Employees in the News. Emergency Management. Survey Manual. Meteorites are fragments of rock or metal that fall to Earth from space. They are very rare, but many people find unusual rocks or pieces of metal and wonder if they might have found a meteorite. These tips for identifying a meteorite were adapted from this excellent guide from the University of New Mexico Meteorite Museum. Please refer to their site for additional information.
Always keep in mind that rocks and minerals must be examined in person for proper identification. For suggestions on where to do that, see: Can you identify my rock or mineral?
A spectacular geological event took place on the Atlantic margin of North America about 35 million years ago in the late part of the Eocene Epoch. Sea level was unusually high everywhere on Earth, and the ancient shoreline of the Virginia region was somewhere in the vicinity of where Richmond is today fig.
Tropical rain forests covered the On a clear night scores of meteoroids streak across the sky. When these meteoroids hit the Earth as meteorites they range in size from pebbles to the 34 ton Ahnighito meteorite that the American explorer Admiral The reported gold contents of meteorites range from 0.
Gold is siderophilic, and the greatest amounts in meteorites are in the iron phases. Some of this imagery is available through internet portals, or the operators can be reached by email. Infrasound Infrasound refers to very low frequency noise, which can travel long distances and is useful for narrowing down the location of an event like a meteorite fall.
No public sources of infrasound data are currently available. Finding meteorite falls in weather radar imagery requires practice and patience. Fortunately the software and data are freely available. Features Signifying a Meteorite Fall Meteorite falls are often but not always linear features, with the long axis often aligned in the direction of ambient winds. Meteorite falls appear in radar imagery after the fireball has gone out, and after meteorites have sufficient time to fall from the fireball terminus roughly 20 km high down to where the radar can detect them approximately 10 km and lower altitudes.
This normally takes about 2 minutes to occur. Falling meteorites then appear at or near the site identified by eyewitnesses or the other sources named above. Meteorites are size-sorted in their fall from the fireball terminus, with large meteorites falling fastest and smaller ones requiring a longer time to reach the ground.
In most meteorite falls, the first meteorites show up on radar 90 seconds to 2 minutes after the fireball terminus, and the last and smallest meteorites disappear from radar about 10 minutes after the event. There are several types of radar data products, but the two most useful for finding meteorites are "Reflectivity" and "Velocity". Reflectivity data show where radar pulses reflect off of falling meteorites Figure 2.
Figure 2: The Mifflin, WI meteorite fall radar map. But if you don't want to take the risk of finding something that could theoretically be confiscated in the future, you're better off searching on privately owned land. Get permission to do so. Step 2. Pick a good spot In a world full of rocks, narrowing your search is key. The best hunting grounds are large, barren expanses where a dark rock — meteorites tend to be blackish — is easy to spot.
Deserts, such as Southern California's Mojave Desert, and icy regions, such as Antarctica, are ideal. Within the Mojave or another desert, ancient, dry lake beds are ideal places to search, because their surfaces have likely been exposed for millennia.
According to O. You can also search in "strewn fields," or zones where meteorites from a single space rock were dispersed as it broke up during atmospheric entry. Since , thousands of stony meteorites have also been recovered in what appears to be two overlapping strewn fields in Gold Basin, Ariz. Lastly, the Great Plains is an area with scant terrestrial rocks, so out-of-this-world ones come in higher proportions. More than one meteorite has been found in a farmer's rock pile, or propping open a screen door.
Step 3. Search for new arrivals Some space rock hunters aren't content to simply look for long-lost meteorites. For folks like Robert Ward, a professional meteorite hunter who last month found a piece of a meteor that was seen crashing through Earth's atmosphere above California the day before, the thrill is finding new arrivals.
Furthermore, when a newly fallen meteorite can be matched with the trajectory of the meteor that deposited it, this enables scientists to determine both its mineral content and what part of space it originated from. 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. 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.
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