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Met Name

Met Type

Thin Sections

13 pounds.   Iron, IIAB

TKW 23 MT. Observed fall February 12, 1947.


   

Steve writes:

Most everyone here already knows about the Sikhote-Alin fall, including how it cast shadows behind people in its mid-morning appearance as it passed at an unusually shallow 41 degree angle to the ground; how its 20 mile smoke trail changed colors as different elements within the meteorite became exposed when more and more of the meteor ablated; and how it exploded not once, but three times during its extended fall through our atmosphere prior to showering the Russian countryside with countless fragments. But while there are already many examples of Sikhote-Alin here on Paul’s MPOD website, there can never be enough of this wonderful fall! So in that vein, I humbly submit yet another few.

The 13 pound example in Photo 1 was purportedly acquired shortly after the fall and stored in a Russian museum for many years before a dealer trade brought it to the U.S. (I acquired it almost 19 years ago from the dealer who negotiated that trade). One of its intriguing features is the contrast between its front and back sides (left and right, respectively, in Photo 1). Like many larger pieces from this fall, its front has a highly regmaglypted, almost satiny texture; the backside, however, is very angular and fractured, with much different surface features. The difference is a consequence of this particular piece having broken off only 3.6 miles above the ground during the third of the meteor’s three explosions – it’s front side displays the more ablated features consistent with a longer time spent burning during entry, while as seen in Photo 2, the less exposed back side bears very few signs of ablation. Photo 3 is a close up of the back side that exhibits a large crack at the bottom consistent with this fracturing. In Photo 4, the bottom of the meteorite shows how the fractures on the back were already propagating through the ablated side of the meteorite as mechanical stresses from extreme surface heat compared to its intensely cold interior were tearing the meteorite apart (flowlines are also visible on this surface, unlike the highly regmaglypted front of the meteorite that is largely absent of these features).

Sikhote-Alin is a coarse octahedrite, as evidenced by the etched pattern in Photo 5’s 293.9 gram, 112 x 76 x 8 mm slice. But some of the smaller shards of the meteorite were sufficiently melted by the intense heat from its prolonged fall that during flight the metal flowed and swirled; the 23.0 gram, 104 x 16 x 4 mm sliced shard shown in Photo 6 was purportedly pulled from a tree and its etched pattern obviously demonstrates this distortion.

Paul Swartz wanted to present some of the detail from photo 6 so he extracted the right half and included it as photo 7.