A Sikhote-Alin Meteorite Discovery: The Missing Link

The February, 1947 fall of the Sikhote-Alin iron in a remote part of eastern Siberia was, by far, the largest recorded meteorite event in history. While Campo del Cielo (Argentina), Muonionalusta (Sweden), and Gibeon (Namibia) may possibly have deposited more meteorites in terms of sheer tonnage, they all took place in prehistoric times. If those events were even seen by early humans, the witnesses lived thousands of years before the advent of writing and so no records exist.

A 137.7-gram Sikhote-Alin meteorite "individual" displaying characteristic regmaglypts (thumbprints)

The eminent Russian meteoriticist, E. L. Krinov, visited the fall site and recovered numerous specimens, which ended up in the Russian Academy of Sciences. Some of his team’s finds were lying on pedestals of snow, never having actually touched the ground, and displayed a blue/grey fusion crust. Krinov wrote an entire book about Sikhote-Alin, but it has, sadly, never been translated into English.

Scientists, and later, collectors, noted that there are two distinctive types of Sikhote-Alin meteorites: shrapnel and individuals. Shrapnel fragments are the result of in-flight explosions of large masses which produced twisted, angular shards reminiscent of bomb case shrapnel, hence their name. Individuals flew though the air as autonomous entities and ablation in the atmosphere caused them to acquire remarkable and sculptural shapes. Individuals frequently display regmaglypts, which are thumbprint-like indentations caused by surface melting.

One face of the 2,785-gram Sikhote-Alin "Missing Link" displays all the typical qualities of shrapnel

One of the intriguing questions about the Sikhote-Alin fall is where and when did the shrapnel-producing detonations take place. After examining a recent acquisition which we call “The Missing Link,” we are able to put forward a hypothesis. Until now, Sikhote-Alins fell into one of two categories, but a recently discovered shrapnel/individual hybrid demonstrates that there are, in fact, three types of Sikhote-Alin meteorite.

The piece in question weighs 2,785 grams and is roughly pentagonal in shape. One large face and two edges are typical of shrapnel specimens: their surfaces are torn and distressed; one face and one edge, remarkably enough, bear the obvious characteristics of individuals in that they are covered with large, oblong regmaglypts.
The exterior face of "The Missing Link" exhibits large and well-formed regmaglypts

The exterior face of "The Missing Link" exhibits large and well-formed regmaglypts

The pioneering American meteoriticist H.H. Nininger noted a correlation between the size of regmaglypts and the size of the individuals upon which they appear: the larger the mass, the larger the thumbprints on its surface. The regmaglypts on our shrapnel/individual hybrid are extremely large: one of them is 32.5 mm in length. This tells us that the original meteoroid—prior to fragmentation—was massive. This fascinating meteorite also suggests that the in-flight fragmentation which formed the Sikhote-Alin shrapnel pieces occurred relatively late, and probably close to the ground. It is also interesting to note that shrapnel specimens are associated with the 100+ craters in the Sikhote-Alin strewnfield. While at first glance this suggests that shrapnel was formed by explosive cratering events, some shrapnel specimens display tiny impact pits, which must have been caused by the in-flight impacts of smaller meteorites.

The regmaglypts on our 2.785-kg specimen took time to form. The original mass needed to heat up and melt during flight, before finally exploding. So, what we are looking at here is a surviving piece of the exterior of one of the largest, or perhaps the largest original masses of Sikhote-Alin. The oversize, well-formed regmaglypts demonstrate that it was once part of a very large individual, while its twisted shrapnel-like areas show that it also fragmented in flight.

Detail of regmaglypts on the 2,785-gram "Missing Link"

Sikhote-Alin is my favorite meteorite, and I have handled literally thousands of specimens over the past decade and a half. “The Missing Link” is the single most intriguing piece out of all of them, and in the words of Aerolite’s operations manager and staff geologist: “Well, that’s just cool!”

Learn more about the Sikhote-Alin witnessed fall >>>

Photographs by Suzanne Morrison © Aerolite Meteorites LLC
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