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parallaxicality
2018-Apr-23, 01:48 PM
Let's say a metallic meteorite about 500 m across were to crash into the Earth. How much energy would be transferred into the Earth, and how much would be thrown back at the meteorite?

kzb
2018-Apr-23, 05:22 PM
I'm not sure I understand the question TBH.

I would say the kinetic energy of the meteorite essentially ends up in or on the Earth.

Strictly speaking it is the mass of the Earth plus the mass of the meteorite, because they will become one merged object.

If some ejecta go into long term orbit or exceed escape velocity, then the portion of the kinetic energy they carry is lost to the Earth.

Is this what you are getting at?

Hornblower
2018-Apr-23, 08:02 PM
The meteorite's kinetic energy is almost entirely transformed into heat. For one that large, there will be a cataclysmic explosion, with some material from the meteorite and the surrounding ground blasted away into space. I have no means of estimating the amount of the ejecta, or the portion of the energy carried away with it.

Swift
2018-Apr-23, 08:35 PM
I don't know if this will answer your question, but the Impact: Earth! model from Purdue (http://www.purdue.edu/impactearth/) is always "fun" to play with.

It can give you information such as:

Energy before atmospheric entry: 5.57 x 10^20 Joules = 1.33 x 10^5 MegaTons TNT

Time for maximum radiation: 11.5 seconds after impact
Your position is inside the fireball.
The fireball appears 1040 times larger than the sun
Thermal Exposure: 2.89 x 10^11 Joules/m^2
Duration of Irradiation: 49.7 minutes
Radiant flux (relative to the sun): 96800
(I think last one was for 20 km from the dino killer)

AGN Fuel
2018-Apr-24, 01:44 AM
I don't know if this will answer your question, but the Impact: Earth! model from Purdue (http://www.purdue.edu/impactearth/) is always "fun" to play with.

(I think last one was for 20 km from the dino killer)

That thermal exposure is remarkable. Sparks an idle question - would tissue destruction occur faster than the nerve signal could travel? In other words, with an assumption of a sharp temperature gradient as the shockwave expanded, would this have been a painless death simply because the signal never had time to reach their dino brains?

Grey
2018-Apr-25, 12:57 PM
That thermal exposure is remarkable. Sparks an idle question - would tissue destruction occur faster than the nerve signal could travel? In other words, with an assumption of a sharp temperature gradient as the shockwave expanded, would this have been a painless death simply because the signal never had time to reach their dino brains?I think that for anything inside the actual fireball from an impact, the answer would be yes.

Cougar
2018-Apr-27, 01:18 AM
Let's say a metallic meteorite about 500 m across were to crash into the Earth. How much energy would be transferred into the Earth, and how much would be thrown back at the meteorite?

Swift's simulator is great:

This is for 500 m diameter, 20 km/sec velocity, the observer is 1,000 km from the strike....


Energy before atmospheric entry: 1.05 x 10^20 Joules = 2.5 x 10^4 MegaTons TNT.

The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 2.7 x 10^5 years.

The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the tilt of Earth's axis (< 5 hundredths of a degree).
The impact does not shift the Earth's orbit noticeably.

Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.
Transient Crater Diameter: 9.8 km ( = 6.09 miles )
Transient Crater Depth: 3.47 km ( = 2.15 miles )
Final Crater Diameter: 13.3 km ( = 8.24 miles )
Final Crater Depth: 644 meters ( = 2110 feet )
The crater formed is a complex crater.
The volume of the target melted or vaporized is 0.801 km^3 ( = 0.192 miles^3 )
Roughly half the melt remains in the crater, where its average thickness is 10.6 meters ( = 34.8 feet ).