Identifying extraterrestrial materials

Thousands of fragments of rock or metal known as meteorites fall to Earth from space each year. Most of these are tiny, ranging from a few millimetres to a few centimetres in diameter.

It is thought that over 99% of all the meteorites found on Earth are fragments of asteroids that originally resided in orbit between Mars and Jupiter. When these fragments leave this region of space, known as the asteroid belt, and travel though outer space they are coined meteoroids. Any meteoroids captured by the Earth’s gravitational force, are sucked in to its atmosphere. Here they decelerate rapidly, causing them to heat up and start to glow (at which point they are renamed meteors or falling stars). Most of the original fragment burns up as it falls, any material that does hit the Earth is called a meteorite.

We have devised a simple, inexpensive and eye-catching experiment that students can do to distinguish between a metallic meteorite specimen and a manmade metallic object, based on its nickel content. This method is based on the classic reaction of nickel(II) ions with dimethylglyoxime. In an alkaline ammonia medium, dimethylglyoxime forms a brilliant red complex with nickel(ii) ions.

Small meteorite specimens (about 5 g) can be purchased for around £6, and each specimen can be reused many times. Using cheap, readily available reagents and the human eye as the detector, this experiment gives results on par with those of the commercial method used as a reference.

As a laboratory exercise with students working in pairs, we estimate this would take approximately 90 minutes. Alternatively a teacher demonstration would only take 15 minutes.

From set up to demonstration, featuring teaching questions and background information to aid discussion, this article details how to create an experiment in which students can identify extraterrestrial materials.