Submit a Picture

Where is My Picture?!

The Queue

Met Name

Met Type

Thin Sections

0.4 grams.   CM2

TKW 12.6 kg. Observed fall 20 September 1950, in Calloway County, Kentucky, US.


   

Steve writes:

At 1:35 AM on September 20, 1950, a brilliant red-orange bolide was seen traversing a north-to-south trajectory over the Jasper County region of southeastern Illinois. Then, following a number of sonic booms, the meteor exploded at approximately 45 km over the neighboring state of Kentucky.

From eyewitness accounts in Illinois, Kentucky, and Tennessee, a likely impact site was calculated. On October 22, 1950, a team from Vanderbilt University began searching the triangulated fall area near Wildcat Creek on Lake Kentucky (in Calloway County about 15 km east of the town of Murray). The researchers personally found only a few small fragments, some as far as 5 km apart. But many masses had been heard to fall in nearby woods, and local farmers provided the team with additional pieces.

The largest specimen – an approximately 15 cm diameter, 3.4 kg mass – was heard by Mr. Ernest Barnett to whistle through the air and strike the ground about 8 meters from his home, embedding itself into a crater 15 cm deep. Another fragment pierced the roof of a house owned by a Mr. Wilkinson; the fact that the floor underneath remained unscathed suggested the meteor had already slowed to near terminal velocity before hitting his house. Other meteorites had fragmented into smaller pieces on impact, with most having at least one surface exhibiting thin (0.2 mm or less) fusion crust. Some additionally had 0.3 mm wide flight marks 1 to 2 mm long, with others even showing regmaglypts.

Murray was later classified as a type CM2 carbonaceous chondrite, and at 12.6 kg is the third largest fall of that type to date (CM carbonaceous chondrites are named for their type specimen Mighei, which fell in the Ukraine in 1889). Most are petrologic type 2 and contain nickel-bearing sulfides and abundant hydrated materials (CM2 meteorites are about 10% water by volume). Aqueous alteration is less than in many other types of carbonaceous chondrites, resulting in more well-preserved olivine-bearing chondrules interspersed within their graphitic carbon and phyllosilicate and magnetite matrix.

Murray – like other carbonaceous chondrites – has nearly solar Mg/Si ratios. A wide range of refractory residue and light-colored inclusions include diamonds, corundum, and grains of other minerals, some of which contain trapped gasses that predate the formation of our solar system. Isotopic anomalies in Murray’s silicon, nitrogen, and carbon suggest they may represent circumstellar grains from carbon-rich stars that predated our sun.

The CM chondrites also contain a wealth of organic compounds, the most famous example being the well-studied Murchison meteorite that fell a half a century ago and has since been found to contain more than 230 different amino acids, some exhibiting strange isotopic signatures that suggest they too may have originated outside of our solar system. Amino acids found in carbonaceous chondrites also show possible evidence of microbial biogenic activity. Initially, 17 amino acids were found in Murray, 11 of which were not among the 20 amino acids that form terrestrial proteins; today, Murray’s identified amino acid count has increased to about 70.

Formaldehyde and sugar chemistry in Murray and Murchison were studied and suggest they may be responsible for the polyols found in these carbonaceous chondrites, with the researchers concluding that polyols present on the early Earth were delivered by asteroids and possibly comets. And a very high deuterium to protium ratio found in Murray’s water suggests it must be extraterrestrial as well.

While I personally have a thin section of Murray, I don’t have an actual physical example of that meteorite. Fortunately, Patrick Cavanaugh – a good friend of mine and a fellow meteorite collector – has a nice piece that he graciously allowed me to photograph for this anniversary MPOD post. Photo 1 shows it from an angle that exhibits both its chondrules and some of its fusion crust. The almost golf ball-sized fragment has one large crusted edge that wraps around an approximately 90 degree corner; Photo 2 shows both of these crusted faces (Photos 3 and 4 offer alternate views in, respectively, crossed-eyes and parallel eyes 3D format). Photo 5 shows broken areas exhibiting Murray’s chondrules, along with another small fusion crusted corner (Photos 6 and 7 offer additional views of a chondrule-rich area in, respectively, crossed-eyes and parallel eyes 3D format).

[A note on 3D image viewing: both crossed-eyes and relaxed eyes examples are offered. For those that struggle with these kinds of images, it’s often easier to click on the particular picture of interest, start with the smallest zoom, cross or relax your eyes as appropriate until the 3D effect is achieved, then increase the zoom while keeping the image in "3D alignment".]



Note from the MPOD Webmaster on 3-D Viewing:

I cannot fuse the stereo-pair images as presented. They are too large for my aged eyeballs to bring together. If you have the same problem, try this:

1) Click on the picture to view the full-resolution photo.

2) Click the 'Smaller' button 10-15 times to shrink the picture to the point where you can fuse the images.

3) Hold the mouse over the 'Bigger' button, fuse the pictures, and click the mouse while keeping the images fused to see how large you can go.

More Info on 3-D Viewing

Carbonaceous chondrites are rarely exciting in thin section, but Murray’s high density of chondrules makes for some reasonably attractive examples, as seen in Photo 8 (xpol on the left and white light on the right). Photo 9 blows up a few areas with some of the more interesting chondrules and other mineral inclusions. A zoomable version of this thin section can be found at Gigapan.

[For viewers new to Gigapan, click on the diagonal arrows to the right of the image to enter full screen mode, then hold down your mouse’s left button to pan around and use its wheel to zoom in and out.]