Meteorite question: serious answers only please!?

Question

How big would a meteorite have to be to be and how fast would it have to travel to penetrate pack ice over a kilometre thick and still pass through about 3 kilometres of sea water to impact the sea bed and leave a crater about 235.6km across and approximately 639.97km in length. I am assuming it hit at a low angle. I f you have information and a website to support it then please share it with me. I am working on a theory that could change the way the world thinks of the 3 greatest events in the history of the world.

thank you Garon.

Answer 1

The trouble here is that the momentum of the meteorite is dependent on its mass, as well as its velocity, along with the angle of impact. The composition of the meteorite is also important, as more or less of it will burn away in the atmosphere as it enters, resulting in different pre-entry and moment-of-impact masses.

Given that you have a specific crater size, that should help with the composition problem; all you really want is the amount of energy released at the moment of impact.

Rick Robinson's First Law of Space Combat states that "An object impacting at 3 km/sec delivers kinetic energy equal to its mass in TNT." The mass and velocity together equal the damage done by an equivalent mass of TNT--that's one "Rick" of damage. The formula for the number of Ricks of damage is:
Ricks = (0.5 * V^2) / 4.5e6
Where V is the velocity in m/s.

Since the median impact velocity on Earth is about 20 to 25 km/s, let's assume the velocity of the incoming meteor is about 25 km/s, for easy math.

How big a bang are we talking about? Well, an approximate area (very approximate!) of the crater you describe is 150,000 square kilometers. Equating that to the blast area of effect for a nuclear weapon turns out to be close to a 6,000 megaton device.

So, we're after a 6,000 megaton impact (not counting the sea ice and water!) at ground level. We've already decided on 25 km/s for the impact velocity, so let's see how many Ricks that is.

(.5 * (25000)^2)/4.5e6 = 69.444 Ricks

So, with 6,000 megatons of TNT as our target value, the mass of the object at impact must be around...

6,000,000,000 tons / 69.444 Ricks = 86,400,000 tons.

Which means, using:
Ma = 1.47e4 * (Ra^3)
where:
Ma = mass of asteroid (kg)
Ra = radius of asteroid (m)
...that the asteroid is about 370 meters across.

Now, this doesn't allow for the sea ice, nor for the water depth--I have no ideas on how to calculate those, at the moment!
There are also inaccuracies in the nuclear blast comparison to the area of effect of the impact; the blast effect would be a circular event from a point source; the impact is an elliptical event from a line source. But, for a rough approximation...

I hope that helps! Good luck!

Answer 2

When another big meteorite hits mars surface,lot of rocks are going up and few of them will reach mars escape velocity which is much less than that of earth. This will be in solar orbit and ultimately earth goes near by path. The mineral combination is perfectly comparable with marsand the trapped gases match the martian atmosphere

Answer 3

that scenario was on the History Channel just the other day.... the asteroid and the pack ice idea... and yes, they too thought it might have been a 'different' reason for a few of our historic happenings.....