Unknown 7m Asteroid Almost Impacted Earth 289
xp65 writes "A previously undiscovered asteroid came within 14,000 km of Earth — just over one Earth diameter, 1/30 the lunar distance — on Friday, and astronomers noticed it only 15 hours before closest approach. On Nov. 6 at around 16:30 EST, a 7-meter asteroid, now called 2009 VA, came only about 2 Earth radii from
impacting our planet. This is the third-closest known non-impacting Earth approach on record for a cataloged asteroid. The asteroid was discovered by the Catalina Sky Survey and was quickly identified by the Minor Planet Center in Cambridge MA as an object that would soon pass very close to the Earth. JPL's Near-Earth Object Program Office also computed an orbit solution for this object, and determined that it was not headed for an
impact." The article notes, "On average, objects the size of 2009 VA pass this close about twice per year and impact Earth about once every 5 years."
Re:How Much Damage? (Score:3, Interesting)
The article doesn't say what level of damage would have resulted from an impact. Anybody want to weigh in?
I remember my old science book said that the one responsible for Meteor Crater was the size of a box car but that's kind of imprecise. It's a question of mass and velocity. The looser, rock-ice bodies tend to explode in the air. We've had a couple historically that were big enough to be mistaken for nuclear tests but they exploded high in the air over remote stretches of ocean.
Re:How Much Damage? (Score:4, Interesting)
From Wikipedia [wikipedia.org]:
If it hit near the center of a large city it could really suck; however, most of the earth's surface is covered by water, desert, mountains, or rural areas, and thus most asteroid impacts of this size do not cause massive loss of life.
Comment removed (Score:4, Interesting)
Re:How Much Damage? (Score:3, Interesting)
Result = no strike (Score:3, Interesting)
I shoved some numbers in, making it quite dense with the recommended average velocity for an asteroid, impact angle etc and got the following results:
Your Inputs:
Distance from Impact: 1.00 km = 0.62 miles
Projectile Diameter: 7.00 m = 22.96 ft = 0.00 miles
Projectile Density: 3000 kg/m3
Impact Velocity: 17.00 km/s = 10.56 miles/s
Impact Angle: 45 degrees
Target Density: 2500 kg/m3
Target Type: Sedimentary Rock
Energy:
Energy before atmospheric entry: 7.79 x 1013 Joules = 0.19 x 10^-1 MegaTons TNT
The average interval between impacts of this size somewhere on Earth is 5.1 years
Atmospheric Entry:
The projectile begins to breakup at an altitude of 54000 meters = 177000 ft
The projectile bursts into a cloud of fragments at an altitude of 34300 meters = 113000 ft
The residual velocity of the projectile fragments after the burst is 13.7 km/s = 8.49 miles/s
The energy of the airburst is 2.75 x 1013 Joules = 0.66 x 10^-2 MegaTons.
No crater is formed, although large fragments may strike the surface.
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.
Re:How Much Damage? (Score:3, Interesting)
The real question is would it impact at all.
How much would burn up after breaking up in the atmosphere.
If one of these impacts every 5 years, and 65% of the earth's surface is water, you would expect 1 of every 3 or 4 to land on dry land, so in 20 years we should have had some impacts in places they can be found.
Since no one here can remember the last one, you have to assume the damage has been minimal.
Re:How Much Damage? (Score:4, Interesting)