If you look up at the sky at night for long enough, you're nearly guaranteed to see a shooting star: a bright, fine light zipping across the sky.
Shooting stars, or meteors, are often the last we'll see of the rock that caused their bright flash in the sky as it burns up in our atmosphere.
Most of the time, the object that caused the shooting star is no larger than a grain of sand, and not much will make it to earth.
But sometimes, they are bigger, and break up into pieces and land on Earth.
The Desert Fireball team from Curtin University have set up cameras across Australia to monitor for big meteors, fireballs, that might leave behind meteorites, to try and track them down quickly.
They know that lots of meteorites haven't been found, and are out there, waiting for discovery.
Gretchen Benedix, an astrogeologist with the Desert Fireball team, says finding a piece of space rock is thrilling every time.
"You do a little happy dance. But it is absolutely 100 per cent over the moon exciting every single time because it's a rock from space," Professor Benedix says.
"It came from space, and it's just so exciting to think, 'oh, where did it come from, what's it going to tell me now?'"
So, what are the chances that you could pick up a piece of space rock?
While meteorites are very rare, they are out there, and it's not impossible you could find one, especially if you know what you're looking for.
Meteors, meteorites, meteoroids?
The names can be a bit confusing: What's an asteroid? A meteorite? A meteoroid?
The best way to be sure you're using the right name is to think of the size and location.
Essentially, asteroids and meteoroids are very old space rocks, orbiting in our solar system, mainly in the asteroid belt between Mars and Jupiter.
All of the planets, including Earth are the product of those rocks colliding and forming together 4.6 billion years ago.
Some pieces were too small, and too far apart from each other to form planets and remained in space, in orbit of the asteroid belt.
Asteroids are the bigger rocks, ranging from a couple of metres in diameter to nearly a kilometre in size and meteoroids are much smaller — usually less than a metre, and can be much, much smaller.
Occasionally, asteroids and meteoroids are disturbed, by colliding with other rocks, and are sent out of the asteroid belt and, sometimes, towards Earth.
A meteoroid or an asteroid is called a meteor when its travelling through our atmosphere, flashing bright. Once it lands, the pieces that makes it to the ground are called meteorites.
Big asteroids have hit Earth, like the 12km-wide asteroid that probably killed the dinosaurs, but that is not likely to happen again anytime soon.
The shooting stars that you can see at night are likely meteors, but they are probably too small to leave behind a meteorite.
The bigger meteors, which appear as much brighter, bigger shooting stars, or fireballs, are more likely to survive some of the entry, breaking up into pieces that scatter and land on the ground as meteorites.
"There are about 60,000 meteorites on the Earth's surface that we have now catalogued. They are still extremely rare material of the solar system," Professor Benedix says.
Where is the best place to look for a meteorite?
No one place is more likely than any other to have a meteor will break up and leave meteorites there, but it is much easier to find a meteorite in some places than others.
Some land in the ocean, or in other places that are difficult to access or search, like thick rainforests.
ABC Science on YouTube
There is one place where scientists who study space rocks love to hunt: Antarctica.
That's because if they find a black rock in Antarctica, they can pretty much guarantee that it is a meteorite. And a black rock among a lot of white ice is very easy to spot.
But while trips to look for space rocks in Antarctica are a little hard to organise, there are some places that are better for meteorite hunting.
It'll be easier to find a meteorite on the ground if the surface is smooth, flat and not already covered in black rocks.
It's definitely worth investigating your own backyard or local park — even better if that area is bare or empty. While meteorites are rare, they are out there!
What to look for: meteorites and meteor-wrongs
- Black crust: Meteorites can be made up of different material, but they all have one thing in common: they all have to have fallen through the Earth's atmosphere and landed on the ground. That journey through the atmosphere up to 60km per second will cause the exterior of the rock to melt, forming a thin, black shiny exterior to form on the outside, called a fusion crust. In rocks that have been on the ground for a while, the fusion crust might have chipped away, revealing that the rock is a different colour inside. That is a helpful sign.
- Heavy: A meteorite is a dense rock, sometimes with iron inside, so it should feel heavier than a normal earth rock of the same size.
- Smooth dents: Looking at the surface of the rock, you might be able to see smooth indentations, which looks like someone has pressed their thumb into the rock and left an impression, like it was soft clay. Those are called regmaglypts. It should have smoothed or rounded edges, rather than sharp rocky points.
- Magnetic: Use a magnet to see if the rock is magnetic. About 90 per cent of meteorites are magnetic. If the rock sticks to your magnet, even faintly, that could be a sign it is a meteorite. But it's not a guarantee, because Earth rocks can be magnetic, like iron-rich earth rocks or magnetite. Industrial by-product can also be magnetic and look like a meteorite.
If you think your rock is a meteorite — or even just a meteor-maybe — send a photo to the team at the Desert Fireball Network, for a meteorite expert to have a look.
Either way, send us a photo of your finds via the ABC Science Facebook page.
Meteorites from Antarctica: Incredible numbers of nearly perfect meteorites are being found in the "blue ice" ablation areas of Antarctica. The photo above shows several specimens collected from the Miller Range icefield by NASA’s Antarctic Search for Meteorites. Image by NASA.
Meteorite find: When meteorite hunters find a specimen in the field, it is photographed on-site with a measurement scale and an identification number visible in the background. NASA image.
The Best Place to Hunt Meteorites
In most parts of the world, a person could search throughout a lifetime and never find a single meteorite. However, a small number of researchers are finding several hundred meteorites each winter in a few special locations in Antarctica.
In most parts of the world, meteorites are extraordinarily difficult to find because meteorites that fall there can be.
- quickly destroyed by weathering
- hard to distinguish from local materials
- hidden by vegetation
- covered by surface materials
Meteorite map: A map of meteorite recovery locations in the Transantarctic Mountains. NASA image.
Advantages of Cold Climate
In Antarctica, freshly fallen meteorites are protected by the cold climate. Iron meteorites do not rust in the cold conditions, and stony meteorites weather very slowly.
Members of the search team move across the ice on foot or by snowmobile looking for meteorites. The dark-colored meteorites contrast sharply with the white snow and ice. Some of the dark objects found are meteorites, but the searchers do find many terrestrial rocks that have been incorporated into the ice by the glaciers. They search by walking or by snowmobile, and which method they use is determined by ice conditions, weather conditions, and the abundance of meteorites present in the area.
Although the cold climate is ideal for preserving meteorites, it presents a huge challenge to the researchers who hunt them. They have to travel to a remote location where they will live in tents in subzero weather. Out on the hunt they face intense cold, fierce wind, and blistering sun. It takes a determined and dedicated person to do this for several weeks each year.
How Antarctic ice transports meteorites: A model of how meteorites fall in a zone of accumulation, are deeply buried by snow, and then flow with the ice to a zone of ablation where they reappear at the surface. NASA image.
Ice Movement and Meteorite Concentration
The two most important reasons why meteorite hunting in some parts of Antarctica is so productive are: 1) ice movements, and, 2) ablation.
The ice of the Antarctic continent is in motion. The ice grows thicker in some areas from snow accumulation, then it slowly flows away from those areas under its own weight. Remember that the continent is covered by a glacier.
The theory of ice movement is shown in the accompanying diagram. It shows how meteorites are buried in zones of snow accumulation. Then the ice moves under its own weight away from these snowfields towards the edge of the Antarctic continent. In some areas rock formations block the flow of ice. Where this occurs, steady katabatic winds can remove the ice by sublimation and mechanical abrasion. Up to ten centimeters of ice per year can be removed by these ablation processes.
Meteorite hunting weather: This photograph shows what conditions can be like for meteorite hunters in Antarctica. It is a very difficult place to live, even for a few weeks. NASA image.
Curating Pristine Meteorites
The meteorites found in Antarctica are in pristine condition. They are not weathered like meteorites found in temperate climates. The original fusion crust, formed by ablation of the meteorite as it fell through the atmosphere, is often preserved.
When a meteorite is found, a snowmobile with a high-resolution GPS receiver is driven to the site to obtain a very accurate location. The meteorite is then photographed in place, recovered, placed into a sterile Teflon bag, assigned a unique field number, logged into a field book, and given a detailed field description. The discovery site is then marked with a flag bearing the meteorite’s identification number.
Meteorite hunters on snowmobiles: Meteorite hunters slowly traverse the ice in a systematic pattern while searching for meteorites. NASA image.
Stone Meteorites from Moon and Mars
Almost all of the meteorites found on Earth are believed to be pieces of asteroids. Some researchers believe that five to six percent are pieces of the asteroid Vesta. They are pieces of Vesta that were dislodged by impacts with other asteroids.
A very small number of meteorites (less than two hundred) have been determined to be pieces of Moon or Mars after careful study. They arrived on Earth after being dislodged by asteroid impacts, travelling through space for millennia, then falling to Earth.
A few of these rare meteorites have been recovered from Antarctica. The lunar meteorites are rocks such as anorthositic breccia, basaltic breccia, gabbro, and mare basalt. An orthopyroxenite rock from Mars has also been found.
|Antarctic Meteorite Information|
| ANSMET, The Antarctic Search for Meteorites: Webpage for the ANSMET Program on the Case Western Reserve University website.|
 Antarctic Meteorite Collection: Information about the US Antarctic Meteorite Program on the NASA website.
 Antarctic Meteorite Recovery Locations: Map showing the location of meteorite recovery sites in the Transantarctic Mountains of East Antarctica, posted on the NASA website, last accessed January 2017.
Access to Meteorite Photos and Data
The meteorites found during these expeditions become government property and are shipped, still frozen, to be thawed under clean room conditions at the Antarctic Meteorite Curation Labs at NASA’s Johnson Space Center. Photographs and data obtained from the meteorite collection are made available to researchers and the general public through the Antarctic Meteorite Newsletter. Check out a few issues if you are interested in meteorites.
And scientists now have a better idea of where to find them.
An artificial intelligence program suggests there may be hundreds of thousands of meteorites left for scientists to discover on the icy fields of Antarctica and reveals what may be the most likely places to unearth them, a new study finds.
Nearly two-thirds of all meteorites recovered on Earth originate in Antarctica. The cold, dry nature of the frozen continent helps preserve these extraterrestrial rocks, and the dark colors of these stones make them stand out against ice and snow. Meteorites were originally part of planetary bodies, and so these space rocks from the bottom of the world have yielded many valuable clues about the nature, origins and evolution of the rest of the solar system.
When meteorites fall on Antarctica, they usually land in the snow-covered regions that span 98% of the continent. Over time, snow accumulates there, compacts and becomes ice, embedding these space rocks within ice sheets that flow toward the margins of the continent.
Most ice-entrapped Antarctic meteorites end up in the ocean. However, some of them get concentrated on the surface of these ice sheets in areas of “blue ice,” where wind and other factors can result in bare ice with an azure hue.
If the way the Antarctic ice is flowing and other features of the climate and terrain are right, meteorites can remain exposed on the surface of blue ice, where researchers can easily recover them during field missions. Nearly all Antarctic meteorites found to date were recovered from blue ice areas.
Many of today’s known meteorite-rich blue ice areas were found by sheer luck and past experience on costly reconnaissance missions. Now scientists have developed a new strategy based on artificial intelligence.
“We found some unexplored areas with a great potential to find meteorites,” study lead author Veronica Tollenaar, a glaciologist at the Free University of Brussels in Belgium, told Space.com.
In the new study, researchers had artificial intelligence software analyze satellite data of the entire surface of Antarctica. Their aim was to identify the zones most likely to harbor as-yet-undiscovered meteorites on the frozen continent based on their similarities to areas where scientists had previously unearthed space rocks. They focused on optical, thermal and radar data of surface features such as temperature, slope and velocity of the ice.
The AI program accurately identified nearly 83% of known meteorite-rich Antarctic zones. All in all, it identified more than 600 potentially meteorite-rich zones on the continent, including many currently unexplored ones, a number of which are relatively close to existing research stations on Antarctica.
“By visiting these locations and using new recovery techniques in the field, such as surveys with drones, we are about to enter a new era of Antarctic meteorite recovery missions,” Tollenaar said.
The new findings suggest that the more than 45,000 meteorites recovered to date from Antarctica comprise just 5% to 13% of all the meteorites there. “Our calculations suggest that more than 300,000 meteorites are still present at the surface of the ice sheet,” Tollenaar said. “The potential remains enormous.”
Given that their AI program is not 100% accurate, researchers might sometimes go to a site the software found promising and not discover any meteorites, Tollenaar cautioned. Still, although unsuccessful missions will prove disappointing, their data will hopefully help refine the AI to make it better in the future, she said.
The scientists detailed their findings (opens in new tab) online Wednesday (Jan. 26) in the journal Science Advances. They also explain the results in a very user-friendly way at this website (opens in new tab) .
As astronomers, we’re always delighted to see a meteorite streak across the night-sky while we’re setting up our scopes or scanning the constellations for our next setup. At other times, we’re carefully observing an area of the sky in anticipation of a meteor shower. On some rare occasions we are left wondering in amazement as a meteorite streaks down and over the horizon. Where did it land? We wonder. And will someone find it?
The answer is that thousands of meteorites land on the Earth’s surface each year. In fact, according to The Monthly Notices of the Royal Astronomical Society, 18,000 to 84,000 meteorites strike the Earth each year, although other estimates put the total annual number as low as 500. To date, it’s reported that 40,000 meteorites have been found. That sounds like a small number, but once again there aren’t that many people who take the time to look for them.
Image credit: NASA.gov
You Can Do It
Most meteorites that we might find are smaller pieces of larger meteoroids that have broken up as they travel through Earth’s atmosphere. The fact is they’re out there and not that many people are looking for them so you have a good chance of discovering one if you know how and where to look, and what to look for.
One Indispensable Tool – The Neodymium Magnet
The one, simple tool every meteorite hunter uses is something called a “Neodymium” magnet attached to the end of a stick or cane. Neodymium magnets attract rare earth metals in addition to the iron that is common in many meteorites. You must be careful though as these magnets are very strong. So keep them out of reach of children and don’t let two attract to each other as they could shatter.
Types of Meteorites
For the record, meteorites typically occur in 3 types.
1. The iron meteorite – consisting mostly of iron. These are the meteorites attracted to the Neodymium magnet, but only 5% of meteorites that reach the earth are of this type.
2. The stony meteorite – or “chondrite” is made up of the rocky material from its source. They often have circular inclusions or “chondrules” from the gases that escaped in the heat of entry and can be any size from fist sized to the smallest pebble. Stony meteorites could be from a planet or asteroid, or pieces flung into space as a result of a planet/asteroid collision. 80 to 95% of the meteorites that fall to Earth are rocky meteorites.
3. The stony/iron meteorite – these usually consist of a 50/50 mix of iron and silicates. They are also very heavy for their size. Only 1 to 5% of falls have this stony/iron combination.
What’s important to remember is that a rock with a stone-like appearance that is attracted to a magnet increases the odds that you may have found a meteorite.
Images by: NASA.gov
What Are the Odds of Finding One Yourself?
While it may seem you’re more likely to find a rocky meteorite given the 95% fall-rate, 80% of the finds are metallic, while only 20% are pure rock. This is due to the ease of finding an iron meteorite with a Neodymium magnet, the fact that metallic meteorites don’t erode as quickly as rocky meteorites, and the striking appearance of most iron/metallic meteorites.
In fact, many meteorite hunters don’t know a rocky meteorite when they find them, or mistake an unusual rock of Earth origin for a meteorite. The common term for this mis-identification is a “meteorwrong.”
Tool Number 2 – A Field Guide to Meteorite Identification
The second tool you might want to consider is either a book that shows you the appearance and types of meteorites, or a club where experienced meteorite hunters can give you some tips and advice. Most look for any magnetic properties, a black, fused outer surface that would indicate some level of exposure to high heat upon entry into the atmosphere, and in some instances a weight that seems greater than you would expect for a rock that size. Be mindful of the fact that after some meteorites have weathered with time the colour can vary from black to either brown, yellow, orange, or a reddish appearance. There are other tests that include sawing a sample in half with a diamond saw to look for a unique pattern in the interior, but that will spoil the sample.
Rust on the exterior of a sample can also indicate a meteorite find, but be careful. Hematite and Magnetite also rust and are attracted to magnets. The easiest way to know is do a streak test. Hematite and Magnetite will both leave a coloured streak on rough piece of porcelain or ceramic or on a geologist’s streak stone. Hematite will leave a rust coloured streak and Magnetite a dark, gray streak. Meteorites leave no streak unless you press extremely hard and it will usually be a very light, grayish colour.
Where to Look
Unfortunately, knowing what they look like and simply assembling tools for a meteorite hunt won’t guarantee you’ll find them. You need to know where to look.
Some of the best meteorite hunting grounds are dry lake-beds; any large, barren expanses where there are few terrestrial rocks; deserts, icy regions (the most meteorites have been found in Antarctica), or something called “strewn-fields.”
Strewn-fields are zones where meteorites from a single space rock were dispersed as it broke into pieces as it exploded in Earth’s atmosphere during entry. Recently, many small pieces of the meteorite that exploded over Chelyabinsk, Russia are being found by people living in the area even when they weren’t looking for them. The strewn-field is enormous.
To locate potential strewn-fields in your area you can check with the local conservation office, or search the internet. Even if you can’t find a strewn field and deserts aren’t particularly common in your area, any walk across open ground with your Neodymium magnet stick might surprise you.
If and when you do find success you might get the bug to continue your meteorite hunts. In that case you might want to add some tools for your expeditions.
Tool Number 3 – GPS and Notebook
A handheld GPS and notebook is a good addition. If you find a meteorite you can identify the position. Who knows, maybe you’ve found a new strewn-field no one knows about. It also helps to remind you where you’ve hunted in the past so you don’t cover the same ground again.
Seamus Anderson points at the egg-size meteorite he found in the Australian desert.
Go outside on a clear night, and if you’re very lucky you will see the sky falling. NASA estimates that 50,000 meteorites from space have been found on Earth.
The shooting stars or fireballs they form as they enter the atmosphere can be beautiful, but they’re hard to track. Of those 50,000, astronomers have been able to plot the past orbits of only about 40.
Which is why Seamus Anderson and his colleagues at Curtin University in Australia may have made an important first. They report they’ve recovered a meteorite in the remote Australian outback—one that once followed an ellipse between the orbits of Venus and Jupiter—and they picked it out of nowhere with two drones and machine learning.
“It was a semi-surprise,” says Anderson, an American who came to Curtin in 2018 to do his Ph.D. work on technology for meteorite searches. “We weren’t expecting to have that much success the first time.”
Curtin’s Space Science and Technology Center, in the city of Perth, runs the Desert Fireball Network, a system of 50 automated cameras that monitor Australia’s night skies for incoming meteors. One night last year, two of the cameras tracked a streak in the sky, and the system calculated that a small rock had probably crashed in the desert scrub of Western Australia, in a region known as the Nullarbor. The observations weren’t ideal—they estimated that the meteorite weighed between 150 and 700 grams and had come down in an area of 5 square kilometers—but Anderson and two colleagues decided to make a field trip. In December, they set out from Perth on a drive of more than 1,000 km looking for a needle in a haystack: one blackened piece of rock on the desert floor, 50 km from the nearest paved road.
In the past, the trip would have been all but pointless. Meteorite hunters usually search the ground on foot, walking back and forth in a grid pattern and hoping they hit pay dirt. Eighty percent of the time, they fail.
“It’s been shown that people are just terrible at these kinds of repetitive tasks,” says Anderson. “A major problem is humans just not paying attention.”
Through repetition, the machine and the researchers learned to deal with false positives: bottles, cans, desert plant roots, and occasional kangaroo bones.
That’s where technology came in. They used off-the-shelf hardware—a quadcopter drone with a 44-megapixel camera and a desktop computer with a good video card. The unusual part was the convolutional neural network they ran on it—machine-learning software not often carried by campers in the outback.
“The holy grail of meteorite hunting right now is a drone that can grid a geographic area, look at the ground, and find meteorites with AI,” says Mike Hankey of the American Meteor Society.
Seamus Anderson [right] poses with his two colleagues, both pointing at the meteorite they just found. The photo was taken with the drone they had used to locate the specimen.Seamus Anderson/Curtin University
A machine-learning system needs training—data about the world from which it can extrapolate—so the researchers fed it drone images of the Nullarbor terrain. Some of them included meteorite samples borrowed from a local museum and planted on the ground. Those images were given a score of 1—a definite meteorite, even if each appeared only as a black dot. Other images showing random terrain nearby were scored as 0—no meteorite here. Through repetition, the machine and the researchers learned to deal with false positives: bottles, cans, desert plant roots, and occasional kangaroo bones.
“It’s like training your kid to figure out what a dog looks like,” says Anderson now. “You could show lots of images of nothing but black Labs—and then, when it sees a picture of a German Shepard, it’s maybe going to freak out and not know exactly what it’s supposed to do. So you have to give it many opportunities to know what a meteorite can look like in that background.”
Top: The incoming meteor and where it landed in Western Australia. Bottom left: The likely orbit of the meteoroid before it hit the Earth. Bottom: The section of desert scientists searched. Seamus Anderson/Curtin University
They began surveying: 43 drone flights over three days, going back and forth at an altitude of about 20 meters, recording 57,255 images. Back at camp, they began to process their images. From the first four flights alone, the algorithm gave 59,384 objects a score of at least 0.7 on that scale of 0 to 1—a lot of possible specimens. The researchers were quickly able to narrow them down to 259 and then 38, which they reinspected with a second, smaller drone. Soon they were down to four, and set out on foot, guided by GPS, to find them.
Before we reach the conclusion, it’s worth pausing to ask why meteorites are worth chasing. Space scientists will say that some date from the beginnings of the solar system. Some contain amino acids, those most basic building blocks of life. A few are large enough to do harm. Others, Anderson points out, contain rare elements, perhaps valuable for future technologies but hard to mine on Earth.
So there was a lot to think about in the desert heat—life, the universe, the reliability of their algorithm—as Anderson and his two comrades paced the ground looking for a blackened rock.
“Then one of my friends on the trip, John Fairweather, said one of the most annoying things you can hear at that moment—like, ‘Hey, is this the meteorite?’” Anderson says. He thought it was a joke. “And I thought, ‘That’s not funny right now, John.’ And I looked over and, literally, he’s got the rock.”
The meteorite, named DFN 09, is shown here with a pen for scale.Seamus Anderson/Curtin University
Anderson looked around to be sure the surroundings matched what the overhead drone image had shown. They did. The rock was a chondrite, a common type of iron-rich meteorite. It was 5 centimeters long, about the size of an egg, and weighed 70 grams. Most important to Anderson, the algorithm had given this particular patch of ground a score of 1.0—a perfect match.
“And I stood there, and I basically just screamed for a minute or two. Yes, it was awesome.”
The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
University of Glasgow provides funding as a member of The Conversation UK.
Wednesday 3 March started just like every other day in 2021. We were working from home. But by mid-afternoon, our colleague Luke had told us to pack our bags and fill our petrol tanks, just in case we got the OK to go on a meteorite hunt.
Four days earlier, a fireball had been spotted flying through the skies in the south of England. The flash had been captured on local people’s doorbell video cameras. It was particularly bright – a sign that meteorites might be waiting to be found.
A piece of rock flying through space is called a meteoroid. When it enters Earth’s atmosphere, causing a flash, what you see is a meteor. If any of the rock makes its way to Earth’s surface, then it becomes a meteorite.
Finding fresh pieces of meteorite is extremely rare. Most meteors visible in the sky are caused by pieces of rock and dust the size of a grain of sand. A small number of these reach the ground as micrometeorites, but they’re really hard to find.
They have to be much bigger to survive the journey through Earth’s atmosphere – where they burn up and cause a flash – and make it to the ground in a big enough piece to be found.
This fireball was first seen on Sunday. By Wednesday, models showed with near certainty at least one meteorite had made it to the ground. The models centred on Winchcombe, a quiet village in Gloucestershire where a family had found a pile of black dirt on their driveway.
By this time, Richard Greenwood from the Open University had visited the family and confirmed it was a meteorite, but the maths told us there were more pieces to be found. We needed experts on the ground searching for fragments before they got contaminated by rain or trodden on by local wildlife.
Meteorite or sheep poo?
Our management team gave us the go ahead to make the trip, confirming that, as scientists doing our work, we weren’t breaking lockdown rules. A team of around 15 researchers from across the UK descended on Gloucestershire on the morning of Thursday, March 4. We had a roughly 16km² area in which meteorites were most likely to have landed – known as a strewn field. We had less than a week to cover this area before heavy rain was forecast to hit.
As we would for any good fieldwork, we started by searching the fields. We systematically covered the land, by walking two metres apart – for maximum coverage as well as social distancing – in a long line going up and down.
We were looking out for small black shiny things on the ground. Given we were in the middle of the Cotswolds, this part wasn’t so hard – there are many shiny black things left behind by the neighbourhood sheep. This abundance of black shiny things did make finding the correct shiny black things really hard, though.
The search was also hindered by the presence of grass, dirt, trees and streams. This is why most meteorites have been recovered from Antarctica and deserts – it’s much easier to spot dark black rocks against snow, ice or sand than it is to spot them in the English countryside.
Most sites of interest were on private land, but every landowner we met was lovely, respectful and understanding of the importance of our work, not to mention excited at the possibility that their field could be the one where a meteorite was recovered. We’re hugely grateful to those who let us search their fields, and indeed the whole community for welcoming us at such a difficult time.
The big find
By Saturday, March 5 spirits were flagging. A few more piles of broken meteorite had been found in gardens or driveways, but we hadn’t spotted any in the field. Our friend Mira Ihasz joined our search team. Mira lives with our search leader, Luke, which is why she was allowed to join the trip under lockdown rules.
She’d been working from her hotel room all week but now came to help us in the search, as an extra pair of eyes. She isn’t a scientist, so whenever she spotted something she had to ask us to check it out.
That morning, Mira spotted eight meteor-wrongs. Then, the ninth thing Mira found, assuming it was yet another sheep poo, turned out to be the very thing we’d been hoping for – a meteorite at last.
It was the biggest piece anyone had found. We’d been lucky. It had landed in soft mud instead of on a hard driveway, so had stayed in tact.
Mira’s fragment – as we fondly started calling it – is a beautiful specimen weighing over 100 grams. On its surface, you can even see marks from its passage through the Earth’s atmosphere. The joy the whole team felt at the time was unmatched. We’re all pretty certain this moment will be the highlight of our careers.
We were lucky to be able to travel for essential work. Please don’t go searching during lockdown if it’s not in your neighbourhood. But if you are local to the Winchcombe area and you come across what you think might be a meteorite, there are a few things you can do.
- Take a photo of what you’ve found.
- Get the GPS coordinates of the location.
- Don’t pick it up with your hands, as this would contaminate it with oil or skin particles.
- Don’t touch it with a magnet, as this would erase crucial information about the magnetic history of the rock.
- Wrap it in aluminium foil or a clean freezer bag and store in a cool dry spot.
- Contact the Natural History Museum as soon as possible with a photograph.
If you do find a meteorite and it goes to the Natural History Museum, it will be part of a national collection archiving this historic event, studied by planetary scientists like us for decades to come.
Including Mira’s fragment, more than 500 grams of he Winchcombe meteorite – as its official name will likely become – were found altogether. Its scientific importance of cannot be understated. It’s a rare type, called a carbonaceous chondrite, with a parent body older than the Earth.
Planetary scientists are excited because carbonaceous chondrites are packed full of organic molecules, such as amino acids. These rocks may be the source of the ingredients for life on Earth. Thanks to the observational efforts of scientists and amateur astronomers, we were also able to calculate the trajectory of the meteorite and work out where it came from in the asteroid belt.
Meteorites are rocks that fall to Earth from outer space. They have fascinated mankind since the beginning of time. They are scientifically valuable objects that help geologists understand the origins of planets and the processes that shape the Earth. Meteorites are rare and they exhibit special features that differentiate them from Earth rocks.
Among characteristics that identify meteorites are a high specific gravity (especially true for irons); a dark color; and a dark glassy or dull crust if fresh or a rind of iron oxide (rust) if weathered. Most meteorites attract a magnet, although some only slightly. Many show aerodynamic shape, and their crusts may be marked with flow structures or shallow depressions called “thumbprints”.
The Lafayette meteorite exhibits flow structures.
Chondrules are almost certain proof that an object is a meteorite. A mixture of nickel and iron that appears as bright metallic flecks in a stone, or that makes up most of the object, also is a positive indicator. The Widmanstatten pattern (see LaPorte meteorite image) is also further proof.
Many tests needed to verify the identity of a meteorite should be performed by an experienced scientist, as much of the scientific information can be lost if the meteorite is improperly handled.
Iron meteorites are mainly made of the nickel-iron minerals kacacite and taenite. But they may also contain other minerals and metals, such as cobalt, copper, and zinc.
Stoney irons consist of about 50 percent nickel and iron and 50 percent silicate minerals. They are of two types: the pallasites and the mesosiderites. Pallasites have large (5-10 mm) glassy grains of olivine in a continuous matrix of nickel-iron. Mesosiderites contain small, bright, irregularly distributed metal flecks in a matrix of plagioclase and pyroxene minerals. Despite their apparent similarity, pallasites and mesosiderites appear to have different histories.
This specimen exhibits shallow depressions called thumbprints.
Stone meteorites are mineralogically the most complex and are the most abundant. They are dominantly made of silicates. Two main types—chondrites and achondrites—are recognized.
Chondrites, the most common (84 percent of falls), contain small (less than 1/8 inch) structured spheres called chondrules. Chondrules are found only in meteorites and contain some of the oldest material known to Man. Their origin is still uncertain, despite many theories proposed to explain them.
Achondrites—the second type of stone meteorites—contain silicates but do not contain chondrules. They resemble basalt from the Earth and represent about 8 percent of falls.
Where meteorites have been recovered in Indiana..
Many rocks and manmade objects appear similar to meteorites. Some suspected meteorites that proved not to be meteorites when examined closely at the Indiana Geological Survey were igneous rocks left by glaciers, sedimentary rock concretions, metallic alloys, and pieces of silicon. Even materials fused together by trash fires can resemble meteorites.
*Meteorites that are seen as they fall and are recovered shortly after landing are classed as falls; those that are accidently found long after falling are classed as finds.
What to Look for in a Meteorite
- Thin, dark glassy-to-dull coating or fusion crusts
- Flow structures or “thumbprints” on outside
- Aerodynamic shape
- High specific gravity
- Metallic nickel-iron
- Widmanstatten pattern
- Small spherical chondrules
- Attracts magnets
The Hangman’s Crossing meteorite exhibits features that are indicators of meteorites.
Think you may have a meteorite?
Members of the public are always welcome to bring rocks and minerals to our Bloomington office for more information, but the IGWS is unable to inspect or evaluate suspected meteorites. For more information on meteorite authentication and testing, please contact the Field Museum, Washington University in St. Louis, or the University of California, Los Angeles.
Polished section of a pallasite meteorite.
A meteorite is a stony or metallic piece of meteor that reached Earth’s surface. Meteorites have been found all over the world, and of the 1,671 verified in the United States as of April 2013, 158 came from Kansas (see Meteorites in the United States).
Meteorites are classified into three main types:
- Stones—composed primarily of silicate minerals (compounds consisting of silicon, oxygen, and various metallic elements); similar to rocks found on Earth.
- Irons—made primarily of iron and nickel in varying proportions.
- Stony-irons—composed of both silicates and metals in approximately equal proportions.
Within these three main categories, meteorites are further subdivided into a number of classes. Meteorites found in Kansas include representative samples of most of the various types of meteorites.
Western Kansas is a good place to find meteorites because the wide-open country has few trees and terrestrial rocks at the surface and most of the region is heavily cultivated but not otherwise extensively developed. Thus, anything out of the ordinary stands out. In addition, western Kansas is semiarid, so meteorites disintegrate more slowly there than in wetter regions.
In 1882, Eliza Kimberly discovered what would become one of the most spectacular meteorite finds in Kansas on her family’s property near the town of Brenham in Kiowa County. The rocks she collected piqued the interest of scientists and meteorite hunters, who have since collected many more. All of the samples are believed to be from one meteorite that broke up on its way down. Over the years, more than three tons of debris from the Brenham Meteorite have been found at the site, including the largest example found in Kansas. In 2005, a 1,400-pound piece was located with a specially designed metal detector. This specimen is an oriented pallasite, a stony-iron body that remained oriented in one position as it fell so that the lead side taking the brunt of the atmospheric heat was sculpted into a rounded or conical shape. Only two larger meteorites of that type have been verified in the world.
Buchanan, R., 2010, Kansas Geology: An Introduction to Landscapes, Rocks, Minerals, and Fossils (2nd ed.): Lawrence, Kansas, University Press of Kansas, 240 p.
Buchanan, R., and McCauley, J. R., 2010, Roadside Kansas: A Traveler’s Guide to Its Geology and Landmarks (2nd ed.): Lawrence, Kansas, University Press of Kansas, 392 p.
Suchy, D. R., 2007, Meteorites in Kansas: Kansas Geological Survey, Public Information Circular 26.
Example image of two meteorites deployed during a field test near Walker Lake, Nevada. The meteorites are marked with orange flags. Note the dark shadow of the quadrictoper drone. Credit: Robert Citron et al.
Planetary scientists estimate that each year, about 500 meteorites survive the fiery trip through Earth’s atmosphere and fall to our planet’s surface. Most are quite small, and less than 2% of them are ever recovered. While the majority of rocks from space may not be recoverable due to ending up in oceans or remote, inaccessible areas, other meteorite falls are just not witnessed or known about.
But new technology has upped the number known falls in recent years. Doppler radar has detected meteorite falls, as well as all-sky camera networks specifically on the lookout for meteors. Additionally, increased use of dashcams and security cameras have allowed for more serendipitous sightings and data on fireballs and potential meteorite falls.
A team of researchers is now taking advantage of additional technology advances by testing out drones and machine learning for automated searches for small meteorites. The drones are programmed to fly a grid search pattern in a projected “strewn field” for a recent meteorite fall, taking systematic pictures of the ground over a large survey area. Artificial intelligence is then used to search through the pictures to identify potential meteorites.
“Those images can be analyzed using a machine-learning classifier to identify meteorites in the field among many other features,” said Robert Citron of the University of California, Davis, in a recent paper published in published in Meteoritics & Planetary Science.
Citron and his colleagues have tested their conceptual drone setup several times, mostly recently in the area of a known 2019 meteorite fall near Walker Lake, Nevada. Their proof-of-concept meteorite classifier deploys a combination of “different convolution neural networks to recognize meteorites from images taken by drones in the field,” the team writes.
While this specific test revealed a number of false positives for rocks previously unidentified, the software was able to correctly identify test meteorites placed by the researchers on the dry lake bed in Nevada. Citron and his team are very optimistic about the potential of their system, particularly in searching for small meteorites and finding them in remote regions.
Citron told Universe Today the main challenge for setting up the system was assembling a training dataset for the machine learning classifier.
“Since a future meteorite fall could occur on any terrain,” he said via email, “the system needed an object detection algorithm trained with examples of many types of meteorites on various terrain types. To create a properly trained object detection network, thousands of example images are required.”
Citron and colleagues assembled images of meteorites from the internet and added in “posed” photos of meteorites from their collection on various terrains. This allowed them to properly train the machine learning model to minimize the number of ordinary rocks flagged as false detections.
They then conducted ten test flights with a quadricopter drone in two locations of the projected Nevada strewn field, which is the area of expected meteorite falls based on trajectory data from four stations of the NASA Meteorite Tracking and Recovery Network, part of the Global Fireball Observatory.
A bright meteor caught by one of the Global Fireball Network’s cameras from the Rancho Mirage Observatory (Eric McLaughlin) on April 7, 2019. Credit: NASA Meteorite Tracking and Recovery Network
“Fortunately, every field test we gain more data that we can incorporate into the dataset and use to retrain the object detection network and improve the accuracy,” Citron said. “So, we will continue to try and improve the detection accuracy. Currently we need a better drone with a higher resolution camera.”
Studying meteorites and knowing their origins helps scientists determine the composition of some 40 asteroid families in the asteroid belt, and also aids in understanding the early evolution of the solar system. The researchers said that the remote camera network information combined with being able to find and study freshly fallen meteorites is crucial in determining what asteroid family might have produced the meteoritic debris, and if it was from a particular collision event.
“If the meteorite can be recovered, a fireball’s light curve and deceleration profile also provides information about how its kinetic energy is deposited in the Earth’s atmosphere,” the team wrote in their paper. “That information can be used to improve predictions at what altitude asteroids of this material type fragment that are big enough to cause damaging airbursts.”
However, finding meteorites from an observed fall can be very difficult, since meteorites can be scattered over a wide area.
“Smaller falls are more frequent but deliver less meteorite fragments which are therefore harder to locate,” Citron said. “It takes approximately 100 man-hours to find one meteorite fragment, so if we can improve on that we can sample more of these small falls and get better insight into the orbits and therefore source regions of incoming meteors.”
An example of a small, freshly-fallen meteorite in situ, found and photographed by Geoffrey Notkin. This specimen is Ash Creek, an L6 stone meteorite, which fell on February 15, 2009 in McLennan County, Texas, following a bright daytime fireball. This was the first time Doppler radar was used to locate specimens. Credit: Geoffrey Notkin
Citron said that his team’s drone system is intended for smaller falls that would not attract meteorite hunters. But the team’s work has attracted the admiration of one noted meteorite hunter, Geoffrey Notkin of the Discovery Channel’s “Meteorite Men.”
“Dr. Citron’s current work in this area is fascinating, especially his bold experiments with drones in real-world situations,” Notkin said via email. “The most exciting concept here is the coupling of modern drones with machine learning that can recognize the visual characteristics of meteorites in situ. Given time, this methodology could eliminate some of the tedium of searching for freshly-fallen meteorites on foot and also facilitate recoveries in areas that are difficult or dangerous for humans to search in person.”
Notkin added that he has long thought that drones and uncrewed aerial vehicles (UAVs) could play a useful role in meteorite recovery, and in fact, he carried out some early experiments in 2010 and 2011, but the drones and UAVs of the time were either not advanced enough or not available to non-military personnel.
But as technology continues to improve, Citron said, and “with a larger training dataset, updated classification scheme, and improved imaging hardware, machine learning coupled to an autonomous drone survey could prove a valuable tool for increasing the number of meteorite fragments found from fresh falls.”