If a meteorite the size of a pea landed on the road in front of you, what sort of impact would it have?
How big would it have been when it entered the atmosphere and would it have been visible during the day?
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$\begingroup$ There's still the mystery of "tiny holes in glass". Like this - these holes - normally blamed on irresponsible use of airguns - were found in surfaces where the airgun use would be very unlikely, e.g. very high floors of skyscrappers. Especially considering the first 2mm or so of the hole seems melted. A somewhat plausible suspicion is micrometeorites. $\endgroup$ – SF. Nov 24 '15 at 9:25
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$\begingroup$ The impact could be a devastating sequence of events that lead to the destruction of all life as we know it. If the rock is carrying some form of life at least :) scientificamerican.com/article/were-meteorites-the-origi $\endgroup$ – ThePlanMan Nov 24 '15 at 16:11
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Asteroids, Meteorites, and Comets has this to say:
Meteorites between the size of a grain of sand and about four inches (10 cm) in diameter create a bright light trail and usually burn up in the atmosphere. Meteorites between about four inches (10 cm) and 3 feet (1 m) may survive the burning of entry to land on the Earth's surface. Meteorites larger than a meter or two usually detonate in the upper atmosphere, releasing energy equivalent to several thousand tons of TNT, though they may make it to the surface.
It goes on to say meteorites of this size lose about 30 to 60 percent of their mass as they fall, so a pea-size one wouldn't have been much bigger when it started - something like an iron marble, which would be likely to survive entry. Unless what landed was only a fragment of something bigger, if that was the case it could have come from something huge. An example here (section 9) cites 2008 TC3, of 104 to 105 kg, of which only 280 pieces totalling 4 kg were recovered.
As they pass through the air, meteoroids lose almost all their speed (unless they are really big). Most weigh less than 2 grams when they hit the atmosphere, and yet they create a bright streak of light kilometers long, visible to us on the ground dozens of kilometers away. That is the energy involved, but it is all spent high in the atmosphere, heating it and the air it passes through glowing hot. That friction shortly slows the object to its terminal velocity. A meteorite starts at 11 to 70 km/s (25 000 to 160 000 mph), slows to 2 to 4 km/s (4500 to 9000 mph) by the time it stops glowing, and slows further to 0.1 to 0.2 km/s (200 to 400 mph) before atmospheric drag balances the pull of gravity, and then it stays at that speed.
For comparison, an average bullet is travelling about twice as fast when it leaves a gun. Kinetic energy rises with the square of velocity, so the pea meteorite would have about a quarter of its energy, if it was iron, meaning it would be about the same size and density. If it hit a road, it would put a small pit in the surface of it maybe, barely noticeable. A stone meteorite that size could have maybe a third of the energy of an iron pea one. You wouldn't want to be hit by it, but it probably wouldn't kill you.
This was a credible report of a small boy being hit possibly by a meteorite fragment, as other fragments were found around. It only gave him a gash that needed 3 stitches, so probably not quite pea size. Here is an article on a bunch of fragments falling in a Chicago suburb. Some of them were large enough to do significant damage.
answered Nov 24 '15 at 5:31
