[meteorite-list] Asteroid Discoveries May Outpace Ability to Assess Threat to Earth
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:48:13 2004
Asteroid Discoveries May Outpace Ability to Assess Threat to Earth
By Robert Roy Britt
19 October 2001
After hunting asteroids for two centuries, astronomers achieved a minor
milestone earlier this month when the tally of known space rocks whose
orbits are well established surpassed 30,000, three times the total less
than 3 years ago.
There was no press release. The people who do the counting are too busy for
And soon they will be busier. The tally is expected to double in a matter of
months and likely soar a startling six-fold or more within 3 years. And
these are just the well-studied rocks. Roughly 150,000 more have been
spotted but need further study before their orbits can be known well enough
to put them in the books.
Why the bounty? Telescopes are getting bigger and better, and the high-tech
electronic cameras that record the observations are able to see things that
were invisible just a few years ago.
As a result, asteroids are being found at such a dramatically increasing
rate that some astronomers say the discoveries may soon overwhelm the
ability to properly catalogue the objects and do critical follow-up
observations that could reveal if an asteroid is on a collision course with
Astronomers stress that there is almost no immediate threat that the planet
will be hit.
Any large asteroids bearing down on Earth would likely be discovered decades
in advance, experts say. But smaller objects often go undetected and could
destroy a city. And no one can say if or when a surprise impact might occur.
For now, however, it is the data load that most worries some astronomers.
Several leading asteroid researchers interviewed by SPACE.com warned of a
looming bottleneck in the worldwide network of computers and researchers who
determine the future paths of thousands of asteroids that are detected every
month. One crucial link in the process depends mostly on amateur astronomers
who help to put together painstaking details of an asteroid's path after it
has been first spotted.
"The increasing number of new asteroids will eventually overwhelm observers
who do the follow-up," said Benny Peiser, an expert on the threat of
asteroids at Liverpool John Moores University in the United Kingdom.
The flood of data also could overload the computers and staff of the primary
international clearinghouse for asteroid information, the Minor Planet
Center in Cambridge, Massachusetts.
The global asteroid monitoring system is a sometimes-loose collaboration of
private institutions and government agencies, along with the amateur
astronomers and several dozen professional asteroid researchers around the
The amateur component has developed rapidly over the past decade, often on
an ad hoc basis.
The professional side of things is marked by frequent disagreement between
its most fervent and productive asteroid hunters. They argue over how much
information should be provided to the public and how quickly it should be
released. They debate definitions, procedures, and the fine points of risk
But the scientists all agree on one thing: Earth will one day be targeted by
a potentially devastating asteroid, and they aim to avert disaster by
spotting it in advance.
The most worrisome rocks are the big ones: Asteroids larger than 1 kilometer
(0.62 miles) across suspected of hitting Earth every 100,000 to 300,000
years, says Michael Paine, a volunteer with Planetary Society in Australia.
Paine tracks the varying estimates of asteroid impact risks made by several
research groups. A collision from an object this large would rock the
planet, disrupt the global climate for years and could render some species
Asteroids 100 meters (328 feet) across or larger slam into the planet every
1,000 to 3,000 years, Paine says. Such an event could eliminate a city or
create a tsunami that might inundate shore communities and even large cities
along multiple coastlines.
If and when such a calamity is foreseen, precautions could include
evacuating areas to avoid any local disaster that might be rendered by a
small asteroid. In the future, a spacecraft might be sent to destroy or
deflect a larger incoming object, saving the planet Hollywood style.
The first priority of business on everyone's list is to find more space
rocks. Lately, this is not a problem, and the success of asteroid hunters
grows more stunning by the month.
The first asteroid, Ceres, was discovered in 1801. It took nearly 200 years
-- until 1999 -- for astronomers to find and number the next 9,999 cousins
of Ceres. But with advances in telescope technology and additional human and
optical resources devoted to the task, the count has tripled since then. On
Oct. 2, it reached 30,716.
"I'm guessing we ought to be up to 200,000 in 2004," said Brian Marsden, who
serves in a part-time capacity as director of the Minor Planet Center,
"assuming we can physically keep up with it."
The center, which operates under the auspices of the International
Astronomical Union, processes the world's asteroid observations and connects
major observing programs to the individuals who do follow-up observations.
The center processes more than 70,000 observations on a busy day, Marsden
said. The tremendous amount of data stems from this fact: Although a nearby
asteroid can often be recognized from data on a single night, some must be
observed over several months, even years, to determine their ultimate path
In September, a record 1,642 asteroids were officially numbered by the Minor
Planet Center. But there are many more asteroids that have been spotted. In
all, some 150,000 are already known. Most of these have not been observed
well enough to determine their orbits precisely. Only when an asteroid's
path is pinned down with certainty does it get an official number.
To keep up with the growing workload, Marsden and his two colleagues
frequently put in 16-hour days and work six or seven days a week, he said.
Looking for killers
Most asteroids pose no threat to Earth, traveling around the Sun between the
orbits of Mars and Jupiter. But the gravity of Earth and other planets can
cause an asteroid's path to change with each orbit. Of greatest concern are
asteroids 1 kilometer or larger that stray close enough to our neck of the
solar system that they could one day cross paths with the Earth.
Researchers disagree on how many of these Near Earth Asteroids there might
be, but the leading estimates range from 700 to 1,200. Roughly 500 have been
found, none of which poses a threat anytime in the next century.
But smaller objects are tougher to spot, and some are discovered just days
before they pass by Earth.
On Oct. 8 of this year, for example, an asteroid thought to be between 50
and 100 meters in diameter zoomed by our planet at little more than twice
the distance to the Moon -- a whisker by the standards of our solar system's
size. The object was first detected just two days prior. Its path was
determined only the day before the close encounter.
Search programs "red flag" such nearby objects, which move more quickly
against the background of stars as compared to more distant asteroids.
Scientists say it is critical to note these fast-movers and quickly do
follow-up observations to make sure Earth is not in their sights.
That's where the amateurs come in.
Around 100 highly qualified but unpaid astronomers are often well equipped
and are viewed as every bit as capable as professional astronomers. But
there simply won't be enough of them as the ability of professionals to spot
smaller asteroids improves and the data load grows.
"Sooner or later things are going to come to a crunch," Marsden says.
Glitches and Bickering
Marsden is confident that his small crew can keep an eye on things for now,
but he says more funding is required to hire two more people, as well as
someone to maintain the sometimes-glitchy computer system that processes
asteroid data and supplies the follow-up observers with the data they need
to go hunting.
Delays of 24 hours or more have occasionally occurred in the past, Marsden
said, due either to computer problems or the fact that he and his two
colleagues are putting in seven-day weeks in an effort to keep up.
The growing workload has begun to generate tension and cause workers to snap
at each other -- something that never used to happen, Marsden said.
Meanwhile, the Minor Planet Center's funding is dropping. The bulk of its
money has traditionally come from subscriptions to its publications of
asteroid data. But with the transformation from printed to electronic
publishing, fewer research institutions, libraries and individual
astronomers are willing to pay for the data.
NASA provides about half of the center's budget (Marsden's own salary comes
from his position with the Smithsonian Institution). Yet it is NASA that
funds many of the major search programs that generate the data that pours
into the Minor Planet Center.
David Morrison, an asteroid researcher and director of the space program at
NASA's Ames Research Center in California, agrees that the increasing pace
of discovery may overwhelm the cadre of amateur astronomers doing follow-up
observations, no matter how well equipped they might be.
Morrison said that any asteroid aiming for Earth can be discovered decades
before the impact, assuming it is bright enough to be picked up with current
"The problem is not that we won't see it soon enough," he said. "The problem
is that we won't spot it at all."
But once an asteroid is discovered, Morrison said, there's no reason it
can't be properly processed. Morrison thinks management of the growing
bounty of data needs to extend beyond the Minor Planet Center.
"We'll need to distribute the workload among a number of international
organizations that already have the capability to process these data,"
At least three organizations around the world have the needed computer
programs. One, in Arizona, is called the Lowell Observatory
Near-Earth-Object Search (LONEOS). Lowell scientists used to process their
own asteroid data, but a grant that funded the effort was not renewed. So
now they are forced to forward mostly raw data to the Minor Planet Center.
Bruce Koehn, a research scientist who does the programming for the LONEOS
effort, said his colleagues would prefer to process their own data. He said
there are several reasons why distributing the workload is a good idea.
"The Minor Planet Center can easily become overwhelmed," Koehn said.
Equally important, he said, is that having multiple groups do the
calculations provides a check and balance for overall accuracy. It also
creates an environment where new and improved methods will be developed by
one group and adopted by others.
Regardless, the future might not be as grim as others think, according to
Most large asteroid survey programs do some of their own follow-up work, he
said. As the pace of discovery increases, he thinks these survey teams will
be forced to do more of their own follow-up. And other search projects
currently in the planning stages have included follow-up observing as part
of their strategy, he said.
In addition, two groups currently do some calculations that contribute to
the overall knowledge base and double-checking. One team is at the
University of Pisa and another at NASA's Jet Propulsion Laboratory.
Too many hubs?
Some researchers say the Minor Planet Center should remain the hub of
"The Minor Planet Center has the expertise, links and contacts," said
Jonathan Tate, founder and director of Spaceguard UK, an group that
advocates increased search efforts. "They are a central node, and to
distribute this would produce further complications, both practical and
Tate agreed that more funding is needed to allow the center to keep pace.
One way to cope with the increasing workload is to fund and foster greater
international cooperation and new search projects, several experts say.
Efforts are under way to establish a multinational professional search
program in Europe, says Peiser, the UK researcher. The idea was jumpstarted
last year when a task force set up by the British government recommended
sweeping changes to how governments should view the threat of asteroids.
Among the official recommendations of the task force:
"We suggest that the United Kingdom and other governments, together with the
International Astronomical Union, NASA and other interested parties, seek
ways of putting the governance and funding of the Minor Planet Center on a
robust international footing, including the Center's links to executive
agencies should a potential threat be found."
The Minor Planet Center has not yet benefited from the call to action.
Small fish in a big cosmic sea
Meanwhile, astronomers around the world grapple with a simple fact: They
cannot see most asteroids smaller than 1 kilometer until they are relatively
nearby. The technology exists, but it has not been devoted to the task. The
reason goes back to decisions made roughly a decade ago.
Early discussions spearheaded by NASA resulted in the goal of finding 90
percent of all Near Earth Asteroids in a decade's time. Scientists talked of
setting the limit lower, to include objects down to 100 meters, but they
knew that would have meant finding a lower percentage of the many more
objects they'd be looking for. Several scientists involved in the
discussions argued that the bulk of the danger rests with asteroids larger
than 1 kilometer anyway.
As Morrison puts it: "Only these can create impacts that could have global
consequences and perhaps end civilization as we know it."
So NASA funding for asteroid search programs today is driven primarily by
the goal of finding objects 1 kilometer or larger. Many smaller objects are
found in the course of these searches. But some researchers think it is time
to begin focusing on the smaller rocks.
"We need bigger telescopes to come down to the 100-meter limit," Tate said.
"There is a substantial risk from undetected 100-meter sized objects."
If Tate gets what he wants, then Marsden's prediction of 200,000 numbered
asteroids by 2004 would later be superseded by quantities about which no one
is willing to venture a guess. Millions of small asteroids are thought to
"Then things will really start booming," Marsden said.
Which would, of course, greatly exacerbate the problem of follow-up
"The amateurs doing follow-up are doing sterling work," Tate said, "but it
is a bit odd that something as important as this is not a matter for
Received on Fri 19 Oct 2001 11:28:08 AM PDT