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What gives meteorites their shape? New research reveals a "Goldilock's" response



  What gives meteorites their shape? New research reveals a
Meteoroids coming from outer space are randomly shaped, but many of them, which land on earth as meteorites, appear to be hacked in cones. To explore the forces that produce cone-shaped meteorites, scientists replicated meteorites moving through outer space: clay objects, attached to a rod, served as "mock meteorites" that erode as they move through water. Credit: NYU's applied mathematics laboratory

Meteorides coming from outer space are randomly shaped, but many of them, which land on earth as meteorites, are cut into cones. Scientists have now pondered how the flight's physics in the atmosphere leads to this transformation.

The progression, which was discovered through a series of replication experiments in New York University's Applied Mathematics Lab, includes melting and erosion during flight that ultimately results in an ideal form that meteorites close through the atmosphere. The results are reported in the journal Proceedings of the National Academy of Sciences (PNAS) .

"Narrow or narrow cones turn and tumble, while wide cones flutter and coats back and forth, but we discovered between these are cones flying straight with their point or top leader," explains Leif Ristroph, an assistant professor in NYU's Courant Institute of Mathematical Sciences, which led the study. "Incredibly, these" Goldilock's "cones of" fair "angles exactly match the forms of eroded clay derived from our experiments and real conical meteorites."

"By showing how the shape of An object affects its ability to fly straight, our study sheds some light on this long-standing mystery as to why so many meteorites come to earth are conical, "he adds.

The forces behind the special forms of meteorites, which are meteors or" shooting stars " who survive the fiery flight through the atmosphere and earth on earth, has long been a mystery.

"The forms of meteorites are not as they are in space, because they are actually melted, eroded and transformed by atmospheric flight, "explains Ristroph. "While most meteorites are randomly shaped" blobs ", surprisingly many – some say about 25 percent – are" oriented meteorites "and complementary samples of these are almost like perfect cones."

To explore the forces that produce cone-shaped meteorites, the researchers, including Jun Zhang, a professor of physics and mathematics at the Courant Institute and NYU Shanghai, replicated meteorides traveling through outer space: clay objects, attached to a rod, served as " mock meteorites "that erode while moving through water.

Finally, the clay objects held in the water stream were cut to cones of the same angle as conical meteorites, not too slender and not too wide.

However, the researchers recognized the limitations of this experimental design: unlike the Lejobjects, the actual flying meteoroids are not kept in a fixed position and can freely rotate, tumble and spin. This difference raised the following question: What does meteorites allow to maintain a fixed orientation and successfully reach the earth?

The team, which also included Khunsa Amin and Kevin Hu, both NYU students and Jinzi Huang, a graduate student at NYU at the time of work, then conducted additional experiments exploring how various shaped cones fell through water. Here they discovered that narrow cones flip over while wide cones flutter. But between these two, "just right" conforms flying straight.

"These experiments tell an original story of oriented meteorites. The very aerodynamic forces that melt and transform meteorides in flight also stabilize their posture so that a cone shape can cut and eventually reach the earth," observes Ristroph. "This is another interesting message we learn from meteorites, which are scientifically important as" alien visitors "to the earth whose composition and structure tell of the universe."


Oldest meteorite collection on earth found in one of the driest places


More information:
Khunsa Amin el al., "The role of form-dependent flight stability in the origin of oriented meteorites", PNAS (2019). www.pnas.org/cgi/doi/10.1073/pnas.1815133116

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New York University




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What does meteorites give their shape? New research reveals a "Goldilock's" response (2019, July 22)
July 22, 2019
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