Where to find meteorites, the Pareto chart way

The smoke shows the Chelyabinsk meteorite's path.It’s an amazing thing when a mass of rock and iron streaks through space and enters Earth’s atmosphere. So naturally, the Chelyabinsk meteor has attracted a great deal of attention. We’re fascinated by the images and captivated by the stories. And, if you’re interested in statistical analysis, you start to wonder a little bit about meteorites.

The nice thing is that the Meteoritical Society has a large database with information about meteorites recovered on Earth. The database has over 50,000 records.

It’s particularly neat to see where people find meteorites with recoverable masses. A Pareto chart in Minitab is useful for this statistical analysis because it lets you show the most popular categories and combines the remaining ones into a single category. That way, the chart stays legible without your needing to do any special work in the data. There are, after all, 148 recovery countries and regions in the database—too many categories to show legibly on a bar chart. For example, here’s what a bar chart looks like with all 148 countries and regions:

The bar chart with 148 categories is illegible.

If you stare at it long enough, you can just about make out that France is in the lower half of the list. Just about everything else is guessing.

Here’s the same data on a Pareto chart that combines the bottom 5% of the data into one category:

The pareto chart shows where 95% of meteorites are found.

Now it’s easy to see that Antarctica dwarfs all the other locations when we’re looking at the number of meteorites recovered. Apparently, it’s not so much that more meteorites land in Antarctica, they’re just much easier to find there.

We can also look at the most popular locations by mass of meteorite fragments in the database. For this Pareto chart, I combined the categories after I reached 50% of the recovered mass:

The pareto chart shows where 50% of meteorites are found by mass.

Only 4 countries account for half of the recovered mass of meteorites in the database. The differences in the charts are interesting because they point out where huge meteorites have struck. For example, Namibia has 19 meteorites in the database. That count ties Namibia with Kazahkhstan and Mauritania for 37th place in terms of number. But Namibia is the second highest in terms of mass because it has a single meteorite in the database that’s incredibly massive—60 metric tons. Greenland is similar, with fragments from a single meteorite that sum up to a mass of 58.2 metric tons. All of the countries on this graph have a meteorite with a mass of more than 24 metric tons.

The journal Nature estimates that the Chelyabinsk meteorite is the largest object to hit Earth since 1908, when another meteorite struck Russia. In the database, that Tunguska meteorite has 13.4 recovered grams. That’s good enough to tie for number 32,841 in terms of mass. We don’t yet know how much of the Chelyabinsk meteorite we’ll find, but if the amount is similar to the Tunguska meteorite, we can’t expect a rush of genuine meteorite souvenirs popping up on eBay.

The photo of the meteor trace is by Alex Alishevskikh and licensed for reuse under this Creative Commons License.


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