Impact Effects
Credit: Robert Marcus, H. Jay Melosh, and Gareth
Collins
Please note: the results below are estimates based on current (limited)
understanding of the impact process and come with large uncertainties; they should be used
with caution, particularly in the case of peculiar input parameters. All values are given to
three significant figures but this does not reflect the precision of the estimate.
IMPACT 1
Your
Inputs:Distance from Impact: 10.00 km = 6.21 miles
Projectile
Diameter: 2000.00 m = 6560.00 ft = 1.24 miles
Projectile Density: 3000 kg/m
3
Impact Velocity: 20.00 km/s = 12.42 miles/s
Impact Angle: 45 degrees
Target
Density: 2500 kg/m
3 Target Type: Sedimentary Rock
Energy:Energy before atmospheric entry: 2.51 x
10
21 Joules = 6.00 x 10
5 MegaTons TNT
The average interval
between impacts of this size somewhere on Earth during the last 4 billion years is 3.1 x
10
6years
Major Global
Changes:The Earth is not strongly disturbed by the impact and loses
negligible mass.
The impact does not make a noticeable change in the Earth's rotation
period or the tilt of its axis.
The impact does not shift the Earth's orbit
noticeably.
Crater
Dimensions:Transient Crater Diameter: 19.5 km = 12.1 miles
Transient Crater Depth: 6.89 km = 4.28 miles
Final Crater Diameter: 28.8 km =
17.9 miles
Final Crater Depth: 0.814 km = 0.506 miles
The crater formed is a
complex crater.
The volume of the target melted or vaporized is 15.7 km
3 =
3.77 miles
3 Roughly half the melt remains in the crater, where its average
thickness is 52.7 meters = 173 feet
Thermal
Radiation: Time for maximum radiation: 1.36 seconds after impact
Your position is inside the fireball.
The fireball appears 617 times larger than the
sun
Thermal Exposure: 1.19 x 10
10 Joules/m
2 Duration of
Irradiation: 353 seconds
Radiant flux (relative to the sun): 33800
Effects of Thermal Radiation:
Clothing ignites
Much of the body suffers third degree burns
Newspaper ignites
Plywood flames
Deciduous trees ignite
Grass ignites
Seismic Effects:
The major seismic shaking will arrive at approximately 2 seconds.
Richter Scale
Magnitude: 8.5
Mercalli Scale Intensity at a distance of 10 km:
X. Most masonry
and frame structures destroyed with their foundations. Some well-built wooden structures
and bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides.
Water thrown on banks of canals, rivers, lakes, etc. Sand and mud shifted horizontally on
beaches and flat land. Rails bent slightly.
XI. As X. Rails bent greatly. Underground pipelines completely out of service.
Ejecta: The ejecta will arrive
approximately 45.2 seconds after the impact.
Your position is beneath the
continuous ejecta deposit.
Average ejecta Thickness: 1290 m = 4230 ft
Air Blast:
The air blast will arrive at approximately 30.3 seconds.
Peak Overpressure:
8.79x107 Pa = 879 bars = 12500 psi
Max wind velocity: 7540 m/s = 16900 mph
Sound Intensity: 159 dB (Dangerously Loud)
Damage Description:Multistory wall-bearing buildings will
collapse.
Wood frame buildings will almost completely collapse.
Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient
collapse.
Highway truss bridges will collapse.
Highway girder bridges will collapse.
Glass windows will shatter.
Cars and trucks will be largely displaced and grossly distorted and will require rebuilding
before use.
Up to 90 percent of trees blown down; remainder stripped of branches and
leaves
IMPACT 2
Your
Inputs:Distance from Impact: 10.00 km = 6.21 miles
Projectile
Diameter: 2000.00 m = 6560.00 ft = 1.24 miles
Projectile Density: 3000 kg/m
3
Impact Velocity: 50.00 km/s = 31.05 miles/s
Impact Angle: 45 degrees
Target
Density: 2500 kg/m
3 Target Type: Sedimentary Rock
Energy:Energy before atmospheric entry: 1.57 x
10
22 Joules = 3.75 x 10
6 MegaTons TNT
The average interval
between impacts of this size somewhere on Earth during the last 4 billion years is 1.3 x
10
7years
Major Global
Changes:The Earth is not strongly disturbed by the impact and loses
negligible mass.
The impact does not make a noticeable change in the Earth's rotation
period or the tilt of its axis.
The impact does not shift the Earth's orbit
noticeably.
Crater
Dimensions:Transient Crater Diameter: 29.2 km = 18.1 miles
Transient Crater Depth: 10.3 km = 6.4 miles
Final Crater Diameter: 45.5 km = 28.2
miles
Final Crater Depth: 0.934 km = 0.58 miles
The crater formed is a complex
crater.
The volume of the target melted or vaporized is 98.3 km
3 = 23.6
miles
3 Roughly half the melt remains in the crater , where its average thickness
is 147 meters = 483 feet
Ejecta:Your
position was inside the transient crater and ejected upon impact
IMPACT 3
Your Inputs:Distance from
Impact: 10.00 km = 6.21 miles
Projectile Diameter: 2000.00 m = 6560.00 ft = 1.24
miles
Projectile Density: 3000 kg/m
3 Impact Velocity: 70.00 km/s = 43.47
miles/s
Impact Angle: 45 degrees
Target Density: 2500 kg/m
3 Target
Type: Sedimentary Rock
Energy:Energy
before atmospheric entry: 3.08 x 1022 Joules = 7.35 x 106 MegaTons TNT
The average
interval between impacts of this size somewhere on Earth during the last 4 billion years is 2.1
x 107years
Major Global Changes:The
Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does
not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The
impact does not shift the Earth's orbit noticeably.
Crater
Dimensions:
Transient Crater Diameter: 33.8 km = 21 miles
Transient Crater Depth: 12 km = 7.43
miles
Final Crater Diameter: 53.8 km = 33.4 miles
Final Crater Depth: 0.982 km =
0.61 miles
The crater formed is a complex crater.
The volume of the target melted
or vaporized is 193 km
3 = 46.2 miles
3 Roughly half the melt remains
in the crater , where its average thickness is 214 meters = 703 feet
Ejecta:Your position was inside the transient crater
and ejected upon impact
IMPACT 4
Your Inputs:
Distance from Impact: 20.00 km = 12.42 miles
Projectile Diameter: 200000.00 m = 656000.00 ft = 124.20 miles
Projectile Density:
3000 kg/m3
Impact Velocity: 50.00 km/s = 31.05 miles/s
Impact Angle: 45
degrees
Target Density: 2500 kg/m3
Target Type: Sedimentary Rock
Energy:
Energy before atmospheric
entry: 1.57 x 1028 Joules = 3.75 x 1012 MegaTons TNT
The
average interval between impacts of this size is longer than the Earth's age.
Such
impacts could only occur during the accumulation of the Earth, between 4.5 and 4 billion
years ago.
Major Global Changes:
The
Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does
not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The
impact does not shift the Earth's orbit noticeably.
Crater
Dimensions:
Transient Crater Diameter: 1060 km = 658 miles
Transient Crater Depth: 375 km = 233 miles
Final Crater Diameter: 2640 km =
1640 miles
Final Crater Depth: 3.17 km = 1.97 miles
The crater formed is a
complex crater.
The volume of the target melted or vaporized is 9.88X107 km3
= 2.37X107 miles3
Roughly half the melt remains in the crater , where its
average thickness is 112 km = 69.5 miles
See:
http://www.lpl.arizona.edu/~marcus/CollinsEtAl2005.pdf for the mathematics and
http://www.lpl.arizona.edu/impacteffects/ for the actual
program.
ASTEROID 2004 MN
An edited version of the 2004
MN4 story originally posted on SPACE.com at 9:58 a.m. ET on Dec. 24:
Scientists
said Thursday that a recently discovered asteroid has a chance of hitting Earth in the year
2029, but that further observations would likely rule out the impact scenario.
The
asteroid is named 2004 MN4. It was discovered in June and spotted again this month. It is
about a quarter mile (400 meters) wide
2004 MN4 is now being tracked very carefully by
many astronomers around the world, and we continue to update our risk analysis for this
object. Today's impact monitoring results indicate that the impact probability for April 13,
2029 has risen to about 1.6 percent, which for an object of this size corresponds to a rating
of 4 on the ten-point Torino Scale. Nevertheless, the odds against impact are still high, about
60-to-1, meaning that there is a better than 98 percent chance that new data in the coming
days, weeks, and months will rule out any possibility of impact in 2029.
With a half-dozen
or so other asteroid discoveries dating back to 1997, scientists had announced long odds of
an impact -- generating frightening headlines in some cases -- only to announce within hours
or days that the impact chances had been reduced to zero by further observations. Experts
have said repeatedly that they are concerned about alarming the public before enough data
is gathered to project an asteroid's path accurately.
Asteroid 2004 MN4 is an unusual
case in that follow-up observations have caused the risk assessment to climb -- from Torino
level 2 to 4 -- rather than fall.
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