‘Alien’ minerals never found on Earth identified in meteorite
The minerals discovered in a 33,400-pound meteorite offer an exciting peek into the collisions that rocked our early solar system.
Published December 14, 2022
6 min read
A pockmarked ruddy red boulder sat for many years on the edge of the town El Ali in Somalia, near a popular well where herders and their animals gather to slake their thirst. Knowledge of the stone, which weighs more than 33,400 pounds, had been passed down through generations of camel herders, who used its metallic surface as an anvil to sharpen their blades. The history of the boulder goes back to the dawn of the solar system.
Known as the El Ali meteorite, the hunk of metal plunged through Earth’s atmosphere at some unknown date in the past. Scientists recently revealed that it brought with it at most three minerals that are not naturally found on Earth. Each mineral’s chemistry, crystal form and chemistry contain clues to events that took place millions of miles away and many billions of years ago.
Although the minerals may not dramatically alter our understanding of our celestial neighborhood, researchers hope these cosmic secrets discovered in plain sight could help fill in the details about the chaotic collisions of our early solar system.
“Every new mineral–each and every one–has a voice and a story to tell,” says Chi Ma, a meteorite mineralogist at the California Institute of Technology, who discovered one of the new minerals and helped confirm the other two.
The discovery of three new minerals is the latest twist in the multi-year dispute over the fate of the El Ali meteorite. Prospectors of a small mining company found the stone in 2019 while searching for opal. The following year, after the Somali government was unwilling to pay the multi-million dollar price tag, the mining company exported the meteorite to China, says geologist Abdulkadir Abiikar Hussein of Almass University in Mogadishu, Somalia, who inspected the meteorite upon the government’s request.
Now the space rock still has no buyer and Hussein fears that it will be cut into smaller chunks for sale, forever destroying a priceless piece of national heritage. He hopes that the new discoveries will wake up the government and make it possible to buy the thing and return it to Somalia. “
Surprises in stone
While generations of camel herders had known about the meteorite, which is the ninth largest ever found, it wasn’t scientifically documented until a few years ago. Prospectors noticed the strangely smooth boulder and heard a metallic sound when they struck it with a hammer. It was suspected to be an iron meteorite, which is an object from space made mainly of iron and nickel. Many of these objects are similar to our planet’s metallic centre.
The prospectors sent small samples of the meteorite to scientists for confirmation and further analysis, and a piece fell into the hands of Chris Herd, curator of the meteorite collection at the University of Alberta.
While studying the slice of rock, he noticed several crystals with unusual compositions. His intuition was confirmed by later analysis and a comparison with synthetically created minerals. Herd named one mineral elaliite, after the meteorite itself, and the second elkinstantonite, after Lindy Elkins-Tanton, a planetary scientist at Arizona State University and principal investigator of NASA’s upcoming Psyche mission that will explore a metallic asteroid.
Elkins-Tanton learned of Herd’s plan for the mineral’s name soon after the Psyche mission missed its launch date because of issues during software testing, and her morale was low. She pauses to say, “To say that it lifted my spirits–” “I was so touched. “
CalTech’s Ma, who has previously discovered dozens of new minerals, identified the third mineral, calling it Olsenite to honor the late Edward Olsen, a former curator at the Field Museum of Natural History in Chicago who had postulated the existence of the mineral that now bears his name.
Our planet has roughly 5,800 minerals, while only about 480 have been found in meteorites. Many of those meteoritic minerals are truly alien–some 30 percent don’t form naturally on Earth.
The newly discovered minerals were found in inclusions, which look like microscopic polka dots scattered across the sample slices of the meteorite. Herd said that the team is still trying to determine the exact conditions under which they formed. However, the presence of new minerals in the polka dots provides clues as to when and how they formed.
As the molten metal of a meteorite slowly cools and solidifies, different minerals crystallize at different times, which leaves behind certain “incompatible” elements that concentrate in the dwindling pool of liquid. The new minerals formed after almost all the metal had cooled, and only tiny molten blobs were left. These molten blobs eventually crystallized to form the inclusions.
The overall chemistry of the rock reveals that this cooling process likely didn’t happen in the core of an asteroid, as is believed happened for most other iron meteorites. The metal likely crystallized at the surface of the planetary body following a collision that turned solid surfaces molten.
These colliding bodies may have been the cores of destroyed asteroids, or perhaps they were primitive space rocks known as chondrites, which have a significant amount of metal mixed with rock. Either way, they likely smashed together at stunning speeds–these collisions happen in the asteroid belt today with objects speeding faster than 11,000 mph.
Studying the mineralogy of meteorites is “armchair solar system exploration, in a lot of ways,” Herd says. “We are trying to limit the range of conditions that have existed within different planet bodies. “
Meanwhile, on Earth, the debate about the meteorite’s future continues. Hussein said that if the meteorite is sold to a third party then a portion of the proceeds will be given to the local governments. He said that many Somalis don’t like the solution and believe it shouldn’t have been exported. It should be at home. “
The author of 5 books, 3 of which are New York Times bestsellers. I’ve been published in more than 100 newspapers and magazines and am a frequent commentator on NPR.