Near-Earth objects pose threat, general says
WASHINGTON — This summer, much of the world watched as India
and Pakistan faced-off over the disputed Kashmir region,
worried that the showdown could escalate into a nuclear war.
Coincidentally, U.S. early warning satellites detected
an explosion in the Earth’s atmosphere June 6, at the height
of the tension, with an energy release estimated to be 12
kilotons.
Fortunately the detonation, equivalent to the blast that
destroyed Hiroshima, occurred over the Mediterranean Sea.
However, if it had occurred at the same latitude a few hours
earlier, the result on human affairs might have been much
worse, said Brig. Gen. Simon P. Worden, U.S. Space
Command’s deputy director for operations at Peterson Air
Force Base, Colo.
Had the bright flash, accompanied by a damaging shock wave,
occurred over India or Pakistan, the resulting panic could have
sparked a nuclear war, Worden recently told members of the
congressionally mandated Commission on the Future of the
U.S. Aerospace Industry in testimony here.
Although U.S. officials quickly determined that a meteor caused
the explosion, neither India nor Pakistan have the
sophisticated sensors that can determine the difference
between a natural near-Earth object impact and a nuclear
detonation, Worden said in written testimony.
This is one of many threats posed by NEOs, especially as more
and more nations acquire nuclear weapons, said Worden, who
appeared before the commission as a scientist who has studied
NEOs and as a space expert familiar with the technologies that
can be used to address the NEO threat.
In recent years, the Department of Defense has been working
to provide data about asteroid strikes to nations potentially
under missile attack and to the scientific community; however,
it takes several weeks for the data to be released since much of
it is gathered from classified systems.
Worden suggested that a NEO warning center be established
that can assess and release this data as soon as possible to all
interested parties while ensuring sensitive data is safeguarded.
He recommended to the commission that a natural impact
warning clearinghouse could be formed by adding no more than
10 people to current U.S. Space Command early warning
centers.
This organization would catalog and provide credible warning
information on future NEO impact problems, as well as rapidly
provide information on the nature of an impact.
In order for this clearinghouse to provide accurate information,
NEOs must first be detected, cataloged and their orbits
defined.
Current ground-based systems are already cataloging large
kilometer-sized objects but have a difficult time finding smaller
NEOs. Most sail by the earth unnoticed until they have passed,
he said.
“Just about everyone knows of the ‘dinosaur killer’ asteroids,”
Worden said. “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.”
The smaller strikes, while not exactly commonplace, have
occurred on several occasions over the past century, with
potentially devastating results, he said.
“An object probably less than 100 meters in diameter struck
Tunguska in Siberia in 1908, releasing the energy equivalent to
a 10-megaton nuclear blast,” Worden said. “In 1996, our
satellite sensors detected a burst over Greenland equal to a
100-kiloton yield. Had any of these struck over a populated
area, perhaps hundreds of thousands might have perished.”
An even worse catastrophe would be an ocean impact near a
heavily populated shore by one of these Tunguska-sized
objects.
“The resulting tidal wave could inundate shorelines for hundreds
of miles and potentially kill millions,” Worden explained.
“There are hundreds of thousands of objects this size that
come near the Earth,” he said. “We know the orbits of just a
few. New space-surveillance systems capable of scanning the
entire sky every few days are needed. They could enable us to
completely catalog and warn of objects (less than 100 meters
in diameter).”
According to Worden, this does not mean other groups, in
particular the international scientific community, should not
continue their independent efforts. But the United States is
likely, for the foreseeable future, to have most of the required
sensors to do this job. He added that DOD has the discipline
and continuity to ensure consistent, long-term focus.
“I believe various aspects related to NEO impacts, including the
possibility that an impact would be misidentified as a nuclear
attack, are critical national and international security issues,” he
said. “The focus of NEO mitigation efforts should shift to
smaller objects. The near-term threats are much more likely to
come from these ‘small’ objects, and we might be able to divert
such objects without (resorting) to nuclear devices.”
The National Defense Authorization Act for Fiscal Year 2001
established the Commission on the Future of the U.S.
Aerospace Industry. The commission was formed to study the
future of the U.S. aerospace industry in the global economy,
particularly in relationship to national security, and provide
recommendations to the president and Congress.
