Near-Earth objects (NEOs) pose a threat to our global security, and not just from a catastrophic impact. A large meteorite exploding in Earth's atmosphere could trigger a nuclear war.

Such a scenario was in the making on June 6, 2002. Just as the tensions between India and Pakistan were reaching their boiling point, a meteor exploded as it entered the atmosphere over the Eastern Hemisphere, causing an energy release of 12 kilotons, equivalent to the blast that destroyed Hiroshima. Fortunately, the bright flash and damaging shock wave of the detonating meteorite occurred over the Mediterranean Sea, just west of the disputed Kashmir region. If the explosion had happened a little earlier while it was over the countries in conflict, the confusion and panic could easily have sparked a nuclear response from either country.

While the United States was able to quickly determine the source of the explosion, India and Pakistan, as well as most other countries, do not have the resources available to distinguish whether an explosion's source is natural or man-made. Brigadier General Simon P. Worden, the U.S. Space Command's deputy director for operations at Peterson Air Force Base in Colorado, would like to change that.

The Department of Defense already tries to notify nations that are facing potential missile attack of meteorite strikes; however, the data they collect is through classified systems, which can result in a several-week delay before the information is released. Worden recently told the Commission on the Future of the U.S. Aerospace Industry in Washington, D.C., that an NEO warning center could be established to assess and release the data more quickly without jeopardizing sensitive information. He believes that no more than 10 extra people in the current centers would be required to catalog and provide warning of future NEO threats.

Ground-based telescopes are already detecting and defining the orbits of large, kilometer-sized objects. But there is no good system currently in place to find smaller NEOs. "Just about everyone knows of the 'dinosaur killer' asteroids," Worden says. "These are objects, a few kilometers across, that strike on time scales of tens of millions of years. While the prospect of such strikes grabs people's attention and makes great catastrophe movies, too much focus on these events has been counterproductive. We need to focus our energies on the smaller, more immediate threats."

In 1908, the well-known Tunguska meteorite exploded in the skies above Siberia and devastated an area 80 kilometers in diameter. This space chunk was probably not more than 100 meters in diameter but exploded with the energy equivalent of a 10 megaton nuclear blast, even though it never hit the ground. In 1996, a meteorite exploded over Greenland with a force of 100 kilotons (much greater than the June Mediterranean blast of 12 kilotons). If the Greenland or Tunguska events had occurred over populated areas, they would have caused massive fatalities.

In addition to igniting a nuclear war, another worst-case scenario is a 100-meter or smaller meteorite striking the ocean near a heavily populated seacoast. "The resulting tidal wave could inundate shorelines for hundreds of miles and potentially kill millions," says Worden.

"There are hundreds of thousands of objects this size that come near Earth. We know the orbits of just a few," Worden sums up. His call for the creation of a better NEO detection system would make Earth safer from threats from above. Until then, we have to wait until after an event occurs before we learn about it and hope that these incidents are limited to isolated corners of the globe.

There is nothing like answeringyour own question. Kinda like talking to your self:

http://rsd.gsfc.nasa.gov/goes/text/9712.greenland/9712.greenland.html

Greenland meteor on 9 December 1997

last updated 9 June 1998

A big meteor impact probably occurred in Southern Greenland at 61 25N, 44 26W on Tuesday, December 9th approximately 0811 UTC (05:11 am local time). The position is on the ice cap approximately 50 kilometers NE of Narsarsuaq Airport.

Since then, data surveilance equipment has confirmed a bright flash but not an impact. The event may have been further west than originally reported. Running updates on the Greenland meteorite event can be obtained at http://www.astro.ku.dk/~holger/ and at http://www.dcrs.dtu.dk.

DOD Satellite Observations

"On 9 December 1997, sensors aboard DOD satellites detected the impact of a meteoroid at 08:15:55 UTC roughly midway between Nuuk and Qaqortoq, Greenland. The object broke into at least 4 pieces. One piece detonated at an altitude of about 46 km at 62.9 degrees North Latitude, 50.9 degrees West Longitude. The remaining 3 pieces detonated in close proximity to one another at altitudes between 28 km, at 62.9 degrees North Latitude, 50.1 degrees West Longitude and 25 km at 62.9 degrees North Latitude, 50.0 degrees West Longitude."

USAF NEWS RELEASE

From:   Headquarters Air Force Technical Applications Center   
        Office of Public Affairs            
        Patrick AFB, Fl.,
        32925-3002
        (407)-494-9915

Date: June 8, 1998

****************************************************************************
On 9 December 1997 at approximately 08:15:55.2 UT, sensors aboard a
U.S. Department of Defense satellite recorded the bright flash of
an apparent meteoroid disintegrating in the atmosphere over
Greenland. The peak radiated intensity recorded on this event 
was 9.5E10 watts/sr (using a 6000K blackbody model for the
radiation). Correspondingly, the total radiated energy of the
event was 2.7E11 Joules.

        (If you have questions call MSgt Rene Uzee, Air Force Technical
Applications Center Public Affairs at, (407) 494-4403.)

*****************************************************************************
PLEASE NOTE: THIS USAF BOLIDE INFORMATION RELEASE AND ALL PREVIOUS RELEASES 
CAN BE FOUND ON THE WWW AT
http://phobos.astro.uwo.ca/~pbrown/usaf.html
*****************************************************************************

Individuals interested in obtaining graphical lightcurve information
for this event should send an email with their names, fax numbers and 
a description of their intended use of this information to 
peter@danlon.physics.uwo.ca

NOAA Satellite Observations

6 hours later, the NOAA polar-orbiting weather satellites observed a large cloud over southeastern Greenland. These AHVRR images were posted on the internet at http://www.ddorf.rhein-ruhr.de/~aknoefel/greenland .

There was speculation that the cloud was related to the meteor because of its unusually high, crisp appearance.

GOES Satellite Observations

NASA's Laboratory for Atmospheres collects and posts real time images from the GOES weather satellite. These were used to examine the time-series of Greenland images gleaned from the full-disk scans taken by GOES-8 once every three hours in the second week of December.

GOES-8 visible image on 9 December 1997

The GOES-EAST visible image at 1445 UTC gives a nice view of a distinct high cloud over southern Greenland near local noon:

corresponding coastline map:

The "+" marks the reported impact point at 61.4N, 44.4W. Latitude and longitude lines are sketched at 2 degree intervals, based on the reported GOES earth-navigation. At this time, the navigated map's coastlines fall 3 pixels south and one pixel west of the observed coastlines, within the GOES earth-navigation error tolerances of 4 visible pixels.

Unfortunately, Greenland is too dark in December to provide visible images during the other GOES-8 observation times, such as 1145 and 1745 UTC.

GOES-8 infrared images on 9 December 1997

Fortunately, Greenland can be seen every three hours in the GOES-8 thermal infrared channel ("I04", or Imager channel 4 at 11 microns) with lower resolution:

GIF animation

coastline map ("+" marks impact point)

0245 UTC (local midnight)

0545 UTC

0845 UTC (30 minutes after impact)

1145 UTC

1445 UTC (local noon)

1745 UTC

2045 UTC

2345 UTC

A cold, high cloud appears over southeastern Greenland at 0845 UTC, 30 minutes after the reported impact, with faint hints of cloud formation along the center ridge of the southern Greenland ice cap at 0545 UTC.

This cloud formation appears to be part of a normal storm development in the lee of the ice cap.

GOES-8 infrared movies for 8 to 12 December 1997

One can see the normal cycle of storm cloud development during the week in this region by viewing the GOES-8 infrared images of Greenland starting from the day before the meteor impact, and ending three days later:

8-to-12 December 1997, as a GIF movie (1.1 MBytes)
8-to-12 December 1997, as a QuickTime movie (Cinepak format, 0.5 MBytes)

Conclusion, based on GOES-8 Images

The cloud formation and development over southeastern Greenland on 9 December 1997 looks like a normal storm, similar to the storm on 12 December.

It does not look like a single ejection cloud, nor a long contrail.

Nevertheless, the time-of-formation is a remarkable coincidence with the reported meteor impact.

Mail To:Dennis.Chesters@gsfc.nasa.gov

GOES Project Scientist
GOES Project

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