Space meteoroids are randomly shaped, but many of them that land as meteorites on Earth are cut in cones. Scientists have now discovered how the physics of flight in the atmosphere leads to this transformation.
The progression discovered by a series of replication experiments at New York University's Applied Mathematics Lab involves melting and erosion during flight, ultimately leading to an ideal shape as meteoroids fling through the atmosphere. The findings are reported in the journal Proceedings of the National Academy of Sciences (PNAS) .
"Lean or narrow cones tilt and wobble as wide cones flick and rock to and fro, but we've discovered cones that fly perfectly straight with their tip or tip," explains Leif Ristroph, assistant professor at the Courant Institute of Mathematical Sciences of NYU, who led the study. "Astonishingly, these 'Goldilocks' cones with the 'just right' angles exactly match the shapes of eroded clay from our experiments and actual conical meteorites."
"Demonstrating How the Shape of an Object Affects Its Flying Capabilities Our study is all about why so many meteorites arriving on Earth are cone-shaped.
The forces behind the peculiar forms of meteorites, the meteors or "shooting stars" are a mystery that survives the fiery flight through the atmosphere and land on earth.
"The shapes of the meteorites are not like those in space, since they are actually melted by the flight of the atmosphere , eroded and reshaped, "explains Ristroph." While most meteorites are randomly shaped & # 39; blobs & # 39; are surprisingly many – some say about 25 percent – & quot; oriented meteorites & quot ;, and whole samples of them almost look like perfect cones. "
To explore the forces that are cone-shaped The meteorites, too which also included Jun Zhang, a professor of physics and mathematics at the Courant Institute and New York University in Shanghai, replicated meteorites that traveled through space: clay objects attached to a pole served as "pseudo-meteorites," and water eroded during the movement
The clay objects held in the water flow were finally cut into cones with the same angularity as conical meteorites – not too slender and not too wide.
However, the researchers recognized the limitations of this experimental setup: in contrast to the clay objects, the actually flying meteoroids are not kept in a fixed position and can spin freely, stagger and dr This distinction raised the following question: How can meteorites maintain a fixed orientation and successfully reach the earth?
The team, which included Khunsa Amin and Kevin Hu, both students of the NYU, and Jinzi Huang, then a NYU PhD student, then carried out further experiments examining how differently shaped cones fell through water. Here they discovered that narrow pegs tip over while wide pegs flutter. In between, however, are "just the right" conical shapes that fly straight.
"These experiments tell a story of origin for oriented meteorites: the very aerodynamic forces that melt and transform meteorites in flight also stabilize their position, creating a cone. The shape can be carved and ultimately reach the earth," notes Ristrophic. "This is another interesting message we receive from meteorites that are of scientific importance as 'foreign visitors' of the Earth and whose composition and structure tell us something about the universe."
Earth's oldest meteorite collection in one of the driest places
Khunsa Amin el al., "The role of shape-dependent flight stability in the formation of oriented meteorites", PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1815133116
What gives meteorites their form? New research reveals an answer to "Goldilocks" (2019, 22 July)
retrieved on July 23, 2019
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