File:Allende meteorite (52803099125).jpg

English: Allende is the most studied meteorite in the world. Thousands of scientific papers have been written about the meteorite and its components. It contains tiny pre-solar grains formed in the gaseous surroundings of dying stars long before the formation of our solar system 4.56 billion years ago. Also present in Allende are prominent white clasts, known as calcium-aluminum inclusions (CAIs) — among the first particulate matter to form in the solar nebula from which our solar system was born.

Allende fell to Earth on February 8, 1969 at 1:05 AM near Chihuahua, Mexico. The huge fireball of entry lighted up thousands of square miles of Northern Mexico and Southwestern United States, as bright as the mid-day sun.

Allende fell just months before the Apollo program was to return the first moon rocks. This was a time of great excitement and energy among planetary scientists. The curator of the Lunar Receiving Laboratory at JSC Houston, Bert King, heard the reports on his car radio and jumped on a plane to Mexico to bring back samples to "the most sophisticated space-rock laboratory ever built. Falls of this magnitude are once-in-a-lifetime events, and to have a cosmochemist on the scene within days was a first. The arrival of this precious carbonaceous cargo acted as a dress rehearsal for the arrival of the Apollo 11 moon rocks that were scheduled to arrive in Houston within a matter of months; it also gave NASA scientists plenty of opportunity to test the brand new analytical instruments they had prepared for the analysis of Apollo samples. Thanks to its size and rarity, and the fortunate timing of its fall, Allende is probably the most studied rock in history." (Tim Gregory, Meteorite, pp.111-3.)

Several new minerals have been discovered in Allende including the titanium oxide panguite named after the ancient Chinese god Pan Gu who separated yin from yang, the earth from the sky.

"There was found to be a small amount of carbon (including crystalline diamond), and many organic compounds, including amino acids, some not known on Earth. Iron, mostly combined, makes up about 24% of the meteorite. Detailed study in 2020 have even identified iron and lithium-containing protein of extraterrestrial origin, first such discovery in meteorite." (Wikipedia)

The charcoal-hued matrix is filled with a galaxy of inclusions including a centimeter-sized CAI, the oldest matter we can touch, 30 million years older than Earth. It was a CAI in Allende, one called "SJ101", that was the oldest one ever discovered and determines the age of our solar system: 4,567,180,000 years old.

"A 1977 analysis at California Institute of Technology of isotopes of the elements calcium, barium and neodymium in the meteorite indicated that those elements came from some source outside the early clouds of gas and dust that formed the Solar System. This supports the theory that shockwaves from a supernova – the explosion of an aging massive star – triggered the formation of the Solar System. As further evidence, the Caltech group said the meteorite contained Aluminum 26, a short-lived rare isotope of aluminum. This acts as a "clock" on the meteorite, dating the explosion of the supernova to within less than 2 million years before the Solar System was formed. Subsequent studies have found isotopic ratios of krypton, xenon, nitrogen and some other elements whose forms are also unknown in the Solar System. The conclusion, from many studies with similar findings, is that there were a lot of substances in the presolar disc that were introduced as fine "dust" from nearby stars, including novas, supernovas, and red giants. These specks persist to this day in meteorites like Allende, and are known as presolar grains." (Wikipedia)

469g Carbonaceous chondrite – CV3 in the MetBull, distinguished by large (mm-sized) chondrules, many of which are surrounded by igneous rims, large refractory inclusions and abundant matrix. And from the Meteorite book, "all carbonaceous chondrites are sedimentary rocks that beautifully preserve pieces of cosmic sediment that formed in the collapsing nebula. Allende is the most famous of them all." (p.113.)