it was our responsibility to try. This might have been why most of the search team, after covering most of the fall line over two days, decided to head back home on the Friday night. The University of Glasgow team, however, decided to stay over the weekend to fill in the final few gaps in our search map. Then the unbelievable happened. Early on the Saturday morning, Mira Ihasz, a volunteer with the University of Glasgow search team, found a beautiful, perfectly fusion-crusted, and mostly intact, 150 g piece of the meteorite in a sheep field. Cue pandemonium as we all just screamed and jumped for joy. It was everything we could do to maintain social distance when all we wanted to do was hug each other at having achieved what many had thought to be impossible: the search and recovery of a meteorite fall in the UK.
What A Week
Several other stones were subsequently found by members of the public from the area, bringing the total final mass of the fall to >500 g, most of which were recovered before substantial rainfall. There are many amazing aspects to the recovery of the Winchcombe meteorite, but perhaps the most wonderful is that the Wilcock family (as well as the Carrick, Bond, and Godfrey families) elected to generously donate all of the material they found, or that was found on their land, to the NHM for scientific research.
The Winchcombe meteorite has now been officially classified as a CM2 carbonaceous chondrite and has energized the UK planetary science community (Meteoritical Bulletin Database – Winchcombe). Carbonaceous chondrite meteorites are really important, because they are one of the first rocks to form in our Solar System some 4.5 billion years ago, and they contain a lot of water and organic matter. Therefore, meteorites such as that which fell on Winchcombe rained down on the early Earth as it formed and their contents may have provided the water for our oceans and the organic material to from a nice habitable ‘soup’ from which life could emerge and evolve. Fragments of Winchcombe have been sent out to every laboratory in the country for what is set to be one of the most comprehensive studies of a single stone since the fall of the Allende meteorite in 1969. The fragment recovered from the Bond family’s field by the University of Glasgow team is now on display at the NHM.
The whole Winchcombe experience just shows what great things can be achieved when science works as a diverse international effort, combining the expertise of academics and citizen scientists to build together something that is greater than the sum of its parts. It is a great first result for UKFAll to build on. Let’s hope it’s not another 30 years of hurt until the next one.
Amos J (2021) Meteorites may be just north of Cheltenham. BBC.com. Retrieved August 2021, https://www.bbc.co.uk/news/science-environment-56241511
Colas F and 386 coauthors (2020) FRIPON: a worldwide network to track incoming meteoroids. Astronomy & Astrophysics 644: A53, doi: 10.1051/0004-6361/202038649
Devillepoix HAR and 48 coauthors (2020). A global fireball observatory. Planetary and Space Science 191: 105036, doi: 10.1016/j.pss.2020.105036
Jenniskens P (2020) Review of asteroid-family and meteorite-type links. Proceedings of the International Astronomical Union, Volume 14, Symposium A30: Astronomy in Focus XXX, August 2018, pp 9-12, doi: 10.1017/S1743921319003235
Jenniskens P and 65 coauthors (2021) The impact and recovery of asteroid 2018 LA. Meteoritics & Planetary Science 56: 844-893, doi: 10.1111/maps.13653
Meteoritical Bulletin Database – Glatton. https://www.lpi.usra.edu/meteor/metbull.php?code=10930 (accessed 18 August 2021).
Meteoritical Bulletin Database – Winchcombe. https://www.lpi.usra.edu/meteor/metbull.php?sea=Winchcombe&sfor=names&ants=&nwas=&falls=&valids=&stype=contains&lrec=50&map=ge&browse=&country=All&srt=name&categ=All&mblist=All&rect=&phot=&strewn=&snew=0&pnt=Normal%20table&code=74388, (accessed 18 August 2021)
Rowe J (2021) Observing & recovering the Winchcombe meteorite. Journal of the British Astronomical Association 131: 134-136