On Saturday, 23 June, a fresh meteorite was recovered in Botswana’s Central Kalahari Game Reserve (CKGR). It is one of the fragments of asteroid 2018 LA which collided with Earth on the 2nd of June, turned in a meteor fireball and detonated over Botswana a few seconds after entering the atmosphere, an event witnessed by a number of spectators in South Africa and Botswana. It is only the third time in history that an asteroid inbound to hit Earth was detected early and only the second time that fragments of it could be recovered.
After disruption, the asteroid fragments scattered over a wide area, blown by the wind while falling down. Calculations of the landing area were done independently by a NASA-sponsored group from the U.S.A. and experts of the Finnish Fireball Network (FFN), which used astronomical data as well as information from meteorological wind-models and security camera videos. Together with eye-witness observations this helped to define the fall area well enough to warrant the deployment of a search expedition.
The first meteorite was found after five days of intense search in the CKGR by a team of geoscientists from the Botswana International University of Science and Technology (BUIST), the Botswana Geoscience Institute (BGI) and The Okavango Research Institute (ORI). The Botswana Department of Wildlife and National Parks granted access and deployed their park rangers to provide protection and participate in the search.
The importance of the find is two-fold: It has enormous scientific value and it allows to better calibrate the so-called “Earth Defence” against impacting asteroids. For the scientists, a meteorite is a free-of charge delivery of a sample from the early forming stages of our solar system that would otherwise require expensive space missions to recover. Hence a fresh fall preserves that information in a pristine state, unaltered by mechanical or chemical weathering.
Of perhaps more practical importance is the Earth Defence aspect: Explosions of larger asteroids entering the Earth’s atmosphere can release far more energy than the strongest nuclear bombs. In the mid-1990ies, the international political leadership has started a process to set up a land- and satellite-based scanning system to map out the asteroids that could potentially cross Earth’s orbit. If we know the material properties of the objects that are about to hit Earth, the appropriate planetary defence measure can be chosen.
This is possible only if the data obtainable by remote observation can be linked with the explosion behaviour and the material fallen to the ground. This event and the recovered meteorite are only the second opportunity in history to do so.
Meteorites are protected under Botswana law .The meteorite samples will be curated by the Botswana National Museum and investigated further by a research consortium including scientists from Botswana, South Africa, Finland, and the USA.