Comets Not Likely The Cause Of Earth's Mass Extinctions

In fact, astronomers know the inner solar system has been protected at least to some degree by Saturn and Jupiter, whose gravitational fields can eject comets into interstellar space or sometimes send them crashing into the giant planets. he work also shows that many long-period comets that end up in Earth-crossing orbits likely originate from a region astronomers have long believed could not produce observable comets. A long-period comet takes from 200 years to tens of millions of years to make a single orbit of the sun. The Oort Cloud is a remnant of the nebula from which the solar system formed 4.5 billion years ago. It begins about 93 billion miles from the sun (1,000 times Earth's distance from the sun) and stretches to about three light years away (a light year is about 5.9 trillion miles). The Oort Cloud could contain billions of comets, most so small and distant as to never be observed.That point was reinforced July 20 when a huge scar appeared on Jupiter's surface, likely evidence of a comet impact.

It also was believed that inner Oort Cloud bodies could reach Earth-crossing orbits only during the rare close passage of a star, which would cause a comet shower. But it turns out that even without a star encounter, long-period comets from the inner Oort Cloud can slip past the protective barrier posed by the presence of Jupiter and Saturn and travel a path that crosses Earth's orbit.

Fructose Impairs Memory In Rats

Amy Ross, a graduate student in the lab of Marise Parent, associate professor at Georgia State's Neuroscience Institute and Department of Psychology,

"What we discovered is that the fructose diet doesn't affect their ability to learn,"

Although humans do not eat fructose in levels as high as rats in the experiments, the consumption of foods sweetened with fructose — which includes both common table sugar, fruit juice concentrates, as well as the much-maligned high fructose corn

"The bottom line is that we were meant to have an apple a day as our source of fructose," Parent said. "And now, we have fructose in almost everything." Moderation is key, as well as exercise, she said.

syrup — has been increasing steadily. High intake of fructose is associated with numerous health problems, including insulin insensitivity, type II diabetes, obesity and cardiovascular disease.

Parent said. "But they can't seem to remember as well where the platform was when you take it away. They swam more randomly than rats fed a control diet."

fed a group of Sprague-Dawley rats a diet where fructose represented 60 percent of calories ingested during the day.