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rynner2 What a Cad!
Great Old One Joined: 13 Dec 2008 Total posts: 20319 Location: Under the moon Gender: Male |
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| krakenten Great Old One Joined: 03 Feb 2012 Total posts: 175 Gender: Unknown |
 Posted: 18-02-2013 04:09 Post subject: |
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There will be impacts. We may be able to alter courses, or otherwise deflect objects, but there will be objects heading for Earth.It's quite odd we never see any on the Moon, one questionable report from the 1200s is all we have.
One thing , meteorites are not hot when they impact. Eons in the near absolute zero of deep space causes them to be cold sinked, and even though they become incandescent in their fall, all that does is form a black carbon coating as the outer surface burns, the inner object remains cold. Kind of like Baked Alaska.
The Shoemaker-Levy impact on Jupiter gives us an idea of how bad it might be, bad as a single impact might be, a 'string of pearls' strike might be a lot worse, almost like a machine gun burst.
This could be the harbringer of more, larger objects. Or not, the Universe is uncertain. If it can happen, it will, sooner or later. When?, that's the great question. |
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| rynner2 What a Cad!
Great Old One Joined: 13 Dec 2008 Total posts: 20319 Location: Under the moon Gender: Male |
| Posted: 18-02-2013 08:27 Post subject: |
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| krakenten wrote: | | There will be impacts. We may be able to alter courses, or otherwise deflect objects, but there will be objects heading for Earth. It's quite odd we never see any on the Moon, one questionable report from the 1200s is all we have. |
The moon is a much smaller target. Also, it is much less massive than Earth, so wouldn't attract passing meteoroids so strongly.
Also, it's probable that the Earth acts as a kind of physical and gravitational shield. Maybe there are more frequent lunar impacts on the far side, which we can't see from Earth, and which wouldn't be 'shielded'. |
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| Monstrosa Joined: 07 Feb 2007 Total posts: 480 |
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| krakenten Great Old One Joined: 03 Feb 2012 Total posts: 175 Gender: Unknown |
| Posted: 18-02-2013 16:41 Post subject: |
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Thank'ee kindly, Monstrosa. I ought to have googled before I wrote.
To the esteemed Rynner, I say that the reasoning is good, yet some experts say that Luna serves us as a shield from impacts, being far enough out to be the first object encountered.
Recent events seem to kick that to the divil, eh?
The back side of Luna is rarely observed, it requires an orbiter to do so. For all we know, all sorts of Lovecraftian nasties have pitched camp there since last we looked.......of course ,there is "Someone Else is on the Moon", which goes beyond the fringe to the bare hardwood.....
People insist on calling it the Dark Side, when in fact, it's never dark there. I know I have to think twice about that.
Perhaps we can look for another century of meteor impact free days, or maybe not.
Watch the skies! |
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| rynner2 What a Cad!
Great Old One Joined: 13 Dec 2008 Total posts: 20319 Location: Under the moon Gender: Male |
| Posted: 18-02-2013 18:04 Post subject: |
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| krakenten wrote: | To the esteemed Rynner, I say that the reasoning is good, yet some experts say that Luna serves us as a shield from impacts, being far enough out to be the first object encountered.
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Only if they come from the right direction! But even then the moon is a small target, with low gravity, so they could just miss the moon and still hit us!
Can you quote any of these experts who reckon the moon is a good shield?
I guess that for every meteoroid the moon stops from hitting the earth, there are there are 10 (or 100 or a 1000..) that the Earth protects the moon from.
The earth is 81 times more massive than the moon, so the moon's gravity well is just a dimple on one side of the Earth's much deeper gravity well. Think of the Apollo astronauts: to get off Earth, and out to the moon, they needed a ginormous Saturn multistage rocket. But to get off the moon, and back to earth, all they needed was a couple of tin cans with fireworks attached!  |
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| Kondoru Unfeathered Biped Joined: 05 Dec 2003 Total posts: 5719 Gender: Unknown |
| Posted: 18-02-2013 19:27 Post subject: |
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| Some meteorites have been proved to be ice |
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| krakenten Great Old One Joined: 03 Feb 2012 Total posts: 175 Gender: Unknown |
| Posted: 18-02-2013 19:56 Post subject: |
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I remembered that shield thing from long ago. I see it was wrong. I might even have confused it with the role of Jupiter.
I'll always defer to Rynner, his google-fu is strong!
I have also read that green fireballs are caused by an oxygen reaction. I've seen several of those.
It's nearly certain that a big impactor will come along, one day. Best we be prepared, or resigned to extinction.
We all gotta go sometime. |
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| Mythopoeika Boring petty conservative
Joined: 18 Sep 2001 Total posts: 8820 Location: Not far from Bedford Gender: Unknown |
| Posted: 18-02-2013 20:30 Post subject: |
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| krakenten wrote: | | I remembered that shield thing from long ago. I see it was wrong. I might even have confused it with the role of Jupiter. |
I must say I always regarded the Moon as a shield for Earth, and never thought of it the other way round.
I guess it's because the Moon has so many impact craters, trapping us into thinking this way. If Earth had no atmosphere too, I think it'd look a lot like the Moon. |
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| rynner2 What a Cad!
Great Old One Joined: 13 Dec 2008 Total posts: 20319 Location: Under the moon Gender: Male |
| Posted: 18-02-2013 20:52 Post subject: |
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| Mythopoeika wrote: | I must say I always regarded the Moon as a shield for Earth, and never thought of it the other way round.
I guess it's because the Moon has so many impact craters, trapping us into thinking this way. If Earth had no atmosphere too, I think it'd look a lot like the Moon. |
Quite right. Everything round 'ere got a right good bashing, even before there were green fields! 
http://en.wikipedia.org/wiki/Late_Heavy_Bombardment
| Quote: | | The Late Heavy Bombardment (commonly referred to as the lunar cataclysm, or LHB) is a hypothetical event around 4.1 to 3.8 billion years ago (Ga).[1] During this event an extraordinary large number of the impact craters on the Moon would have formed, and by inference an extraordinary large number of impacts on Earth, Mercury, Venus and Mars would have happened as well. |
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| Kondoru Unfeathered Biped Joined: 05 Dec 2003 Total posts: 5719 Gender: Unknown |
| Posted: 18-02-2013 22:17 Post subject: |
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| Im glad people are getting used to the idea that rocks (and even iron!) fall from the sky... |
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| krakenten Great Old One Joined: 03 Feb 2012 Total posts: 175 Gender: Unknown |
| Posted: 18-02-2013 22:55 Post subject: |
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Once, the idea of a meteor provoked loud guffaws, scorn, and that peculiar self-rightous contempt so typical of the intellectual elite.
Jefferson once said, "Rocks cannot fall from the sky because there are no rocks in the sky!"
This might have come from the idea of the 'thunderstone'. Stone arrowheads and shark teeth were often called thunderstines, and indeed, to this day lightning bolts are sometimes drawn with a sort of triangular tip. This was known to be false.
In 1803, there was a fall of stones in France, which got the idea studied again. The answer?
Cthulhu!
th |
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| krakenten Great Old One Joined: 03 Feb 2012 Total posts: 175 Gender: Unknown |
| Posted: 18-02-2013 22:56 Post subject: |
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Once, the idea of a meteor provoked loud guffaws, scorn, and that peculiar self-rightous contempt so typical of the intellectual elite.
Jefferson once said, "Rocks cannot fall from the sky because there are no rocks in the sky!"
This might have come from the idea of the 'thunderstone'. Stone arrowheads and shark teeth were often called thunderstines, and indeed, to this day lightning bolts are sometimes drawn with a sort of triangular tip. This was known to be false.
In 1803, there was a fall of stones in France, which got the idea studied again. The answer?
Cthulhu! |
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| rynner2 What a Cad!
Great Old One Joined: 13 Dec 2008 Total posts: 20319 Location: Under the moon Gender: Male |
| Posted: 22-02-2013 10:17 Post subject: |
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One of biggest ever asteroid impact zones found in Australia
Scientists have discovered a 200-kilometre-wide (125-mile-wide) impact zone in the Australian outback they believe was caused by a massive asteroid smashing into Earth more than 300 million years ago.
4:06PM GMT 20 Feb 2013
Andrew Glikson, a visiting fellow at the Australian National University, said the asteroid measuring 10 to 20 kilometres in diameter was a giant compared to the plunging meteor that exploded above Russia a week ago.
While that event set off a shockwave that shattered windows and hurt almost 1,000 people in the Urals city of Chelyabinsk, Mr Glikson said the consequences of the Australian event would have been global.
"This is a new discovery," Mr Glikson told AFP on Wednesday, describing the impact zone in South Australia's East Warburton Basin.
"And what really was amazing was the size of the terrain that has been shocked. It's now a minimum of 200 kilometres (in diameter), this makes it about the third biggest anywhere in the world."
The basin has evidence of some 30,000-square kilometres of terrain that has been altered by some kind of shock, which Mr Glikson first began studying after another scientist showed him rock samples that displayed structural anomalies.
"Following that I spent many months in the lab doing a number of tests under the microscope to measure the crystal orientations... and determined that these rocks underwent an extraterrestrial impact or shock," he said.
"We are dealing with an asteroid which is least 10 kilometres in size.
"It would have had a global impact, not just regional."
Besides leaving a vast crater, now buried under more than three kilometres of sediment, it would have released huge amounts of dust and vapour that would have blanketed the Earth.
"We think it was part of a cluster. We think it could be... about 360 million years ago. There were a number of other very large impacts at that time. That cluster we know has caused mass extinction," Mr Glikson said.
Glikson, from ANU's Planetary Science Institute and School of Archaeology and Anthropology, said despite the recent Russian meteor and the 45-metre wide asteroid dubbed 2012 DA 14 that whizzed past Earth last week, events of the scale of the Australian asteroid were extremely rare.
"They fall once in every several tens of millions of years," he said comparing it to once a century for the meteor shower.
"I don't think we have to worry about it, not as much as we have to worry about nuclear accidents or about climate change."
http://www.telegraph.co.uk/science/space/9883335/One-of-biggest-ever-asteroid-impact-zones-found-in-Australia.html |
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| ramonmercado Psycho Punk
Joined: 19 Aug 2003 Total posts: 17657 Location: Dublin Gender: Male |
| Posted: 22-02-2013 14:32 Post subject: |
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| Quote: | Asteroids no match for paint gun, says professor
February 22nd, 2013 in Space & Earth / Space Exploration
Enlarge
Asteroids are a constant threat to Earth.
(Phys.org)—There is research that is off the wall, some off the charts and some off the planet, such as what a Texas A&M University aerospace and physics professor is exploring. It's a plan to deflect a killer asteroid by using paint, and the science behind it is absolutely rock solid, so to speak, so much so that NASA is getting involved and wants to know much more.
Dave Hyland, professor of physics and astronomy and also a faculty member in the aerospace engineering department at Texas A&M and a researcher with more than 30 years of awards and notable grants, says one possible way to avert an asteroid collision with Earth is by using a process called "tribocharging powder dispensing" – as in high pressured – and spreading a thin layer of paint on an approaching asteroid, such as the one named DA14 that came within 17,000 miles on Feb. 15.
This video is not supported by your browser at this time.
What happens is that the paint changes the amount by which the asteroid reflects sunlight, Hyland theorizes, producing a change in what is called the Yarkovski effect (which was discovered by a Russian engineer in 1902). The force arises because on a spinning asteroid, the dusk side is warmer than the dawn side and emits more thermal photons, each photon carrying a small momentum. The unequal heating of the asteroid results in a net force strong enough to cause the asteroid to shift from its current orbit, Hyland further theorizes.
The kind of paint used is not the kind found at your local hardware store, Hyland explains.
"It could not be a water-based or oil-based paint because it would probably explode within seconds of it entering space," he notes.
"But a powdered form of paint could be used to dust on the asteroid and the sun would then do the rest. It cures the paint to give a smooth coating, and would change the unequal heating of the asteroid so that it would be forced off its current path and placed on either a higher or lower orbit, thus missing Earth.
"I have to admit the concept does sound strange, but the odds are very high that such a plan would be successful and would be relatively inexpensive. The science behind the theory is sound. We need to test it in space."
As for getting the paint on the asteroid, a practical way to do this was discovered by a former student of Hyland's, Shen Ge, who has since started a new space company. The "tribocharging powder dispenser" would spray a mixture of inert gas and charged dry-paint powder at the asteroid that would attract the powder to its surface through electrostatics. Then solar wind and UV radiation would cure the powder, giving a smooth, thin coat on the surface.
Getting the paint in the asteroid's path in a timely manner will certainly be a challenge, Hyland observes.
"The tribocharged powder process is a widely used method of painting many products," he says. "It remains only to adapt the technology to space conditions."
NASA has approached Hyland for developing such a project to test the theory, and the Earth may need it quickly. An asteroid called Apophis is due in 2029 and will come closer than many communications satellites in orbit right now. It will fly by on April 13 (Friday the 13 to be exact) of 2029 and make a return trip in 2036, and it's estimated to be more than 1,000 feet in length and is appropriately named for an evil Egyptian god of chaos and destruction. There is no chance of its hitting Earth in 2029, but a small chance in the next close approach in 2036, Hyland notes.
Asteroids have hit Earth before. One hit off the Yucatan coast of Mexico about 65 million years ago and is believed to have caused the eventual extinction of the dinosaurs. And in 1908, the fabled "Tunguska event" occurred in Siberia in which an asteroid or meteor exploded several miles above the Earth, flattening trees and killing livestock over 800 square miles.
The explosion is now estimated to have been 1,000 times more powerful than the A-bomb dropped on Hiroshima.
"There are thousands of asteroids out there, and only a small percentage of them are known and can be tracked as they approach Earth," Hyland adds.
"The smaller ones, like DA14 are not discovered as soon as others, and they could still cause a lot of damage should they hit Earth. It is really important for our long-term survival that we concentrate much more effort discovering and tracking them, and developing as many useful technologies as possible for deflecting them."
Provided by Texas A&M University
"Asteroids no match for paint gun, says professor." February 22nd, 2013. http://phys.org/news/2013-02-asteroids-gun-professor.html |
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