Universe Today

Meteorites are natural objects that come from outer space and manage to survive both the impact pressure of the atmosphere and the actual impact on the ground below.

Meteorite impacts have punctured the Moon's surface, forming the craters we see there. They could have also formed similar craters here on Earth but these may have been eroded and covered by tectonic and volcanic activities through time.

People who are fascinated with meteorites are able to retrieve these objects by listening to accounts of witnesses who have spotted the meteorites on their way to the Earth's surface. A meteorite that is observed while still speeding Earthward through the atmosphere is known as meteor. If you see many of these in a minute or in an hour, then most likely, you're looking at a meteor shower.

Solitary meteors are often called shooting stars or falling stars. Specimens of meteorites that have been retrieved after being observed either by the retriever or someone else (as mentioned earlier) are dubbed "falls". On the other hand, those that are found through other means are aptly dubbed "finds".

The success in finding "falls" can be improved with the use of cameras dedicated to spotting them. For instance, the Pribram meteorite that fell in the Czech Republic in 1959 was first captured in photographs taken by a camera designed for this purpose. Through the images, the approximate location of the meteorites were determined.

"Finds" far outnumber "falls", with over 31,000 finds compared to only 1,000-plus falls. How is this possible? Well, here's the basic idea. If you know that a vast track of land is not abundant with rocks, the chances of finding one that is actually a meteorite may be high – especially if you know how a meteorite may look like.

This strategy was first proposed by Harvey H. Nininger when he set out to find meteorites in the Great Plains of the United States.

It is not common for people to retrieve a meteorite right after it falls to the ground. That is, if you're expecting to find a big chunk comparable to the crater it creates, you can forget about it. Most meteorites (or most of it) vaporize during impact.

This is the reason why Daniel M. Barringer, in his quest to prove that the Canyon Diablo crater was caused by a meteor, couldn't find a large chunk of meteorite that should have caused the 1.2 km wide and 170 m deep hole in the desert. His search for the missing fragment dragged for 27 years, to no avail.

Some people were lucky enough not having to wait that long. Dr. Frank Ciampi from Lorton, Virginia, USA, was able to retrieve a meteorite after it fell through the roof, through the fire wall, through the ceiling, and finally landing on the floor.

Here are some of the references from Universe Today for the article above.

Meteorite Smashes Through Roof of Doctor's Office (Video)

New Findings On Alan Hills Meteorite Point to Microbial Life

Meteorite May Hold Clues to Solar System Formation

Of course, you can also find more information at NASA. Hera are some links:
Meteor
Evidence Of Meteor Impact Found Off Australian Coast

Alternatively, you can also listen to an interesting episode about craters in Astronomy Cast.

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A meteorite came through the roof of a doctor's office in Lorton, Virginia, USA. No one was hurt, but a hole was punched through the roof and ceiling. "It came through the roof, through the fire wall through the ceiling and hit the floor," said Dr. Frank Ciampi in this video from WUSA TV. When he heard the noise, he thought a set of bookshelves had fallen down. The rock broke into pieces, but put together are about the size of a tennis ball. A planetary scientist at the Smithsonian Institution's Museum of Natural History, Cari Corrigan, confirmed the rock is a meteorite. She says the meteorite weighs just over a half pound (.22 kg) and was probably traveling about 350 kph (220 mph) when it struck the building.
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Campo del Cielo is the area between the Argentinian provinces of Chaco and Santiago del Estero where a large number of iron meteorites have been found. The area is about 1,000 km northwest of Buenos Aires. The meteor field is 3 km by 20 km and contains at least 26 different impact craters. The largest of which is 115 m by 91 m. The best estimate of the age of the craters is between 4,000 and 5,000 years. The craters were first discovered by Europeans in 1576, but had been known and worshiped by aboriginal Indians for hundred of years before that. The craters and the area around contain many fragments of what is believed to be a single iron meteorite. The total weight of the pieces recovered exceeds 100 tons. That makes the meteorite the heaviest one ever recovered on Earth. The largest fragment, consisting of 37 tons, is the second heaviest single-piece meteorite recovered on Earth, after the Hoba meteorite.

Campo del Cielo was found by the Spanish in 1576. The governor of the local province sent men to look for it after hearing that it was the place where the natives found the iron that they used in their weapons. Whether he wanted to deprive the Indians of their source or needed iron for his soldiers weaponry is unknown. The expedition found a large mass of metal protruding out of the soil. They assumed it was an iron mine and brought back a few samples, which were described as being of unusual purity. The governor documented the expedition in Seville. The report was quickly forgotten as were many reports from functionaries of the time. There were two additional ventures to Camp del Cielo. In 1774, Don Bartolome Francisco de Maguna rediscovered the iron mass which he called "the Table of Iron". Maguna thought the mass was the tip of an iron vein. The next expedition, led by Rubin de Celis in 1783, used explosives to clear the ground around the mass and found that it was probably a single stone. Celis estimated its mass as 15 tons and abandoned it as worthless. He himself did not believe that the stone had fallen from the sky and assumed that it had formed by a volcanic eruption. However, he sent the samples to the Royal Society of London. Those samples were later analyzed and found to contain 90% iron and 10% nickel and other trace elements and was assigned to a meteoric origin. The use of the meteorites for weapons and the blasting make it impossible to know the exact size of the original meteorite.

The Campo del Cielo crater field contains at least 26 craters, as I said earlier. At least two of the craters contained thousands of small iron pieces. Such an unusual distribution suggests that a large body entered the Earth's atmosphere and broke into pieces which fell to the ground. The size of the main body is estimated as larger than 4 meters in diameter. The fragments contain an unusually high density of inclusions for an iron meteorite, which might have facilitated the disintegration of the original meteorite. Samples of charred wood were taken from beneath the meteorite fragments and analyzed for carbon-14 composition. The results indicate the date of meteorite to be between 4,200 and 4,700 years ago, which would be about 2,200–2,700 years B.C. The average composition of the Campo del Cielo meteorites is 6.67% Ni, 0.43% Co, 0.25% P, 87 ppm Ga, 407 ppm Ge, and 3.6 ppm Ir, with the rest being iron.

Campo del Cielo is an awesome impact event. Here on Universe Today we have a great article about the 10 most impressive craters on Earth. Here is an article about Campo del Cielo. Astronomy Cast offers a good episode about craters that is very detailed.

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Early Nov. 18th, eyewitnesses reported an explosion in the atmosphere above Colorado, Utah, Wyoming and Idaho in the western United States. Some said the fireball "turned night into day" and produced shock waves that shook the ground when it exploded just after midnight Mountain Standard Time. Infrasound recordings of the blast suggest a small asteroid hitting Earth's atmosphere and exploding with an energy of 0.5 to 1 kiloton of TNT. As the sun rose in the morning, remnants of the explosion were visible as noctilucent clouds over the region. The best video of the extremely bright event was just recently released, from the University of Utah's Eccles Observatory.
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A network of time-lapse cameras set up in the Nullarbor Plain desert of Western Australia has allowed researchers to track a fallen meteorite to the ground, and enabled them to determine its original orbit and parent body. The meteorite has a composition different than that of other meteors, leading researchers to believe that it originates from a different parent body than most meteorites that impact Earth. The Desert Fireball Network, a project coordinated by the Imperial College of London, was able to track the meteor when it entered the atmosphere, giving researchers an impact location and information on where it originated. Read more…

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A possible meteorite fall near in northern Latvia on Sunday left a crater approximately 20 meters (66 feet) in diameter and 10 meters (33 feet) deep. UPDATE: Many reports now say the impact was a fake; The Bad Astronomer says "shovel" marks were found around the perimeter of the crater; additionally, a burning impactor is highly unlikely (see video below). And here's an article from the Associated press. , and another from Yahoo news, where a phone company in Latvia admits the "crater" was a publicity stunt.

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Three golf ball-sized fragments have been found from a meteorite that created a brilliant fireball seen over Ontario, Canada on September 25, 2009. The first meteorite fragment recovered did some damage to the windshield of a Nissan Pathfinder, and now two other fragments have been found on nearby properties. The meteor made headlines initially because it was captured on video by Western’s Southern Ontario Meteor Network (SOMN) on seven of its ‘all-sky’ cameras. The brightness was estimated to be approximately 100 times brighter than a full moon.
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If conspiracy theorists have so-called damning evidence that the lunar landings were portions of an elaborate hoax, the collection of moon rocks is one very tangible proof that can sufficiently counter all those arguments. Nowhere on Earth can you find rocks having the same characteristics as those brought by the Apollo missions.

You don't have to be a science genius to see that moon rocks look different. Their peculiar appearance, particularly the presence of tiny craters, can be attributed to the heavy dose of meteoroid impacts the moon's surface receives every minute. Since the Earth has an atmosphere, while the Moon does not, such tiny craters are not as common in rocks found here. Small meteoroids that enter the atmosphere easily disintegrate after burning.

Another thing is that, Earth is mainly protected from high energy cosmic rays by its magnetic field. The moon, having a much weaker external magnetic field, does not have the same level of protection. As such, high energy cosmic ray bombardment on the lunar surface can produce isotopes that aren't common here on Earth. Such rare isotopes are found in the Moon rocks.

To simplify, it's more difficult to replicate the same conditions on the Moon to produce such rock characteristics than to simply go there. Furthermore, the Moon rocks were distributed to more than a hundred laboratories in different countries all over the world. These labs have conducted research and produced scientific papers out of them.

It would be virtually impossible to pay a great number of respectable institutions worldwide just to corroborate a grand hoax.

40 years after the Apollo missions collected moon rocks, scientists have still been able to extract new information from them.

About a month ago (August 2009), University of Cambridge's Materials Chemistry Professor Derek Fray and his team presented a paper showing how oxygen can be extracted from them. Fray revealed that three tons of Moon rocks would be required to produce one ton of oxygen using three 1-meter high reactors which he and his team designed. These findings make colonization of the moon all the more possible.

Still, there is even more information that scientists hope to unravel. Hopefully, for example, further studies conducted on moon rocks can reveal more about extremely large meteorite impacts on Earth. This story has been hidden by our planet's active geology … but not by the moon. The huge craters on the lunar surface is evidence that such a violent event occurred in the past.

A piece of lunar rock might just be enough to tell us that story.

If you want to read more about Fray's device that extracts oxygen from Moon rocks, we've got exactly what you need here in Universe Today. Just click on that link. We also have an article featuring secrets that may be revealed from moon rocks even 40 years since the Apollo missions brought them to Earth.

Here's an article from NASA that debunks the hoax theory using the Moon rock arguments. Another article about Moon rocks from the same site.

Episodes about the moon from Astronomy Cast. Lend us your ears!

Shooting Lasers at the Moon and Losing Contact with Rovers
The Moon Part I

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A brilliant fireball seen over Ontario, Canada on September 25, 2009 was captured by seven all-sky cameras of the University of Western Ontario's Southern Ontario Meteor Network (SOMN.) The fireball was seen widely by observers throughout southern Ontario and adjacent areas. The fireball was first detected by Western's camera systems at an altitude of 100km, and moving southeastwards at 20.8 km/s. From the data collected, the researchers believe the meteoroid was initially about a meter wide, or about the size of a child's tricycle. At its brightest, the fireball was approximately 100 times as bright as the full moon.
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The first asteroid to have been spotted before hitting Earth, 2008 TC3, crashed in northern Sudan one year ago on October 6. Several astronomers have been trying to piece together a profile of this asteroid, pulling together information from from meteorites found at the impact site and the images captured of the object in the hours before it crashed to Earth. “We have a gigantic jigsaw puzzle on our hands, from which we try to create a picture of the asteroid and its origins,” said SETI Institute astronomer Peter Jenniskens, who worked at the crash site, "and now we have with a composite sketch of the culprit, cleverly using the eyewitness accounts of astronomers that saw the asteroid sneak up on us.” Their description? 2008 TC3 looked like a loaf of walnut-raisin bread.
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It's amazing what a rover can find laying by the side of the road. The Mars Exploration Rover Opportunity has found a rock that apparently is another meteorite. Less than three weeks ago, Opportunity drove away from a larger meteorite called "Block Island" that the rover examined for six weeks. Now, this new meteorite, dubbed "Shelter Island," is another fairly big rock, about 47 centimeters (18.8 inches) long, that fell from the skies. Block Island is about 60 centimeters (2 feet) across and was just 700 meters (about 2,300 feet) away from this latest meteorite find. At first look, the two meteorites look to be of a similar makeup; Opportunity found that Block Island was is made of nickel and iron.

This image was taken during Oppy's 2,022nd Martian day, or sol, (Oct. 1, 2009).

See below for a 3-D version of this image created by Stu Atkinson.
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It may seem that spotting a shooting star is a rarity. Some people even feel extremely lucky when they spot one and instinctively make a wish. Actually, shooting stars or meteors hitting earth territory occur by the millions … every single day.

Before we proceed, let's define some terms first. Because they all sound very similar, the terminology can be confusing.

First, a meteoroid is any inanimate body in space that can measure between the size of a particle of sand to a boulder. The moment it enters the Earth's atmosphere, it burns up (due to friction) and forms a streak of light. At this point, it is now called a meteor. Finally, if it manages to reach the ground (many don't – they simply disintegrate), it is then called a meteorite.

Here, we will focus on all meteors hitting Earth. That means, we will include both those that enter the Earth's atmosphere and those that end up reaching the ground.

The shooting stars that we see at night (perhaps we can start calling them meteors now) occur in the mesosphere, some 75 km to 100 km above us. As they go through their high speed plunge toward the bottom of the atmosphere, they ignite. In most cases, they disintegrate and never reach altitudes lower than 30 km above sea level.

The meteors that disintegrate are relatively small – about the size of pebbles. Larger ones don't appear as streaks of light. Instead, they resemble fireballs. These are the ones that can survive the burn and reach the ground. Remember, you're supposed to call them meteorites now, right?

Since meteorites have already undergone extensive burning in the atmosphere, you can be sure their size will have substantially reduced when they hit the ground. As such, most meteorites that have been found are quite small.

Another reason for this is that, in most cases, meteors that are too large explode in the atmosphere. Therefore, it is only their debris that eventually reach the surface. In very rare instances, some large ones manage to remain intact. The meteorite found in Grootfontein, Namibia weighs 60 metric tons, and is the largest ever to be found.

You don't have to be lucky to spot a meteor. In fact, if you know when to watch for them, you can spot over a hundred in one night. It would be difficult to count them all though. The event wherein meteors hitting Earth in great numbers at a given time and in a particular region in the sky is called a meteor shower.

One such well-publicized event just happened two months ago. The Perseids meteor shower is visible in the middle of July of every year. So if you want to make hundreds of wishes in one night, just drop by this website to be updated whenever a meteor shower is expected.

We have some articles in Universe Today that are related to meteors hitting earth. Here are two of them:

• 2009 Perseid Meteor Shower – Double Peaks This Year!
• Meteor Shower Alert on March 22! Camelopardalids and March Geminids Arrive…

Meteor-related articles brought to you by NASA, here are the links:

• Meteor
• The Perseids are Coming

Tired eyes? Let your ears help you learn for a change. Here are some episodes from Astronomy Cast that just might suit your taste:

• Meteor Showers. Yes, the sky is falling.
• Getting Started in Amateur Astronomy

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One of the great things about the Mars Exploration Rovers is that we get to see these scrappy little vehicles ramble across the surface of Mars, and watch science in action. Case in point: the meteorite found by Opportunity, dubbed "Block Island." Scientists are debating all sorts of things about this watermelon-sized rock. How old is it? What is it made of? Where could it have come from? But not only are we learning about this alien rock, we're also learning about the Red Planet itself and its environmental history.

See below for a new 3-D version of Block Island created by Stu Atkinson.
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