Pallasites

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Pallasites

I have fallen in love with the meteorites at The Field Museum, namely the pallasites. Pallasites are rare stony-iron meteorites, meaning they are made up of nearly equal parts meteoric irons and embedded silicates, resulting in what could be described as a cosmically designed mosaic of space magic.  Pallasites are historically some of the largest meteorites to be discovered on earth. There are two pictured here:  

The top two photographs show a portion of the Esquel pallasite - Found in 1951 in Chubut, Argentina.  It had a reported recovered weight of ~1,500 kg (3,300+ lbs), which would make it one of the largest pallasites ever found. Imagine 1.5 tons of space metal crashing into the surface of the earth! 

The bottom two images are of the Springwater pallasite - Found in 1931 in Saskatchewan, Canada, with a recovered weight of ~68 kg (150 lbs). 

Both of these fantastic specimens can be seen on the second floor of The Field Museum, across the hall from the Grainger Hall of Gems. 

‘Space Gem’ asteroids created in space-borne mash-ups  |


A tiny fraction of meteorites on Earth contain strikingly beautiful, translucent, olive-green crystals embedded in an iron-nickel matrix. Called pallasites, these “space gems” have fascinated scientists since they were first identified as originating from outer space more than 200 years ago.

Now a new study published this week in Science (Nov. 16) shows that their origins were more dramatic than first thought. Using a carbon dioxide laser, a magnetic field, and a sophisticated recording device, a team of geophysicists, led by John Tarduno at the University of Rochester, has shown that the pallasites were likely formed when a smaller asteroid crashed into a planet-like body about 30 times smaller than earth, resulting in a mix of materials that make up the distinctive meteorites.

“The findings by John Tarduno and his team turn the original pallasite formation model on its head,” said Joshua Feinberg, assistant professor of earth sciences at the University of Minnesota, who was not involved in the study. “Their analysis of the pallasites has helped to significantly redefine our understanding of how these objects formed during the early history of our solar system.”

Pallasites are made of iron-nickel and the translucent, gem-like mineral olivine, leading many scientists to assume they were formed where those two materials typically come together – at the boundary of the iron core and rocky mantle in an asteroid or other planetary body. Tarduno discovered that tiny metal grains in the olivine were magnetized in a common direction, a revelation that led the researchers to conclude that the pallasites must have been formed much farther from the core. continue reading