Scientists have published an analysis of a meteorite fragment collected after a close collision of an asteroid with the Earth in 2008. They show that the parent asteroid was huge, and the results suggest that special water-retaining asteroids may be larger and have a different mineral composition than previously thought.
The findings of the study were published this week in the journal Nature Astronomy and look at the chemical composition of the fragments of these meteorite fragments.
The story of the fragments begins in October 2008, when scientists became aware of an asteroid colliding with Earth. They knew that most of the rocks would burn as they entered the Earth’s atmosphere, and that the remains, if any, would fall in the wind-covered sands of the Nubian Desert. It provided a unique opportunity for an international team of researchers, including NASA scientists, to predict the arrival of rocks and then comb the sand for any surviving fragment.
Although the asteroid was relatively small — only about nine tons — its detritus was small; less than 8 pounds meteorites were collected from the desert. Together they are called the Almahata Sitta, after the nearby train station. It was the first time that an asteroid was spotted and then its meteorite remains were collected.
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Since his recovery, various parts of the Almahata Sitta have been analyzed, revealing information about the origin and chemical composition of various parts of the asteroid. A sample of meteorites that the team studied–called AhS 202 – it was so small that you could fit 10 specimens on it, but it came from a huge space rock, the starting point that precedes the merging of the fragment with the rock mass of Almahat Sitt. The team used infrared and X-ray light to study the sample. They discovered that the fragment was carbon chondrite, a type of meteorite that formed during the early days of the solar system and that may have brought water to Earth, which led to … all of this. Previously, it was generally not thought that carbon chondrites could come from parent bodies (originating asteroids) with a diameter of more than about 100 kilometers.
But researchers have found tremolite in their tiny fragment, a mineral that needs tremendous pressure. The existence of Tremolite in the sample suggests that the diameter of the asteroid’s origin is in range 398 at more than 1,119 miles (640 at more than 1,800 kilometers),, putting him in the wheelhouse of Ceres, the largest object –a dwarf planet, actually“In the asteroid belt.”
“This is evidence of a very large parental body that we didn’t know existed before,” said Vicky Hamilton, a scientist at the Southwestern Research Institute and lead author of a recent paper, noting that this is the first known presence since tremolite in carbon chondrite. “The fact that we have no other evidence of this in our meteorite collections helps confirm what we already suspected, and that is that the meteorites we manage to find on Earth are a biased pattern.”
As asteroids make their way through space, they will have to make contact with other bodies. These conglomerations of metals and minerals coalesce and disintegrate as their trajectory continues. When a meteorite is actually found on Earth, it is a concise collection of stories from space, and the only way to read it is to do a whole series of analyzes.
“You can have one group of scientists looking at one piece of a meteorite and another group looking at another piece of the same meteorite, and you’ll see two different parts of the history of the solar system,” Hamilton said.
So Hamilton’s piece could talk about some sources of a massive asteroid, while another piece of the Almahata Sitta could hint once the existence of a protoplanet. The electroscopic work the team has recently done is a kind of reverse engineering, to move from what looks like a typical space rock to its specific story, in this case a reference to a massive parent asteroid. It’s like finding a crumb on your kitchen counter – it could be from anywhere – but if you look at it chemically, you might find out the temperature and pressure that led it to it, and whether that crumb really came from this morning’s toast or last week’s birthday cake.
Although much rarer than other types of asteroids, new information about carbon chondrites could fall from the sky at any moment. The only question is whether the meteorites are awake – or lucky – enough to spot them.