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Old 2009-03-28, 14:24   #34
cheesehead
 
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Nature: "Astronomy: The rock that fell to Earth"

Online story at http://www.nature.com/news/2009/0903...l/458401a.html

PDF with several nice photos at http://www.nature.com/news/2009/090325/pdf/458401a.pdf

Poster at http://www.nature.com/news/2009/0903...01a/box/1.html

Quote:
When an asteroid was spotted heading towards our planet last October, researchers rushed to document a cosmic impact from start to finish for the first time. Roberta Kwok tells the tale.

Around midnight on 6 October 2008, a white dot flitted across the screen of Richard Kowalski's computer at an observatory atop Mount Lemmon in Arizona.

. . .

As the countdown progressed, Jacob Kuiper fretted. Kuiper, an aviation meteorologist on the night shift at the Royal Netherlands Meteorological Institute in De Bilt, had seen an e-mail about the incoming asteroid. And he was worried that no one would see the explosion in the sparsely populated Nubian Desert.

With less than 45 minutes left, Kuiper realized he could notify Air France-KLM — the airline to which he routinely issued weather reports — which probably had planes flying over Africa. About ten minutes later, pilot Ron de Poorter received a message print-out in the cockpit of KLM flight 592, flying north from Johannesburg to Amsterdam. The message gave the latitude and longitude of the predicted asteroid impact. De Poorter calculated that he would be a distant 1,400 kilometres from the collision. Still, at the appointed time he and his co-pilot dimmed the instrument lights and peered northeast.

. . .

From the cockpit of his plane, de Poorter saw flickerings of yellowish-red light beyond the horizon, like distant gunfire. The flash woke a station manager at a railway outpost in Sudan. In a village near the Egyptian border, people returning from morning prayers saw a fireball that brightened and flared out, according to accounts collected later by researchers.

. . .

But for Peter Jenniskens, an astronomer at the SETI Institute in Mountain View, California, the spectacular light show was not enough. For weeks after the asteroid hit, Jenniskens, who studies meteor showers, waited to hear whether someone had found the fallen meteorites. No news emerged. "Somebody needed to do something," he says.

Jenniskens flew to Sudan in early December and met with Muawia Hamid Shaddad, an astronomer at the University of Khartoum who had already obtained pictures of the fireball's trail from locals. Together, they drove north from Khartoum to the border town of Wadi Halfa, asking villagers where the fireball had exploded in the sky. These eyewitness accounts convinced Jenniskens that the rock had disintegrated high in the atmosphere — in good agreement with US satellite data — and that any fragments were most likely to be found southwest of Station 6, a tiny railroad outpost in the Nubian Desert.

Desert search


On 6 December 2008, Jenniskens and Shaddad set out with a group of 45 students and staff from the University of Khartoum to scour the area. Team members lined up about 20 metres apart over a kilometre-wide strip, facing a sea of sand and gravel interspersed with hills, rocky outcrops and dry winding riverbeds. Flanked by two pairs of cars and trailed by a camera crew from news network Al Jazeera, the line of searchers began marching slowly east, like the teeth of a massive comb being dragged through the desert.

Towards the end of the day, a car approached Jenniskens with news that a student might have found a meteorite. "I remember thinking, 'oh no, not again'," says Jenniskens, who had already fielded several false alarms. Still, he jumped in the car and drove to the student, who presented him with a small square fragment, about a centimetre and a half across with a thin, glassy outer layer. The surface resembled the crust that meteorites form after being melted and solidified, and the rock's deep black colour suggested it was freshly fallen. It was the team's first meteorite — and the first time that scientists had ever recovered a meteorite from an asteroid detected in space (see Nature 458, 485–488; 2009).

... the most recent field campaign, completed in March, brought the tally to about 280 fragments weighing a total of several kilograms.

Jenniskens couriered a sample to Mike Zolensky, a cosmic mineralogist at the NASA Johnson Space Center in Houston, Texas. Examining the rock, Zolensky discovered that it contained large chunks of carbon and glassy mineral grains resembling sugar crystals. Tests at other labs confirmed that the sample was a ureilite, a type of meteorite thought to come from asteroids that have melted during their time in space. Only 0.5% of objects that hit Earth yield fragments in this category. But 2008 TC3's pieces are strange even for ureilites: they are riddled with an unusually large number of holes, says Zolensky. "It boggles the mind that something that porous could survive as a solid object," he says.

The findings suggest that 2008 TC3 broke from the surface of a larger asteroid, as the pores would have been crushed if they were near the rock's centre, says Zolensky. He suggests that future studies of the meteorites' chemistry could help reveal the history of its parent asteroid. Moreover, the new finds might eventually yield clues to how planets form, he says, because the asteroid had melted during its history, a process that young planets go through.

. . .

Jenniskens and his team concluded the asteroid belonged to a group called F-class asteroids. These asteroids reflect very little light, and scientists had been unsure what they were made of. The new evidence "opens a huge window", says Glenn MacPherson, a meteorite curator at the Smithsonian Institution in Washington DC, who was not involved in the studies of 2008 TC3. Although not all F-class asteroids may be the same, he says, the data suggest at least some of them may contain the same material as ureilites, such as carbon and iron.

. . .

... Discovering 2008 TC3 was like finding "a man in a dark grey suit 50% farther away than the Moon", says Kowalski ...

Last fiddled with by cheesehead on 2009-03-28 at 14:40
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Old 2009-08-04, 02:37   #35
Batalov
 
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The predictably unusual point of view from xkcd
(apparently warmed up by the Jupiter impacts, once again):

http://xkcd.com/618/

(don't forget to mouse over the comic after you are done watching).
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Old 2009-08-04, 03:51   #36
cheesehead
 
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Quote:
Originally Posted by Batalov View Post
(don't forget to mouse over the comic after you are done watching).
Wow! I've been missing all the mouseovers -- never thought of doing that.
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Old 2009-08-04, 04:45   #37
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Quote:
Originally Posted by cheesehead View Post
Wow! I've been missing all the mouseovers -- never thought of doing that.
Now you need to start again at #1.
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Old 2009-08-04, 13:05   #38
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Might want to see: http://userscripts.org/scripts/searc...titles&x=0&y=0
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Old 2013-11-21, 05:45   #39
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Just caught our own Graff (Gareth williams of the MPC) on PBS' Nova, Asteroid: Doomsday or Payday?.

(Gareth's snip was more on the "doomsday" side of things, rather than the "DIY asteroid mining for fun and profit" side. :)
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Old 2013-11-21, 20:55   #40
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Quote:
Originally Posted by ewmayer View Post
Just caught our own Graff (Gareth williams of the MPC) on PBS' Nova, Asteroid: Doomsday or Payday?.

(Gareth's snip was more on the "doomsday" side of things, rather than the "DIY asteroid mining for fun and profit" side. :)
I missed the initial broadcast, but my wife just called me to let me she'd got a call
from her mother about the show, so she (my wife, not my mother-in-law) recorded
the rebroadcast this afternoon.

Graff
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Old 2013-11-21, 21:29   #41
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You seem to be quite the Nova regular - immediately following the aforementioned show there was one on the one-shot-only sungrazing primordial Oort cloud comet Ison, which will reach perihelion on 28 Nov. [a week from today], after which we get to find out if it survives its close approach to bless us earthlings with a possibly spectacular december show as it swings back out towards the night sky [if it survives, that is].

The episode begins with Gareth at his computer(s), hard at work saving the planet from destruction as usual. Gareth, I hope you make shameless use of the "sure, he may be a medical doctor and save a life here or there, but I save the entire planet on a near-weekly basis" angle at the local singles bars, if you are single.
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Old 2013-11-22, 03:53   #42
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Quote:
Originally Posted by ewmayer View Post
Gareth, I hope you make shameless use of the "sure, he may be a medical doctor and save a life here or there, but I save the entire planet on a near-weekly basis" angle at the local singles bars, if you are single.
Considering the post above you said "I missed the initial broadcast, but my wife just called me to let me she'd got a call
from her mother about the show, so she (my wife, not my mother-in-law)recorded
the rebroadcast this afternoon.

Graff", I'm gonna take a stab in the dark and say he's not single...
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Old 2013-11-22, 04:54   #43
ewmayer
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Quote:
Originally Posted by c10ck3r View Post
Considering the post above you said "I missed the initial broadcast, but my wife just called me to let me she'd got a call
from her mother about the show, so she (my wife, not my mother-in-law)recorded
the rebroadcast this afternoon.

Graff", I'm gonna take a stab in the dark and say he's not single...
Hey, a lot can happen in 24 hours when you're a Hollywood star. :)
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