As Melosh explained in a Purdue University News press release :. If the air can move through the passages in the meteorite, it can easily get inside and blow off pieces. To solve the mystery of where the meteoroid's mass went, Tabetah and Melosh constructed models that characterised the entry process of the Chelyabinsk meteoroid that also took into account its original mass and how it broke up upon entry.
They then developed a unique computer code that allowed both solid material from the meteoroid's body and air to exist in any part of the calculation. As Melosh indicated:. Most of the computer codes we use for simulating impacts can tolerate multiple materials in a cell, but they average everything together. Different materials in the cell use their individual identity, which is not appropriate for this kind of calculation.
This new code allowed them to fully simulate the exchange of energy and momentum between the entering meteoroid and the interacting atmospheric air. During the simulations, air that was pushed into the meteoroid was allowed to percolate inside, which lowered the strength of the meteoroid significantly. In essence, air was able to reach the insides of the meteoroid and caused it to explode from the inside out.
Iron meteoroids are much smaller and denser, and even relatively small ones tend to reach the surface. Writer: Kayla Zacharias, , kzachar purdue. Source: Jay Melosh, , jmelosh purdue. Note to journalists: A copy of the paper is available here. Air penetration enhances fragmentation of entering meteroids.
The break-up of the meteoroid was characterized by intense fragmentation that dispersed most of the original mass. We implement a two- material computer code that allows us to fully simulate the exchange of energy and momentum between the entering meteoroid and the interacting atmospheric air. The spherules closely resembled extraterrestrial dust that van Ginneken had studied before—grains embedded in immense ice cores retrieved from the nearby Japanese Antarctic station at Dome Fuji and from the French-Italian station at Dome Concordia on the other side of the continent.
Those grains are roughly , years old, an age that scientists can calculate based on their position in the ice cores—buried 1. Because of the similarities between the samples, the team reasoned that the grains were all formed during the same event. Given the lack of craters in Antarctica, plus the spherules scattered across the continent, they suspected some kind of mega-Chelyabinsk-like airburst occurred in the distant past.
So Natalia Artemieva , from the Planetary Science Institute, used computer simulations to test whether a more complex type of airburst might have occurred. Boslough suspects that one of these events is the culprit behind mysterious, million-year-old glass scattered across the Eastern Sahara —smooth, yellow fragments resembling sea glass that have puzzled scientists because of their otherwise unexplainable presence in the middle of the desert.
Touchdowns can pack a deadly punch, obliterating whatever is beneath them. The new research, however, could provide a way to detect other touchdowns in the geologic record, allowing scientists to gain a better understanding of the threat these events pose to Earth. The trouble starts, he says, with pinning an age on the spherules, which is extremely hard to do.
Koeberl says that if these types of impacts are common, there should be ample evidence of their existence in the geologic record—but touchdown impacts have not been definitively found before. He is also not convinced that the oxygen isotope ratio points toward mixing with ice. Scientists hoping to figure out how frequently airbursts occur are also turning their eyes to the skies and making a detailed census of objects that could explode overhead.
In the meantime, better understanding how big of a blast an airburst could produce will be crucial for helping people in its path get out of the way in time. All rights reserved. Frozen detectives In February , van Ginneken visited Antarctica—a dream trip for him—in search of cosmic breadcrumbs. Share Tweet Email. Read This Next Wild parakeets have taken a liking to London. Animals Wild Cities Wild parakeets have taken a liking to London Love them or hate them, there's no denying their growing numbers have added an explosion of color to the city's streets.
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