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Most meteoroids burn up in the atmosphere, so they don't impact the Earth's surface. Factors that seem important include:

  • size and mass of the meteoroid
  • angle of meteoroid's path through the atmosphere
  • latitude where meteoroid enters Earth's atmosphere
  • speed of meteoroid relative to Earth's movement

Are there other factors that are needed to calculate if a meteoroid will burn up in the atmosphere? How do we calculate if a meteoroid will completely burn up in the atmosphere?

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  • $\begingroup$ time of day is allso important,if it falls in the morning one need to add the speed of earth and if it falls in the evening one need to subtract the speed of earth. $\endgroup$ – trond hansen Jul 9 '17 at 16:26
  • $\begingroup$ I'm sure you could apply Buckingham Pi theorem to derive such an answer. $\endgroup$ – BarocliniCplusplus Jul 9 '17 at 20:50
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The density & composition of the meteoroid would be important.

There are three main types of meteoroids:

  • Iron
  • Stone, &
  • Iron-Stone

Iron meteoroids are dense & would be somewhat resistant to burning up.

Stone meteoroids are composed of grains of material. The composition of these meteoroids is 75-90 percent silicates. They tend to resemble terrestrial rocks.

Iron-stone meteoroids contain approximately equal amount of iron and stone material.

Another factor to consider is the shape of the meteoroid. A meteoroid that is rounded will have better streamlining properties that a meteoroid that is more angular or elongated in shape. Being more streamlined, less of the meteoroid will be exposed to burning air as it travels through the air at high speed. Also, the more streamlined the meteoroid the more likely one aspect will be exposed to high heating than a meteoroid that is more angular and rotating/tumbling as it travels through the air.

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In order to calculate when and how quickly burnup happens, one needs to understand the process of burnup first.

When an object from space enters an atmosphere, this happens at orbital speeds, which at the rest-frame of the atmosphere corresponds to very high mach-numbers. For the space-shuttle this was around 30 and is more or less the lowest attainable mach number coming from low earth orbit (LEO). If one takes a look at the Mach numbers that meteoroids achieve (as you correctly stated, that depends on the latitude, and day/night) i.e. the published numbers from the Swedish fireball network the Mach numbers can reach and surpass ~100.

I'm mentioning the Mach number, because the shock heating that results from the supersonic atmospheric entry is a strong function of it. As soon as it gets hot inside of the shock, where the meteoroid is sitting (several thousand K) the rock is evaporating into the atmosphere. That's a process that is well understood, and the main uncertainties are the Mach numbers.

Break-up can occur during atmospheric entry, as the turbulent fluctuations around the shock are very strong and can cause the meteoroid material to rupture. This is strongly depending on what the meteoroid is made of (think how an icy meteoroid will rupture much more easily than one made of pure iron) and is thus intrinsically unknown.

After breakup the surface area of the fragments is much higher than before, which causes evaporation to go much quicker, and the same process as above starts over again, until the meteoroid evaporates completely or crashes into the Earth.

Thus, we cannot reliably predict of a meteoroid will burn up or not. However guesstimates are possible based on the size of the object.

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