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Posted: 18-05-2013 17:22 Post subject:

Bright explosion on moon visible from Earth, NASA says

An explosion on the moon was caused by a meteor hitting the surface and was visible on Earth to the naked eye.

The explosion was caused by a meteoroid that hit the lunar surface
It was visible on Earth without a telescope

NASA sees hundreds of lunar meteoroid impacts on the moon each year
The meteoroid was traveling 56,000 mph when it banged into the moon
(CNN) -- A meteoroid struck the surface of the moon recently, causing an explosion that was visible on Earth without the aid of a telescope, NASA reported Friday. But don't be alarmed if you didn't see it; it only lasted about a second.

"It exploded in a flash nearly 10 times as bright as anything we've ever seen before," said Bill Cooke, of NASA's Meteoroid Environment Office.

NASA astronomers have been monitoring the moon for the past eight years, looking for explosions caused by meteoroids hitting the lunar surface. It's part of a program to find new fields of space debris that could hit Earth.

NASA says it sees hundreds of detectable lunar meteoroid impacts a year.

None however can match the size of the explosion they say they saw March 17. NASA says the meteoroid was about 40 kilograms and less than a meter wide, and it hit the moon's surface at 56,000 mph. It glowed like a 4th magnitude star, NASA says, thanks to an explosion equivalent to 5 tons of TNT.

"It jumped right out at me, it was so bright," said Ron Suggs of the Marshall Space Flight Center.

Cooke says Earth was pelted by meteoroids at about the same time, but they hit the moon because it has no atmosphere to protect it.

"We'll be keeping an eye out for signs of a repeat performance next year when the Earth-moon system passes through the same region of space," Cooke said.

If you're wondering how there can be an explosion on the moon, without oxygen, NASA has the answer for you. It says the flash of light comes not from any type of combustion -- as we typically think of explosions -- but rather by the glowing molten rock at the impact site.

SOURCE: http://www.cnn.com/2013/05/18/tech/moon-explosion/index.html?hpt=hp_c3

Posted: 19-09-2013 08:09 Post subject:

Here's a theory I've not heard before:

Does gold come from outer space?
By William Kremer, BBC World Service

The idea that gold came from outer space sounds like science fiction, but it has become well-established - it's pretty much received opinion in the field of earth sciences. How did this bizarre theory take hold, and is it here to stay?

For the chieftains of pre-Columbian America, the dazzling yellow stuff they found glinting at the bottom of streams or buried in the rocky ground captured the power of the sun god. They dressed themselves in battle armour wrought from the enchanted metal, believing it would protect them.
They were sadly deceived.

Gold, an unusually soft metal, wasn't any match for the steel of the Spanish. But the Native Americans may well have been right in believing the element was otherworldly.

"Why do you find nuggets of gold on the surface of the Earth?" asks science writer John Emsley. "The answer to that, is that they've arrived here from space in the form of meteorites."

This theory has come in the last few decades to be held by the majority of scientists as a way of explaining gold's abundance. There may only be 1.3 grams of gold per 1,000 tonnes of other material in the Earth's crust (the rocky shell of the planet that is around 25 miles thick) but that's still too much to fit with the standard models of our planet's formation.

After its birth four-and-a-half billion years ago, the surface of the Earth heaved with volcanoes and molten rock. Then, over tens of millions of years, most of the iron sank down through the outer layer, known as the mantle, to the Earth's core. Gold would have mixed with the iron and sunk with it. Matthias Willbold, a geologist at Imperial College London, likens the process to droplets of vinegar collecting at the bottom of a dish of olive oil.
"All the gold should be gone," he says.

It isn't though. So science has had to come up with an explanation, and the answer currently favoured is - a meteoric shower.

"The theory is that after the core formed there was a meteoric shower that struck the Earth," says Willbold. "These meteorites contained a certain amount of gold and that replenished the Earth's mantle and the continental crust with gold."

Willbold says the theory fits with the pattern of meteorite activity as scientists understand it, climaxing with a huge storm that took place more than 3.8 billion years ago, referred to as the "terminal bombardment". The meteorites punched out the craters we see on the moon and came from an asteroid belt that still exists between Earth and Mars.

This idea of the gold-laden-meteorite "veneer" was first proposed following the Apollo moon landings of the 1970s. Scientists examining rock samples from the moon's mantle found much less iridium and gold than they did in samples from the surface of the moon or from the earth's crust and mantle. It was proposed that the moon and Earth had been battered by iridium-rich meteorites, known as chondrites, from outer space. While the precious fallout from this meteoric shower lay scattered on the surface of the moon, on Earth the planet's internal activity had churned it into the mantle too.
The idea, called the "late veneer hypothesis", has become a fundamental theory in planetary science.

It also helps to explain many other anomalies in the Earth's composition - it is thought that the same meteorites delivered the carbon, nitrogen, water and the amino acids that are vital to all life on the planet.
"They are basically the building blocks of Earth," says Willbold.

Two years ago, he and a team from the universities of Bristol and Oxford examined some rocks from Greenland which had their origins in a part of the Earth's mantle that was insulated from meteorite activity for a crucial period some 600 million years. The team did not look at the gold content of the 4.4-billion-year-old rocks, but at tungsten. Tungsten has some similarities to gold but exists in different forms or isotopes, and this provides scientists with more historical information.

"The tungsten-isotopic composition of these rocks was basically really different from the tungsten-isotopic composition of other rocks," says Willbold.
He infers that the Greenland rocks are a remnant of Earth's composition prior to the start of the late veneer meteorite shower, postulated to have taken place between 4.4 and 3.8 billion years ago.

Willbold's influential study, published in Nature in September 2011, provides the most compelling evidence yet for the late veneer hypothesis. This hypothesis seems the best explanation for the unusual tungsten-isotopic profile of Willbold's Greenland rocks, just as it seemed to explain the different quantities of gold and iridium in the mantles of the Earth and the Moon in the 1970s.

But the hypothesis has been challenged.
Last year, Mathieu Touboul and a team from the University of Maryland examined some different rocks, this time from Russia and significantly younger than those in the Greenland study - a mere 2.8 billion years old.

These younger rocks had their full complement of elements known as siderophiles - the iron-loving group of metals that includes gold - but in terms of tungsten isotopes, the rocks turned out to be very similar to Willbold's. And yet they date from after the time proposed for the late veneer bombardment.

"We reach a different conclusion about what is generating these tungsten anomalies inside the rocks," says Touboul. He thinks differences in the Earth's mantle might have caused tungsten isotopes to develop in different ways.
Touboul though still believes the late veneer hypothesis is right - he just doesn't think that tungsten isotope measurements provide a demonstration of it.

Other scientists think it's time for a major rethink.
"I used to accept the late veneer hypothesis back when we had so little data that it seemed to be a sensible interpretation, but I think it's past its prime now," says Munir Humayun of Florida State University.
"It seemed so elegant, but there were so many gaps in the data. We presumed a lot and knew very little back then."

Humayun says the original 1970s studies on moon and Earth rocks produced imprecise results, at variance with more sophisticated follow-up studies from the 1990s.

One of these studies, from the University of Maryland, found less resemblance than expected between the Earth's rocks and chondrites - the iridium-rich meteorites. "This is where the late veneer failed in my opinion," says Humayun. "The answer came back that none of the known meteorite types were anything like the veneer."

Scientists also began to find metals like gold much deeper in the Earth's mantle than they had anticipated. This could be explicable if the Earth underwent a much bigger meteoric barrage than originally supposed, and at an earlier point in time. But the way Humayun sees it, the late veneer hypothesis stopped answering old questions - and started posing new ones.

He is one of a small group of scientists who subscribe to an alternative theory. Their proposition is that all the gold in the Earth's crust - or the overwhelming majority of it - was here on Earth all along. Most of it certainly alloyed with iron and migrated to the Earth's core, but a significant proportion - perhaps 0.2% - dissolved into a 700km deep magma "ocean" within the Earth's outer mantle.
Later, the gold was brought back up to the crust by volcanic action. This is the stuff we wear round our necks and on our fingers today.

This theory requires gold and other siderophile elements to be more soluble than has previously been thought, otherwise insufficient quantities would have dissolved in the magma.
Experiments by two scientists at Nasa - Kevin Righter and Lisa Danielson - indicate that gold's solubility in mantle rocks does increase with high pressures and temperatures.

However, it has not yet been possible to measure in a lab the solubility of all the highly siderophile elements over the full range of temperatures and pressures of the Earth's mantle, so for now this proposed explanation for the abundance of gold also remains no more than a hypothesis. But it is attracting interest and was bashed against the late veneer theory at length in a session last month at geochemistry's annual international symposium - the Goldschmidt Conference in Florence.

Matthias Willbold, who attended the session, says the consensus in the room was that the late veneer hypothesis was still the best explanation for the unusual tungsten-isotopic profile of his Greenland rocks.
He adds that, unlike Humayun, most scientists believe that chondritic meteorites are a "match" for concentrations of metals in the Earth's mantle and crust. But he says he accepts that the case for the late veneer hypothesis is not exactly sewn-up.

"You can never be absolutely sure," he says. "But the beauty of our model at the moment is that all the numbers match up very well." His isotope measurements indicate that about 0.5% of the Earth's mantle mass fell in the form of meteorites (that's 20 billion billion tonnes, if you were wondering). This figure matches geologists' current best guess, based on the overall concentrations of precious metals in the Earth's mantle and crust. Willbold describes this match as a "smoking gun".

But Humayun says that the extent to which geochemists believe it depends on their precise field of study.

Analytical geochemists - the group of researchers that measures trace elements in rocks - have come to see their research as crucial to understanding the emergence of life on Earth. Humayun says that experimental geochemists - the group of scientists attempting to recreate the conditions of the mantle in the lab - are more open-minded.

"It's about how you make your money! If you're an experimentalist, then you're eating the late veneer guys' lunch by doing these experiments.
"Why the analytical community likes the idea (of a late veneer) so much is something that continues to trouble me. It's because of this relevance they have tied in to the origin of life. There's a lot riding on it!"

http://www.bbc.co.uk/news/magazine-22904141

Pics, side-bars and diagrams on page.

Posted: 19-09-2013 18:44 Post subject:

This 'gold from space' idea makes a lot of sense to me.
I'd go a bit further and say that it might be from the Moon. Meteorite hits moon, molten rock flies off and heads to Earth.
AFAIK, there's a lot of gold on the Moon.

Or...alternatively, it is periodically spat out from the Sun. Perhaps that's how it ended up on the Moon.

Posted: 20-09-2013 09:33 Post subject:

The sun's not hot enough to make gold. At the moment it's only making helium. Just as well, when it gets hot enough to fuse stuff higher than hydrogen, it will be very uncomfortable here.

I don't think it will ever make gold, I think it'll peak around nitrogen or oxygen or something.

Posted: 20-09-2013 19:29 Post subject:

Posted: 20-09-2013 20:20 Post subject:

Posted: 20-09-2013 20:43 Post subject:

Posted: 22-09-2013 11:43 Post subject:

And as you can see from the Wiki link, when it runs out of Hydrogen, and starts on Helium, it starts the Red Giant stage when the Sun is predicted to spread out past the Earth's orbit.

Posted: 30-09-2013 08:23 Post subject:

Fireball filmed soaring across US sky
A fireball has been caught on camera soaring brightly across the sky above Ohio, leading to numerous 911 calls by worried residents.
[Video - not very dramatic]
9:37AM BST 29 Sep 2013

The fireball was recorded on an all-sky Nasa camera in Ohio operated by Bill Cooke of the Meteoroid Environmental Office on Friday 27 September at 23.33 local time.
In the footage, a bright light can be seen making its way across the sky before moving out of sight of the camera.

The American Meteor Society recorded over 400 witness sightings across the mid-west of the fireball which is thought to have been a meteor or debris from space.
There were reports that police from across the mid-west received calls from worried residents about the bright light in the sky.

http://www.telegraph.co.uk/news/newstopics/howaboutthat/10342327/Fireball-filmed-soaring-across-US-sky.html

Posted: 01-10-2013 15:09 Post subject:

These all-sky NASA cameras are good for spotting fireballs and so on. They would also be good for spotting UFOs, if there were any - but they haven't seen any yet.

Posted: 02-10-2013 00:04 Post subject: