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Re: Searching for Micrometeorites in Snow
Posted: Wed Mar 31, 2010 3:49 am
by Amir
thanks a lot Gorkow, for your previous explanations.
the majority of micrometeorites & i guess almost all of the ones you find do have metal in them (Fe,...), so considering earth magnetic field, does it mean that we'd find a huge amount of them in poles? which would also have a greater "real meteorite/volcanic particle" ratio?
Re: Searching for Micrometeorites in Snow
Posted: Wed Mar 31, 2010 4:53 am
by Chris Peterson
Gorkow wrote:The samples were very interesting...
Indeed. I operated a micrometeorite collection experiment for about 18 months. This consisted of an 8-foot square aluminum collection surface, which drained to a magnet and a set of graded sieves. The entire thing was in a remote mountain location, very far from any industrial sources. We collected a large number of candidate objects (assessed by optical microscopy), both metallic and otherwise, and examined a dozen of the best with SEM/x-ray dispersion spectroscopy. Everything appeared terrestrial. Material fell onto the collector either dry, and was flushed with clean water, or in rain, or in snow. What we collected didn't seem to change much- the deposition rate was fairly constant year round.
Re: Searching for Micrometeorites in Snow
Posted: Wed Apr 07, 2010 1:20 am
by Gorkow
Amir wrote: earth magnetic field
I think the magnetic force on the large particles would be much smaller when compared to the gravitationally force, and as a result the magnetic field could be neglected. With that said i think the magnetic field should be considered for iron particles <10microns. This is just my intuition, so a calculation could prove me wrong.
On to the Great news. We got a micrometeorite. I compared the composition of the particle on page 6, to other micrometeorites collected.
https://docs.google.com/fileview?id=0B7 ... NWE1&hl=en
and our particle falls in the micrometeorite composition. It is close to the volcanic composition area but due to the particle size there is no volcano close enough to our collection location.
cheers
Gorkow
Re: Searching for Micrometeorites in Snow
Posted: Sun Apr 25, 2010 3:18 pm
by wonderboy
I know a lot of searching goes on in the arctic for meteorites, but would the heat from the space debri not melt its way through the layers of ice covering the arctic meaning they would be quite hard to spot, or would it be cooled enough (since its the arctic) by the time it hits the ice. My thinking is that the friction between the very fast moving rock which is already hot and the cool air would still be enough to keep the rock warm and therfore embed it in the ice. I have no idea how deep, but i would imagine deep enough to make it hard to find.
Re: Searching for Micrometeorites in Snow
Posted: Sun Apr 25, 2010 3:37 pm
by Chris Peterson
wonderboy wrote:I know a lot of searching goes on in the arctic for meteorites, but would the heat from the space debri not melt its way through the layers of ice covering the arctic meaning they would be quite hard to spot, or would it be cooled enough (since its the arctic) by the time it hits the ice. My thinking is that the friction between the very fast moving rock which is already hot and the cool air would still be enough to keep the rock warm and therfore embed it in the ice. I have no idea how deep, but i would imagine deep enough to make it hard to find.
Meteorites are usually very cold when they hit. Their temperature while still in space depends on their composition, but figure that they are about the temperature of a rock in the Sun (since that's basically what they are). When they enter the atmosphere, their outside burns away by ablation. This is very fast, and the ablation carries away heat efficiently. The interior temperature of the stone is hardly affected. The surviving material then spends several minutes falling at ~100 m/s through -40°C air, which rapidly cools it down. Meteorites have been observed to break open when they strike, and the interior frosts up. So any meteorites landing on ice are likely to just lie there.
In fact, the Tagish Lake meteorite in Canada a few years ago did just that. There were thousands of fragments all laying on top of the frozen lake surface. Over a few days, many melted through the ice and fell into the lake simply because they absorbed energy from the Sun and warmed up. If you live in a place with frozen ponds you can easily duplicate this process by tossing a fist-sized black stone out onto the ice. In sunny cold weather it will sink a little every day.
Re: Searching for Micrometeorites in Snow
Posted: Thu May 13, 2010 3:19 pm
by The Code
Hi folks
Found this for you guys.
http://www.cosmosmagazine.com/news/3441 ... rctic-snow
Quote:
'SYDNEY: Two tiny meteorites recently recovered from Antarctic snow contain material dating back to the birth of our Solar System, and may provide clues about the delivery of organic matter to Earth.
Researchers believe that these micrometeorites likely came from the cold, comet-forming outer regions of the gas and dust cloud that comprised the early Solar System, and sample its composition.
Discovered in 2006, the particles measure less than 0.25 mm across and survived their journey through Earth's atmosphere relatively unscathed. More importantly, scientists found that they contain unusually high amounts of organic matter.'
Mark
Re: Searching for Micrometeorites in Snow
Posted: Wed May 26, 2010 2:32 pm
by RJN
NYT: From Trees and Grass, Bacteria That Cause Snow and Rain
http://www.nytimes.com/2010/05/25/science/25snow.html
David Sands, a plant pathologist, says the blanket of snow draped over the mountains around town contains a surprise. The cause of most of it, he said, is a living organism, a bacterium, called pseudomonas syringae. ... The accepted precipitation model is that soot, dust and other inert things form the nuclei for raindrops and snowflakes.
Re: Searching for Micrometeorites in Snow
Posted: Tue Dec 07, 2010 8:21 pm
by Céline Richard
Hello
I attach pictures of a micrometeorite, named Concordia, which comes from the website:
http://www.futura-sciences.com/fr/news/ ... des_19964/
I translate a few things, about
researches for a possible origin of micrometeorites :
From Futura Science: "Indeed, it fells micrometeorites all the time on Earth, which can be easily harvested in the Antartic ices. But they look like a lot to what we know from cometary dusts (we analyzed samples from the cometa Wild II, thanks to the mission Stardust).
Those micrometeorites were mainly likely to proceed from the the asteroids belt, which we think more devoid/lacking of little carbon bodies: we were leading to a defect/anomaly; moreover the isotopic abundances didn't tally.
Nowadays (article published on July 22th 2009), we think (thanks to simulations, following the Nice model, i didn't heard about it) cometas, formed a little further than giant planets, more than 4 billions years ago, would have been ejected towards the current asteroids belt, and thus would have been trapped there (kept here).
According to the dirty snowball of Whipple (yes, i translate the truth!!), comets are less compact than classic/standard asteroids. During collisions with them inside the asteroids belt, it would have been fragmented much more easily. Thus the micrometeorits we receive on Earth would be the remains and pieces of evidence of this pollution of the belt by transneptunian objects (here i guess =micrometeorites)."
If you go to wikipedia, there is the definition for transneptunian objects:
A trans-Neptunian object (TNO; also written transneptunian object) is any minor planet in the Solar System that orbits the Sun at a greater distance on average than Neptune.
And, if you go on "minor planet", there is:
A minor planet is an astronomical object in direct orbit around the Sun that is neither a dominant planet nor a comet.
So a micrometeorite can be a transneptunian object.
Have a very nice day!
Céline
