U.S. CitiesCity-Data Forum Index
Go Back   City-Data Forum > General Forums > Science and Technology > Space
 [Register]
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
View detailed profile (Advanced) or search
site with Google Custom Search

Search Forums  (Advanced)
 
Old 04-29-2012, 07:15 PM
 
Location: Texas
5,070 posts, read 9,078,959 times
Reputation: 1632

Advertisements

Earlier theories suggest the turbulence ended by about 3.7 billion years ago.


Yet there’s evidence for enormous impacts as recent as 1.8 billion years ago on Earth. And the moon’s impact history isn’t resolved either, with some scientists questioning the ages of lunar basins and the type of asteroids that may have scarred its face. These discrepancies suggested to Bottke that the original story needed some revising. “Where are these impactors coming from? We must be missing a source,” he says.
Reply With Quote Quick reply to this message

 
Old 05-03-2012, 01:53 PM
 
Location: Londonderry, NH
41,490 posts, read 52,118,411 times
Reputation: 24647
Rest asured that god has not run out of rocks.
Reply With Quote Quick reply to this message
 
Old 05-04-2012, 09:26 AM
 
Location: Wasilla, Alaska
17,825 posts, read 20,504,794 times
Reputation: 6500
The Paleoproterozoic era (2.5 to 1.6 billion years ago) is suppose to be when cyanobacteria first evolved. It has been suggested that Earth's orbit was further from the sun at that time, with a higher rotational speed. It is estimated that Earth's year would have been 450 days, with a rotational period of 20 hours during this period. Continental collisions during this era are also credited for some of the oldest mountain formations, such as the 1.9–1.8 billion year-old Trans-Hudson range in North America. Eventually forming the super-continent "Columbia" during the Mesoproterozoic era (1.6 to 1 billion years ago).

Saturn and Jupiter were locked together in a 2:1 resonance at that time, pushing Neptune and Uranus further away from the sun, and pushing Mars, Earth, and Venus closer toward the sun. The asteroid belt was also much wider at that time, extending out toward the orbit of Mars.

Source: Astrophysics and Space Science, Volume 16, Number 2 - SpringerLink

The Late Heavy Bombardment (LHB) period is suppose to have occurred 4.1 to 3.8 billion years ago, but I see no reason why it would have just abruptly ended 3.8 billion years ago. Perhaps the bulk of the asteroids and comets impacted with the Earth and moon during the LHB, and just tapered off gradually over a 2 billion year period.
Reply With Quote Quick reply to this message
 
Old 05-04-2012, 12:28 PM
 
Location: Texas
5,070 posts, read 9,078,959 times
Reputation: 1632
Quote:
Originally Posted by Glitch View Post
The Paleoproterozoic era (2.5 to 1.6 billion years ago) is suppose to be when cyanobacteria first evolved. It has been suggested that Earth's orbit was further from the sun at that time, with a higher rotational speed. It is estimated that Earth's year would have been 450 days, with a rotational period of 20 hours during this period. Continental collisions during this era are also credited for some of the oldest mountain formations, such as the 1.9–1.8 billion year-old Trans-Hudson range in North America. Eventually forming the super-continent "Columbia" during the Mesoproterozoic era (1.6 to 1 billion years ago).

Saturn and Jupiter were locked together in a 2:1 resonance at that time, pushing Neptune and Uranus further away from the sun, and pushing Mars, Earth, and Venus closer toward the sun. The asteroid belt was also much wider at that time, extending out toward the orbit of Mars.

Source: Astrophysics and Space Science, Volume 16, Number 2 - SpringerLink

The Late Heavy Bombardment (LHB) period is suppose to have occurred 4.1 to 3.8 billion years ago, but I see no reason why it would have just abruptly ended 3.8 billion years ago. Perhaps the bulk of the asteroids and comets impacted with the Earth and moon during the LHB, and just tapered off gradually over a 2 billion year period.
Interesting. I wonder if this came in to play?
Reply With Quote Quick reply to this message
 
Old 05-04-2012, 12:49 PM
 
Location: Wasilla, Alaska
17,825 posts, read 20,504,794 times
Reputation: 6500
Quote:
Originally Posted by Brian.Pearson View Post
I read that earlier this week. Taking into consideration that the half-life of samarium-146 is 34% less than we had previously thought, it could change the timeline by almost that much. Instead of the LHB being between 4.1 and 3.8 billion years ago (using the older, and longer half-life for 146Sm), it would have occurred 2.7 to 2.0 billion years ago.

Which begs the question, are they using the new 68 million year half-life for 146Sm when they came up with their 1.8 billion year estimate, or were they using the old 103 million year half-life for 146Sm?

It would also mean that the Earth could not be any older than 2.97 billion years old, and Thea would have impacted with Earth to create the moon only 2.64 billion years ago.
Reply With Quote Quick reply to this message
 
Old 05-04-2012, 05:46 PM
 
Location: Texas
5,070 posts, read 9,078,959 times
Reputation: 1632
I think they'll be talking about that a little more down the road...to see if there are any clarifications or whatnot.
Reply With Quote Quick reply to this message
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.

Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.


Reply
Please update this thread with any new information or opinions. This open thread is still read by thousands of people, so we encourage all additional points of view.

Quick Reply
Message:

Over $104,000 in prizes was already given out to active posters on our forum and additional giveaways are planned!

Go Back   City-Data Forum > General Forums > Science and Technology > Space
Similar Threads
Follow City-Data.com founder on our Forum or

All times are GMT -6. The time now is 10:33 AM.

© 2005-2019, Advameg, Inc. · Please obey Forum Rules · Terms of Use and Privacy Policy · Bug Bounty

City-Data.com - Archive 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 - Top