Almahata Sitta meteorite, River Nile, Sudani

Regional Level Types
Almahata Sitta meteorite	Meteorite Fall Location
River Nile	State
Sudan	Country

Classification: Ureilite - anomalous, polymict.

3.95 kg, hundreds of stones.

Almahatta Sitta — I. First recovered meteorite from a predicted asteroid-earth collision. II. Largest Ureilite fall, an enigmatic and uncommon meteorite type. III. A very unusual Ureilite

The Almahatta Sitta meteorite is the first instance of a meteorite recovery following the detection of a very small asteroid on a collision course with the earth. Approximately 20 hours after the discovery of asteroid 2008 TC3, the asteroid exploded 35-40 km above the Nubian desert — spraying hundreds of small fragments over a 28 x 5 kilometers. Several stones are over 200 g in mass, but most are quite small. The fragments are dark and usually roundish in shape. The meteorite belongs to the relatively rare class of asteroids called “Ureilites” (after the prototype Novo Urei, an 1886 fall). Almahatta Sitta is the most massive of the six witnessed Ureilite falls.

The Ureilites are composed primarily of olivine and pyroxene (pigeonite is particularly prominent). However, ureilites are best known for their diamonds — quite small, but seemingly indicating enormous pressures from shocks suffered in ancient impacts. The ureilites also usually contain a number of minor opaque minerals such as kamacite (meteoritic iron) and troilite (an iron sulfide). The ureilites are particularly intriguing because their microscopic textures may have been due to both vapor condensation and to shock impact. Both the relative importance and the timing of these nebular and collisional processes does not appear to be a settled matter at this time.

A 2018 study suggests that the relatively large size of the diamond crystals show this meteorite came from a parent body of between moon and mars size that was catastrophically disrupted by an impact during the first ten million years of the solar system.

Other Regions, Features and Areas containing this locality

References