Friday, September 7, 2007

आसमान से आया फरिश्ता

A New Theory Attributes The Demise Of The Giants To Disease-Carrying Bugs

Did insect stings wipe out dinosaurs

New York: Dinosaurs became extinct from the effects of a massive asteroid hitting Earth 65 million years ago, scientists have long maintained. But, a new theory has suggested that the mightiest creatures may have succumbed to attacks by disease-carrying insects.
According to the theory propounded by professor George Poinar of the Oregon State University and his wife Roberta, the demise of the dinosaurs and the rise and evolution of the insects, particularly the biting and disease-carriers, are linked to each other.
“We can’t say for certain that insects are the smoking gun, but we believe they were an extremely significant force in the decline of the dinosaurs. We also don’t suggest that the appearance of biting insects and the spread of disease are the only things that relate to dinosaur extinction.
“Other geologic and catastrophic events certainly played a role. But by themselves, such events do not explain a process that in reality took a very, very long time, perhaps millions of years. Insects and diseases do provide that explanation,” the ScienceDaily quoted Poinar as saying. The couple have entailed their concept in a recently released book ‘What Bugged the Dinosaurs? Insects, Disease and Death in the Cretaceous’.
In their book, the authors have argued that insects provided a plausible and effective explanation for the slow, inexorable decline and eventual extinction of dinosaurs over thousands of years. This period is known as the famous ‘K-T Boundary’ about 65 million years ago.
There is evidence that some catastrophic events, such as a major asteroid or lava flows, also occurred at this time — but “these provide no complete explanation for the gradual decline of dinosaur populations, and even how some dinosaurs survived for thousands of years after the K-T Boundary.”
Insects and disease, on the other hand, may have been a lot slower, but ultimately finished the job, according to the researchers. Poinar and Roberta claimed to have based their theory on a study of the plant and animal life forms found preserved in amber millions of years ago — amber has the unique ability to trap very small animals and display them neatly. This phenomenon has been invaluable in scientific and ecological research, and among other things, formed the scientific premise for the movie ‘Jurassic Park’.
“During the late Cretaceous Period, the associations between insects, microbes and disease transmission were just emerging. We found in the gut of one biting insect, preserved in amber from that era, the pathogen that causes leishmania — a serious disease still today, one that can infect both reptiles and humans.
“In another biting insect, we discovered organisms that cause malaria, a type that infects birds and lizards today. In dinosaur feces, we found nematodes, trematodes and even protozoa that could have
caused dysentery and other abdominal disturbances. The infective stages of these intestinal parasites are carried by filth-visiting insects,” he said. AGENCIES

छोड गये बालम, हमे हाय अकेला छोड गये .......DEEP IMPACT

Distant space collision spelt doom for dinos


A computer-generated image shows that
the parent object of asteroid Baptistina, which was approximately 170 km in diameter, was disrupted 160 million years ago when it was hit by another asteroid estimated to be 60 km in diameter (left). The extinction of the dinosaurs 65 million years ago can be traced to the collision between the two monster rocks in the asteroid belt nearly 100 million years earlier. The two pictures on the right show remnants of the collision impacting the Earth and Moon

A collision 160 million years ago of two asteroids orbiting between Mars and Jupiter sent many big rock chunks hurtling toward Earth, including the one that zapped the dinosaurs, scientists said.

Their research offered an explanation for the cause of one of the most momentous events in the history of life on Earth — 10-km-wide meteorite striking Mexico’s Yucatan peninsula 65 million years ago.

That catastrophe eliminated the dinosaurs, which had flourished for about 165 million years, and many other life forms, and paved the way for mammals to dominate the Earth and the eventual rise of humankind, many scientists believe. The impact is thought to have triggered a worldwide environmental cataclysm, expelling vast quantities of rock and dust into the sky, unleashing giant tsunamis, sparking global wildfires and leaving Earth shrouded in darkness for years.

US and Czech researchers used computer simulations to calculate that there was a 90% probability that the collision of two asteroids — one about 170 km wide and one about 60 km wide — was the event that precipitated the Earthly disaster.

The collision occurred in the asteroid belt, a collection of big and small rocks orbiting the sun about 100 million miles from Earth, the researchers report in the journal Nature.

The asteroid Baptistina and rubble associated with it are thought to be leftovers, the scientists said. Some of the debris from the collision escaped the asteroid belt, tumbled toward the inner solar system and whacked Earth and our moon, along with probably Mars and Venus, said William Bottke of the Southwest Research Institute in Boulder, Colorado, one of the researchers.

The collision is believed to have doubled for a while the number of impacts occurring in this part of the solar system.
In fact, while the bombardment of this region of the solar system due to this shower of debris peaked about 100 million years ago, the scientists said the tail end of the shower continues to this day.

Bottke said many existing near-Earth asteroids can be traced back to this collision.

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