An illustration of the early solar system, when the body of the meteorite planet Almata Sitta may have existed. (NASA)
Ten years ago, an astronomer from Arizona discovered an asteroid that was headed directly to Earth. He quickly summoned the help of colleagues and observers of casual stars, who tracked the space rock as it exploded in the sky, raining shrapnel over the Nubian desert in Sudan. Students from the University of Khartoum volunteered to search for fragments, and eventually recovered more than 600 pieces of the meteorite now known as Almahata Sitta. It was the first time scientists had traced an asteroid in the sky to a rock they could hold in their hands.
But that's not even the best thing about Almahata Sitta. Hardly.
A new study published in the journal Nature Communications reports that the meteorite contains small diamonds, yes, diamonds. Those diamonds contain even smaller impurities called "inclusions." And within those inclusions are signatures of a planet long lost, as big as Mars, a relic of 4,500 million years that was destroyed during the first days of the solar system.
T these samples come from a time that we do not have access to, "said Farhang Nabiei, materials scientist at the Swiss Federal Institute of Technology in Lausanne and lead author of the new report. Sitta Mite meteorite formed during an era of transition in the solar system, when the dust and gas swirling around the sun merged into planetary embryos and then grew into planets.
"And we are part of the planets", Nabiei said, "This is part of the story of how we came to be."
Almahata Sitta belongs to a class of rocks known as ureilites, partially differentiated, not made of the primitive material that made up the solar nebula, but neither They are as well blended and baked as the rocks that come from modern planets, unlike other meteorites, which can be traced back to parent bodies such as asteroids, Mars or the Moon, when comparing the proportions of different varieties of elements, these rocks do not have a known source. They seem to have formed inside bodies that no longer exist.
And they always contain tiny specks of diamonds.
Peter Jenniskens, a meteor astronomer at the NASA Ames Research Center and the SETI Institute in Mountain View, California, discovers a fragment of the Almata Sitta meteorite. (NASA Ames Research Center / SETI / Peter Jenniskens)
Because the crystals are very small, less than a fraction of a percentage of an inch in diameter, many researchers assumed that they formed when graphite (an alternative form of carbon) "Shocked" by a collision with another body. But Nabiei and her colleagues noticed that the diamonds in Almahata Sitta were of a magnitude greater than those that result from a shock event. They suspected that these crystals could have formed in the same way as diamonds on Earth, under the incredibly high temperatures and pressures that exist inside a planet, and only then broke with a shock wave into smaller fragments.
"Then this opens a completely new idea," Nabiei said. Diamond is so strong that it serves as a powerful protective packaging for anything trapped inside; it is the security vault of nature, capable of preserving samples for billions of years.
"I thought that if diamonds were formed inside a planet, inside a parent body, they could have trapped some material from their environment," Nabiei said. The river. "And in fact they did."
The impurities trapped within the Almata Sitta diamonds, crystals of chromite, phosphate and iron-nickel-sulfur, are the first to have been discovered in an extraterrestrial diamond. They could only have formed under incredible pressure, the equivalent of diving 600 kilometers inside the Earth or trying to hold 100,000 tons with their own hands.
To create these conditions, Nabiei said that the main body of the meteorite would have to have been a planet at least as large as Mercury and possibly as large as Mars.
What happened to this lost world? Nabiei can not say with certainty. Many researchers believe that the early inner solar system was filled with large protoplanets that pulled and pulled each other's orbits until they finally crashed, joined or disintegrated. Towards the end of that era, some 100 million years after the birth of the solar system, only the four current terrestrial planets remained.
Nabiei believes that all urelites are likely to come from the same parent body, a protoplane that lasted only a few million years before it was destroyed in a collision. He plans to look for similar meteorites and look for inclusions that can provide clues about their origins.
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