Telescope Reviews: A Few Good Meteorites

Pesyanoe, Kurgan region, Russia

Aubrite Ca-poor achondrite

Fell: October 2, 1933

A total of 3393 grams of aubrite meteorite fell in the form of several stones constituting the 13th fall (of 18) for the year 1933. The largest single stone on this fall named Pesyanoe was 905 grams.

Unlike calcium-rich achondrites like the eucrites, Ca-poor stones including Pesyanoe have a light colored fusion crust, and in this case, the crust on Pesyanoe looks dirty grey in color.

The namesake and type specimen for the aubrite meteorites is the Aubres meteorite that fell near Nyons, France, on September 14, 1836. Outside the hot and cold desert finds, there are less than a dozen members of the aubrite class, with a vast majority of those witnessed to fall.

Aubrites have distinctive light-colored fusion crust, with a snowy white interior. They are usually friable stones so they crumble apart easy. Because of their high enstatite compositon, aubrites are also known as enstatite achondrites.

In addition to their large white enstatite crystals, they also contain varying amounts of olivine, nickel-iron metal, and troilite, among other minerals. This arrangement of minerals in both composition and size suggests that aubrites cooled underground in their parent body under oxygen-free (reducing) conditions.

Violent impacts are likely in the aubrite’s past since the crystals are broken up and mixed around within the stone. Further, the oxygen isotopic composition of enstatite chondrites has led to the suggestion that aubrites might have formed by partial melting of an enstatite chondrite body.

A great interest to scientists is that aubrites have the highest cosmic ray exposure ages of any stony meteorites, with some estimates ranging up to 120 million years.

Reflectance spectra various asteroids showed similarities between the aubrite meteorites and the main belt asteroid 44 Nysa which happens to be the largest E-class asteroid as well as the brightest asteroid. The only known E-class near-earth asteroid is a suspect for the parent body of the aubrite meteorites. The asterod, named 3103 Eger, is an Apollo and that was discovered in 1982 by Miklós Lovas who named after the city of Egerin Hungary.

In an article titled PRE-ACCRETION AND/OR REGOLITH HISTORY OF THE PESYANOE OBRITE MATTER and published in Lunar and Planetary Science (2003), the authors posit the following conclusions about Pesyanoe:

The pictures that follow are of the specimen of Pesyanoe in my collection. From what I’ve read in collection catalogues, this particular piece is the second largest sample of Pesyanoee in any collection in the world. A majority of the preserved Pesyanoe material, a sum around 1790g, still resides in the Academy of Sciences in Moscow, Russia.

The picture immediately below shows the dirty grey crust on my sample along with a classic Russian Academy of Sciences meteorite label consisting numbers on cloth tape. This specimen also arrived to me with a beautiful hand-written specimen card from the Academy of Science containing a matching specimen number.

My guess is that the circular greenish features on the crust are on top of large enstatite crystals.