Post by 1dave on Jan 2, 2020 11:49:08 GMT -5
www.npr.org/sections/thetwo-way/2016/06/15/482195719/scientists-say-theyve-unearthed-a-completely-new-kind-of-meteorite
"All interpretations about how the solar system formed are based on the meteorites that fall on earth today. And 80% are ordinary chondrite and the assumption is then that these meteorites are the type of material that dominates ... that it's typical material for the solar system. But now we have the very, very first little clue, or indication, that there may have been other meteorites that were more common in the Earth's distant past."
The meteorite is 3.1 by 2.6 by 0.8 inches large. It is surrounded by a gray reduction halo, in the otherwise red limestone. Oxygen was consumed when the meteorite weathered on the seafloor. The coin in the image has a diameter of just under 1 inch.
Nature Communications
Scientists Say They've Unearthed A Completely New Kind Of Meteorite
Scientists say that in a Swedish quarry, they've uncovered a meteorite unlike any other documented on the planet.
Its chemical makeup is unique among the 50,000 meteorites known on Earth, as Birger Schmitz of Sweden's Lund University tells The Two-Way. "This does not resemble anything ... even if we look at the big types that exist today and look at the broad ranges, this one falls completely outside of everything," he says.
What's more, the "mysterious object," which is about the size of a tennis ball, could "lead to a better understanding of possible large-scale astronomical perturbations affecting both Earth and the solar system," the scientists wrote in a newly published paper in Nature Communications.
But before we get to those lofty heights — this story actually begins in a trash pile.
Twenty-four years ago in southern Sweden, at the dump pile of a quarry where workers cut into ancient seafloor to make tiles, Schmitz says they noticed unusual black dots on a stone. It turned out to be a meteorite. Since then, scientists have collaborated with the quarry workers to extract over 100 of the meteorites.
Until this latest discovery, the meteorites found at this site were all a type called ordinary chondrites. Ordinary chondrites represent 85 percent of all meteorites found on Earth, and all 85 percent originate from the same parent asteroid, broken into smaller pieces following a major collision.
Schmitz says that there are indications "that there was a smaller body hitting the bigger one, and they must have met in some sort of head-on collision, otherwise the energy would not be that high." For the past two decades, the team had been expecting to find a second type of meteorite sample originating from the smaller body.
As the years went by, "we shrugged our shoulders ... it started to become very boring," Schmitz says. A new batch came in from the quarry, and he handed it over to a student. But then:
"One day the student came back and said, 'One of these you've given me is something completely different.' So he showed me the grains and we were completely puzzled. We had no clue, no idea what it could be. It was found in 2011 and it has taken five years to find out what it is."
Schmitz explains that all previously known meteorites have a unique combination of chromium and oxygen isotopes that form a unique "fingerprint."
But as you can see on this chart, this sample (Ost 65) falls outside all known combinations.
This table plots the oxygen and chromium isotope composition of meteorites that have fallen to Earth in recent times. The newly discovered meteorite (Ost 65) falls outside all known categories.
Nature Communications
Schmitz adds that scientists think this meteorite is from the same collision as the others in the quarry because of its level of cosmic ray exposure, which measures "the amount of time a meteorite has been flying around in space as a small object." This supports the claim that all of the meteorites at the site were formed during a single event.
He says that the discovery could have broader significance:
"All interpretations about how the solar system formed are based on the meteorites that fall on earth today. And 80% are ordinary chondrite and the assumption is then that these meteorites are the type of material that dominates ... that it's typical material for the solar system. But now we have the very, very first little clue, or indication, that there may have been other meteorites that were more common in the Earth's distant past."
The object may be the first documented "extinct" meteorite — meaning the parent body was "consumed by collisions," according to the paper.
It argues that this could be a window into the history of the solar system: "Apparently there is potential to reconstruct important aspects of solar system history by looking down in Earth's sediments, in addition to looking up at the skies."
Its chemical makeup is unique among the 50,000 meteorites known on Earth, as Birger Schmitz of Sweden's Lund University tells The Two-Way. "This does not resemble anything ... even if we look at the big types that exist today and look at the broad ranges, this one falls completely outside of everything," he says.
What's more, the "mysterious object," which is about the size of a tennis ball, could "lead to a better understanding of possible large-scale astronomical perturbations affecting both Earth and the solar system," the scientists wrote in a newly published paper in Nature Communications.
But before we get to those lofty heights — this story actually begins in a trash pile.
Twenty-four years ago in southern Sweden, at the dump pile of a quarry where workers cut into ancient seafloor to make tiles, Schmitz says they noticed unusual black dots on a stone. It turned out to be a meteorite. Since then, scientists have collaborated with the quarry workers to extract over 100 of the meteorites.
Until this latest discovery, the meteorites found at this site were all a type called ordinary chondrites. Ordinary chondrites represent 85 percent of all meteorites found on Earth, and all 85 percent originate from the same parent asteroid, broken into smaller pieces following a major collision.
Schmitz says that there are indications "that there was a smaller body hitting the bigger one, and they must have met in some sort of head-on collision, otherwise the energy would not be that high." For the past two decades, the team had been expecting to find a second type of meteorite sample originating from the smaller body.
As the years went by, "we shrugged our shoulders ... it started to become very boring," Schmitz says. A new batch came in from the quarry, and he handed it over to a student. But then:
"One day the student came back and said, 'One of these you've given me is something completely different.' So he showed me the grains and we were completely puzzled. We had no clue, no idea what it could be. It was found in 2011 and it has taken five years to find out what it is."
Schmitz explains that all previously known meteorites have a unique combination of chromium and oxygen isotopes that form a unique "fingerprint."
But as you can see on this chart, this sample (Ost 65) falls outside all known combinations.
This table plots the oxygen and chromium isotope composition of meteorites that have fallen to Earth in recent times. The newly discovered meteorite (Ost 65) falls outside all known categories.
Nature Communications
Schmitz adds that scientists think this meteorite is from the same collision as the others in the quarry because of its level of cosmic ray exposure, which measures "the amount of time a meteorite has been flying around in space as a small object." This supports the claim that all of the meteorites at the site were formed during a single event.
He says that the discovery could have broader significance:
"All interpretations about how the solar system formed are based on the meteorites that fall on earth today. And 80% are ordinary chondrite and the assumption is then that these meteorites are the type of material that dominates ... that it's typical material for the solar system. But now we have the very, very first little clue, or indication, that there may have been other meteorites that were more common in the Earth's distant past."
The object may be the first documented "extinct" meteorite — meaning the parent body was "consumed by collisions," according to the paper.
It argues that this could be a window into the history of the solar system: "Apparently there is potential to reconstruct important aspects of solar system history by looking down in Earth's sediments, in addition to looking up at the skies."
