Answers

 

1. How can you tell a meteorite from a normal rock?

Well, it’s not a big problem when the meteorite is fresh. Due to frictional heating as it travels at high speed through the atmosphere the outer surface of the meteorite melts. This melted material is swept off the back of the meteorite during most of its flight, but as the objects slows it freezes onto its outer surface, forming a thin, black layer known as “fusion crust”. The sample of the Chelyabinsk meteorite below exhibits a beautiful fusion crust layer, that even shows flow lines formed when the melted material was being swept away from the stone during its atmospheric flight.

Cheljabinsk_meteorite_fragment

But things get a bit more tricky for meteorite “finds”, those samples that were not observed to fall and may have become quite weathered. The Meteorite Market website provides some clear information about the sorts of features that help to tell a space rock from a terrestrial one.

2. Where are the best places to find meteorites?

Unfortunately, the United Kingdom is not a good place to find meteorites, mainly because we have plenty of terrestrial rocks lying about to confuse things. Even if you find a piece of metal-rich material it is unlikely to have come from space and more likely to be related to our long industrial heritage. The best places to search for meteorites turn out to be deserts, both hot and cold. The Catch a Shooting Star website has all the details, just follow this link to “Hunting for Meteorites“.

3. How old are meteorites and how do we know?

Meteorites are the oldest objects you can handle. in fact objects in meteorites known as calcium aluminium-rich inclusions or CAIs for short, are used to date the age of the Solar System at 4,567 million years old. Further details can be found on this site, just follow the link to “How old is the Solar System“.

4. What is a meteorite?

A meteorite is a piece of natural space debris that survives its entry through the atmosphere and lands on Earth.

5. Where do meteorites come from?

Most meteorites are fragments from small asteroids that originated in the asteroid belt located between the orbits of Mars and Jupiter. However, we also have meteorites that came from the Moon and Mars.

6. What are meteorites made of?

Meteorites can look pretty much like rocks that you would find on Earth. However, the most common types contain metal that you don’t find in terrestrial rocks and some meteorites are made of pure metal. So meteorites are often divided into three types: stones, irons and stony-irons.

7. How often do meteorites land on Earth?

Meteorites arrive on Earth all the time, but most of them go unwitnessed and either fall into the sea or land in an under populated area. However, most years about five or six meteorites are witnessed during their atmospheric entry and then material is collected from the Earth’s surface. Estimates of how much space material arrives on Earth vary wildly, but a lower limit would be about 100, 000 tonnes a year.

8. How big are they?

Meteorites come in a range of sizes from a fraction of a millimetre to many metres. The largest intact meteorite is the Hoba meteorite which was found in Namibia in 1920 and measures approximately 1m x 3m and weighs about 60 tonnes. The Chelyabinsk meteorite that exploded over Russia in February is estimated to have been 17 metres in diameter and to have weighed 12,000 tonnes, which is heavier than the Eiffel tower!

9. How much could you expect to pay for a meteorite?

Meteorites are rare and precious objects so they are collected and traded by both enthusiasts and professional dealers. At the low end one could pay 1$ to2$ per gram for a weathered “ordinary chondrite”. At the other end of the scale a meteorite from the Moon or Mars will fetch as much as $2000 a gram. It is not uncommon for a fist-sized ~300g specimen Martian or Lunar meteorite to fetch well over half a million dollars!

10. What’s the risk that planet Earth will be wiped out by a meteorite?

Planet Earth was in fact formed from collisions between small asteroids at the birth of the solar system. However, there is now no chance that an asteroid, even a very big one could destroy the Earth, it’s just too big. Large asteroids of the size that killed the dinosaurs (~10km diameter) have only hit the Earth a few times in the last 600 million years, so we are pretty safe.

11. Did the dinosaurs really get wiped out by a meteorite?

There seems little doubt that a major mass extinction at the Cretaceous-Tertiary boundary 66 million years was caused by a meteorite impact into the area now occupied by the Yucatan peninsula in Mexico. The buried impact structure, known as the Chicxulub crater, is about 180 km in diameter.

12. What’s the difference between an asteroid and a meteorite?

An asteroid is a rocky object that orbits in space whereas a meteorite is a piece of space debris that survives atmospheric entry and lands on Earth. In 2008 a 4m diameter asteroid 2008 TC was tracked before entry and exploded over Sudan and pieces that were recovered were given the name Almahata Sitta.

13. What’s the difference between a shooting star and a meteorite?

A shooting star is another name for a meteor. These are small grains of space dust that burn up in the upper atmosphere at heights of about 120 km above the Earth. A meteorite is a piece of natural debris that makes it to the Earth’s surface.

14. What is the difference between a meteor and a meteorite?

Same answer as Q.13.

15. What can we learn from meteorites?

Meteorites are extremely varied and provide a wealth of knowledge about the origin and evolution of the Solar System. They are the oldest objects you can touch. They are 4,567 million years old! Some even contain dust that predates the Solar System. Almost everything we know about the origin of the Earth comes from the study of meteorites?

16. Have traces of life ever been found in a meteorite?

No, but some meteorites do contain amino acids the building blocks of life.

17. What percentage of meteorites that land on Earth are recovered?

Unfortunately it’s only a tiny percentage. You need the right conditions to find meteorites. Hot and cold deserts are best.

18. Where are the best places to find meteorites?

Antarctica and hot deserts such as the Sahara are the best places to locate meteorites. The American search for meteorites in Antarctica alone has already found more than 20,000 samples.

19. Do meteorites fall on the Moon and other planets?

Yes, there are named meteorites brought back from the Moon and official meteorites located on the surface of Mars by rovers.

20. Do meteorites hit satellites?

Yes, this is a big problem. In fact when the Earth passes through a known stream of cosmic dust safety measures have to be taken to protect satellites.

21. Why should the general public be interested in meteorites?

Meteorites tell us about how the Solar System formed and about the origin of life on Earth. They also pose a potential hazard as seen in the case of the Chelyabinsk meteor strike.

22. Why is it important to study meteorites?

Not only do meteorites help us to understand our own solar system but they also contain information about stars that preceded our own Sun.

23. What motivates scientists to study meteorites?

Lots of reasons really. Meteorites are the ultimate rocks. They are the oldest, most fascinating objects you could ever hope to handle.

24. Why are meteorites exciting?

These exciting rocks hold so much information about the origins of our Solar System, our Earth and even perhaps how life formed.

25. What sort of analysis can you do on meteorites?

A vast range of techniques are used to analyse meteorites. In fact many important analytical breakthroughs have come about as a result of meteorite studies.

26. Why did the media get so excited by the Russian meteor strike?

The fall of the Chelyabinsk meteorite was a once in a lifetime event. Not only that but it was fully recorded on CCTV and dash cams. In addition, for the first time we saw that a meteor strike was a potentially dangerous event.

27. How could you tell a meteorite from a normal rock?

It can be tough but there are a few clues. A meteorite has a thin dark outer layer called a fusion crust. It may contain metal and may have a distinctive sculptured surface. The most common type known as ordinary chondrites contain glassy spheres known as chondrules.

28. How many people are killed by meteorites each year?

None. As far as we know there has never been a fatality as a result of a meteorite.

29. Where can you go meteorite hunting?

The best place is North Africa in particular Morocco. There are also lots for sale on eBay!

30. Can meteorites be used for anything useful?

Meteoritic iron was used by a range of native peoples for axes and harpoons. Meteorites are traded for often large amounts of money. But the most useful aspect about meteorites is that they can help us to better understand how the Solar System in which we live.

Scientist