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Meteorites near you

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I've always assumed that meteorites are quite rare, and as far as ones of any size are concerned that's true. But I was surprised recently to find that thousands of very small "micrometeorites" land on the Earth's surface constantly. Typically they are less than a millimetre in size and weight only a tiny fraction of a gram. If they enter the atmosphere at the right angle and velocity they may suffer some heating but still survive to ground level.

How common are they? Very. A back-of-an envelope calculation suggests that one falls on each square meter about once a fortnight on average. Think of that! You have probably added one to your stock of meteorites during the course of today.

They have been collected in places such as polar regions and in certain geological strata. But finding them in inhabited parts of the world is challenging because of the swarms of other dust-sized particles, many of them of human origin. However recent painstaking research has found undisputed micrometeorites in urban gutters. These are promising sites, because they collect run-off, probably separate out heavier particles (think of panning for gold) and probably trap less contamination from road dust and the like.

If you wanted to find your own, how would you start? First get a neodymium magnet (like the one I mentioned in a previous post about iron in cornflakes, and easily obtained). Put this in a plastic bag and swirl it around in gutter gloop.

Then enclose this in another plastic bag, and pull the magnet out of the inner bag. Voila! Candidate particles will have been collected between the bags.

Now comes the hard part. Almost all will be metallic grains created by human activity. So you will have to examine your finds under a microscope and carefully pick out the stardust. Not at all easy, but luckily there is a book by a dedicated enthusiast.

Read more here about Project Stardust


Images from here


Permalink 3 comments (latest comment by Jon Hirst, Saturday, 28 Jan 2017, 19:00)
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Dr Who?

Star dust

Visible to anyone in the world
Edited by Richard Walker, Saturday, 13 Feb 2010, 05:27

Hello stardust

For that's what you are, reader.  Here's the story, please read it, it concerns you and I.  Sorry it is a bit long but it took billions of years to happen, so it is hard to squeeze into one blog post.

Long long ago when the universe first began there was only hydrogen.  Later some helium formed.  Then some lithium and probably a little beryllium. Even a little carbon.  But nothing very heavy.

After quite a while some large stars formed.  In the heart of these stars helium was forged from hydrogen and the change threw off lots of energy. The helium could even form other elements by combining and this too produced energy. This energy flow kept the stars inflated, although gravity was trying to make them contract.

Over time these stars began to run out of hydrogen and helium, and eventually they collapsed.  This is what causes a supernova!  The star implodes violently in a short time -- days only -- but then as it smashes in on itself all sort of new elements are formed by the pressure -- including many necessary to life.  Before the implosion there might have been a little carbon perhaps but no iron for blood, or oxygen for breathing.

Now this explosion blew the heavy elements formed out at great velocities and over billions of year the atoms ended up with some other dust, and some hydrogen and helium, and gravity made it swirl together.  This formed a new star and some planets.

But some of the little planets were too small for their gravity to hold on to all the hydrogen and helium they began with. Part of their hydrogen combined with oxygen to make water, which has remained.  But mostly what was left was heavier elements -- think rocks. Still all the same the wet bits on the surface acted a home for the evolution of life.

Of course this life used many heavy atoms from supernovas billions of light-years away and billions of year before.  You and I would not exist without the dust from those ancient stars.

Literally stardust.





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