Signs Supplement - Meteors, Asteroids, Comets, and NEOs
- October 2004
DENVER - Several
9News viewers e-mailed us with accounts of what appeared to
be a low-flying meteor.
One witness says he was walking through Bow Mar around 6:00
a.m. Tuesday and saw a shooting star, comet or something traveling
from north to south at about 15 degrees off the horizon. It
was travelling horizontal and according to witnesses was much
larger than any shooting star they'd ever seen.
Another witness in Fort Collins saw a similar event around
5:50 a.m. It was described as a flying object which was believed
to be a meteor. It was moving fast and straight from east
to west and had a huge trail of fire behind it.
We contacted the Denver Museum of Nature & Science and
workers there also received calls about the flash in the sky.
The Denver Museum of Nature & Science would like anyone
who saw the event to record what they saw at a web site specifically
designed for that.
Meteorites are generally
named after the region or town near where they were found.
Here are the five Colorado meteorites that fell to Earth with
• Johnstown, July 1927. (Eventually 27 fragments were
• Denver, 1961. (This meteorite crashed through the
roof of a warehouse in northeast Denver.)
• Cañon City, 1973 . (Crashed through a garage
• Elbert County, 1998. (Many witnessed a fireball;
eventually three fragments were recovered.)
• Berthoud, Oct. 5, 2004, at 1:30 p.m. (Fell one day
after other reports of a daylight fireball in Colorado.)
BOULDER - Out of a clear
blue sky, a bit of space history as old as the solar system
and no bigger than a softball slammed into the soft, wet earth
beside a Berthoud family's home Oct. 5.
John Whiteis saw light and a little bit of dirt move. His
wife, Meghan, saw a dark streak. Their 19-year-old son, Casper,
heard something like this:
"We were kind of trying to figure out what we had just
witnessed," said John Whiteis, a former auto mechanic
and self-described Star Trek fan.
At first he thought it might be a piece of a passing plane.
But there were none overhead.
Maybe a model rocket launched by a neighbor, they wondered.
A few moments passed before the family realized what they
had just seen: a shiny, black meteorite plunging at more than
100 mph into a pasture , just 75 feet from their home.
Scientists say meteorites pepper the Earth's atmosphere
daily, almost every hour. Most burn up as "shooting stars."
Some land in sizes as small as a grain of sand.
The Whiteis family, however, witnessed only the fifth confirmed
sighting of a meteorite hitting the ground in Colorado since
On Monday, the family gathered at the University of Coloradoto
talk about their discovery along with a panel of geologists
Judging by their reactions, it was a close call as to which
group was more excited by the find: the family or the scientists.
"Isn't this exciting?" CU geologist Steve Mojzsis
gushed. "Thank you for bringing the meteorite in."
CU planetary scientist Nick Schneider d escribed his reaction
when he first heard Casper Whitei s' rendition of how the
meteorite sounded as it landed.
"I got chills up and down my spine hearing that description,"
Schneider said. "I get a zing from this rock."
"This came from outer space. It probably took a million
years to get here," he added. "If you're feeling
a little bit old, just come and touch this and it'll put things
If not for some furniture the Whiteis family bought at an
auction last weekend, this meteorite might have fallen to
It rained on Monday, so the furniture stayed in the vehicle.
On Tuesday, John Whiteis was home from work early, so in came
the furniture. And down came the meteorite.
It took the family about 25 minutes after impact to locate
A smooth black surface about the size of a golf ball peeked
out from under the dirt.
John Whiteis turned back to the house to get a shovel. But
before he could get there, Casper had grabbed a hammer and
dug it out of the earth.
By then it was cool to the touch, said Casper, an aeronautics
engineering student at AIMS Community College, who hopes to
study at CU some day.
While meteorites have value to collectors and can fetch
up to $1 a gram, the Whiteis family say their two-pound meteorite
is not for sale. Instead they plan to let CU scientists study
the rock and put it on public display.
Scientists at CU also hope to study the meteorite and compile
other eyewitness accounts of any fireball sightings that day
to determine its trajectory .
On Saturday, with permission from local property owners,
scientists and volunteers hope to search up to four square
miles of the area around the Whiteis home for other fragments.
BEIJING, Oct. 12 (Xinhuanet)
-- A team of French and Egyptian scientists say they've discovered
the biggest meteorite field on Earth.
The meteorite site, with more than a hundred traces of crashed
meteorites has been found in the region of the Egyptian-Lebanese
A spokesman of the French scientific research center CNRS,
says the meteorite shower remains had hit the earth about
50 million years ago and covered the territory of 5,000 square
Craters ranging from 20 meters to one kilometer in diameter
have been created as a result of the clash. Meteorite remains
are buried at an 80-meter depth.
Until recently, an Argentine meteorite field of 60 square
kilometers has been considered the biggest in the world.
|The common perception that
dinosaurs were edging towards extinction when a huge meteorite
wiped them out 65 million years ago is false, says a new study
that claims the animals were in their prime when disaster struck.
The variety of species existing around the end of the Cretaceous
period suggests that they were diversifying at a remarkable
rate, with an explosion of genetic diversity that was reflected
in their success dominating the planet.
Scientists from the University of Rhode Island at Kingston,
in the United States, established that at least 245 dinosaur
genera - the "families" from which species emerge
- lived during the late Cretaceous era, from 99 million to
65 million years ago.
They included some of the best known dinosaurs, such as tyrannosaurus
rex and the three-horned triceratops.
Peter Sheehan, from the Milwaukee Public Museum, who took
part in the research, told New Scientist magazine: "The
lifestyles of dinosaurs became much more diverse. By the late
Cretaceous, we have much more specialised animals."
The first dinosaurs evolved about 230 million years ago and
were all much the same.
By the late Jurassic period, which began about 160 million
years ago, they had produced about 40 different genera, or
Then in the Cretaceous era which followed there was an e
xplosion of dinosaur diversity, according to a new anal ysis
of fossils from around the world.
Dr Sheehan said the diversity of plant-eating dinosaurs of
the period was "absolutely breathtaking". For example,
hadrosaurs evolved a duck-billed jaw filled with teeth for
chewing vegetation, while the rhinoceros-like ceratopsians
grew elaborate horns.
But the controversy over the dinosaurs' evolutionary path
looks likely to continue: on Tuesday a paper published in
the scientific journal Trends in Ecology and Evolution by
Professor David Penny of Massey University in New Zealand
and Dr Matt Phillips of Oxford University claimed the precise
opposite - that birds and mammals began to "out-compete"
dinosaurs about 80 to 90 million years ago, well before the
end of the Cretaceous era.
"The combined evidence fro m fossils and molecules
appears to support an expansion of birds and mammals, and
a decline of pterosaurs and dinosaurs, starting many millions
of years before the end of the Cretaceous," the scientists
What is not in doubt however is that there was a serious
meteor strike on the Earth roughly 65 million years ago, in
the Bay of Mexico. That is reckoned to have thrown up so much
dust into the atmosphere that it cooled the planet abruptly,
making it much harder for the cold-blooded dinosaurs to survive,
and giving warm-blooded animals including mammals the evolutionary
|A new-found field of impact
craters may mark the site of a recent comet strike.
We have identified an exceptional field of meteorites and impact
craters stretching from the town of Altötting to the area
around Lake Chiemsee in southeastern Bavaria, Germany. While
there are many meteorite "strewnfields" known around
the world, few contain significant craters. The Chiemgau field,
which falls within an ellipse 36 miles long and 17 miles (58
by 27 kilometers) wide, holds at least 81 impact craters ranging
from 10 to 1,215 feet (3 to 370 meters) in size. Many more craters
may lie hidden in heavily forested areas within the ellipse,
and farming activities in the region may have destroyed others.
In autumn 2000, a group of amateur archaeologists working
the area around Lake Chiemsee discovered pieces of metal containing
minerals not found previously in the region. Werner Mayer,
the independent scholar who led the amateur team, noticed
that the material was associated with what appeared to be
impact craters, most of which showed clear rims. In 2004,
four other scientists joined Mayer to form the Chiemgau Impact
Research Team: Kord Ernston, a geologist at the University
of Würzburg; independent scholar Gerhard Benske; Michael
Rappenglück, an astronomer with the Institute for Interdisciplinary
Sciences in Gilching; and Ulrich Schüssler, a University
of Würzburg mineralogist.
strewnfields with craters
of largest crater
||1,215 feet (3700m)
||607 feet (158m)
||   ; 9
||36 0 feet (110m)
|Campo del Cielo
||328 feet (100m)
||312 feet (95m)
||87 feet (26.5m)
||380 feet (116m)
Geological evidence makes clear the site's extraterrestrial
connection. Sandstone boulders and small, weathered rock fragments
called cobbles in and around the craters are completely coated
by silica glass, which requires unusually high temperatures.
We believe the cobbles were superheated and ejected in the
impact. We found bluish-gray, dark green, and black glass-like
material in unusual shapes — such as teardrops and dumbbells
— indicating rapid cooling and solidification during
The peculiar minerals found throughout the site in clude
the iron-silicon alloys gupeiite (Fe3Si) and xife ngite (Fe5Si3),
both of which were identified in a meteorite discovered in
the Yanshan Mountains of China in 1984. Gupeiite was also
found in FRO 90036, a ureilite-class meteorite found in the
Frontier Mountains of Antarctica, and related minerals were
found in Dhofar-280, a meteorite that probably came from the
When did the impact occur? Archaeological finds in the area,
as well as the ages of trees within the craters, tell us the
impact occurred in historical times. The oldest tree we found
rooted in a crater wall is at most 500 years old, and we found
xifengite and gupeiite beneath the retaining walls of Burghausen
Castle, which has been dated to the 15th century a.d. At another
site, we unearthed impact-related minerals along with Celtic
artifacts. The artifacts seem to have been strongly heated
on one side. This pushes the earliest date for the impact
to the late Roman period, between 480 b.c. and 30 b.c. Radiocarbon
dates from ash samples we removed from layers in several craters
are not yet available.
The growth patterns of Irish oaks slowed dramatically between
a.d. 536 and 545, indicating a much cooler climate. Historical
records refer to famine and a dimmed Sun during this period.
Many have argued this so-called "dust-veil event"
was the aftermath of a large (0.3 mile, or 500m) comet fragment
exploding high in Earth's atmosphere. To date, no craters
related to such an event have been found.
However, the rings also show slowed growth around 207 b.c.
Roman authors wrote about showers of stones falling from the
sky and terrifying the populace. In 205 b.c., because of
these events, the Senate ord ered that a conical meteorite
known as the Needle of Cybele (which had been worshipped in
Asia Minor in connection with the fertility goddess Cybele)
be brought to Rome. On the rim of the largest crater, named
Tüttensee, archaeologists have found Roman relics from
about a.d. 200. This, in addition to the heated coins from
the late Roman period we found at the Chiemgau impact site,
lead us to favor this early date.
We believe an asteroid or comet fragment exploded above southeastern
Germany in the late Roman period. Our candidate impactor is
a low-density object, perhaps something like the C-class asteroid
253 Mathilda. Astronomers believe Mathilda was once completely
shattered but reassembled as a loose aggregate of material
— that is, a rubble pile. Given the material we recovered
and the length of the ellipse of scattered debris, we suggest
the impacting body was more likely a comet fragment —
rich in methane, ammonia, and water, with a relatively small
fraction of rocky matter.
We estimate the projectile had a diameter of about 0.7 mile
(1.1 km) and a mean density about 30 percent greater than
water (1.3 g/cm3). It entered Earth's atmosphere at a speed
of 27,000 miles per hour (43,000 km/h) and broke up at an
altitude of 43 miles (70 km). The main mass of the projectile
struck the ground at 2,200 miles per hour (3,500 km/h), releasing
an amount of energy equivalent to 106 million tons of TNT.
Based on the size distribution of the craters — the
larger ones are in the southern part of the field, the smaller
ones in the northern part — we conclude the meteoroid
came out of the northeast and m oved southwest. Multiple fragmentation
events may account for the cratered area's large size.
What would people on the ground have experienced? About 2
seconds after the strike, people 6 miles (10 km) away would
have felt the ground shake as it would in a magnitude 6.0
earthquake. The air blast, arriving 30 seconds after impact,
would have swept through at a speed of 500 miles per hour
(800 km/h) and produced a peak pressure of about 1.4 atmospheres
(142,000 Pa), easily collapsing buildings, especially wooden
ones. Even from 10 km away, sound from the impact would have
reached 103 decibels — loud enough to cause strong ear
pain. Up to 90 percent of the trees would have blown over;
the rest would have lost their branches.
We found a thin layer of ash in and between the craters.
The for est beneath the blast would have ignited suddenly,
burning until the impact's blast wave shut down the conflagration.
Dust may have been blown into the stratosphere, where it would
have been transported around the globe easily, so it may be
possible to trace the event in ice cores from Greenland or
In any case, the impact undoubtedly had a major effect on
the environment and people then living in the vicinity of
Altoetting-Chiemgau. The region must have been devastated
for decades. We are currently looking for gaps in the historical
and archaeological records during the time we propose for
the impact to better understand both the event itself and
its cultural effects.
|By JOEY HOLLEMAN
Posted on Fri, Oct. 15, 2004
SHILOH — Hundreds
of thousands of Midlands residents taking the southern route
to Myrtle Beach each summer pass within a few miles of Woods
Bay State Natural Area. Only a handful take the left turn
and head for the park.
That's probably a good thing. Woods Bay in the summer is
only for hearty souls with lots of bug repellent.
Between the first frost of fall and the first 90-degree day
of spring, however, Woods Bay is the ideal place to spend
an afternoon experiencing the intriguing geological phenomenon
of the Carolina bay.
These oval-shaped, swampy depressions crop up throughout
the Atlantic coastal plain, but they are as mysterious as
they are common. Scientists aren't sure why the bays almost
always have a northwest to southeast orientation. They are
intrigued by the sand rims that usually form on the southeast
and sometimes the northwest edges of the oval. They are perplexed
how the bays formed in the first place.
One theory is that a meteor br oke into pieces, which impacted
throughout the Southeast thousands of years ago. Folklorists
like to claim the Carolina bays are dinosaur footprints.
Modern scientists can only say for sure that the ovals are
disappearing under housing developments and shopping centers
as the growing Southeastern population spreads out. That's
why the state felt the need to buy and protect the 1,541 acres
of Woods Bay straddling the Sumter-Clarendon county line in
The park opened in 1975 but never has drawn many people.
In 2003-2004, Woods Bay ranked last among the 46 state parks
in attendance, with only 2,124 visitors.
That frustrates park manager Geoff Akins, who has to remind
himself what one of his supervisors told him about the park:
"We're not popular. We're important."
One reason for the low attendance is the park is a long way
from any large population area, nearly a half-hour drive from
Florence or Sumter. Another is it's hard to get your hands
"One of the unfortunate things about the park is so
much of it is inaccessible," Akins said. "I've had
a lot of people walk around the nature trail and think they've
seen the whole park."
living in southern Germany during Roman times may have witnessed
a comet impact 5,000 times more destructive than the Hiroshima
atom bomb, researchers say.
Scientists believe a field of craters around Lake Chiemsee,
in south-east Bavaria, was caused by fragments of a huge comet
that broke up in the Earth's atmosphere.
Celtic artefacts found at the site, including a number o
f coins, appear to have been strongly heated on one side.
This discovery, together with evidence from
ancient tree rings and Roman reports of "stones falling
from the sky", has led researchers to conclude that the
impact happened in about 200BC.
However the claim still needs to be verified by other experts.
The crater field was uncovered after amateur archaeologists
working in the area found pieces of metal containing unusual
A team of geologists led by Kord Ernston,
from the University of Wurzburg in Germany, went to the site
and discovered evidence of a cataclysm that would have left
the region devastated for decades.
Not only would trees and homes have been
flattened for many mi les by the blast, but the local climate
would have changed for years afterwards.
Tree rings show that vegetation growth slowed
down in around 207BC, possibly because of the "nuclear
winter" effect of dust blotting out the sun.
More than 80 craters were found in an elliptical area 36
miles long and 17 wide, ranging in size from 10 to 1,215 feet
across. The largest, filled with water, now formed Lake Tuttensee.
Around the site the team found clues that suggested an impact
from space, including rock heated into glass and minerals
associated with meteorites.
The most likely cause was a low-density comet, 0.7 miles
(1.1 kilometres) wide, that broke up at an altitude of 43
miles and fell in pieces to Earth, the scientists reported
in Astronomy Magazine.
They wrote: "The m ain mass of
the projectile struck the ground at 2,200 miles per hour,
releasing an amount of energy equivalent to 106 million tons
The bomb that destroyed Hiroshima at the
end of the Second World War had an explosive force of just
20,000 tons of TNT.
The scientists gave a graphic description of what it might
have been like to experience the impact.
"About two seconds after the strike,
people six miles away (10 kilometres) would have felt the
ground shake as it would in a magnitude six earthquake. The
air blast, arriving 30 seconds after impact, would have swept
through at a speed of 500 miles per hour and produced a peak
pressure of about 1.4 atmospheres, easily collapsing buildings,
especially wooden ones.
"Even from 10 kilometres away, sou
nd from the impact would have reached 103 decibels –
loud enough to cause strong ear pain. Up to 90% of the trees
would have blown over; the rest would have lost their branches."
Forest beneath the blast would have ignited
suddenly, and continued to burn until the shock wave blew
the fire out, said the scientists.
The conflagration had left a thin layer of ash in and between
Roman authors at the time wrote about showers of stones falling
from the sky and terrifying the local population.
Because of these events, the Senate in 205BC ordered that
a conical meteorite known as the Needle of Cybele, which had
been worshipped in Asia Minor, be brought to Rome.
"The impact undoubtedly had a major effect on the e
nvironment and people then living in the vicinity of Altoetting-Chiemgau,"
wrote Ernston's team.
"The region must have been devastated
for decades. We are currently looking for gaps in the historical
and archaeological records during the time we propose for
the impact to better understand both the event itself and
its cultural effects."
Dr Benny Peiser, a leading expert on impact events from Liverpool
John Moore's University, said the report should be treated
with caution until more was known.
He said the date was speculative, and pointed out that asteroids
or comets a kilometre wide struck the Earth on average only
once every 500,000 years. Generally such a large impact would
cause much more severe and obviously traceable damage.
"In short, this is an an intriguing find, but I remain
sceptical for the time being," said Dr Peiser. "The
impact cratering research community has not assessed these
claims yet. That's what needs to be done next."
Perry A. Gerakines, an assistant
professor in the department of physics at the University of
Alabama at Birmingham, explains.
We have extensive evidence that Earth
has already been hit by asteroids many times throughout history-the
most famous (or infamous) example is probably the asteroid or
comet that created the Chicxulub crater in the Gulf of Mexico
and may have contributed to the extinction of the dinosaurs
at the end of the Cretaceous Period 65 million years ago. A
more recent but less devastating example, called the Tunguska
event, occurred in 1908, when a meteor or comet exploded over
the wilderness of Siberia, damaging farmland and leveling trees
for miles around. Because most of the earth is covered by oceans,
there may also be many small impacts that go unnoticed.
There are thousands of small bodies that we call asteroids
or meteoroids in orbit aroun d the sun. Many of these objects
are called near-Earth asteroids (or NEAs) because they have
orbits that repeatedly bring them close to, or intersect with,
Although the odds of any one particular asteroid ever impacting
Earth are quite low, it is still likely that one day our planet
will be hit by another asteroid. At the current rate of impacts,
we would expect about one large asteroid
to impact Earth every 100 million years or so. For that
reason several programs, such as the Lincoln Near-Earth Asteroid
Research (LINEAR) project at the Massachusetts Institute of
Technology, have been undertaken around the world to discover
and monitor potentially Earth-threatening asteroids.
When a new asteroid is discovered, astronomers analyze it to
determine whether its orbit around the sun could bring it
close to the Earth. They take successive images of the asteroid
over the course of days after its discovery in order to predict
its probable orbital path for the near future. The predicted
orbit is then compared to the orbit and position of Earth
to check for any times when they might pass close to each
Although scientists can calculate a most-likely
orbit from these early observations, each single observation
of the asteroid's position contains some uncertainty. Most asteroids
are small objects, a few meters to a few tens of meters across,
and even the resolving power of a large telescope cannot determine
their positions exactly. The uncertainties in an asteroid's
position lead to uncertainties in how well we can determine
its speed and direction of travel. A s a result, a large number
of possible orbits for an asteroid can be predicted within these
windows of uncertainty.
Careful computer simulations are used to calculate the future
orbital path of the asteroid, with randomly chosen initial positions
and velocities that fall within the margin of error of the telescopic
observations to date. A large number of these simulations are
generated for each asteroid. The probability that any particular
one will actually hit Earth is given by the fraction of the
extrapolated paths that leads to an impact. For example, if
one million different possible orbits are calculated, and one
of those leads to an impact, then we say that the odds of the
asteroid hitting our world are one million to one.
The uncertainties in an asteroid's orb it are greatest in the
hours just after its discovery, and thus the calculated probability
of an impact also tends to be the highest at these times.
As we monitor an asteroid over the course of the weeks or
months that follow, its orbit becomes more and more certain,
and we become more knowledgeable about its position at a given
date in the future. We can then rule out many possible paths
it may take. In most cases, monitoring the asteroid over a
few weeks quickly leads to an impact probability of very nearly
in the sky could be clues to the massive mystery explosion
which rocked part of Greater Manchester yesterday.
They were seen by midwife Jeanette Vagg as she drove home
just minutes before the huge bang was heard.
And an expert at Jodrell Bank Observatory
in Cheshire believes the cause could be a bolide - a meteor
between the size of a hazelnut and a tennis ball.
"When it hits the atmosphere, it shatters," said
astronomer Ian Morison. "A loud explosion would be heard
and the debris could break into a million little bits. It
seems like a reasonabl e explanation for what happened."
Other theories for the massive noise in the Salford area
include the an unlicensed industrial firework and a build-up
of flammable gases in disused mine workings.
But Jeanette is convinced that meteorites are the answer.
Jeanette, who works at Trafford General, said: "I was
driving home through Urmston towards Stretford and I saw them
in the sky.
"They were black at the bottom
with flames coming off them in a line. They were falling and
one was a bit higher than the other. My first reaction
was to think 'I hope they're not bombs'. I drove a bit further
and looked again, but they had gone."
As reported in yesterday's MEN, dozens of
people called the police and fire service after hearing the
blast at about 7.30am.
Chief Supt Brian Wroe of Salford police said: "The industrial
firework is one of several possible explanations, as is an
"Officers have met with residents in the Old Clough
Lane area of Worsley where we first received reports of an
explosion. We have also spoken to the fire service, the gas
companies and the local authority and not been able to find
any rational explanation.
"We are keeping an open mind as we haven't been able
to find any evidence of damage or destruction."
The blast was heard by people in Chorlton, Farnworth, Walkden,
Worsley and Pendlebury. But police and the fire service have
been unable to identify the source despite searching the area.
The investigation has now been closed unless members of
the public suggest new lines of inquiry.
Earthquake experts today denied that a quake could have taken
place in Greater Manchester.
Experts from the British Geological Society launched an investigation,
but said that there was no evidence of any earthquake activity
in the region.
Halley's co met won't
return until 2061, but pieces of the celestial body are streaking
across the sky. The heavenly show, known as the Orionids meteor
shower, peaks Wednesday night, when sky-watchers may observe
two dozen meteors per hour.
Though the comet remains distant, Earth is passing through
the comet's ancient debris field—with dramatic results.
"Over time comets leave a trail of debris along their
orbits," explained Kelly Beatty, executive editor of
Sky and Telescope and editor of Night Sky magazine.
Each time a comet orbits the sun, the star's heat strips
comets of dust and ice. Scientists believe that Halley's comet
sheds some 20 feet (6 meters) of dust and ice particles on
"For a select few [comets], the Earth goes through their
orbits at the same time every year," Beatty said. "The
analogy I like to use is a garbage truck full of sand. As
it barrels down the road, the sand billows out the back end.
And that's what Earth plows through."
Earth passes near Halley's cigar-shaped orbit debris field
twice each year: the Orionids shower fall in October, the
Aquarids shower in May.
The tiny particles of ice and rock, some as small as a grain
of sand, put on quite a show as shooting stars or meteor showers.
"What we see is not the particle burning up,"
Beatty said. "What we're really seeing is the particle
transferring all that energy to the air molecules along its
path and causing them to become superheated to the point that
they are incandescently hot."
Meteor particles are among the smallest celesti al objects
that can be seen by the human eye.
"For anyone who has eaten a bowl of Grape Nuts, the
little nuggets in there are a pretty good match in size, shape,
density, and even color of what a typical meteor particle
looks like from space," Beatty said. [...]
The Chicxulub meteorite
impact is largely credited with the extinction of 50 percent
of the world's species, in cluding the dinosaurs. But could
there have been more than one meteorite impact 65 million
Astrobiology Magazine -- Rather than a single meteorite impact
65 million years ago, could Earth have been hit with a scattershot
of several rocks from space?
It may have happened before. There is evidence that about
35 million years ago, at least five comets or asteroids collided
with Earth. If the effects of a single large meteorite impact
seem overwhelming, imagine how life on Earth would reel from
a barrage of rocks from space.
One way such impact clustering happens is to have a single
bolide break up as it approaches a planet. The comet Shoemaker-Levy
9 provides a recent example. Before striking the planet Jupiter
in 1994, the comet was torn into 21 different pieces by
Jupiter's immense gravity. These fragments struck Jupiter
over 5.6 days, some creating large fireballs as they entered
Jupiter's vast gaseous atmosphere.
Earth's gravity is no where near as powerful as Jupiter's,
so the same scenario would not happen to Earth. Yet many asteroids
are thought to be rubble piles, loosely bound by gravity,
and such an asteroid could rip apart as it approached our
But if an asteroid "rubble pile" broke up before
it entered Earth's atmosphere, the pieces would only result
in one crater, or at most two, because most of the pieces
would fall into the same hole.
"Once such a rubble pile enters Earth's gravity it's
too late," says Christian Koeberl, a geochemist at the
University of Vienna in Aust ria. "It would only get
into the attraction field of Earth's gravity a few hours before
it hits at best, and this is not time enough to spread it
However, having an asteroid break up as it approaches Earth
is not the only way to end up with multiple craters.
Within the asteroid belt that orbits the sun between Mars
and Jupiter, collisions between asteroids sometimes occur.
The resulting fragments can then rain down on Earth. Simon
Kelley, a geologist at the Open University in England, says
that such a collision occurred 470 million years ago, and
many of those fragments traveled to Earth. In fact, some of
the fragments still are impacting Earth today.
A similar shower of fragments can come
from a collision within the Oort cloud, a comet-filled region
in the outer-most portion of the solar sy stem. Kelley
says such a cometary shower may be responsible for the cluster
of impact craters dated to be 35 million years old, including
two of the largest impact craters on Earth: the 100 kilometer
Popigai crater in Siberia, and the 90 kilometer Chesapeake
Bay crater off the shore of Maryland. This cometary shower
is thought to have lasted for 2 to 3 million years.
Looking over the Planetary and Space Science Centre's Earth
Impact Database, several of the crater dates overlap. Much
of this overlap reflects the limitations of current dating
techniques, where ages can't be narrowed down further than
hundreds of thousands of years. But it is possible that some
of the craters point to a multiple impact scenario.
The Boltysh crater in the Ukraine may be proof that multip
le impacts occurred during the Cretaceous-Tertiary (K-T )
extinction. Kelley has dated the crater to be about 65 million
The Boltysh crater had previously been assigned ages ranging
from 88 million to 105 million years old, a variation that
arose due to the different dating methods used. Kelley used
Argon-Argon dating to determine the correct age for the crater.
The crater rocks melted in the heat of impact, and when they
cooled they trapped argon out of the air. Different isotopes
of argon decay at different rates, so by measuring the ratio
of argon isotopes, Kelley was able to estimate when the rocks
melted, within a margin of error of plus or minus 600,000
The margin of error prevents scientists from saying Boltysh
was definitely part of the same meteorite strike as Chicxulub.
And Kevin Pope of Geo Eco Arc Research points out that while
Chicxulub has been linked directly to the K-T boundary and
extinctions by the stratigraphy of its ejecta, the same is
not true for Boltysh.
"Craters the size of Boltysh form every few million
years, so the fact there is a crater this size close to the
boundary is no surprise," says Pope.
The Boltysh crater measures only 24 kilometers in diameter
- compared to Chicxulub's nearly 200-kilometer-wide monster
- so even if the smaller meteorite that made this crater hit
around the same time as Chicxulub, its effects wouldn't have
been as catastrophic.
But if Boltysh did occur around the same time as Chicxulub,
it could aid in our understanding of the K-T extinction event.
Craters can act as time capsules, preserving information about
the environment at the moment of impact. Comet Shoemaker-
Levy left enormous scars on Jupiter. Credit: NASA
Like Chicxulub, the Boltysh crater is buried underground.
But while Chicxulub filled with seawater, the Boltysh crater
became a fresh water lake. Kelley is writing a paper with
Dave Jolley at the University of Sheffield on the microflora
and fauna they have found in the Boltysh crater fill. They
hope to determine how rapidly life recovered in the vicinity
of the impact, and how that recolonization occurred.
As for other K-T impact craters, Kelley notes that the record
is very poorly dated. He plans to study other craters, currently
dated to be from the Devonian (around 380 million years ago)
to the Eocene (34 million years ago), to see if their ages
are accurate. By determining the correct dates f or impact
craters, scientists will be able to better understand how
often multiple impact events have occurred in the past.
So do multiple impacts play a role in mass extinctions? Kelley
says that as far as we know, they don't. For instance, Kelley
says there is no evidence that the barrage of comets 35 million
years ago led to a mass extinction event.
"The effects would have been truly devastating locally,
but they didn't amount to global catastrophes," says
Kelley. "You can argue that minor extinctions are associated,
but not a K-T-like event."
A single large meteorite impact like Chicxulub may be more
harmful to life than a cluster of several smaller meteorites
or comets spread out over a million years or less. Yet determining
why certain species die out can often be difficult. Extinctions
are a natura l part of the cycle of life, and may occur due
to a whole host of interrelated factors, including competition
for food, climate change, and even sea level change. Perhaps
tossing a few meteorites into the mix also can upset the scales,
tipping some species too far off balance to recover.
Six … long …
Solar physicist David Hathaway has been checking the sun
every day since 1998, and every day for six years there have
been sunspots. Sunspots are planet-sized "islands"
on the surface of the sun. They are dark, cool, powerfully
magnetized, and fleeting: a typical sunspot lasts only a few
days or weeks before it breaks up. As soon as one disappears,
however, another emerges to take its place.
Even during the lowest ebb of solar activity, you can usually
find one or two spots on the sun. But when Hathaway looked
on Jan. 28, 2004, there were none. The sun was utterly blank.
It happened again last week, twice, on Oct. 11th and 12th.
There were no sunspots.
"This is a sign," says Hathaway, "that the
solar minimum is coming, and it's coming sooner than we expected."
The blank sun on Oct.
11, 2004, photographed by the ESA/NASA Solar and Heliospheric
Solar minimum and solar maximum--"Solar Min" and
"Solar Max" for short--are two extremes of the sun's
11-year activity cycle. At maximum, the sun is peppered
with spots, solar flares erupt, and the sun hurls billion-ton
clouds of electrified gas toward Earth. It's a good time for
sky watchers who enjoy auroras, but not so good for astronauts
who have to be wary of radiation storms. Power outages, zapped
satellites, malfunctioning GPS receivers--these are just a
few of the things that can happen during Solar Max.
Solar minimum is different. Sunspots are fewer--sometimes
days or weeks go by without a spot. Solar flares subside.
It's a safer time to travel through space, and a less interesting
time to watch polar skies.
Hathaway is an expert forecaster of the solar cycle. He keeps
track of sunspot numbers (the best known indicator of solar
activity) and predicts years in advance when the next peak
s and valleys will come. It's not easy:
"Contrary to popular belief," says Hathaway, "the
solar cycle is not precisely 11 years long." Its length,
measured from minimum to minimum, varies: "The shortest
cycles are 9 years, and the longest ones are about 14 years."
What makes a cycle long or short? Researchers aren't sure.
"We won't even know if the current cycle is long or short--until
it's over," he says.
counting sunspots for centuries. This plot shows sunspot
numbers from 1610 to 2000. Data are also available for the
current cycle (1996-2004): click
But researchers are making progress. Hathaway and colleague
Bob Wilson, both working at NASA's Marshall Space Flight Center,
believe they've found a simple way to predict the date of
the next solar minimum. "We examined
data from the last 8 solar cycles and discovered that Solar
Min follows the first spotless day after Solar Max by 34 months,"
The most recent solar maximum was in late 2000. The first
spotless day after that was Jan 28, 2004. So, using Hathaway
and Wilson's simple rule, solar minimum
should arrive in late 2006. That's about a year earlier
th an previously thought.
The next sola r maximum might come early, too, says Hathaway.
"Solar activity intensifies rapidly after solar minimum.
In recent cycles, Solar Max has followed
Solar Min by just 4 years." Do the math: 2006 + 4 years
By that time, according to NASA's new vision for space exploration,
robot ships will be heading for the moon in advance of human
explorers. If Hathaway and Wilson's prediction is correct,
those robots will need good shields. Solar flares and radiation
storms can damage silicon brains and electronic guts almost
as badly as their organic counterparts.
For now, says Hathaway, we're about to experience "the
calm before the storm." And although he's a fan of solar
activity--what solar physicist isn't?--he's looking forward
to the lull. &quo t;It'll give us a chance to see if our
'spotless sun' method for predicting solar minimum really
Solar Max will be back soon enough.
The Solar System could
be teeming with almost invisible comets, according to some
astronomers' calculations. If the
y are right, such extra comets would significantly increase
the risk of a catastrophic impact with Earth.
These objects have never been observed, but the astronomers
argue that 'dark comets' provide a likely explanation for
an astronomical puzzle: we can only see a tiny fraction of
the comets that theory predicts.
Astronomers think that many comets come from the Oort cloud,
a field of billions of icy objects that lies up to 100,000
times farther away from the Sun than the Earth does and marks
the outer boundary of our Solar System. The icy objects are
sometimes driven towards the Sun by gravitational tides generated
by the shifting masses of stars in our Galaxy. When this happens
they become comets, orbiting the Sun every 20 to 200 years
on paths that lie at an angle to the planets' orbits.
Given the s ize of the Oort cloud, astronomers
have calculated that there should be about 3,000 comets in
these orbits, 400 times more than are actually observed.
The common explanation for this discrepancy is that the
comets quickly disintegrate into smaller lumps after just
one or two orbits, says Bill Napier, a recently retired astronomer
who worked at the Armagh Observatory, Northern Ireland. But
his mathematical model now suggests that, if this were true,
the debris should cause many more major meteorite showers
on Earth than we see, perhaps up to 30 every year.
In a paper to be published in the Monthly Notices of the
Royal Astronomical Society1, Napier concludes that the predicted
comets are out there after all; we just cannot see them.
Little fluffy clouds
Napier worked with Chandra Wickramasinghe, an astronomer
at Cardiff University in Wales, to explain the comets' invisibility.
Wickramasinghe has suggested that Sedna, the most distant
body identified in our Solar System, could have an orbiting
twin that is dark, fluffy and made of tarry carbon compounds
(see "Sedna 'has invisible moon'").
As Sedna may be a member of the Oort cloud, Napier thinks
that other members of the cloud could be equally dark. Once
ejected, the tarry comets would simply suck up visible light,
he says, remaining cloaked in darkness. "Photons go in,
but they don't come out."
"It's an intriguing possibility," says Alan Fitzsimmons,
an astrophysicist at Queen's University of Belfast in Northern
Ireland. "But while we have seen dark objects before,
Bill is proposing something much, much darker tha n anything
we've ever detected."
NASA's Stardust probe, which is bringing back samples of
dust from the comet Wild 2, lends some support to Napier's
idea. In June this year it reported finding lots of tarry
carbon compounds spraying from the comet2.
The dark comets would present a major challenge to astronomers
searching the skies for objects that might collide with the
Earth. "They're so black you can't
see the damn things," says Napier. "These things
will just come out of the dark and hit you with no warning.
It looks as if we're dealing with a substantial impact hazard
that people haven't clicked into yet."
However, although they reflect almost no visible light,
the dark comets should give out a tiny glow of heat, visible
as infrared radiation. The infrared Spitzer Space Telescope,
which has been operating from Earth orbit for just over a
year, has not seen any dark comets. But this could be because
it focuses on very small, distant parts of the sky, says Napier.
Fitzsimmons disagrees, saying that if these objects existed
in the numbers proposed by Napier, either Spitzer or near-Earth
object surveys such as Spacewatch, based at the University
of Arizona in Tucson, would have picked them up by now.
A new space telescope might provide the answer.
Earlier this month, NASA announced that it would launch an
orbiting infrared telescope called the Wide-field Infrared
Survey Explorer (WISE) in 2008, which will map much wider
areas of the sky. Given enough time, it should be able to
detect the dark c omets, says Napier.
measuring variations in satellite orbits, scientists have
found the first direct evidence of one of the hallowed tenets
of Albert Einstein's theory of general relativity -- that
the Earth and other large celestial bodies distort space and
time as they rotate.
Researchers reporting yesterday in the journal Nature said
improved satellite data had enabled them to show the effect
known as "frame-dragging" with a degree of precision
never previously possible.
"We impro ved our accuracy by orders of magnitude,"
said geodesist Erricos C. Pavlis of NASA's Goddard Space Flight
Center in Greenbelt and the University of Maryland at Baltimore.
"In a while, we should be able to do even better."
Scientists expect that the results of the experiment, by
Pavlis and Ignazio Ciufolini of Italy's University of Lecce,
will be reinforced by NASA's ongoing Gravity Probe B, a satellite
mission designed to measure frame-dragging and another Einsteinian
effect by a different method -- calculating gyroscope deviations
"Gravity Probe B is less systematic, but will provide
higher accuracy -- within a margin of error of less than 1
percent," said Michael Salamon, NASA's discipline scientist
for fundamental physics. "What this research [ye sterday's
report] means is that GPB may not in fact pro vide the first
direct evidence of frame-dragging."
In the early 20th century, Einstein theorized that the gravity
of large bodies such as the Earth distorts space and time,
much the way a bowling ball would stretch a rubber sheet held
aloft on all four corners.
Frame-dragging occurs, he said, because the Earth's rotation
pulls space-time along with it. Salamon likened the effect
to dipping a spoon into a cup of honey and turning it. Close
to the spoon the honey twists, but the effect dissipates with
Scientists have wanted to prove Einstein's theory since the
dawn of the space age. Gravity Probe B, conceived more than
40 years ago, is measuring frame-dragging from a satellite
by focusing a telescope on a distant "guide star"
and measuring how the a xes of gyroscopes deviate from their
original positions pointing directly at the star.
Pavlis and Ciufolini used satellites in a completely different
way. They closely tracked the orbits of LAGEOS and LAGEOS2,
passive satellites covered with "retroreflectors"
that reflect laser beams from ground stations, giving precise
measurements of distance from the station to the satellite.
The satellites' orbits are slightly distorted -- not perfectly
circular or elliptical -- because irregularities in Earth's
surface jog them. But even after subtracting this surface-caused
"noise," the researchers were still left with orbits
that deviated slightly from what they should have been. The
difference, they said, reflected frame-dragging.
"The satellite orbits ar e not perfect because the
Earth is not perfect," S alamon said. "So subtract
them out, and what you're left with are the effects of space
time. The results are better with two satellites, and three
would have been even better."
The key to the experiment's success was better data on Earth's
gravity field -- a better map of the Earth-induced orbital
distortions. This information, collected by another new satellite,
enabled Ciufolini and Pavlis to shrink their margin of error
dramatically from the 20 percent they obtained from an earlier
"There was a tremendous amount of criticism then, and
a lot of people said 20 percent was on the edge of being acceptable,"
Salamon said. "This result, between five and 10 percent,
is a lot cleaner."
MOUNT VERNON - Several
Knox County residents reported seeing a mysterious
blue glow in the sky last night. It was actually a
Sarah Graham and Carri Yost, Mount Vernon Nazarene University
students, witnessed the shower about 11:15 p.m. The students
were traveling on Lower Gambier Road near Ohio 229 when, according
to Graham, The atmosphere turned blue, th en there was a little
split in the sky and an orange color appeared. It happened
very quickly.” A 9-1-1 dispatcher confirmed that it
was indeed a meteor shower over Licking County.
According to NASA, on any night, at any location, a few meteors
can be seen each hour. These are called sporadic meteors,
or simply sporadics. Occasionally, though, intense meteor
displays fill the sky with tens, hundreds, or even thousands
of meteor trails. These displays are called meteor showers.
Many meteor showers can be predicted, as they repeat every
year when the earth passes through the path of a comet. The
bits of debris left behind by the comets, most
no larger than a grain of sand,
create a spectacular light sho w as they enter the earth’s
Was it a bird? A plane?
A lot of people are wondering what lit up the sky around 11:15
p.m. on Sunday.
The mysterious blue light was seen
flying over Ohio, Indiana and Pennsylvania. The fireball
was left by Halley's Comet and was part of a meteor shower
that peaked last week.
All those who saw it say it really was a sight.
Judy Spaulding says, "It was just amazing. We
thought it was lightning but it couldn't have been it
was blue an d it lit up the whole the sky. It was weird.
That's all I can say. It was weird."
"You think maybe UFO. You never know with everything
that going on," says Carl Lovingshimer.
An amateur astronomer in Hocking County in southeast Ohio
says a fireball lit up the sky for about
two seconds and then left a trail of light and smoke that
lasted for several minutes.
He describes fireballs as large, bright meteors.
Craig Kelly from COSI says, "When the earth plows through
that, that's when you see a meteor show. This time it was
hitting the Earth at 66 kilometers per second."
It is unknown where the meteor landed.
It is believed to have landed somewhere on earth, but
no reports just yet.
COLUMBUS, Ohio -- The following
are viewer e-mails to NBC 4 after they saw a bright flash of light
in the sky Sunday night in Central Ohio.
*At 11:20 p.m. over in the sky northeast of Pataskala Ohio,
we just saw a strange flash of light, it
was blue-green, it lit up our street and then orange smoke
(was) in the sky.
*I live off of Holt Road in Grove City. As I was driving home
this evening around 11:15 p.m., I saw a bright flash of light,
looked up and saw what looked to be a streak of fire that quickly
dimmed. At first I thought the flash of light was lightni ng,
but then I saw the streak in the sky. I've seen "shooting stars," but this was extremely bright
and I had never seen one "burning out" so clearly before.
* I was on I-270 driving and at approximately 11:18 p.m., I saw
what was probably a large meteor that looked like it was traveling
east and lit up the sky.
* My husband and I were driving in Pickerington toward Baltimore
and we saw something amazing in the sky. It looked like something
exploded, making a white flash, then the
entire sky was glowing bright blue. We saw something that
seemed to be burning, falling in the direction of I-70. The trail
of the object was also glowing orange, and then it turned to smoke
*There was a flash of blue light in the sky, like an explosion
It was bright enough to light up my block.
*I was laying in bed last night looking out my bedroom window
when I saw the blue light just beneath the crack in my window
shade. It was like a turquoise-blue light
lighting up the sky. The sight reminded me of a light bulb
that had just burnt out after you turn on the switch except it
was a pretty blue color.
*I was on I-71 North last night, maybe 40 minutes outside of
Columbus, when the whole sky lit up a bluish-green
color and then there was a giant flash of white. It looked
like a firework, but my friend and I knew it was too far away
to be a firework. We thought maybe it was a meteor or even an
alien spacecraft. It was quite beautiful
*I was returning home from a concert sometime aft er 11 p.m.
last night. As I opened the front door to my house, suddenly the
whole sky seemed to light up for a brief instant in a bright shade
of blue. I turned around to face the eastern sky, and I
saw in the distance a bright blue ball of light and a trail of
white and yellow "sparks" emanating from it, streaking
across the sky. It looks like an offshoot from a fireworks
display, only clearly at a much higher altitude than fireworks
-- and no sound. As the "sparks" trailed off, they left
a faint, hazy glowing trail in the sky for several minutes. I
opened the door and called to my wife to come and see, but by
the time she made it out, the trail had nearly vanished.
*I saw it last night as I was standing out talking to a friend.
It did not "streak across the sky." It dropped from
the sky down.
*First of all there was the bright blue flash that lit up the
whole sky area, I was facing slightly away from it so it was in
the edge of my sight when it exploded, but I turned quickly to
it. I saw something twirling down leaving
a glowing trail like no other meteorite I have ever seen. I then
saw something large drop below it very fast but not like a meteorite.
*The stream was not sparking, it was glowing, as seen from here.
It was obviously glowing residue. It did
not fade away as I have seen all other meteorites fade. It
gradually spread out and the glowing got dimmer. If you did not
know it was there and looked in the sky you might not see it.
Know ing it was there I kept watching. You could see the str
eam slowly spreading out with the spiraling route seen easier.
* At no point did I think, not now do I believe it was a meteorite,
It had the appearance of either a plane exploding then falling
from the sky, Or a space capsule exploding then falling from the
sky in a swirling motion as some planes do when they lose
control suddenly and crash.
*The stream looked like the space capsule that exploded after
take off, and spiraled up, but this was in reverse.
*I saw the light in Galloway. The only reason I did was because
my dogs started going crazy, very agitated
and barking right before it happened and I got up to put
them outside. It looked like a spotlight
from a helicopter it was so brigh t, only it was blue.
*I am a resident in Athens, Ohio. I saw the light last night
when I was leaving my friend's house at 11:21 p.m. to be exact.
It did undoubtedly leave the sky bright blue for a split second.
However, it burned, literally, red like
it was on fire and left a trail of smoke behind it. The
smoke lingered in the air for some time after it disappeared.
*I walked outside Sunday onto the porch around 11:15 p.m. and
happened to be looking toward the eastern sky. That's when I saw
it the object in the sky. The sky lit up
like a welder's torch and the entire neighborhood lit up like
a silent flash of lightning. The object was traveling northeast
as it exploded instantly leaving a broad long trail of glowing
ember s that remained visible for nearly 20 seconds. It was a
clearly visible over porch lights and a bright moon. I consider
myself lucky to have seen such a magnificent show.
*I live in southern Ohio, in Jackson County, and I saw the meteor.
It came from the east, lighting up the sky as it traveled, leaving
a long, bright trail. It disappeared over the northern horizon.
The light was bright enough that the dogs outside started barking.
*The meteor last night provided a little extra "scare"
for me and three of my friends. We had just gotten out of "The
Grudge," a new scary movie with Sarah Michelle Gellar, and
we were all a little spooked. As we were walking out to our car
there was a sudden booming sound and the
entire sky lit up. We looked up and saw a streak across
the sky. Everyo ne in the parking lot just stopped what they
were doing and looked up to the sky. I think everyone got a little
Halloween spook out of the meteor.
YAXCOPOIL, Mexico (Reuters) -
One minute you're a big T-Rex, the next you're toast.
Challenging conventional theory, new scientific research suggests
the dinosaurs may have been scorched into extinction by an asteroid
collision 65 million years ago that unleashed 10 billion times more
power than the Hiroshima nuclear bomb.
Earth's temperatures soared, the sky turned red and trees all over
the planet burst into flames, said atmospheric physicist Brian Toon
of the University of Colorado.
Among the few survivors would have been animals living in water
or burrowed in the ground like turtles, small mammals and crocodiles.
"Essentially, if you were exposed you were
broiled alive. That is probably what happened to the dinosaurs.
They were big creatures that didn't have anywhere to hide,"
Scholarly debate over how the dinosaurs died is fierce and the
theory put forward by Toon and others adds one more twist to the
greatest forensic mystery of all time.
Despite opposition from some scientists, the idea that the dinosaurs
were killed by an asteroid that slammed into Mexico's Yucatan peninsula
has won general acceptance since it was first mooted in the early
Under that argument, academics say the giant reptiles mostly froze
or starved to death when a huge cloud of particles kicked up by
the meteorite blocked the world's sunlight for months.
But Toon, the co-author of a study published in the Geological
Society of America Bulletin in May, reckons the dinosaurs' end
was even more dramatic .
Creatures living near ground zero would have been vaporized immediately
while those in the Caribbean area and southern United States would
have drowned in 330-feet-high (100-metre) tsunamis when the asteroid
impacted near today's Gulf of Mexico shoreline at a speed of 33,750
mph (54,000 kph).
Then, a column of red-hot steam and dust soared thousands of miles
(km) into space and most of it fell back toward Earth within a few
hours, turning the heavens into hell.
"The entire sky would be radiating at you.
It would be like standing next to a giant fire; you'd be burned
very severely," Toon said, whose research is based on mathematical
and computer models.
Land dinosaurs all around the world perished from the intense
heat of several hundred degrees Fahrenheit, said Toon.
He agrees with other scientists that the dust cloud later cooled
and blocked out the sun, but says the land dinosaurs were already
history by that time.
The darkness finished off many of the remaining marine reptiles
and fish by killing plankton and disrupting the food chain, said
Research conducted by a Cardiff
University astronomy scientist suggests that a
comet colliding with earth is actually more likely than was previously
Professor Chandra Wickramasinghe, Honorary Professor Bill Napier
and research student Janaki Wickramasinghe of Cardiff University’s
centre for Astrobiology believe that some comets are not visible
using current astronomical scanning equipment.
They argue that if this is the case, international programmes
designed to detect near-earth asteroids, and ways to reduce the
worst effects of them colliding with Earth may need to be urgently
Professor Wickramasinghe said, "It’s
possible that we are missing many of these Earth-threatening
objects and we need to think again ab out mitigating strategies
- some of which assume decades or centuries of warning before
The team has found that the surfaces of inactive
comets, if composed of loose, fluffy organic material like cometary
meteoroids, develop such small reflectivities - they appear invisible.
The near-earth objects may therefore be dominated by a population
of fast, kilometres-wide bodies, too dark to be seen with current
A new NASA mission will scan the entire sky with an infrared
telescope - like a powerful set of night vision goggles to search
for cool, or failed, stars, called brown dwarfs, and also dark
comets and cometary fragments, of the type proposed by Professor
Wickramasinghe and his team, that pose a previously unrecognised
threat to our planet.
An Action News viewer captured a fireball in the sky.
Brooks Efaw of Hamilton, New Jersey was videotaping his son's
birthday party when he saw it on Saturday afternoon.
Other viewers have contacted us since we first showed the tape
on Action News at five to say they saw it too. So what was it?
The FAA and the National Weather Service say they have no activity
NASA says the fireball was probabl y space junk re-entering
the earth's atmosphere.
|WAS it a bird, was it a plane ...
no it was a meteor.
Rumours have been flying thick and fast since a bright light
with a short flame and trail of white behind it crossed over the
Murraylands at 10.25am on Friday.
Listeners t o the local radio station were lead to believe a
meteorite landed on in a field of cows on a property just outside
Mannum. The rumours then escalated over the weekend with no-one
just too sure of exactly what happened.
But it can be confirmed a meteor did cross over the Murraylands
on Friday, but it did not land.
Astronomical Society of South Australia technical information
officer Tony Beresford said a meteor had been seen in areas from
Renmark to Adelaide before fading out.
The meteor was brighter than the full moon and left a trail of
dust which took about 10 minutes to dissipate.
A sonic boom, which occurs when the meteor enters the atmosphere
below 30 kilometres, was heard at Renmark and Gumeracha.
Mr Beresford has called on people in the Murray Bridge area to
contact him if they heard the sonic boom, however he doubted
it would have been noticed over the general traffic noise in the
city centre without being mistaken for a car backfiring.
"I would be interested to see the footprint ... so anyone
in the immediate vicinity of Murray Bridge who heard the boom
I would appreciate hearing from them," he said.
The meteor travelled north-west across the State before breaking
|The Sun has
been more active in the last 70 years than it has for the previous
8000, according to an analysis of tree rings dating back 11,400
years. But researchers say its recent bout of hyperactivity
does not account for the rapidly rising temperatures recorded on
Earth over the last three decades.
Sunspots are surface concentrations of the star's magnetic field
and the more there are, the more energy the Sun is emitting. The
dark features have been observed and recorded regularly since
Scientists have tried to reconstruct previous sunspot activity
using ice cores and tree rings. These contain isotopes, such as
carbon-14 and beryllium-10, created when high-energy particles
from deep space, called cosmic rays, slam into the atmosphere.
Fewer cosmic rays reach the Earth when the Sun is very active,
because the charged particles from the Sun deflect them.
Now, a team led by Sami Solanki of the Max-Planck-Institut fur
Sonnensystemforschung in Katlenburg-Lindau, Germany, has analysed
records of trees preserved in riverbeds and bogs that date back
11,400 years to produce the most precise study yet of sunspot
Back in time
The team started by using sunspot records to calibrate models
of how carbon-14 in tree rings correlate withsolar activity. The
models "reproduce the observed record
of sunspots extremely well, from almost no sunspots during the
seventeenth century to the current high levels", writes
Paula Reimer, a paleoclimate exp ert at Queen's University, Belfast,
UK, in an article a ccompanying the research paper in Nature.
They then extrapolated the tree ring data backwards
in time and discovered that no period in the last 8000 years has
been as active as the last 70. About 75 sunspots have appeared
every year in this period, compared to an annual average of about
30 over the last 11,400 years.
"We are living in extraordinary times as
far as solar activity is concerned," says study co-author
Manfred Schussler. "Extended periods of high activity seem
to be much more rare than we previously thought."
Indeed, the data also showed that high activity periods only
occurred for about 10% of the period studied, and tended to last
for about three decades. "That's one
of the interesting things - this latest cycle has already lasted
longer than most do," says Reimer.
Inside the Sun
Models of the Sun can account for the well-known 11-year-long
cycle of solar activity but the underlying reason for the 70-year
high is unknown. "There is a consensus that the magnetic
field underlying the solar activity is generated in the solar
interior, but the details of this mechanism are still not understood,"
Schussler told New Scientist.
Furthermore, previous data from carbon-14 studies of tree rings
suggest patterns change on scales of 200 years. "It seems
like that periodicity should be driven by the Sun, but people
argue back and forth on this all the time," Reimer told says.
That is because the total energy emitted by the Sun actually
changes by a relatively small amount as the nu mber of sunspots
The new research will allow scientists to see if past climate
changes "are too large to be explained by the sunspot cycle
alone", Reimer says.
She notes that the current upsurge in sunspots is not enough
to account for the approximate 0.5°C rise from pre-industrial
temperatures over the last 30 years.
Journal reference: Nature (vol 431, p 1047, p 1084)
The team will be tracking asteroids
with high-performance telescopes
A team of astronomers has stepped up a project which one day could
help to preserve the Earth from annihilation.
The team from Queen's University in Belfast is monitoring asteroids
in space to see if they are on a collision course with our planet.
Their crucial data will be fed into an international programme for protecting
the Earth from any future impact.
On average 30 to 40 Near-Earth Objects (NEOs) - asteroids or
comets on a path to Earth - are discovered each month.
More than 3,000 NEOs have now been found so far.
Now a team of astronomers at Queen's will be tracking these
objects each week using large high-performance telescopes.
The UK Astrometry and Photometry Programme (UKAPP) for Near-Earth
Objects, based at the university, is using the Faulkes Telescope
North, which is physically located on the Hawaiian island of Maui.
At the end of this year they will also start using the twin
Faulkes Telescope South at Siding Spring, Australia.
The telescop es' mirror size of 2m allows astronomers to see
We are looking at a series of asteroids two or three times a
week now with these telescopes in Hawaii and Australia.
Dr Alan Fitzsimmons, Reader in Observational Astrophysics at the
university and the project's leader, told the BBC's Good Morning
Ulster that it was likely that the Earth would be hit by an asteroid.
"In fact, we know that an asteroid will hit us at some
point in the future.
"Of course, these things are out there and they just randomly
hit us when the Earth gets in the way.
"However, generally it is not a 24-hour or even a 45-minute
warning that we get. It is normally timescales of years or even
Dr Fitzsimmons said that his project was acting as an "early,
early wa rning system for the Earth".
He said that these long lead times gave scientists at the European
Space Agency time to develop a strategy for dealing with an asteroid
on a collision course.
Any object smaller than 50 metres across will not usually make
it through the Earth's atmosphere intact so Dr Fitzsimmons is
training his telescope on asteroids which are 50 to 100 metres
across or larger.
"We are looking at a series of asteroids two or three times
a week now with these telescopes in Hawaii and Australia,"
"There are 30 or 40 new objects discovered every month
that we want to keep an eye on.
"So we only concentrate on the ones that do pass particularly
close to us or are predicted to pass close in the next century
Vadodara, October 31: Forensic
experts and geologists in village Nandgaon, about 18 kms from
the nearest police station in Kaprada, South Gujarat, are trying
to ascertain whether a black stone weighing a kg
which fell in one of the farms, is a meteorite.
Villagers reported a loud bang and falling of a burning stone
in a farm on Sunday evening. The fallen stone had created a little
crater on the ground.
Villages like Nandgaon and Dharampur and other neighbouring villages
in the hilly areas near the Maharashtra-Gujarat border have been
experiencing unseasonal rains for past couple of days. However,
on Saturday evening, the villagers reported hearing a loud bang-like
noise and a streak of fire across the sky. The villagers
first thought it was an aeroplane or a fireball, but it turned
out to be a black stone which had fallen in a farm in the village,
said a Kaprada police station personnel.
With rumours rife that the incident had led to burning of trees
and could be a likely meteor, Kaprada pol ice personnel reached
the spot and brought the stone to t he police station. It
must be some stone boulder which might have fallen down due to
the rains. There are no burnt trees or anything of sort in the
area, said Abhaysinh Chudasama, Valsad DSP, who also
visited the village.
Taking no chances, Chudasama added that a geologist from Valsad
district collectorate had been summoned to check the stone.
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