Would This Meteor Make a Huge Crater?

Here is a fun little video to promote Eden TV's Science Month.

I think a meteor this size would do more than just crush a car. Let's do a simple calculation.

How Big?

Here is a frame from the end of the video.

I am really not sure about the type of car this smashed. If I give it a rough estimate, the meteorite seems to be approximately a sphere with radius 1 meter. But what really matters is the mass. The mass depends on the density. This site puts the density of stoney type meteorites around 3.5 g/cm³ and iron type around 7-8 g/cm3.

Looking online at meteorites (I am absolutely a non-expert when it comes to meteorites - just to be clear), the Eden TV meteorite (Edeneorite) kind of looks like an iron meteorite. But there is a case of a meteorite hitting a car. The famous Peekskill meteorite.

The Peekskill meteorite was a stoney type and the Eden TV rock looks partially similar - so let me go with a density of 3.5 gm/cm³. This would put the mass of the rock at 1.47 x 10⁵ kg (16 short tons). Compare that mass to the mass of some type of SUV (like the Toyota Highlander) which only has a mass of 1,800 kg.

Just placing a meteorite this massive on an SUV would probably crush it.

How Much Energy?

This is the real question. How much kinetic energy would a rock this large have when it hit the ground? First, some assumptions:

• The rock started SUPER far from the Earth and at rest (clearly not true).
• There was no energy lost due to the atmosphere (again, not true).
• The mass of the rock didn't change as it went through the atmosphere (yup, this is wrong too).

So, why do I make three wrong assumptions? Do three wrongs make a right? Well, each one of these assumptions makes the problem much easier than if I didn't assume them. Also, in the end something could happen. What if I get a meteorite energy around the same value as a baseball. Or maybe I find that the meteor has the same energy as blast from the Death Star. In either of these cases, the value will be wrong but still say something about the real energy. Ok?

Since we are dealing with energy, we obviously need to use the work-energy principle. Let me take the rock plus the Earth as the system. In that case, I need two positions. One with the rock far away and one with the rock on the surface of the Earth.

Here there are two types of energy. There is kinetic energy and gravitational potential energy. Since I am dealing with objects far from the surface of the Earth, I need to use the real form of the gravitational potential energy.

G is the gravitational constant and M_E is the mass of the Earth. The starting distance (R_far) is very large so that the second term in the potential energy is almost zero. I could solve for the final speed of the rock, but I just need the energy. Putting in values for the stuff I know, I get a final kinetic energy of 9 x 10¹¹ Joules.

Fine, that is a big energy. But how big? The Wikipedia page on nuclear weapon yeilds lists energies in terajoules. So, my estimate for the energy of this meteor impact would be around 0.9 TJ and be smaller than the estimated 50-60 TJ of the early nuclear weapons. However, in terms of TNT equivalent this would be about 200 tons of the explosive.

Even if I overestimated by a factor of 100, this would still be 2 tons of explosives. I am fairly certain that 2 tons of TNT would leave a crater with no sign of the vehicle it crashed into.

One More Comparison

What is something that could possibly smash that Eden TV vehicle like that? What if I dropped a similar vehicle from about 10 meters? Surely that would smash both cars up quite a bit? How much energy would be in the dropped car right before it collides? For this calculation, I can use the simple form of gravitational potential energy.

Using a dropped car mass of 1,800 kg the car would have 1.7 x 10⁶ Joules of energy. This would be equivalent to 3.8 x 10^-4 kg 0.4 kg of TNT explosives (Wikipedia page on TNT equivalent). Big difference.

In the end, I think Eden TV could have picked a more realistic looking meteorite. Or maybe that was the point. Put up a video with something that inspires people to explore this interesting question.