Great Balls of Fire!

Have you seen the footage of a meteorite fire ball passing through our atmosphere on 28 February? Our team have been working to help scientists find where it made landfall in Gloucester: on a suburban driveway! Since 2019, Amgueddfa Cymru National Museum Wales has been part of the SCAMP (System of Asteroid and Meteorite Paths) UK network, part of UK Fireball Alliance which spots, tracks and helps to locate meteorite falls. Jana Horak our Head of Mineralogy & Petrology explains how and invites you to join her and some of her curatorial colleagues for a behind the scenes, online tour of our meteorite collection during our Amazing Astrology weekend 20-21 March.

Every year curators in the Museum examine, numerous samples of possible meteorites, found by the public. Scientists estimate that around 44,000 kilograms of rock fall from space and land on Earth every day, this may sound a lot, but this equates to a cube just 2.3 meters across. Within the UK alone, it is estimated that 10-20 meteorites a year reach the ground, although the last one to be found was in Cambridgeshire in 1991. In Wales, just two meteorites have been collected to date, as both fell close (or through!) human habitation, both in North Wales. Look at our Mineralogy of Wales pages for more information.

But if we don’t see a meteorite fall, how do we know where to look for them? In arid regions, such as the Sahara Desert, the dark outer layer of a meteorite contrasts with the paler stony desert surface, making the meteorite relatively easy to spot. In Wales, however, our temperate climate produces a well-developed soil and vegetation cover, so a falling stone is easily lost.

The SCAMP camera on the Museum Roof in Cardiff, which records fireball activity, It recorded the Gloucester fireball (28^th February 2021) and has contributed to helping to find samples.

When a space rock hurtles towards Earth, pulled by Earth’s gravity, the glow of the fireball or ‘shooting star’ alerts us to this intruder. If we can record the direction (or path) of the fireball, we may be able to pin-point where the meteorite falls. Since 2019, Amgueddfa Cymru National Museum Wales has been part of the SCAMP (System of Asteroid and Meteorite Paths) UK network, part of UK Fireball Alliance (https://www.ukfall.org.uk/) which does just that. A special camera on the roof at National Museum Cardiff, records the motion of any passing fireball. From this data the rate and direction of travel can be determined, and by combining information from other UK cameras, can calculate the location where the meteorite hits the ground.

Since we have had the camera installed, we have recorded several fireballs, but only two are calculated to have resulted in a meteorite fall. The first, near Salisbury in November 2020, was considered too small to attempt to recover, but the recent larger one near Gloucester (28^th February 2021) will be a test of the system, as it is estimated to include a piece about the size of an orange.  Should you encounter a recently fallen meteorite it is best to wrap it in some clean aluminium foil or place it in a bag without handling it. It is really important not to test it with a magnet as this may destroy valuable information. You can make contact with us here at the Museum to confirm anything you find.

A sample of the Chelyabinsk meteorite which fell in the Russian Federation in February 2013.

So how might you know if you have found a meteorite, if you don’t see it fall? Although the internal texture of meteorites may vary, the most characteristic feature of them is a fusion crust. This is the dark outer layer, a few millimetres thick, produced by friction melting as the rock as it sped through the atmosphere. When hot and travelling fast, the melt layer is stripped away, reducing the size of the rock, and smoothing its outline. As it slows down, cools and stops glowing the melt layer cools and solidifies, to produce a typically dark and smooth outer surface, which may be crossed by a series of small cracks. The Chelyabinsk meteorite which fell in western Siberia, in February 2013, has a very fresh and well-developed fusion crust .

The most common specimens we see which might be confused with a meteorite are; hematite, particularly where it has a smooth bulbous form, marcasite nodules from the Chalk of the southern England, and samples of slag, a product of Wales’ industrial past. Slag commonly has rounded gas bubble cavities on the surface, something that is uncommon or absent from meteorite fusion crusts.

If you think you have found a meteorite contact the Department of Natural Sciences 

Amazing Astronomy, 20 - 21 March 2021

Full information about our AMAZING ASTRONOMY weekend here