Chance of Asteroid collision with Earth not just science fiction
Pastor Dale Morgan
*Chance of Asteroid collision with Earth not just science fiction*
ALAN FISCHER
Tucson Citizen
Imagine if you will a huge asteroid hurtling through space on a
high-speed collision course with Earth.
The story of the discovery of this space object - which could
potentially obliterate life as we know it from the face of our planet -
and the scramble to avoid such a catastrophic collision, could make a
fine episode of Rod Serling's "Twilight Zone" or even a big-budget movie
starring Bruce Willis.
But real life mirrors such TV and cinematic fiction here as local
astronomers discover and track Near Earth Objects with the potential to
pass close to - or even hit - the Earth or nearby planets.
A March 2007 NASA report to Congress outlines methods of deflecting or
mitigating the threat posed by asteroids by using nuclear explosives or
other means.
While 220 tons of interplanetary material enter the Earth's atmosphere
each day - most in the form of space dust and other tiny objects that
burn up before hitting the surface - it would take only one sizable
asteroid to have a huge impact on our planet and its inhabitants,
researchers said.
Meteor Crater's 550-foot-deep, 4,000-foot-wide hole in northern Arizona
was blasted about 50,000 years ago by a nickel-iron meteor about 50
meters, or 164 feet, in diameter (about half a football field length).
It weighed 300,000 tons and hit the surface at an estimated 28,600 mph.
"A 50-meter object could make a pretty miserable day for a city-sized
area because of the blast damage," said Lindley Johnson, program
executive for NASA's Near Earth Object Program.
"The impact of a 1-kilometer object (3,280 feet - about 11 football
fields in length) would wipe out an entire state," he said. "It would
pretty much take out all of southern California, or take care of all of
Arizona.
"The 1-kilometer damage threshold would have worldwide consequences. It
would throw enough dust and gas into the atmosphere to cut off energy
from the sun, cause the death of crops and totally upset the biosphere
and food chain."
An impact 65 million years ago that some scientists believe led to the
demise of dinosaurs on Earth was caused by an object 6 or 7 miles in
diameter that caused a crater 180 miles in diameter in the Gulf of
Mexico, Johnson said.
"There are still a lot of these objects out there," he said. "The Earth
could be impacted again. This process has been going on since the solar
system was formed.
"The problem is, we don't know when the next one will happen. It could
be a thousand years. It could be tomorrow. The object is to find them as
early as possible to have enough time to develop a mitigation technique."
Looking for asteroids
High atop Mount Lemmon and Mount Bigelow north of town, and at a site in
Australia, members of the University of Arizona's Catalina Sky Survey
search the sky most nights seeking asteroids and other Near Earth
Objects. NEOs are objects traveling through space that have or will come
within 130 million miles of our sun, said Ed Beshore, survey operations
manager for Catalina
Sky Survey.
During a recent cold January late afternoon, Steve Larson, principal
investigator for Catalina Sky Survey, prepares for a long night of
observing using a 1.5-meter telescope atop Mount Lemmon.
As darkness settles, the observatory dome is opened to equalize the
temperature between the telescope and the below-freezing air.
Larson installs in the scope's computer system a database locating the
300,000 known asteroids - updated each day - to avoid repeating the
discovery of already-found asteroids.
He then precisely calibrates the sighting mechanism of the telescope
before beginning a 12-hour shift seeking moving items in the night sky.
The telescope's field - the area it can see at one time - is one square
degree of the sky, a box that would contain nine full moons.
"That telescope can go deep," Beshore said. "It can see items about 1
million times fainter than the faintest star in the sky you can see with
the human eye on a clear night."
Larson commands the telescope to photograph nine adjoining fields in the
sky, with a 30-second exposure on each, before moving on to photograph
the next field.
The process automatically repeats four times, and telescope software
analyzes the four images of each field to see if anything moved during
the 10-minute lapses between each exposure.
The computer alerts the operator of any detected motion, and human
judgment is needed to determine if the flagged item is actually an
object moving through space or a false detection.
The telescope operator is posed with 50 to 100 reviews per field
surveyed, or up to 10,000 choices per night, Larson said.
When a moving object is identified as a potential NEO, its position is
automatically reported within minutes to the Minor Planet Center in
Cambridge, Mass., so that other astronomers, amateur and professional,
can further investigate, Larson said.
This process continues throughout the night, with small chunk after
small chunk of sky observed.
Observers typically work three-night shifts, one observer at each of the
two Mount Lemmon-area scopes. In addition to Larson and Beshore, team
members include Andrea Boattini, Alex Gibbs, Al Grauer, Rik Hill and
Rich Kowalski.
In addition to the 1.5-meter scope atop Mount Lemmon, the team operates
a 0.7-meter Schmidt camera-only telescope on Mount Bigelow.
The team also does NEO surveys using a 0.5 meter scope at Australia's
Siding Spring Observatory. It is operated by Australian National
University Research School in Astronomy scientists Robert McNaught,
Gordon Garradd and Donna Burton, who are paid by UA with NASA funds.
Catalina Sky Survey observers accounted for 70 percent of NEOs
discovered last year, Beshore said.
"We discover thousands of new asteroids each year," he said. "We found
460 NEOs last year," but most were smaller than 1 kilometer and not an
immediate direct threat to Earth.
"Chances of a large object hitting the Earth are slim, but the
consequences are huge," Beshore said.
Project beginnings
The U.S. government began funding the discovery and cataloging of
objects that could potentially hit Earth about 10 years ago, said NASA's
Johnson.
Congress directed NASA to find and track 90 percent of NEOs 1 kilometer
or larger in size within 10 years, he said.
About 800 NEOs of that size have been discovered, he said.
The project, funded at $4 million per year, is expected to run through
2012, Johnson said.
A new project seeking to discover 90 percent of NEOs 140 meters in size
or larger was proposed in 2005 and may need additional funding, he said.
There are currently four NASA-funded teams seeking NEOs: Catalina Sky
Survey, UA's Spacewatch Survey on Kitt Peak, the Lowell Observatory in
Flagstaff and the Lincoln Near Earth Asteroid Research project in
Socorro, N.M., Johnson said.
The U.S. effort was sparked by the comet Shoemaker-Levy 9's dramatic
collision with Jupiter in 1994, opening officials' eyes to the potential
of a similar collision here, he said.
Movies vs. reality
The 1998 movie "Armageddon" portrayed Bruce Willis and his crew landing
on a threatening asteroid and blowing it up using a nuclear weapon just
before it hits Earth.
Such movie drama may be grounded in reality, researchers said.
NASA's Near-Earth Object Survey and Deflection Analysis of Alternatives
report to Congress in March 2007 states that nuclear explosions are
assessed to be 10 to 100 times more effective than non-nuclear alternatives.
Destroying an incoming asteroid with a nuclear weapon would not be the
best option unless it was really close to impact, Johnson said.
"If you just blew it up, pieces would still be coming toward you like a
shotgun blast and could do more damage," he said. "You want to keep the
mass contained."
The preferred course of action - a blast that could remove a small
portion of the asteroid - would cause the object's path to change
slightly so it passes by harmlessly, he said.
Other options include hitting the asteroid with a spacecraft to alter
its path or parking a spacecraft neary the asteroid so the gravitational
attraction would alter the course away from us.
Researchers at conferences and forums have looked into the best ways to
prevent an asteroid from hitting Earth, he said, but a concrete plan has
not been approved.
The effort would take several space missions, each valued at more than
$1 billion, he estimated.
The first would be a flight to characterize the target to better
understand what we are working with, he said.
For example, a metallic asteroid would need a different plan than a
rocky asteroid.
Once a plan for neutralizing the asteroid is set, a mission would be
sent to take care of the danger. And a backup mission would also be
sent, just in case the first fails, he said.
"Based on estimates to mount a mission like that, it would probably be a
few billion dollars, less than $10 billion," he said. And well worth it,
he said, to save life as we know it.
"If we had to do something like that, cost wouldn't be too much of a
factor," he said.