A fireball lights up the skies over Dayton, Ohio. Image credit and copyright: John Chumack.
It happens a few times every year.
Last week, we poured our morning coffee, powered up our laptop and phone, and prepared to engage the day.
It wasn’t long before the messages started pouring in. ‘Bright fireball over the U.S. West Coast!’ ‘Major event lights up the California skies!’ and variations thereof. Memories of Chelyabinsk came immediately to mind. A bit of digging around ye ole web revealed video and a few authentic stills from the event.
Now, I always like to look these over myself before reading just what other experts might think. Chelyabinsk immediately grabbed our attention when we saw the first videos recording the shock wave of sound generated by the blast. ‘That sucker was close,’ we realized.
Thursday’s (Wednesday evening Pacific Time) event was less spectacular, but still interesting: the nighttime reentry of the Long March CZ-7 rocket body NORAD ID 2016-042E as it broke up over the U.S. West Coast.
How do we know this, and what do we look for? Is that flash a meteor, bolide, reentry or something stranger still?
Most good meteor footage comes from video recorders that are already up and running when the event occurs, to include security and dashboard cameras, and mobile phones already recording another event, such as a concert or game. How fast can YOU have your smartphone camera out and running? We only recently learned that a quick double tap of the home button will bring the camera on our Android to bear, no unlock needed.
If the event occurs on a Friday or Saturday night with lots of folks out on the town on a clear evening, we might see multiple captures come streaming-in of the event. Just such a fireball was witnessed over the United Kingdom on Friday evening, September 21st, 2012.
Likewise, the fakes are never far behind. We’ve seen ’em all, though you’re welcome to try and stump us. Such ‘meteor-wrongs’ that are commonly circulated as authentic are the reentry of Mir, the 1992 Peekskill meteor, Chelyabinsk, the reentry of Hayabusa, and screen grabs from the flick Armageddon… has anyone ever been fooled by this one?
Meteors generally have a very swift motion, and occur with a greater frequency as the observer rotates forward into the path of Earth’s motion around the Sun past local midnight. Remember, it’s the front of the windshield that picks up the bugs rolling down the highway.
Evening meteors, however, can have a dramatic slow, stately motion across the sky, as they struggle to catch up with the Earth. If they reach a brilliance of magnitude -14 — about one whole magnitude brighter than a Full Moon — said meteor is known as a bolide.
Sometimes, such a fireball can begin shedding fiery debris, in a dramatic display known as a meteor train or meteor precession. Such an event was witnessed over the northeastern United States on July 20th, 1860.
Bright meteors may exhibit colors, hinting at chemical competition. Green for nickel (Not kryptonite!) is typically seen. MeteoriteMen’s Geoffrey Notkin once told us a good rule of thumb: if you hear an accompanying sonic boom a few minutes after seeing a meteor, it’s close. Folks often think what they saw went down behind a hill or tree, when it was actually likely more than 50 miles distant — if it hit the ground at all.
Is that a meteor or a reentry? Reentries move slower still, and will shed lots of debris. Here’s what we’re looking at to judge suspect sighting as a reentry:
Heavens-Above: A great clearing house for satellite passes by location. One great tool is that Heavens-Above will generate a pass map for your location juxtaposed over a sky chart.
Aerospace Corp current reentries: Follows upcoming reentries of larger debris with refined orbits.
Space-Track: The U.S. Joint Space Operations Command’s tracking center for artificial objects in orbit around Earth. Access is available to backyard satellite spotters with free registration. The most accurate source for swiftly evolving orbital elements.
SeeSat-L: This message board always lights up with chatter whenever a possible reentry lights up the skies worldwide.
Stranger Skies
Bizarre sights await the keen eyed. A tumbling rocket booster can often flare in a manner similar to Iridium satellites. Satellites way out in geostationary orbit can flare briefly into naked eye visibility during ‘GEOSat flare season’ near the weeks surrounding either equinox.
Some gamma ray bursts, such as GRB 080319B flare up briefly above magnitude +6 into naked eye visibility from far across the Universe. As of yet, there’s never been a reliable observer sighting of such an event, though it should be possible… probably someone far back in humanity’s history witnessed just such a brief flash in the sky, pausing silently to wonder just what it was…
Kaboom! Image credit: NASA/Pi of the Sky.
Going further back still, a nearby supernova or gamma-ray burst would leave a ghostly blue afterglow from Cerenkov radiation as it pummeled our atmosphere… though it would be a deadly planet-sterilizing indigo glow, not something you’d want to see. Thankfully, we live in the ‘Era of Mediocrity,’ safely outside of the 25-50 light year ‘kill zone’ for any potential supernova.
And what if those lights in the sky really were the vanguard of an alien invasion force? Well, if they really did land rayguns ablaze on the White House lawn, you’ll read it first here on Universe Today!
Osterplana 65, the meteorite at the heart of a mystery. This meteorite is different than the thousands of other meteorites in collections around the world. Image: Birger Schmitz
470 million years ago, somewhere in our Solar System, there was an enormous collision between two asteroids. We know this because of the rain of meteorites that struck Earth at that time. But inside that rain of meteorites, which were all of the same type, there is a mystery: an oddball, different from the rest. And that oddball could tell us something about how rocks from space can change ecosystems, and allow species to thrive.
This oddball meteorite has a name: Osterplana 65. It’s a fossilized meteorite, and it was found in a limestone quarry in Sweden. Osterplana 65 fell to Earth some 470 mya, during the Ordovician period, and sank to the bottom of the ocean. There, it became sequestered in a bed of limestone, itself created by the sea-life of the time.
The Ordovician period is marked by a couple thing: a flourishing of life similar to the Cambrian period that preceded it, and a shower of meteors called the Ordovician meteor event. There is ample evidence of the Ordovician meteor event in the form of meteorites, and they all conform to similar chemistry and structure. So it’s long been understood that they all came from the same parent body.
The collision that caused this rain of meteorites had to have two components, two parent bodies, and Osterplana 65 is evidence that one of these parent bodies was different. In fact, Ost 65 represents a so far unknown type of meteorite.
The faint grey lines in this electron image of Ost 65 are called “shock deformation lamellae” and they are evidence that Ost 65 was the result of a collision. Image: B. Schmidt
The study that reported this finding was published in Nature on June 14 2016. As the text of the study says, “Although single random meteorites are possible, one has to consider that Öst 65 represents on the order of one per cent of the meteorites that have been found on the mid-Ordovician sea floor. “It goes on to say, “…Öst 65 may represent one of the dominant types of meteorites arriving on Earth 470 Myr ago.”
The discovery of a type of meteorite falling on Earth 470 mya, and no longer falling in our times, is important for a couple reasons. The asteroid that produced it is probably no longer around, and there is no other source for meteorites like Ost 65 today.
The fossil record of a type of meteorite no longer in existence may help us unravel the story of our Solar System. The asteroid belt itself is an ongoing evolution of collision and destruction. It seems reasonable that some types of asteroids that were present in the earlier Solar System are no longer present, and Ost 65 provides evidence that that is true, in at least one case.
Ost 65 shows us that the diversity in the population of meteorites was greater in the past than it is today. And Ost 65 only takes us back 470 mya. Was the population even more diverse even longer ago?
The Earth is largely a conglomeration of space rocks, and we know that there are no remnants of these Earthly building blocks in our collections of meteorites today. What Ost 65 helps prove is that the nature of space rock has changed over time, and the types of rock that came together to form Earth are no longer present in space.
Ost 65 was found in amongst about 100 other meteorites, which were all of the same type. It was found in the garbage dump part of the quarry. It’s presence is a blemish on the floor tiles that are cut at the quarry. Study co-author Birgen Schmitz told the BBC in an interview that “It used to be that they threw away the floor tiles that had ugly black dots in them. The very first fossil meteorite we found was in one of their dumps.”
According to Schmitz, he and his colleagues have asked the quarry to keep an eye out for these types of defects in rocks, in case more of them are fossilized meteorites.
Finding more fossilized meteorites could help answer another question that goes along with the discovery of Ost 65. Did the types and amounts of space rock falling to Earth at different times help shape the evolution of life on Earth? If Ost 65 was a dominant type of meteorite falling to Earth 470 mya, what effect did it have? There appear to be a confounding number of variables that have to be aligned in order for life to appear and flourish. A shower of minerals from space at the right time could very well be one of them.
Whether that question ever gets answered is anybody’s guess at this point. But Ost 65 does tell us one thing for certain. As the text of the study says, “Apparently there is potential to reconstruct important aspects of solar-system history by looking down in Earth’s sediments, in addition to looking up at the skies.”
The Egyptian Pyramids; instantly recognizable to almost anyone. Image: Armstrong White, CC BY 2.0
The spread of metallurgy in different civilizations is a keen point of interest for historians and archaeologists. It helps chart the rise and fall of different cultures. There are even names for the different ages corresponding to increasingly sophisticated metallurgical technologies: the Stone Age, the Bronze Age, and the Iron Age.
But sometimes, a piece of evidence surfaces that doesn’t fit our understanding of a civilization.
Probably the most iconic ancient civilization in all of history is ancient Egypt. Its pyramids are instantly recognizable to almost anyone. When King Tutankhamun’s almost intact tomb was discovered in 1922, it was a treasure trove of artifacts. And though the tomb, and King Tut, are most well-known for the golden death mask, it’s another, little-known artifact that has perhaps the most intriguing story: King Tut’s iron dagger.
King Tutankhamun’s Golden Death Mask, one of the most stunning human artifacts in existence. Image: Carsten Frenzl, CC BY 2.0
King Tut’s iron-bladed dagger wasn’t discovered until 1925, three years after the tomb was discovered. It was hidden in the wrappings surrounding Tut’s mummy. It’s mere existence was a puzzle, because King Tut reigned in 1332–1323 BC, 600 years before the Egyptians developed iron smelting technology.
King Tut’s iron dagger was concealed in the wrappings surrounding the boy-king’s mummy. Image: Daniela Comelli/Polytechnic University of Milan
It was long thought, but never proven, that the blade may be made of meteorite iron. In the past, tests have produced inconclusive results. But according to a new study led by Daniela Comelli, of the Polytechnic University of Milan, and published in the Journal of Meteoritics and Planetary Science, there is no doubt that a meteorite was the source of iron for the blade.
The team of scientists behind the study used a technique called x-ray fluorescence spectrometry to determine the chemical composition of the blade. This technique aims x-rays at an artifact, then determines its composition by the spectrum of colors given off. Those results were then compared with 11 other meteorites.
In the dagger’s case, the results indicated Fe plus 10.8 wt% Ni and 0.58 wt% Co. This couldn’t be a coincidence, since iron meteorites are mostly made of Fe (Iron) and Ni (Nickel), with minor quantities of Co (Cobalt), P (Phosphorus), S (Sulphur), and C (Carbon). Iron found in the Earth’s crust has almost no Ni content.
Testing of Egyptian artifacts is a tricky business. Egypt is highly protective of their archaeological resources. This study was possible only because of advances in portable x-ray fluorescence spectrometry, which meant the dagger didn’t have to be taken to a lab and could be tested at the Egyptian Museum of Cairo.
Iron objects were rare in Egypt at that time, and were considered more valuable than gold. They were mostly decorative, probably because ancient Egyptians found iron very difficult to work. It requires a very high heat to work with, which was not possible in ancient Egypt.
Iron meteorites like this one would have attracted the attention of ancient Egyptians. This one is the Bendego meteorite from Brazil. Image: Jorge Andrade – Flickr: National Museum, Rio de Janeiro CC BY 2.0
Even without the ability to heat and work iron, a great deal of craftsmanship went into the blade. The dagger itself had to be hammered into shape, and it features a decorated golden handle and a rounded rock crystal knob. It’s golden sheath is decorated with a jackal’s head and a pattern of feathers and lilies.
Ancient Egyptians probably new what they were working with. They called meteorite iron from the sky in one hieroglyph. Whether they knew with absolute certainty that their iron meteorites came from the sky, and what that might have meant, they did value the iron. As the authors of the study say, “…our study confirms that ancient Egyptians attributed great value to meteoritic iron for the production of precious objects.”
The authors go on to say, “Moreover, the high manufacturing quality of Tutankhamun’s dagger blade, in comparison with other simple-shaped meteoritic iron artifacts, suggests a significant mastery of ironworking in Tutankhamun’s time.”
New research finds that asteroids delivered as much 80 percent of the Moon's water. Credit: LPI/David A. Kring
Over the course of the past few decades, our ongoing exploration the Solar System has revealed some surprising discoveries. For example, while we have yet to find life beyond our planet, we have discovered that the elements necessary for life (i.e organic molecules, volatile elements, and water) are a lot more plentiful than previously thought. In the 1960’s, it was theorized that water ice could exist on the Moon; and by the next decade, sample return missions and probes were confirming this.
Since that time, a great deal more water has been discovered, which has led to a debate within the scientific community as to where it all came from. Was it the result of in-situ production, or was it delivered to the surface by water-bearing comets, asteroids and meteorites? According to a recent study produced by a team of scientists from the UK, US and France, the majority of the Moon’s water appears to have come from meteorites that delivered water to Earth and the Moon billions of years ago.
For the sake of their study, which appeared recently in Nature Communications, the international research team examined the samples of lunar rock and soil that were returned by the Apollo missions. When these samples were originally examined upon their return to Earth, it was assumed that the trace of amounts of water they contained were the result of contamination from Earth’s atmosphere since the containers in which the Moon rocks were brought home weren’t airtight. The Moon, it was widely believed, was bone dry.
The blue areas show locations on the Moon’s south pole where water ice is likely to exist. Credit: NASA/GSFC
However, a 2008 study revealed that the samples of volcanic glass beads contained water molecules (46 parts per million), as well as various volatile elements (chlorine, fluoride and sulfur) that could not have been the result of contamination. This was followed up by the deployment of the Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (LCROSS) in 2009, which discovered abundant supplies of water around the southern polar region,
However, that which was discovered on the surface paled in comparison the water that was discovered beneath it. Evidence of water in the interior was first revealed by the ISRO’s Chandrayaan-1 lunar orbiter – which carried the NASA’s Moon Mineralogy Mapper (M3) and delivered it to the surface. Analysis of this and other data has showed that water in the Moon’s interior is up to a million times more abundant than what’s on the surface.
The presence of so much water beneath the surface has begged the question, where did it all come from? Whereas water that exists on the Moon’s surface in lunar regolith appears to be the result of interaction with solar wind, this cannot account for the abundant sources deep underground. A previous study suggested that it came from Earth, as the leading theory for the Moon’s formation is that a large Mars-sized body impacted our nascent planet about 4.5 billion years ago, and the resulting debris formed the Moon. The similarity between water isotopes on both bodies seems to support that theory.
Near-infrared image of the Moon’s surface by NASA’s Moon Mineralogy Mapper on the Indian Space Research Organization’s Chandrayaan-1 mission. Credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS
However, according to Dr. David A. Kring, a member of the research team that was led by Jessica Barnes from Open University, this explanation can only account for about a quarter of the water inside the moon. This, apparently, is due to the fact that most of the water would not have survived the processes involved in the formation of the Moon, and keep the same ratio of hydrogen isotopes.
Instead, Kring and his colleagues examined the possibility that water-bearing meteorites delivered water to both (hence the similar isotopes) after the Moon had formed. As Dr. Kring told Universe Today via email:
“The current study utilized analyses of lunar samples that had been collected by the Apollo astronauts, because those samples provide the best measure of the water inside the Moon. We compared those analyses with analyses of meteoritic samples from asteroids and spacecraft analyses of comets.”
By comparing the ratios of hydrogen to deuterium (aka. “heavy hydrogen”) from the Apollo samples and known comets, they determined that a combination of primitive meteorites (carbonaceous chondrite-type) were responsible for the majority of water to be found in the Moon’s interior today. In addition, they concluded that these types of comets played an important role when it comes to the origins of water in the inner Solar System.
Images produced by the Lyman Alpha Mapping Project (LAMP) aboard NASA’s Lunar Reconnaissance Orbiter reveal features at the Moon’s northern and southern poles, as well as the presence of water frost. Credit: NASA/SwRI
For some time, scientists have argued that the abundance of water on Earth may be due in part to impacts from comets, trans-Neptunian objects or water-rich meteoroids. Here too, this was based on the fact that the ratio of the hydrogen isotopes (deuterium and protium) in asteroids like 67P/Churyumov-Gerasimenko revealed a similar percentage of impurities to carbon-rich chondrites that were found in the Earth’s coeans.
But how much of Earth’s water was delivered, how much was produced indigenously, and whether or not the Moon was formed with its water already there, have remained the subject of much scholarly debate. Thank to this latest study, we may now have a better idea of how and when meteorites delivered water to both bodies, thus giving us a better understanding of the origins of water in the inner Solar System.
“Some meteoritic samples of asteroids contain up to 20% water,” said Kring. “That reservoir of material – that is asteroids – are closer to the Earth-Moon system and, logically, have always been a good candidate source for the water in the Earth-Moon system. The current study shows that to be true. That water was apparently delivered 4.5 to 4.3 billion years ago.“
The existence of water on the Moon has always been a source of excitement, particularly to those who hope to see a lunar base established there someday. By knowing the source of that water, we can also come to know more about the history of the Solar System and how it came to be. It will also come in handy when it comes time to search for other sources of water, which will always be a factor when trying to establishing outposts and even colonies throughout the Solar System.
Mars! Martian meteorites make their way to Earth after being ejected from Mars by a meteor impact on the Red Planet. Image: NASA/National Space Science Data Center.
Sometimes, the best way to study Mars is to stay home. There’s no substitute for actual missions to Mars, but pieces of Mars have made the journey to Earth, and saved us the trip. Case in point: the treasure trove of Martian meteorites that NASA is gathering from Antarctica.
NASA scientists aren’t the first ones to find meteorites in the Earth’s polar regions. As early as the 9th century, people in the northern polar regions made use of iron from meteorites for tools and hunting weapons. The meteorite iron was traded from group to group over long distances. But for NASA, the hunt for meteorites is focused on Antarctica.
In Antarctica, the frigid temperatures preserve meteorites for a long time, which makes them valuable artifacts in the quest to understand Mars. Meteorites tend to accumulate in places where creeping glacial ice moves them to. When the ice meets a rock obstacle, the meteorites are deposited there, making them easier to find. Recently arrived meteorites are also easily spotted on the surface of the Antarctica ice.
The US began collecting meteorites in Antarctica in 1976, and to date more than 21,000 meteorites and meteorite fragments have been found. In fact, more of them are found in Antarctica than in the rest of the world combined. These meteorites are then shared with scientists around the world.
Collecting meteorites in Antarctica is not a walk in the park. It’s physically gruelling and hazardous work. Antarctica is not an easy environment to live and work in, and just surviving there takes planning and teamwork. But the scientific payoff is huge, which keeps NASA going back.
Meteorites from the Moon and other bodies also arrive on Earth, and are collected in Antarctica. They can tell scientists important things about the evolution and formation of the Solar System, the origin of organic chemical compounds necessary for life, and the origin of the planets themselves.
How Do Martian Meteorites Get To Earth?
A few things have to go right for a Martian meteorite to make it to Earth. First, a meteorite has to collide with Mars. That meteorite has to be big enough, and hit the surface of Mars with enough force, that rock from Mars is propelled off the surface with enough speed to escape Mars’ gravity.
After that, the meteor has to travel through space and avoid a thousand other fates, like being drawn to one of the other planets, or the Sun, by the gravitational pull of those bodies. Or being flung off into the far reaches of empty space, lost forever. Then, if it manages to make it to Earth, and be pulled in by Earthly gravity, it must be large enough to survive entry into Earth’s atmosphere.
The Science
Part of the scientific value in meteorites lies not in their source, but in the time that they were formed. Some meteorites have travelled through space for so long, they’re like time travellers. These ancient meteorites can tell scientists a lot about conditions in the early Solar System.
This the Hoba meteorite from Namibia. At 60 tonnes, it is the largest known intact meteorite. Image: Patrick Giraud, http://creativecommons.org/licenses/by/2.5
Meteorites from Mars tell scientists a few things. Since they’ve survived re-entry into Earth’s atmosphere, they can tell engineers about the dynamics of such a journey, and help inform spacecraft design. Since they contain chemical signatures and elements unique to Mars, they can also tell mission specialists things about surviving on Mars.
They can also provide clues to one of the greatest mysteries in space exploration: Did life exist on Mars? A Martian meteorite found in the Sahara desert in 2011 contained ten times the amount of water as other Martian meteorites, and added evidence to the idea that Mars was once a wet world, suitable for life.
NASA’s program to hunt for meteorites in Antarctica has been going strong for many years, and there’s really no reason to stop doing it, since this is the only way to get Martian samples into a laboratory. Each one they find is like a puzzle piece, and like a jigsaw puzzle, you never know which one will complete the big picture.
Dr. Barbara Cohen is seen with a large meteorite from the Antarctic's Miller Range. Credit: Antarctic Search for Meteorites
Two members of the Antarctic Search for Meteorites 2012-2013 team use tongs to collect a meteorite near the Transantarctic Mountains. Credit: Katherine Joy, University of Manchester / Antarctic Search for Meteorites Program
In the category of why-didn’t-I think-of-that ideas, Dr. Geoffrey Evatt and colleagues from the University of Manchester struck upon a brilliant hypothesis: that a layer of iron meteories might lurk just below the surface of the Antarctic ice. He’s the lead author of a recent paper on the topic published in the open-access journal, Nature Communications.
A possible stony meteorite found during the ANSMET 2014-15 expedition in Antarctica. Credit: Antarctic Search for Meteorites Program
Remote Antarctica makes one of the best meteorite collecting regions on the planet. Space rocks have been accumulating there for millennia preserved in the continent’s cold, desert-like climate. While you might think it’s a long and expensive way to go to hunt for meteorites, it’s still a lot cheaper than a sample return mission to the asteroid belt. Meteorites fall and become embedded in ice sheets within the continent’s interior. As that ice flows outward toward the Antarctic coastlines, it pushes up against the Transantarctic Mountains, where powerful, dry winds ablate away the ice and expose their otherworldly cargo.
Meteorite recovery sites in the Transantarctic Mountains. Credit: NASA
Layer after layer, century after century, the ice gets stripped away, leaving rich “meteorite stranding zones” where hundreds of space rocks can be found within an area the size of a soccer field. Since most meteorites arrive on Earth coated in a black or brown fusion crust from their searing fall through the atmosphere, they contrast well against the white glare of snow and ice. Scientists liken it to a conveyor belt that’s been operating for the past couple million years.
Scientists form snowmobile posses and buzz around the ice fields picking them up like candy eggs on Easter morning. OK, it’s not that easy. There’s much planning and prep followed by days and nights of camping in bitter cold with high winds tearing at your tent. Expeditions take place from October through early January when the Sun never sets.
The U.S. under ANSMET (Antarctic Search for Meteorites, a Case Western Reserve University project funded by NASA), China, Japan and other nations run programs to hunt and collect the precious from the earliest days of the Solar System before they find their way to the ocean or are turned to dust by the very winds that revealed them in the first place. Since systematic collecting began in 1976, some 34,927 meteorites have been recovered from Antarctica as of December 2015.
A team of scientists document the find of a small meteorite found among rocks on the Antarctic ice during the ANSMET 2014-15 expedition. Credit: Antarctic Search for Meteorites Program / Vinciane Debaille
Meteorites come in three basic types: those made primarily of rock; stony-irons comprised of a mixture of iron and rock; and iron-rich. Since collection programs have been underway, Antarctic researchers have uncovered lots of stony meteorites, but meteorites either partly or wholly made of metal are scarce compared to what’s found in other collecting sites around the world, notably the deserts of Africa and Oman. What gives?
This fragment of the massive Sikhote-Alin meteorite that fell over eastern Russia (then the Soviet Union) on Feb. 12, 1947 is a typical iron-nickel meteorite. Another specimen of this meteorite was used in the experiment to determine how quickly it burrowed into the ice when heated. Credit: Bob King
Dr. Evatt and colleagues had a hunch and performed a simple experiment to arrive at their hypothesis. They froze two meteorites of similar size and shape — a specimen of the Russian Sikhote-Alin iron and NWA 869, an ordinary (stony) chondrite — inside blocks of ice and heated them using a solar-simulator lamp. As expected, both meteorites melted their way down through the ice in time, but the iron meteorite sank further and faster. I bet you can guess why. Iron or metal conducts heat more efficiently than rock. Grab a metal camera tripod leg or telescope tube on a bitter cold night and you’ll know exactly what I mean. Metal conducts the heat away from your hand far better and faster than say, a piece of wood or plastic.
Antarctic researchers carefully pack meteorites found along the Transantarctic Range into collection boxes. Looks cold! Credit: Antarctic Search for Meteorites Program / Vinciane Debaille
The researchers performed many trials with the same results and created a mathematical model showing that Sun-driven burrowing during the six months of Antarctic summer accounted nicely for the lack of iron meteorites seen in the stranding zones. Co-author Dr. Katherine Joy estimates that the fugitive meteorites are trapped between about 20-40 inches (50-100 cm) beneath the ice.
Who wouldn’t be happy to find this treasure? Dr. Barbara Cohen is seen with a large meteorite from the Antarctic’s Miller Range. Credit: Antarctic Search for Meteorites Program
You can imagine how hard it would be to dig meteorites out of Antarctic ice. It’s work enough to mount an expedition to pick up just what’s on the surface.
With the gauntlet now thrown down, who will take up the challenge? The researchers suggests metal detectors and radar to help locate the hidden irons. Every rock delivered to Earth from outer space represents a tiny piece of a great puzzle astronomers, chemists and geologist have been assembling since 1794 when German physicist Ernst Chladni published a small book asserting that rocks from space really do fall from the sky.
Like the puzzle we leave unfinished on the tabletop, we have a picture, still incomplete, of a Solar System fashioned from the tiniest of dust motes in the crucible of gravity and time.
Pentax K-1000, 50mm lens, Kodak Ektar 100
Exposure ~ 8 seconds at Dusk,
Capturing a Bright Fireball, breaking up with debri,
Yellow Springs, Ohio. Photo credit: John Chumack
Last Saturday, Feb. 6th, a meteorite reportedly struck a bus driver on the campus of the Bharathidasan Engineering College in southern India. Three students were also injured and several windows were shattered in some kind of explosion. Online videos and stills show a small crater left by the impact. If true, this would be the first time in recorded history a person was struck and killed by a meteorite.
Meteorite or …?
Call me skeptical. Since the purported meteorite weighed about 50 grams — just under two ounces — it would be far too small to cause an explosion or significant impact crater five feet deep and two feet wide as depicted in both video and still photos. There were also no reports of rumbles, sonic booms or sightings of a fireball streaking across the sky, sights and sounds associated with material substantial enough to penetrate the atmosphere and plunge to the ground. Shattered windows would indicate an explosion similar to the one that occurred over Chelyabinsk, Russia in February 2013. The blast wave spawned when the Russian meteorite fractured into thousands of pieces miles overhead pulverized thousands of windows with flying glass caused numerous injuries.
According to a story that ran in The News Minute, a team led by the Indian Space Research Organization (IRSO) recovered an object 2 cm (3/4 inch) in width that weighed 50 grams and looked like a meteorite with “air bubbles on its rigid surface”. There’s also been chatter about meteor showers dropping meteorites to Earth, with various stories reporting that there no active meteor showers at the time of the driver’s death. For the record, not a single meteorite ever found has been linked to a shower. Dust and tiny bits of comets produce most shower meteors, which vaporize to fine soot in the atmosphere.
Now even NASA says that based on images posted online, the explosion is “land based” rather than a rock from space.
There have been close calls in the past most notably in Sylacauga, Alabama On November 30, 1954 at 2:46 p.m. an 8.5 lb rock crashed through the roof of a home not far from that town, hit a radio console, bounced off the floor and struck the hand and hip of 31-year-old Ann Hodges who was asleep on the couch at the time. She awoke in surprise and pain thinking that a space heater had blown up. But when she noticed the hole in the roof and a rock on the floor, Hodges figured the neighborhood kids had been up to no good.
Dr. Moody James shows where Ann Hodges was struck in the hip by an 8.5 lb meteorite that crashed through her roof (right). The photos appeared in the Dec. 13, 1954 issue of Life magazine. Photo by Jay Leviton, Time & Life Pictures, Getty Images
Fortunately her injuries weren’t serious. Ann became a sudden celebrity; her photo even appeared on the cover of Life magazine with a story titled “A Big Bruiser From The Sky”. In 1956 she donated the meteorite to the Alabama Museum of Natural History in Tuscaloosa, where you can still see it to this day. A second meteorite from the fall weighing 3.7 lbs. was picked up the following day by Julius K. McKinney in the middle of a dirt road. McKinney sold his fragment to the Smithsonian and used the money to purchase a small farm and used car.
Claims of people getting hit by meteorites have been on the increase in the past few years with the growth of the social media. Some stories have been deliberately made up and none have been verified. This would appear to be another tall tale if only based upon the improbabilities. In the meantime I’ve dug around and discovered another story that’s more probable and may indeed be the truth, though I have no way as of yet to independently verify it.
Police at the college say that two of the school’s gardeners were burning materials from the garden when the fire inadvertently set off sticks of dynamite that had been abandoned “amid the rocks” when the college was first built. The driver, by the name of Kamaraj and another driver, Sultan, were drinking water nearby when they were hit by the shrapnel and flying glass. Kamaraj began bleeding and was rushed to a hospital but died on the way. More HERE.
In the meantime, we only hope officials get to the bottom of the tragic death.
Asteroid 2015 TB145 isn’t the only cosmic visitor paying our planet a trick-or-treat visit over the coming week. With any luck, the Northern Taurid meteor shower may put on a fine once a decade show heading into early November.
About once a decade, the Northern Taurid meteor stream puts on a good showing. Along with its related shower the Southern Taurids, both are active though late October into early November.
The motion of the radiant of the Northern Taurid meteors from mid-October through mid-November. The shower typically peaks around November 12th annually. Image credit: Stellarium
Specifics for 2015
This year sees the Moon reaching Full on Tuesday October 27th, just a few days before Halloween. The Taurid fireballs, however, have a few things going for them that most other showers don’t. First is implied in the name: the Northern Taurids, though typically exhibiting a low zenithal hourly rate of around 5 to 10, are, well, fireballs, and thus the light-polluting Moon won’t pose much of a problem. Secondly, the Taurid meteor stream is approaching the Earth almost directly from behind, meaning that unlike a majority of meteor showers, the Taurids are just as strong in the early evening as the post midnight early morning hours. As a matter of fact, we saw a brilliant Taurid just last night from light-polluted West Palm Beach in Florida, just opposite to the Full Moon and a partially cloudy sky.
A 2014 Taurid. Image credit and copyright: Brian who is called Brian
In stark contrast to the swift-moving Orionids from earlier this month, expect the Taurid fireballs to trace a brilliant and leisurely slow path across the night sky, moving at a stately 28 kilometre per second (we say stately, as the October Orionids smash into our atmosphere at over twice that speed!)
Ever since the 2005 event, the Northern Taurids seemed to have earned the name as “The Halloween Fireballs” in the meme factory that is the internet. It’s certainly fitting that Halloween should have its very own pseudo-apocalyptic shower. The last good return for the Northern Taurids was 2005-2008, and 2015 may see an upswing in activity as well.
Obviously, something interesting has to be occurring on Comet 2P Encke—the source of the two Taurid meteor streams—to shed the pea-sized versus dust-sized material seen in the Southern and Northern Taurids. With the shortest orbital period 3.3 years of all periodic comets known, the Taurid meteor stream—like Encke itself—follows a shallow path nearly parallel to the ecliptic plane.
Discovered in 1822 by astronomer Johann Encke, Comet 2P Encke has been observed through many perihelion passages over the last few centuries, and passes close to Earth once 33 years, as it last did in 2013.
What constitutes a ‘meteor swarm?’ As with many terms in meteoritics, no hard-and-fast definition of a true ‘meteor swarm’ exists. A meteor storm is generally quoted as having a zenithal hourly rate greater than 1000. Expect activity to be broad over the next few weeks, and the Taurid fireballs always have the capacity to produce the kind of brilliant events captured by security cams and dashboard video cameras that go viral across ye ole Internet.
Watching for fireballs is a thrilling pursuit. These may often leave persistent glowing meteor trails in their wake. We caught the 1998 Leonids from the dark sky deserts of Kuwait, and can attest to the persistence of glowing fireball trails from this intense storm, sometimes for minutes. Again, the 2015 Taurids aren’t expected to reach that level of intensity, though the ratio of fireballs to faint meteors will be enhanced.
The path of the stream isn’t fully understood, and that is where volunteer observations can come in handy. The International Meteor Organization is always looking for reports from skilled observers, as is the American Meteor Society (AMS).
The light curve of the suspected Taurid that hit the Moon on Nov 7th. Image Credit: NASA
There’s even been evidence for a recorded meteorite strike related to the northern Taurid fireballs back in 2015 on the dark limb of the Moon as well, a rare event indeed.
After a slow summer, Fall meteor shower activity is definitely heating up. And though 2015 is an off year for the November Leonids, we’re now almost midway between the 1998-99 outbursts, and the possibility of another grand meteor storm in the early 2030s. And another obscure wildcard shower known as the Alpha Monocerotids may put on a surprise showing in November 2015 as well…
More to come on that. Keep watching the skies, and don’t forget to tweet those Northern Taurid fireball sightings and images to #Meteorwatch!
-Got an image of a Northern Taurid fireball? Send ‘em in to Universe Today for our Flickr forum… we may just feature your pic in an after action round up!
Various meteorites from 2008 TC3.
Credit: P. Jenniskens, et. al. Click image for full description
Asteroids, meteors, and meteorites … It might be fair to say these rocks from space inspire both wonder and fear among us Earthlings. But knowing a bit more about each of them and how they differ may eliminate some potential misgivings. While all these rocks originate from space, they have different names depending their location — i.e. whether they are hurtling through space or hurtling through the atmosphere and impacting Earth’s surface.
In simplest terms here are the definitions:
Asteroid: a large rocky body in space, in orbit around the Sun.
Meteoroid: much smaller rocks or particles in orbit around the Sun.
Meteor: If a meteoroid enters the Earth’s atmosphere and vaporizes, it becomes a meteor, which is often called a shooting star.
Meteorite: If a small asteroid or large meteoroid survives its fiery passage through the Earth’s atmosphere and lands on Earth’s surface, it is then called a meteorite.
Another related term is bolide, which is a very bright meteor that often explodes in the atmosphere. This can also be called a fireball.
Let’s look at each in more detail:
Asteroids An artists impression of an asteroid belt. Credit: NASA
Asteroids are found mainly in the asteroid belt, between Mars and Jupiter. Sometimes their orbits get perturbed or altered and some asteroids end up coming closer to the Sun, and therefore closer to Earth. In addition to the asteroid belt, however, there have been recent discussions among astronomers about the potential existence of large number asteroids in the Kuiper Belt and Oort Cloud. You can read a paper about this concept here, and a good article discussing the topic here.
The asteroid Vesta as seen by the Dawn spacecraft. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA
Asteroids are sometimes referred to as minor planets or planetoids, but in general, they are rocky bodies that do not have an atmosphere. However, a few have their own moons. Our Solar System contains millions of asteroids, many of which are thought to be the shattered remnants of planetesimals – bodies within the young Sun’s solar nebula that never grew large enough to become planets.
The size of what classifies as an asteroid is not extremely well defined, as an asteroid can range from a few meters wide – like a boulder — to objects that are hundreds of kilometers in diameter. The largest asteroid is asteroid Ceres at about 952 km (592 miles) in diameter, and Ceres is so large that it is also categorized as a dwarf planet.
Most asteroids are made of rock, but as we explore and learn more about them we know that some are composed of metal, mostly nickel and iron. According to NASA, a small portion of the asteroid population may be burned-out comets whose ices have evaporated away and been blown off into space. Recently, astronomers have discovered some asteroids that mimic comets in that gas and dust are emanating from them, and as we mentioned earlier, there appears to be a large number of bodies with asteroid-like compositions but comet-like orbits.
How Often Do Asteroids Hit Earth?
Meteor Crater near Winslow, Arizona. Image credit: NASA.
While we know that some asteroids pass very close to Earth’s orbit around the Sun, we’ve been lucky in the history of humanity that we haven’t had a large asteroid hit Earth in the past several thousand years. It wasn’t until satellite imagery of Earth became widely available that scientists were able to see evidence of past asteroid impacts.
One of the more famous impact craters on Earth is Meteor Crater in Arizona in the US, which was made by an impact about 50,000 years ago. But there are about 175 known impact around the world – a few are quite large, like Vredefort Crater in South Africa which has an estimated radius of 190 kilometers (118 miles), making it the world’s largest known impact structure on Earth. Another notable impact site is off the coast of the Yucatan Peninsula in Mexico, and is believed to be a record of the event that led to the extinction of the dinosaurs 65 million years ago. You can see images of some of the most impressive Earth impact craters here.
These days, asteroid impacts are less of a threat. NASA estimates that about once a year an automobile-sized asteroid enters Earth’s atmosphere, creates an impressive fireball and disintegrates before ever reaching the surface. Studies of Earth’s history indicate that about once every 5,000 years or so on average an object the size of a football field hits Earth and causes significant damage. Once every few million years on average an object large enough to cause regional or global disaster impacts Earth. You can find more information about the frequency of impacts in this article from NASA.
Meteors, Meteoroids and Bolides
A bright meteor from September 21, 1994. Credit: John Chumack.
Space debris smaller than an asteroid are called meteoroids. A meteoroid is a piece of interplanetary matter that is smaller than an asteroid and frequently are only millimeters in size. Most meteoroids that enter the Earth’s atmosphere are so small that they vaporize completely and never reach the planet’s surface. When they burn up during their descent, they create a beautiful trail of light known as a meteor, sometimes called a shooting star.
Mostly these are harmless, but larger meteors that explode in the atmosphere – sometimes called bolides — can create shockwaves, which can cause problems. In February 2013 a meteor that exploded over Chelyabinsk, Russia shattered windows with its air blast. This meteoroid or bolide was estimated to be 18 meters (59 feet) in diameter. In 1908, a rocky meteoroid less than 100 meters in diameter is believed to have entered the atmosphere over the Tunguska region of Siberia in 1908 and the resulting shockwave knocked down trees for hundreds of square kilometers
How often is Earth hit by meteroids?
Chelyabinsk fireball recorded by a dashcam from Kamensk-Uralsky north of Chelyabinsk where it was still dawn.
Because of the Chelyabinsk meteor in 2013, astronomers have acquired more information about the frequency of larger meteors that hit Earth, and there is now a growing consensus that the Earth gets hit by bigger space rocks more often than we previously thought. You can read more about that concept here.
This video from the B612 Foundation shows a visualization of the location of 26 space rocks that hit Earth between 2000 and 2013, each releasing energy equivalent to some of our most powerful nuclear weapons. The B612 foundation says that a Hiroshima-scale asteroid explosion happens in our atmosphere on average once a year, but many are not detected because they explode high in the atmosphere, or because most of the Earth’s surface is water and even a large percentage of land is fairly uninhabited by humans.
Estimates vary of how much cosmic dust and meteors enter Earth’s atmosphere each day, but range anywhere from 5 to 300 metric tons. Satellite observations suggest that 100-300 metric tons of cosmic dust enter the atmosphere each day. This figure comes from the rate of accumulation in polar ice cores and deep-sea sediments of rare elements linked to cosmic dust, such as iridium and osmium.
But other measurements – which includes meteor radar observations, laser observations and measurements by high altitude aircraft — indicate that the input could be as low as 5 metric ton per day. Read more about this here.
For a documented list of bolide events, you can check out this page from JPL.
Meteorite A stunning slice of the Glorieta pallasite meteorite cut thin enough to allow light to shine through its many olivine crystals. Credit: Mike Miller
If any part of a meteoroid survives the fall through the atmosphere and lands on Earth, it is called a meteorite. Although the vast majority of meteorites are very small, their size can range from about a fraction of a gram (the size of a pebble) to 100 kilograms (220 lbs) or more (the size of a huge, life-destroying boulder). Meteorites smaller than 2mm are classified as micrometeorites.
Meteorites have traditionally been divided into three broad categories, depending on their structure, chemical and isotopic composition and mineralogy. Stony meteorites are rocks, mainly composed of silicate minerals; iron meteorites that are largely composed of metallic iron-nickel; and, stony-iron meteorites that contain large amounts of both metallic and rocky material.
Meteorites have also been found on the Moon and Mars and conversely, scientists have traced the origination of the meteorites found here on Earth to four other bodies: the Moon, Mars, the asteroid 4 Vesta, and the comet Wild 2. Meteorites are the source of a great deal of the knowledge that we have have about the composition of other celestial bodies.
How Often Do Meteorites Hit Earth?
On Feb. 28, 2009, Peter Jenniskens (SETI/NASA), finds his first 2008TC3 meteorite after an 18-mile long journey. “It was an incredible feeling,” Jenniskens said. The African Nubian Desert meteorite of Oct 7, 2008 was the first asteroid whose impact with Earth was predicted while still in space approaching Earth. 2008TC3 and Chelyabinsk are part of the released data set. (Credit: NASA/SETI/P.Jenniskens)
According to the Planetary Science Institute, it is estimated that probably 500 meteorites reach the surface of the Earth each year, but less than 10 are recovered. This is because most fall into water (oceans, seas or lakes) or land in remote areas of the Earth that are not accessible, or are just not seen to fall.
In short, the difference between asteroids and meteors all comes down to a question of location. Asteroids are always found in space. Once it enters an atmosphere, it becomes a meteor, and then a meteorite after it hits the ground. Each are made of the same basic materials – minerals and rock – and each originated in space. The main difference is where they are when they are being observed.
Mars! Martian meteorites make their way to Earth after being ejected from Mars by a meteor impact on the Red Planet. Image: NASA/National Space Science Data Center.
Mars is often referred to as the Red Planet. But its signature color is only skin-deep – or, I should say, dust-deep. Beneath its rusty regolith Mars has many other hues and shades as well, from pale greys like those found inside holes drilled by Curiosity to large dark regions that are the result of ancient lava flows. Now, researchers think we may have an actual piece of one of Mars’ dark plains here on Earth in the form of a meteorite that was found in the Moroccan desert in 2011.
Mars meteorite NWA 7034 (NASA)
Classified as NWA 7034 (for Northwest Africa) the meteorite is a 320-gram (11 oz.) piece of Martian basaltic breccia made up of small fragments cemented together in a dark matrix. Nicknamed “Black Beauty,” NWA 7034 is one of the oldest meteorites ever discovered and is like nothing else ever found on Earth.
According to a new study on a fragment of the meteorite by researchers from Brown University in Providence, Rhode Island and the University of New Mexico, Black Beauty is a 4.4-billion-year-old chunk of Mars’ dark crust – the only known piece of such to have landed on Earth.
While other meteorites originating from Mars have been identified, they are of entirely different types than Black Beauty.
The researchers used a hyperspectral imaging technique to obtain data from across the whole fragment. In doing this, the measurements matched what’s been detected from Mars orbit by NASA’s Mars Reconnaissance Orbiter.
“Other techniques give us measurements of a dime-sized spot,” said Kevin Cannon, a Brown University graduate student and lead author of a new paper published in the journal Icarus. “What we wanted to do was get an average for the entire sample. That overall measurement was what ended up matching the orbital data.”
In addition to indicating a truly ancient piece of another planet, these findings hint at what the surface of many parts of Mars might be like just below the rusty soil… a surface that’s been shattered and reassembled many times by meteorite impacts.
“This is showing that if you went to Mars and picked up a chunk of crust, you’d expect it to be heavily beat up, battered, broken apart and put back together,” Cannon said.
HiRISE image of dark terrain near Ganges Chasma (NASA/JPL/University of Arizona)
