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7.3 grams.   Eucrite-pmict

TKW 5.1.kg. Observed fall 24 March 1933, New Mexico, US.


     

Steve writes:

At 5:00 AM in the morning on March 24, 1933, early-risers in Wyoming, Colorado, Kansas, Oklahoma, Texas, and New Mexico witnessed several bright fireballs and heard and felt multiple detonations for a hundred miles on either side of Pasamonte’s low-entry-angle flight path. The meteor eventually broke up at an altitude of about 20 miles, leaving a luminous "after-glow" and a thick and twisting, mile-wide and two-hundred-mile-long dust cloud composed of thousands of tons of material that remained visible for 90 minutes after the meteor had passed.

A large number of small stones were strewn over a 28 mile-long path in Union County, New Mexico. Seventy-five stones totaling approximately four kilograms were collected in the two years following the fall; another kilogram or so were found in later years, bringing the total known weight to just over five kilograms. Most pieces were relatively small – even the largest stone weighed just under 300 grams. And many had nice fusion crust over some or all of their surfaces.

Pasamonte has the unique distinction of being the first meteorite to be photographed during its fall. Charles M. Brown, after first seeing it approach, ran into his house to grab his new Kodak Brownie camera. He was able to catch a photo of the actual fireball in flight, and he and others also captured images of the remnant dust cloud. Famous American meteoriticist Harvey Nininger subsequently chronicled the scene, publishing the account in 1934. Some pictures can be found in Figure 3 on page 3 of the link below:

Pasamonte Document (nasa.gov)

Brown’s in-flight photo fortuitously captured the rare shock-generated condensation cloud that occurred just as the meteor passed through the sound barrier (upper left in the above-referenced figure, and also shown in Photo 5 next to a jet Fighter creating a similar cloud). The cork-screw dust tail behind the condensation cloud was a consequence of Pasamonte spinning as it traveled through our atmosphere.

Except for its unusually friable texture, the Pasamonte meteorite did not seem that different from most eucrites, and consequently in 1938 it was given a eucritic breccia classification. In 1967, that classification was changed to a monomict eucrite. Later, a number of geochemical peculiarities and oxygen-isotopes that differ somewhat from the HED achondrites resulted in Pasamonte being again reclassified, this time as an anomalous mafic achondrite polymict breccia. These and other recent findings suggest Pasamonte’s parent body is likely an ancient, moderately large, and as yet unidentified differentiated asteroid.

Pasamonte is a difficult meteorite to acquire. At the time of its fall, a severe drought made it relatively easy for farmers and sheepherders to spot the glossy black meteorites against the flat and barren ranges, and most of those subsequently ended up in museum collections. Today, after decades of farming and ranching, it’s extremely unlikely that any pieces of the friable meteorite have survived.

Our 7.3 gram individual shown in Photos 1 through 4 was purchased from a dealer at the 2019 Tucson show, having just been acquired from an old collection. Photos 6 and 7 give magnified crossed-eye 3D views of its broken window from two different angles, showing both its interior and its glossy black fusion crust with fusion bubbles. (Photos 8 and 9 offer corresponding red-cyan anaglyphs). Photos 10 and 11 are different versions of 6 and 7.



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