Astronomy in the Rain: How to Find Meteorites

Well, the weather forecast for Tuesday, June 5, currently looks grim for the here in Connecticut — rain starts Monday and the first clear day may be Friday. In the event of sudden change in weather patterns, recall that the transit starts at about 6:05 p.m. and will continue past sunset on Tuesday.

So what can an eager amateur astronomer do in the rain? How about going on a meteorite hunt in your backyard?

When the solar system formed, starting some 5 billion years ago, it started from a vast cloud of gas (mostly hydrogen and helium), ice (frozen gas and water) and dust (silicon, iron, nickel, as well as all of the other solid materials we have here on Earth). As this cloud shrank under its own gravity, the majority of the gas formed the Sun, and the ice and dust formed planets, moons, asteroids, and comets. 

Comets are made of frozen gas, water ice, and dust. Periodically they visit the inner solar system, heating up the dust-laden ice, and creating enormous tails behind them of gas and dust which reflect sunlight and can be seen from Earth as some of the most majestic and awe-inspiring objects in the sky. When the comet has passed through the inner solar system several times, its orbit gradually fills with a trail of dust that continues to orbit the Sun long after the comet vanishes from sight.

Many of these dusty comet orbits cross Earth’s orbit. When the Earth passes through a comet’s orbit, we experience a “meteor shower” as the comet’s trail of dust is pulled down through the atmosphere by Earth’s gravity. The individual grains of material — mostly the size of a pea or smaller — traveling at speeds from 25,000 to over 150,000 miles per hour, are heated by friction with the atmosphere to temperatures approaching 10,000 degrees. The meteors mostly vaporize at these temperatures, and it is the bright plasma from this vaporization that we see as a “shooting star."

However, all but the smallest of meteors will burst into very fine dust high up in the atmosphere. This meteoric dust will persist in the upper atmosphere until it is brought down to the ground in a rain storm. And this is where our rainy day adventure begins!

The most unusual piece of equipment you will need in your quest is a microscope, though you may have some success with a powerful magnifier. You will also need a magnet, some string, and either a non-magnetic pair of tweezers, or a toothpick.

Most meteors are made of silicate rock — not appreciably different from the rocks you’ll find in your backyard, and therefore we won’t be looking for these. About 5 percent of meteors are made of nickel-iron alloys. These meteorites will be attracted to a magnet, and that is the key to our success!

During or after a heavy rain, go outside and look for puddles of water, preferably away from areas where cars or other metal objects may have been placed (we want to avoid finding too much rust). If you are planning ahead, you can improve your chances of not getting frustrated later in the quest by placing a clean plastic or glass container outside to collect rain water. If you’re in a hurry, you can place such a container at the outlet of your gutter downspout (assuming your gutters are not made of rusting metal), and collect a good sample in a matter of minutes.

Once you’ve got your container of rain water — either in a puddle or in a container you’ve commandeered for science — tie your magnet onto some string, and dip it into the water. Swish it around for a bit and pull it out. If this is a mud puddle you’re working with, take the magnet to a faucet and gently rinse off any loose dirt.  Examine your magnet carefully — if you have little pieces of what look like sand stuck to it, you’re in business.

Next comes the tricky part. You’ve collected some iron or nickel, but are these bits of stuff meteorites, or just parts of your muffler? Set up your microscope, and pull out a clean microscope slide. Using your non-magnetic tweezers or toothpick, pluck off some of the sand that is stuck on the magnet, and place it on the slide. 

If there is a lot of material, or it is clumped together, do your best to separate it into its parts.  Avoid anything that looks yellow or reddish — that would be rust, not meteorites.

Now, look at what you have on your slide in the microscope. The difference between meteorite material and just plain rocks that have been in your yard for millennia is that the meteorite has seen extremely high temperatures, and has been recently melted. The edges of the meteorite particles will be smoothly rounded, and may show smooth pits.

If you find such things, congratulations! You have in your possession a sample of a comet! 

I have done this activity on a few occasions. The toughest part — for me — has been trying to record my results photographically. In the images accompanying this article, you will find the only reasonable photo I’ve made of a micrometeorite. To see some incredible results, and much better photos (and some proof that I’m not all wet), look at http://micrometeorites.weebly.com/miscellaneous-photos.html.

Have children between 8-18 years old who have an interest in astronomy?  My next astronomy classes start in mid-August, and I have a couple spots left to fill.  Please visit the course site at www.turnerclasses.com for more information.