Yeomans' pointed statement about 73P is apparently in response to vague reports on the World Wide Web that a piece of the comet will hit Earth during the flyby. Although the number of fragments has risen to nearly four dozen, he said none of them poses an impact hazard.

None of the comet's fragments will come closer than 5.5 million miles to Earth during its closest approaches between May 12 and 28 - or more than 20 times the distance between Earth and the Moon.

The main fragment, C, will pass closest to Earth on May 12 at a distance of approximately 7.3 million miles. It will be visible to small telescopes during the morning hours in the constellation Vulpecula, or the Coathanger.

73P is no stranger to astronomers, who have been observing the comet for more than 75 years. They have computed its trajectory repeatedly and have refined the level of precision over time - so 73P's orbit is well known. The real news is that Hubble's images show many more fragments than had been reported by ground-based observers.

The comet is currently comprised of a chain of more than 40 fragments, named alphabetically and stretching across several degrees on the sky. Observers have noted some dramatic brightenings among some of the fragments, which suggests they are continuing to disintegrate - some could disappear altogether.

Hubble caught two of the fragments, B and G, shortly after large outbursts in activity. Hubble also photographed fragment C, which at the time was less active. The resulting images reveal that some sort of destructive process is taking place, in which fragments are continuing to split into smaller chunks.

Hubble has found several dozen house-sized fragments trailing each main fragment. Sequential images of the B fragment, for example, taken a few days apart, suggest the chunks are pushed down the tail by outgassing from the icy, sunward-facing surfaces of the chunks, much like space-walking astronauts are propelled by their jetpacks.

The smaller chunks have the lowest mass, so they are being accelerated away from the parent nucleus faster than the larger chunks. Some of the chunks seem to dissipate completely over the course of several days.

Ancient relics of the early solar system, comet nuclei are porous and fragile mixes of dust and ice. They can break apart from tidal forces when they pass near large bodies, which is what happened to Comet Shoemaker-Levy 9 when Jupiter's gravity tore it to pieces in 1992.

Shoemaker-Levy's fragments all plunged directly into Jupiter's atmosphere two years later, creating gaping holes in gas giant's cloudtops and leaving ugly blackened scars that lasted a year.

Comet nuclei also can fly apart from rapid rotation. Or, they can break up from the thermal stresses as they pass near the Sun, or explosively pop apart like corks from champagne bottles due to the outburst of trapped volatile gases.

"Catastrophic breakups may be the ultimate fate of most comets," said Hal Weaver, a planetary astronomer with the Johns Hopkins University Applied Physics Laboratory, who led the team that made the recent Hubble observations.

The comet is named for German astronomers Arnold Schwassmann and Arno Arthur Wachmann, who discovered it during a photographic search for asteroids in 1930. At the time, 73P passed within 5.8 million miles of Earth, or 24 times the Earth-Moon distance. The comet orbits the Sun every 5.4 years, but it was not seen again until 1979. The comet was missed again in 1985 but has been observed during every return since.

During the fall of 1995, astronomers witnessed a huge outburst from 73P, and shortly afterwards they identified and labeled four separate nuclei as fragments A, B, C and D, with C being the largest and the presumed principal remnant of the original nucleus.

Only C and B were definitively observed during the next return in 2000-2001, possibly because of poor geometry involving Earth's location versus the cometary fragments. This year's better observing circumstances may have aided the detection of all of the new fragments, but it also is possible the disintegration of the comet is now accelerating.

Annual rings are sensitive indicators of the climatic and environmental conditions in which they grow. "If trees become stressed -- for example in particularly dry years -- their trunk growth is less than in good times," Professor Matthias Winiger, of Bonn's Geographical Institute, says. "The annual rings then tend to be correspondingly close together." The analysis of the oxygen absorbed by the wood is even more revealing. For this the ratio of two varieties of oxygen which differ in weight, what are known as isotopes, is measured. "This method is extremely complex, but permits very exact statements to be made about the humidity conditions in the year in question," Professor Winiger explains.

The team of scientists examined four stocks of trees in the Karakorum Mountains and the Himalayas. Juniper trees can live to a ripe old age. In one of the stocks of trees the annual rings could be followed back to 828 A.D. Their wood is thus a very reliable 'climate archive' going back more than 1,000 years. In order to estimate the accuracy of the data, the researchers compared the precipitation graphs based on the annual rings over a reference period with observation data from meteorological stations. However, these have only been available in the mountains of Pakistan since 1898. "For this period of time our method tallies remarkably well with the meteorological data," Professor Winiger emphasises.

The results show that there must have been particularly wet periods in the past, too, e.g. around 1200 or 1350. However, in the late 19th and the whole of the 20th centuries such 'precipitation peaks' were both especially high and remarkably frequent. The development of precipitation in Pakistan thereby shows parallels with the global rise in temperature which has been observable over the past 150 years. Among other effects it influences atmospheric processes, particularly what is known as the atmospheric circulation. By this scientists mean the global air currents which are primarily driven by the warmth irradiated by the sun.

It is presumed that climate change can at least in part be traced back to the green-house gases such as carbon dioxide and steam, which are produced directly or indirectly by human beings. The authors of the study reveal that they are themselves concerned about their findings: they write that "in these sub-tropical and peripheral tropical regions changes in the precipitation rate and distribution and thus in the water balance would have a much greater impact on people's well-being and changes in the eco-systems than the change in temperature on its own."

The epicentre of the moderate quake, which struck at 5.05 p.m. was about 4.4 miles northeast of Hualien on the eastern coast, at a depth of 3.7 miles, the Central Weather Bureau said in a statement.

Earthquakes occur frequently in Taiwan, which lies on a seismically active stretch of the Pacific basin.

One of Taiwan's worst-recorded quakes occurred in September 1999. Measuring 7.6, it killed more than 2,400 people and destroyed or damaged 50,000 buildings.

Purple sea stars began washing up last week in Trail Bay at Sechelt, north of Vancouver. The Canadian Department of Fisheries and Oceans has been unable to determine why they died, agency spokeswoman Michelle Imbeau said.

Bruce Leighton, a marine parasite expert at Simon Fraser University in Burnaby, noted Wednesday that the die-off coincided with the peak of the starfish reproductive cycle, when the creatures are most vulnerable to Orchitophrya stellarum, a protozoan that feeds on sea stars' sperm.

He said the parasite is believed responsible for wiping out purple sea stars in North Vancouver's Indian Arm and eliminating much of the male population of the species in other areas of British Columbia, altering the balance of species.

The parasite is native to the Atlantic but is now found along the British Columbia and Washington state coast, possibly after arriving in ship ballast water or with seafood. East Coast starfish usually survive infestations, scientists said.

Sea stars feed on mussels and barnacles, making more room in the intertidal zone for other creatures that support other marine and bird life and thus helping to maintain biodiversity, Leighton said.

The culprit: a mild, wet winter and early spring, plus unusually warm days.

"We have seen an early and aggressive allergy season, including seasonal pollens and mold spores," said Dr. Clifford Bassett, a Long Island-based allergist and vice-chairman of AAAAI's Public Education Committee.

Shulan agreed. "The buds have been ready to burst, and when we have these warm days, the pollen counts have been just wild," he said.

According to the Allergy and Asthma Foundation of America, which estimates that 50 million Americans are impacted by allergies, the top 10 worst cities to be in right now, in terms of airborne allergens, are:

* Hartford, Conn.
* Greenville, S.C.
* Boston
* Detroit
* Orlando, Fla.
* Knoxville, Tenn.
* Omaha, Neb.
* Sacramento, Calif.
* Washington, D.C.
* Baltimore

There are steps the allergic can take to minimize the sneezing, wheezing and itchy eyes that plague them this season. One is obvious: Avoid the great outdoors. That doesn't mean sealing yourself indoors 24/7, experts said, but some common-sense tips might help.

"First off, get someone else to help you with yard chores -- find someone in the family who's not allergic to do the mowing, for example," said Dr. Sandra McMahan, a senior staff physician specializing in pediatric allergy at Scott & White Memorial Hospital in Temple, Texas.

Pollen counts are always highest in the morning, so try and plan outdoor activities for the afternoon or evening whenever possible. Rain tends to drive allergens out of the air, so planning activities for just after a good rain makes sense, too. "The patient will frequently feel better for a day or so after a rainstorm, because there's less pollen blowing around," said McMahan, who is also an assistant professor of internal medicine at the Texas A & M Health Science Center College of Medicine.

All the experts stressed that keeping windows closed and using air conditioning -- even when the weather is pleasant outside -- can cut the misery for allergic individuals while they're at home.

But what about that perennial springtime passion, gardening? Bassett said green-thumbed Americans can still enjoy their hobby, despite allergies, as long as they follow a few simple steps.

First off, he said, wear gloves and a pollen mask while outside, and work on relatively humid, windless days. Keep soils moist and gardens free of flowering weeds. Shower and shampoo after you come back inside. Rinse off glasses after gardening and keep gardening clothing away from the bedroom.

Bassett also advised against planting the following high-allergen species: amaranthus, crocus, elderberry, juniper, peony, poppy and privet. Some low-allergen alternatives include azalea, begonia, bougainvillea, daisy, dahlia, gladiola, iris, irish moss, marigold, orchids, snapdragon, sunflowers, tulips, violets and zinnias.

And don't forget the secret sex lives of plants: "Planting female trees in one's own yard will attract and then trap incoming airborne pollen from male plants," Bassett warned.

The experts also advised that people back up all of these tips with medication.

"Medications are much better now than they were in the past," McMahan said. "We have the nonsedating antihistamines, which are very helpful and much safer to use. One -- loratadine, generic Claritin -- is now available over-the-counter." There's also an antihistamine nasal spray, Astelin, available by prescription, he added

Besides these, there are what Shulan called the "heavy hitters" -- nasal steroids such as Flonase (now available in a cheaper generic form) as well as Rhinocort, Nasacort and Nasonex.

"Remember though, these drugs take time to start working -- it make take up to two weeks for them to take full effect, although you'll notice some relief in a day or two," Shulan said. "With the nasal steroids, you have to use them regularly throughout the season," he added

So, with proper planning and the right pharmaceuticals, most Americans should be able to cope with even this year's tough allergy season.

But they may have to be patient.

"Here in Albany, the trees start acting up from late March going into June, then the grass takes over in late May, peaking in June and early July," Shulan said. "That should go right through summer till it tapers off sometime in September."

More information

For much more on seasonal allergies, head to the American Academy of Allergy, Asthma and Immunology.

Britain and Ivory Coast prepared to start more poultry slaughtering after discovering viral outbreaks, although Britain said the virus it had detected at a chicken farm was probably not the H5N1 strain dangerous to humans.

China's official Xinhua news agency cited the country's health minister as saying the infected girl, from the southeast Sichuan province, was being treated in a local hospital.

Confirming the news, the World Health Organization said in a statement the girl's diagnosis brought China's laboratory-confirmed cases to 18, 12 of which had been fatal.

"She developed symptoms of fever and pneumonia on April 16. She remains hospitalized," the WHO said.

Just over a week ago on April 18, China's Health Ministry announced the country's 17th confirmed human H5N1 case, that of a migrant worker who died a day later.

Epidemiologists fear that if the virus mutates into a form easily passed between humans it might trigger a pandemic in which millions could die.

Experts generally agree that a pandemic of some kind is overdue, and that H5N1 presents the most likely threat.

So far, however, it remains essentially an animal disease.

205 people have been infected in nine countries, causing 113 deaths, since bird flu re-emerged in Asia in 2003, according to the WHO, a
United Nations agency. In the same time the disease has spread among birds in 45 countries.

BIRD FLU FATIGUE?

In an interview published on Wednesday the acting director of WHO's global influenza program had warned the world it needed to prepare for a long-term fight against bird flu and not give in to fatigue that seemed to have set in.

Keiji Fukuda said the virus's tenacity and persistence increased the risk that it might evolve into a pandemic.

Britain and Ivory Coast looked to be keeping up measures to stop the disease's spread.

The United Kingdom is to cull some 35,000 birds on a poultry farm in the east of the country after a strain of bird flu was detected in chickens.

Preliminary tests showed the virus was likely to be an H7 strain of bird flu, not H5N1, the government's chief vet said.

The Department for the Environment, Food and Rural Affairs said all birds on the farm near Norwich, an area home to some of Europe's biggest poultry farms, would be killed as soon as possible as a precautionary measure.

Ivory Coast also prepared to slaughter chickens and tightened restrictions on poultry movement after reporting outbreaks in two populous parts of its main city Abidjan.

The World Organization for Animal Health (OIE) said late on Wednesday birds infected with H5N1 had been found in separate outbreaks in the Marcory Anoumabo and Treichville suburbs.

Two local clinics had made the diagnosis, which the OIE expected to be confirmed by its own laboratory in Padua, Italy.

"We are going to start killing all poultry in a 3 km (2 mile) radius around the site that has been declared positive," said Bakary Cisse, head of the government's animal disease surveillance task force.

Myanmar appeared to have scored a success with its program of culling and restrictions in recent weeks though, with the U.N. Food and Agriculture Organization agreeing with a decision to lift a ban on the sale and movement of poultry within days.

FAO chief technical adviser Ram Chaudhary said the tough restrictions were no longer necessary because no new outbreaks had been reported for 3 weeks.

"Myanmar was very strict. They had closed down the poultry markets. Nobody could prepare or sell chicken on the street."