revelarts
03-25-2013, 02:24 PM
Asteroid Killed Off Dinosaurs? New Study Suggests Comet Instead Caused Extinction Event
By: Tanya Lewis, LiveScience Staff Writer
Published: 03/22/2013 05:18 PM EDT on LiveScience
Updated March 22 at 5:36 p.m. ET
The rocky object that wiped out the dinosaurs 65 million years ago may have been a comet, rather than an asteroid, scientists say.
The 112-mile (180 kilometers) Chicxulub crater in Mexico was made by the impact that caused the extinction of dinosaurs (http://www.livescience.com/26933-chicxulub-cosmic-impact-dinosaurs.html) and about 70 percent of all species on Earth, many scientists believe. A new study suggests the crater was probably blasted out by a faster, smaller object than previously thought, according to research presented this week at the 44th Lunar and Planetary Science Conference in The Woodlands, Texas.
Evidence of the space rock's impact comes from a worldwide layer of sediments containing high levels of the element iridium, dubbed the Cretaceous-Paleogene (K-Pg) boundary, which could not have occurred on Earth naturally.
The new research suggests the often-cited iridium values are incorrect, however. The scientists compared these values with levels of osmium, another element delivered by the impact.
Their calculations suggested the space rock generated less debris than previously thought, implying the space rock was a smaller object. In order for the smaller rock to have created the giant Chicxulub crater (http://www.space.com/19681-dinosaur-killing-asteroid-chicxulub-crater.html), it had to have been going exceedingly fast, the researchers concluded.
"How do we get something that has enough energy to generate that size of crater, but has much less rocky material? (how do shoehorn this thing in) That brings us to comets," study author Jason Moore, a paleoecologist at Dartmouth College in New Hampshire, told BBC News (http://www.bbc.co.uk/news/science-environment-21709229). [Meteor Crater: Experience an Ancient Impact (http://www.ouramazingplanet.com/ancient-impact-formed-arizona-meteor-crater-0516/)]
Comets (http://www.space.com/53-comets-formation-discovery-and-exploration.html) are balls of ice, dust and rocky particles that are distinguished from asteroids by their highly eccentric orbits and thin, fuzzy atmospheres, called comas or tails. The Chicxulub impact is more compatible with a long-period comet, the results indicated, which can take hundreds, thousands or sometimes millions of years to orbit the sun once.
It is possible that a rapidly moving asteroid (http://www.space.com/51-asteroids-formation-discovery-and-exploration.html) could have caused the Chicxulub impact crater, the researchers said, but the fastest-moving objects that have been observed are mostly comets.
"I think it's some very interesting work," physicist Brandon Johnson of Purdue University, who was not involved in the research, told LiveScience. If the impact were in fact a comet, "it could change things quite a bit," he said – a comet would have rained down a lot more material than an asteroid.
But the findings are debatable: "There's a possibility that a lot of the impacted material could have been ejected at escape velocity, so we couldn't find it on Earth," Johnson said. This means the remnants of the impact could be just a fraction of the mass of the space rock (http://www.livescience.com/16891-falling-space-rocks-meteorites-asteroids-infographic.html), suggesting it could still have been an asteroid.
Geologist Gareth Collins of Imperial College London, U.K., agreed. "Geochemistry tells you — quite accurately — only the mass of meteoritic material that is distributed globally, not the total mass of the impactor," Collins told BBC News, adding, "To estimate the latter, one needs to know what fraction of the impactor was distributed globally, as opposed to being ejected to space or landing close to the crater."
The researchers suggest that 75 percent of the space rock's mass was distributed on Earth, Collins said, but he contends that it could have been less than 20 percent — an amount that could have come from a larger and slower asteroid. In response, the researchers point to studies that suggest the object lost an amount of mass consistent with their findings.
But geophysicist Jay Melosh, also of Purdue University, remains skeptical. "The evidence that they have for a high velocity impact is marginally positive. However, the probability that that high velocity impact is a comet is very low," he said, adding that it's much more likely to be a faster-than-usual asteroid.
Follow Tanya Lewis on Twitter (https://twitter.com/tanyalewis314) and Google+ (https://plus.google.com/117033537877488293678/posts). Follow us @livescience (https://twitter.com/LiveScience), Facebook (http://www.facebook.com/#%21/livescience) & Google+ (https://plus.google.com/101164570444913213957/posts). Original article on LiveScience.com (http://www.livescience.com/28127-dinosaur-extinction-caused-by-comet.html).
Editor's Note: This article was updated to include comments from geophysicist Jay Melosh of Purdue University.
http://www.huffingtonpost.com/2013/03/23/asteroid-killed-dinosaurs-comet-extinction_n_2937296.html?utm_hp_ref=mostpopular
There are some scientist out there that believe the crater was caused by a super volcano, other scientist have other views.
It's great fun speculating, I just wish Science was more humble about it's pronouncements.
Theories on the origin of the moon
Until the Apollo program, there were three theories about the origin of the moon, according to an article written by H. Jay Melosh of the University of Arizona.
* The fission theory, in which the moon was in some way "spun off" during the Earth's formation as it rotated rapidly.
* The capture theory, in which the moon was captured by Earth as it wandered through the solar system and was locked into orbit.
* The "double planet" theory in which the Earth and moon were formed more or less simultaneously.
The problem was the data derived from the Apollo lunar samples could not confirm any of these theories. The moon has no substantial iron core, its rocks are grossly similar to the material in Earth's mantle, but are higher in refractory elements and much lower in volatiles.
The Impact Theory of the origin of the moon
In 1984, a theory was proposed for the origin of the moon. In this scenario, a Mars-sized planet smashed into the young Earth, spewing material from the mantles of both bodies, which subsequently coalesces into the celestial body we now know as the moon. All computer models and the geological data seem to confirm the impact theory. NASA has provided a video showing how the moon likely evolved, based on recent findings of the Lunar Reconnaissance Orbiter.
What is wrong with the impact theory
Since it would be unlikely the other planet thought to have collided with Earth was geologically the same as Earth, the lunar titanium samples should have been different than those found on Earth. But if the findings of other elements such as calcium confirm those found with the titanium samples, scientists have a problem.
Scientists search for an explanation
It is possible material from Earth wound up in the outer part of the moon, with material from the other planet buried deep underneath. Another possibility is that the moon is almost entirely made from material from Earth. Some are even suggesting that Earth briefly had two moons, which collided into one another. If the lost moon had material similar to Earth's, then that might explain the findings.
http://news.yahoo.com/recent-findings-cast-doubt-moon-origin-theory-212400559.html
it's still a mysterious universe
By: Tanya Lewis, LiveScience Staff Writer
Published: 03/22/2013 05:18 PM EDT on LiveScience
Updated March 22 at 5:36 p.m. ET
The rocky object that wiped out the dinosaurs 65 million years ago may have been a comet, rather than an asteroid, scientists say.
The 112-mile (180 kilometers) Chicxulub crater in Mexico was made by the impact that caused the extinction of dinosaurs (http://www.livescience.com/26933-chicxulub-cosmic-impact-dinosaurs.html) and about 70 percent of all species on Earth, many scientists believe. A new study suggests the crater was probably blasted out by a faster, smaller object than previously thought, according to research presented this week at the 44th Lunar and Planetary Science Conference in The Woodlands, Texas.
Evidence of the space rock's impact comes from a worldwide layer of sediments containing high levels of the element iridium, dubbed the Cretaceous-Paleogene (K-Pg) boundary, which could not have occurred on Earth naturally.
The new research suggests the often-cited iridium values are incorrect, however. The scientists compared these values with levels of osmium, another element delivered by the impact.
Their calculations suggested the space rock generated less debris than previously thought, implying the space rock was a smaller object. In order for the smaller rock to have created the giant Chicxulub crater (http://www.space.com/19681-dinosaur-killing-asteroid-chicxulub-crater.html), it had to have been going exceedingly fast, the researchers concluded.
"How do we get something that has enough energy to generate that size of crater, but has much less rocky material? (how do shoehorn this thing in) That brings us to comets," study author Jason Moore, a paleoecologist at Dartmouth College in New Hampshire, told BBC News (http://www.bbc.co.uk/news/science-environment-21709229). [Meteor Crater: Experience an Ancient Impact (http://www.ouramazingplanet.com/ancient-impact-formed-arizona-meteor-crater-0516/)]
Comets (http://www.space.com/53-comets-formation-discovery-and-exploration.html) are balls of ice, dust and rocky particles that are distinguished from asteroids by their highly eccentric orbits and thin, fuzzy atmospheres, called comas or tails. The Chicxulub impact is more compatible with a long-period comet, the results indicated, which can take hundreds, thousands or sometimes millions of years to orbit the sun once.
It is possible that a rapidly moving asteroid (http://www.space.com/51-asteroids-formation-discovery-and-exploration.html) could have caused the Chicxulub impact crater, the researchers said, but the fastest-moving objects that have been observed are mostly comets.
"I think it's some very interesting work," physicist Brandon Johnson of Purdue University, who was not involved in the research, told LiveScience. If the impact were in fact a comet, "it could change things quite a bit," he said – a comet would have rained down a lot more material than an asteroid.
But the findings are debatable: "There's a possibility that a lot of the impacted material could have been ejected at escape velocity, so we couldn't find it on Earth," Johnson said. This means the remnants of the impact could be just a fraction of the mass of the space rock (http://www.livescience.com/16891-falling-space-rocks-meteorites-asteroids-infographic.html), suggesting it could still have been an asteroid.
Geologist Gareth Collins of Imperial College London, U.K., agreed. "Geochemistry tells you — quite accurately — only the mass of meteoritic material that is distributed globally, not the total mass of the impactor," Collins told BBC News, adding, "To estimate the latter, one needs to know what fraction of the impactor was distributed globally, as opposed to being ejected to space or landing close to the crater."
The researchers suggest that 75 percent of the space rock's mass was distributed on Earth, Collins said, but he contends that it could have been less than 20 percent — an amount that could have come from a larger and slower asteroid. In response, the researchers point to studies that suggest the object lost an amount of mass consistent with their findings.
But geophysicist Jay Melosh, also of Purdue University, remains skeptical. "The evidence that they have for a high velocity impact is marginally positive. However, the probability that that high velocity impact is a comet is very low," he said, adding that it's much more likely to be a faster-than-usual asteroid.
Follow Tanya Lewis on Twitter (https://twitter.com/tanyalewis314) and Google+ (https://plus.google.com/117033537877488293678/posts). Follow us @livescience (https://twitter.com/LiveScience), Facebook (http://www.facebook.com/#%21/livescience) & Google+ (https://plus.google.com/101164570444913213957/posts). Original article on LiveScience.com (http://www.livescience.com/28127-dinosaur-extinction-caused-by-comet.html).
Editor's Note: This article was updated to include comments from geophysicist Jay Melosh of Purdue University.
http://www.huffingtonpost.com/2013/03/23/asteroid-killed-dinosaurs-comet-extinction_n_2937296.html?utm_hp_ref=mostpopular
There are some scientist out there that believe the crater was caused by a super volcano, other scientist have other views.
It's great fun speculating, I just wish Science was more humble about it's pronouncements.
Theories on the origin of the moon
Until the Apollo program, there were three theories about the origin of the moon, according to an article written by H. Jay Melosh of the University of Arizona.
* The fission theory, in which the moon was in some way "spun off" during the Earth's formation as it rotated rapidly.
* The capture theory, in which the moon was captured by Earth as it wandered through the solar system and was locked into orbit.
* The "double planet" theory in which the Earth and moon were formed more or less simultaneously.
The problem was the data derived from the Apollo lunar samples could not confirm any of these theories. The moon has no substantial iron core, its rocks are grossly similar to the material in Earth's mantle, but are higher in refractory elements and much lower in volatiles.
The Impact Theory of the origin of the moon
In 1984, a theory was proposed for the origin of the moon. In this scenario, a Mars-sized planet smashed into the young Earth, spewing material from the mantles of both bodies, which subsequently coalesces into the celestial body we now know as the moon. All computer models and the geological data seem to confirm the impact theory. NASA has provided a video showing how the moon likely evolved, based on recent findings of the Lunar Reconnaissance Orbiter.
What is wrong with the impact theory
Since it would be unlikely the other planet thought to have collided with Earth was geologically the same as Earth, the lunar titanium samples should have been different than those found on Earth. But if the findings of other elements such as calcium confirm those found with the titanium samples, scientists have a problem.
Scientists search for an explanation
It is possible material from Earth wound up in the outer part of the moon, with material from the other planet buried deep underneath. Another possibility is that the moon is almost entirely made from material from Earth. Some are even suggesting that Earth briefly had two moons, which collided into one another. If the lost moon had material similar to Earth's, then that might explain the findings.
http://news.yahoo.com/recent-findings-cast-doubt-moon-origin-theory-212400559.html
it's still a mysterious universe