NWA 13307 – Ungrouped Reduced Ultramafic Achondrite

NWA 13307 is an extraordinary ungrouped ultramafic achondrite belonging to a rare population of highly reduced meteorites formed under extremely oxygen-poor conditions in the inner Solar System. Its unusual mineralogy and isotopic signature provide a rare glimpse into the earliest differentiated planetesimals that formed close to the young Sun.

Showing 1-1 of 1 item(s)

NWA 13307 Achondrite 27.47 g – Reduced Ultramafic End Cut

NWA 13307 Achondrite 27.47 g – Reduced Ultramafic End Cut 2

Available

NWA 13307 – Ungrouped Reduced Ultramafic Achondrite

NWA 13307 Reduced Ultramafic Achondrite – End Cut with Fusion Crust – 27.47 g

$9,614.00

A rare 27.47 g end cut from NWA 13307, one of the most unusual reduced achondrites known. This specimen preserves part of its fusion crust while revealing the pale ultramafic interior linked to a highly reduced inner Solar System parent body.

A Unique Ungrouped Achondrite

NWA 13307 is a highly magnesian protogranular websterite composed predominantly of nearly pure diopside and enstatite with exceptionally low iron contents. Detailed petrographic investigations revealed an unusual and highly reduced mineral assemblage including accessory daubreelite and Ti-Cr-bearing troilite.

Remarkably, no olivine, metal or plagioclase were observed, making NWA 13307 fundamentally different from most known achondrites. Its mineralogical composition places it among an extremely rare category of reduced ultramafic meteorites linked to the innermost regions of the early Solar System.

A Window into the Innermost Solar System

NWA 13307 belongs to a rare suite of highly reduced meteorites sharing isotopic affinities with aubrites, Al Haggounia 001, Ksar Ghilane 022 and NWA 15915. These meteorites exhibit a distinct non-carbonaceous isotopic signature believed to originate from reservoirs located close to the young Sun.

Such meteorites may represent fragments of Mercury-like differentiated bodies formed under extremely oxygen-poor conditions in the inner protoplanetary disk.

Insights from Recent Isotopic Studies

Recent isotopic work presented for the Goldschmidt Conference in Montréal revealed that this suite of reduced meteorites displays nearly identical and extremely low µ26Mg* values despite strongly variable Al/Mg ratios. This suggests formation in reservoirs already depleted in radioactive ²⁶Al.

Deficit-dating models indicate relatively late differentiation of these parent bodies:

Approximately 4.5 million years after CAIs assuming homogeneous ²⁶Al distribution.
Approximately 2 million years after CAIs if the innermost Solar System was already depleted in ²⁶Al.

Their Fe and Si isotopic compositions define a coherent inner-disk signature consistent with material formed in the hottest and most reduced regions of the protoplanetary disk.

A Fragment of an Unknown Planetary Body

NWA 13307 is likely a fragment from an unknown differentiated planetary body that formed during the earliest stages of Solar System evolution. Its characteristics support a scenario of prolonged accretion and delayed melting of reduced planetesimals after most radioactive heating had already decayed.

These results imply that impacts and gravitational energy may have played a significant role in the evolution of these bodies, offering important new insights into planetary formation processes in the inner Solar System.

Scientific Importance

Because of its unique mineralogy, reduced chemistry and isotopic characteristics, NWA 13307 represents far more than a rare meteorite. It is an exceptional scientific specimen preserving evidence of ancient differentiated bodies that may no longer exist today.

Frequently Asked Questions

What type of meteorite is NWA 13307?

NWA 13307 is an ungrouped highly reduced ultramafic achondrite classified as a protogranular websterite.

Why is NWA 13307 scientifically important?

It belongs to a rare population of highly reduced inner Solar System meteorites that may represent material from Mercury-like differentiated bodies formed close to the young Sun.

What minerals are present in NWA 13307?

The meteorite is composed mainly of nearly pure diopside and enstatite with accessory sulfides including daubreelite and Ti-Cr-bearing troilite.

What makes its composition unusual?

No olivine, metal or plagioclase were identified despite detailed petrographic studies, which is highly unusual for achondritic meteorites.

How old is the parent body differentiation?

Current isotopic models suggest differentiation occurred between approximately 2 and 4.5 million years after CAIs depending on assumptions regarding radioactive 26Al distribution.