Monthly Favourite Meteorite (SaU 290)

Sayh al Uhaymir 290 (SaU 290)

Sayh al Uhaymir 290 (SaU 290) was initially discovered in the Al Wusta region in Oman on February 13th, 2004 with subsequent pieces found later that year on November 6th. The meteorite was fragmented over an area of about 10m and 64 dark brown fragments were recovered with a Total Known Weight of 1.796kg. SaU 290 was intially thought to be an anomalous type-3 Enstatite Chondrite but oxygen isotopes ruled this out and it has since been classified as an exceedingly rare Carbonaceous Chondrite (CH3).

While this meteorite is relatively visually unremarkable, it is actually a very important specimen. It is primarily composed of small chondrules (<20μm) of various textural types with about 15% fine grained metal. A few small "matrix lumps" and rare refractory inclusions are also present. A number of studies have been completed in regards to the very high solar gas concentrations in SaU 290 which have actually been determined to be the highest of any member of the CH3 class.

The refractory inclusions or CAI's, have revealed a lot about the CH chondrite parent-body and early solar system. Zhang and Hsu (2009) have stated that that the highly refractory nature of CAIs in CH chondrites reflects a distinct population of refractory inclusions. They go on further to say:

"The different population of refractory inclusions was probably due to various formation regions or formation episodes with different physical-chemical conditions. If refractory inclusions were formed in different nebular regions, the formation regions could have different dust/gas ratios, cooling rates, and peck heating temperatures. For instance, the more refractory inclusions are probably related to higher peak heating temperatures, which require that their formation region is closer to the center of the protoplanetary disk. The refractory nature of refractory inclusions in SaU 290, compared to those in other groups of chondrites, requires higher peak heating temperatures. If refractory inclusions were formed in different nebular regions, the formation region of refractory inclusions in SaU 290 is probably closer to the center of the protoplanetary disk than those of other groups of chondrites. If CAIs were formed in a common region of the solar nebula, those in SaU 290 were probably formed earlier than those of other groups of chondrites."

The study also makes mention that while the iron grains have been weathered, refractory inclusions (CAI's & AOA's (Amoeboid Olivine Aggregates)) show no evidence of terrestrial weathering. This is important because it suggests that refractory inclusions retain their chemical and mineralogical features in nebular and/or parent body settings. They also mention:

"Both regular and irregular refractory inclusions in SaU 290 have sharp interfaces with surrounding objects. This indicates that thermal metamorphism on its parent body did not severely affect refractory inclusions. In addition, no low-temperature alteration minerals were observed in refractory inclusions, indicating low-temperature secondary alteration processes have minimal effects on the refractory inclusions. Therefore, refractory inclusions in SaU 290 are pristine and mainly record high-temperature processes in the early solar nebular setting."

The 2.38g Partslice below is part of the Meteorites Australia Collection (MA.07.0042).

Refractory inclusions and aluminum-rich chondrules in Sayh al Uhaymir
290 CH chondrite: Petrography and mineralogy.
Aicheng ZHANG & Weibiao HSU. (4.13MB)

Noble gas study of new Enstatite SaU 290 with high solar gases.
J. PARK, R. OKAZAKI, K. NAGAO & R. BARTOSCHEWITZ. (50.8KB)

SaU 290 (CH3) - 2.38g Partslice

SaU 290 (CH3) - 2.38g Partslice
SaU 290 (CH3) - 2.38g Partslice

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