- An asteroid flew past Earth last week so close that it
nearly entered an orbital halo where weather satellites roam. Scientists
spotted it March 15 and watched it zoom by just three days later. It posed
no threat, but there are hundreds of thousands more where that one came
from.
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- And while asteroid http://www.space.com/scienceastronomy/asteroid_animation_040319.html
2004 FH, as it is known, was watched calmly by astronomers, a more frightening
scenario unfolded two months earlier:
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- An unprecedented asteroid scare in January had astronomers
worried for a few hours over a rock that had a 1-in-4 chance of hitting
Earth during the next few days. At the time, some of the scientists were
unsure who should be notified. The event has prompted NASA to set up a
formal process for notifying top officials in the future of any impending
impacts, SPACE.com has learned.
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- The plan, which has existed on an informal basis for
months but was not known to all the key scientists involved, could be put
out for review this summer and finalized by the end of the year.
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- The blueprint will be limited to spelling out lines of
communication within NASA, but it might spur other governmental officials
to begin considering how to respond to a threat from beyond if NASA administrator
Sean O'Keefe were to be informed of one, said Lindley Johnson, the top
official for Near Earth Object Observation at NASA Headquarters.
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- For now, there is no established chain of command to
the White House in relation to possible asteroid impacts, nor is there
any plan for what government agencies should do regarding possible evacuations
or emergency preparations.
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- Tense hours
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- Key NASA scientists who monitor potentially threatening
space rocks already knew what to do on the night of Jan 13-14 when an apparent
cosmic bogey was detected, Johnson said in a recent telephone interview.
But there was concern and confusion, both among NASA scientists and between
them and other astronomers who play vital roles in tracking newfound space
rocks.
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- Few involved in the somewhat ad hoc global system of
asteroid hunting knew exactly who should call whom as the situation unfolded.
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- It all began with a routine observation.
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- The Lincoln Near Earth Asteroid Research (LINEAR) observatories
in New Mexico had recorded four images of an object moving across the sky.
The measurements were sent as part of a daily batch to the Minor Planet
Center in Cambridge, Mass, on the Tuesday in January.
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- At the Minor Planet Center, researcher Tim Spahr carried
out a daily duty, using a computer program to generate trajectories for
the newfound object. Spahr posted the results -- along with paths for other
newly detected objects -- to a web page monitored by professional and amateur
astronomers. The amateurs do the bulk of the follow-up observations that
help the Minor Planet Center pin down the paths of newfound asteroids.
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- The presumed asteroid was temporarily designated AL00667.
Spahr left for the day.
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- Within an hour, European amateur astronomer Reiner Stoss
saw the posting and realized that AL00667 would be six times closer to
Earth within a day. He posted a message to the Minor Planet Mailing List,
which other asteroid hunters and researchers monitor.
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- The object was thought to be relatively small. At the
time, astronomers estimated it was 100 feet (30 meters) wide. Were a rock
that size to target Earth, scientists aren't sure what would happen. Something
slightly smaller would probably http://www.space.com/scienceastronomy/asteroid_breakup_030716.html
explode brilliantly but harmlessly in the atmosphere, theory predicts.
Something slightly larger could explode closer to the ground and devastate
an area the size of a small city.
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- What to do
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- Alan Harris, of the Space Science Institute in Boulder,
CO, saw Stoss' message and checked the orbit path posted on the Minor Planet
Center web site, which all the astronomers knew was preliminary and could
have wide error margins. Harris realized that the orbit path posted would
have the asteroid, considered a Near Earth Object (NEO), hitting Earth
the next day.
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- At 7:09 p.m. EST, Harris alerted several colleagues,
including Don Yeomans, head of the Near Earth Object Program Office at
NASA's Jet Propulsion Laboratory (JPL).
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- Yeomans called the Minor Planet Center to try and get
access to the original data set (the actual observations are not posted
on the Minor Planet Center web site until after an official announcement
circular is published, usually in a couple days). Spahr, not realizing
he'd posted an orbital path that went right through the Earth, had gone
to dinner.
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- It took about 30 minutes before Yeomans and his colleagues
heard back from Brian Marsden, director of the Minor Planet Center, who
was working late that evening. After another 20 minutes, Yeomans and his
JPL team had the observational data and calculated the rock had about a
25 percent chance of impact.
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- Meanwhile, other possible paths based on the sketchy
data showed the rock could also miss Earth be a wide margin. More observations
were needed.
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- Clark Chapman of the Southwest Research Institute, also
in Boulder, had been apprised of the situation, too.
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- "As I was driving home, I was thinking that this
must be a mistake," Chapman recalled last week. Asteroid experts have
seen many threats of impacts, predicted for future years, come and go over
the course of a day or two as new observations provided a more accurate
picture of a space rock's path. Never, however, have they faced such an
apparently imminent threat.
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- Chapman had begun keeping a narrative of the unusual
situation. At one point early on, this log included musings over whether
NASA or the White House should be alerted, but he says it was not something
he seriously contemplated.
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- Many in the media reported that the astronomers had pondered
calling the White House. Chapman says the media got it wrong.
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- During the critical period when JPL had calculated a
10 to 40 percent chance of impact, "there's nothing in the narrative
that says a thing about the White House," Chapman said. He and NASA's
http://www.space.com/scienceastronomy/astronomy/morrison_interview_020702-1.html
David Morrison, who was also involved in the e-mail communications, both
say there was never any serious consideration of calling the president.
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- "The real issue that we did discuss was when, if
at all, it would be appropriate for any of us, especially Don Yeomans to
notify officials in the Office of Space Science at NASA Headquarters,"
Morrison said, adding that he did wonder who should be called if it became
necessary.
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- Hours passed as cloudy skies prevented follow-up observations.
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- Finally, in the wee hours of Jan. 14, the spot where
AL00667 would have been if it were heading earthward was found to be empty.
(The object was later calculated to be larger, and computers showed it
would come nowhere close to Earth. It was then given a permanent designation
of 2004 AS1.)
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- Lack of preparation
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- In hindsight, astronomers say the episode reveals a system
not prepared to properly find and evaluate small asteroids that could hit
Earth within hours or days of being spotted.
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- "We were all surprised about what happened,"
Chapman told SPACE.com.
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- NASA spends a modest $3.5 million per year as part of
the Spaceguard Survey search for large asteroids, the sort that could cause
global damage, including a global "winter" that might last years
and could kill off some species and possibly threaten civilization. Were
one of these objects bigger than 0.6 miles (1 kilometer) found to be on
an Earth-impact trajectory, scientists agree the warming time would almost
certainly be years or decades.
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- But very little money is spent to catalogue and process
the observational data, which includes the serendipitous discoveries of
many small asteroids that could destroy a city or devastate a country.
The smaller objects typically go unnoticed until they are very near the
planet (and most of them pass by without incident -- were it otherwise
you'd know).
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- Only about 3 or 4 percent of NASA's asteroid spending
goes toward follow-up work. The Minor Planet Center, meanwhile, operates
on a shoestring budget relying partly on subscriptions to its data mailings.
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- "For the most part, we had not previously contemplated
the possibility of discovery by the Spaceguard Survey of a small asteroid
on its final plunge toward Earth," said Morrison, an astrobiologist
and asteroid expert at NASA's Ames Research Center. "Indeed, it is
exceeding unlikely for such an event to occur."
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- But low odds don't mean it won't happen tomorrow, or
next month.
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- "If we simply trusted the odds, we would probably
pack up and go home, since no impact is likely within our lifetimes,"
he said. "But it is the possibility of an improbable impact that motivates
us."
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- Within 48 hours of the January scare, Chapman says, the
Minor Planet Center made changes to its software so that this precise kind
of situation can't happen again. In fact, he notes, a similar scenario
arose two weeks later but did not cause alarm.
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- Clarifying roles
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- After the January AL00667 event, Lindley Johnson, the
NEO chief at NASA Headquarters, sent a memo to Yeomans, Chapman and other
asteroid researchers clarifying that he, Johnson, should be called by Yeomans
if a serious and immediate threat were ever deemed real.
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- Yeomans has known this for months and has had Johnson's
phone number, Johnson and Chapman say.
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- "I think the system worked the way it was supposed
to," Johnson says of the winter scare.
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- He credits the Minor Planet Center for having quickly
sought follow-up observations, as it routinely does for any potentially
threatening object. And importantly, unlike a half-dozen or so http://www.space.com/scienceastronomy/asteroid_scares_030909.html
other asteroid scares dating back to the late 1990s, this one did not play
out in the media, but rather was resolved by astronomers before the any
public false alarms were sounded.
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- Johnson allows that the chain of command was informal,
"and still is until we draft a formal plan. But we always kind of
knew that if we got a call from the astronomers -- in particular Don Yeomans
-- about how we'd handle it back here. There are only two to three layers
of bureaucracy between me and the administrator [Sean O'Keefe]. So it's
not like it would take much time to get the word up."
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- What O'Keefe would do with any such information is not
spelled out anywhere.
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- "To my knowledge there's been no discussions at
that level as to what would be done," said Johnson, a retired Lieutenant
Colonel who served 23 years in the U.S. Air Force. "It's going to
be up to him [O'Keefe] to take it from there." Johnson said that the
plan he's formalizing might "prompt O'Keefe to think, 'Okay now what
do I do?'"
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- Johnson stresses out that NASA's directive has been limited
to conducting a scientific survey for the larger objects right now.
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- "We have not been authorized or appropriated funding
to be operating a network capable of providing accurate and credible warning
for near term (hours to days) impacts, be they large or small objects,"
he said.
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- A busy future
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- Astronomers estimate there are about 1,100 asteroids
larger than 0.6 miles (1 kilometer) that sometimes inhabit the same general
space as Earth. These are the potential civilization destroyers. More than
half have been found and some 90 percent are expected to be catalogued
by 2008. So far, none are headed our way anytime soon.
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- Asteroid hunters agree they need to figure out what to
do beyond 2008.
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- NASA has http://www.space.com/scienceastronomy/asteroid_search_030910.html
studied the costly possibility of expanding the asteroid search to purposely
include smaller objects, of which there are probably hundreds of thousands
that cross the orbit of Earth. The effort would require new telescopes
and more astronomers' time.
-
- If such a search is ever undertaken, significant new
funds would have to be devoted to follow-up observations and cataloguing,
too.
-
- "When we start talking about the smaller objectsthat's
going to require some additional capability to handle orbits and observations,"
Johnson said. "We'd be dealing with thousands of objects a week instead
of tens."
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- This article is part of SPACE.com's weekly Mystery Monday
series.
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- Copyright © 2004
- http://www.SPACE.com/
- SPACE.com.
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