Posted on 04/02/2006 2:13:59 PM PDT by SunkenCiv
Did a planetary wobble kill the dinosaurs?Bruce Runnegar from the University of California at Los Angeles' Center for Astrobiology... and his colleagues used computer models to map out the Solar System for the past 250 million years. In particular, they looked at the perihelion of each planet - the point in its orbit where it is closest to the Sun. The perihelion of Earth rotates around the Sun with a period of hundreds of thousands of years. Because of subtle tugs and pulls between the planets, this period changes slightly with time... Their model suggests one of these blips significantly changed Mercury's orbit 65 million years ago. This wobble would have pulled at the asteroid belt, increasing the chances that asteroids in the Hungarias region would be knocked out of place. Now the researchers are running a fresh set of models to see how much the orbits of these asteroids changed. It wouldn't have been enough to send a shower of asteroids into the Earth, but Runnegar says the wobble could have sent a single asteroid onto collision course with our planet... Now he is planning to run his models forward in time, to see when the next potentially catastrophic planetary wobble will be.
by Nicola Jones
New Scientist
June 27 2001
Asteroid 1950 DAWhen high-precision radar meaurements were included in a new orbit solution, a potentially very close approach to the Earth on March 16, 2880 was discovered to exist. Analysis performed by Giorgini et al and reported in the April 5, 2002 edition of the journal Science ("Asteroid 1950 DA's Encounter With Earth in 2880: Physical Limits of Collision Probability Prediction") determined the impact probability as being at most 1 in 300 and probably even more remote, based on what is known about the asteroid so far. At its greatest, this could represent a risk 50% greater than that of the average background hazard due to all other asteroids from the present era through 2880, as defined by the Palermo Technical Scale (PTS value = +0.17). 1950 DA is the only known asteroid whose hazard could be above the background level.
Don Yeomans, Site Manager
NASA Near Earth Object Program
garbageseeker, I tossed your name on the end because I know you've expressed interest in something like this.
Explosions In Space May Have Initiated Ancient Extinction On Earth
Science Daily | 4/12/05 | NASA/Goddard Space Flight Center
Posted on 04/12/2005 4:12:15 PM EDT by doc30
http://www.freerepublic.com/focus/news/1382310/posts
http://www.freerepublic.com/focus/f-news/1048934/posts?page=44#44
http://www.freerepublic.com/focus/f-news/1048934/posts?page=46#46
http://www.freerepublic.com/focus/f-news/1070173/posts?page=21#21
http://www.freerepublic.com/focus/f-news/1278524/posts?page=30#30
http://www.freerepublic.com/focus/f-news/1354126/posts?page=28#28
http://www.freerepublic.com/focus/f-news/1608702/posts?page=14#14
Starburst caused Ordovician mass extinction: scientists
Posted on : Mon, 11 Apr 2005 00:00:00 GMT | Author : Nigel Wright
News Category : Space
http://www.earthtimes.org/articles/show/2373.html
I'm sure we'll have our comet/asteriod deflector in place by then. :-)
We could call it the weeble. :')
Eye witness report:
...The Swansons and the Uhlrichs in Lituya Bay rose in alarm to gaze in unbelieving wonder and terror. Swanson and his wife later insisted that the terminal ice mass of Lituya Glacier rose into view from behind a headland up the bay, with great masses falling from its face, and then fell majestically into the water, creating a wave that went over the whole headland. It then caromed down the bay, scouring the shores of their trees, obliterating the mountaineer's campsite, overrunning Cenotaph Island and its lone cabin, and killing the Wagners and all but killing the Swansons in a surfboard kind of plunge of their two boats across 40-foot high LaChausee Spit to destruction in the sea outside - a wave of such improbability as to strain the credulity of later investigators, and to remain a scientific puzzle...
http://wcatwc.arh.noaa.gov/web_tsus/19580710/narrative1.htm
Sounds like a wild ride.
Moving the Orbits of PlanetsThe mechanism was described in 1984 by Julio Fernandez and Wing Ip. In a one-planet solar system, the outward scattering of comets by the planet would cause the planet to spiral in towards the sun. In the real solar system, the motions of the planets are inter-dependent, causing some to move outwards and others inwards. What connects the planets is the transfer of comets (and angular momentum) from one to the other. Neptune scatters comets out to the interstellar medium and inwards, where some meet Uranus and are scattered again. The process repeats down to the innermost big planet Jupiter. Fernandez and Ip showed that massive Jupiter anchors the flow of angular momentum caused by the ejection of comets. It spirals towards the sun but Saturn, Uranus and Neptune drift outwards. It is the outward migration of Neptune that has had (apparently) observable effects on the Kuiper Belt by trapping the Plutinos...
by David Jewitt
September 2004
Meanwhile, the Doppler discovery of extrasolar planets orbiting very close to their parent stars has raised a different problem. Many of the planets are so close to their stars (<0.1 AU), and so hot, that they cannot be supposed to have formed where we now observe them. By inference, they could have formed at larger distances (several AU) and then migrated inwards. What would cause this inward migration? As with the solar system case, the root cause may be an exchange of angular momentum with material surrounding the planets at their formation. In particular, if the extrasolar planets formed in massive disks, then torques between the planets and the disks could drive the former inwards.
THANKS
My pleasure.
Is Phoebe A Kuiper Belt Object?Phoebe is a 200 km scale irregular satellite of Saturn. With a retrograde orbit (inclination 178 deg), Phoebe cannot have formed in a Saturn-associated accretion disk and, instead, is inferred to have been captured from an independent orbit around the Sun... The two main possibilities are that... Phoebe was captured from heliocentric orbit near Saturn, probably in association with planet formation itself... OR... Phoebe was captured from a more distant reservoir, possibly the Kuiper Belt. We do not possess any way to decide clearly between these possibilities. Recently, Kuiper Belt capture has been widely publicised and two (not wholly convincing) strands of evidence have been supplied.
by David Jewitt
Last updated Jun 2006
Weighed in being the appropriate metaphor, considering who's on the cover. ;')
Earth's Oxygen EnigmaScientists have long believed that blue-green algae arose 3.5 billion years ago, pumping out oxygen and causing the oceans to fill with rust. Over the next billion years the algae transformed Earth's atmosphere, allowing oxygen-breathing life to evolve. Carrine Blank of Washington University in St. Louis... compared genetic sequences from 53 different groups of bacteria -- including blue-green algae, also known as cyanobacteria -- to construct a detailed family tree. The results confounded her expectations. "Cyanobacteria arose fairly late, about 2.2 or 2.3 billion years ago. That explains why we see this very sudden increase in oxygen, around 2.2 to 2 billion years ago, which has always been a big mystery," she says. The finding implies that something else caused the ocean rusting.
by Kathy A. Svitil
February 11, 2003
Carrine Blank of Washington University in St. Louis
Comet's course hints at mystery planet [ from 2001 ]
Govert Schilling | last updated February 5th, 2002 | Govert Schilling
Posted on 08/18/2006 5:36:59 PM EDT by SunkenCiv
http://www.freerepublic.com/focus/f-chat/1686125/posts
Four theoretical causes of the Permian extincion event.
To what extent could the first event have triggered one or more of the other three effects?
ping, many celestial articles, including impact.
Hydrogen sulfide is found at depth in the oceans, either as a product of inorganic processes deep in the Earth, or as a biological byproduct. A large ocean impact (or a series of impacts from a former single object that broke up) would release that. However, with large impacts, that wouldn't be the only problem. :')
one of those old-fashioned topics, with a catastrophism focus:
The Origin of Sex: Cosmic Solution to Ancient Mystery
Source: Reuters
Published: Tuesday July 10 09:57 AM EDT
Author: Robert Roy Britt, Senior Science Writer, SPACE.com
Posted on 07/11/2001 09:23:06 PDT by Junior
http://www.FreeRepublic.com/forum/a3b4c7d6a4873.htm
[original, dead link]
http://dailynews.yahoo.com/h/space/20010710/sc/the_origin_of_sex_cosmic_solution_to_ancient_mystery_1.html
[also at http://www.space.com/scienceastronomy/solarsystem/origin_sex_010710.html ]
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