Was It Designed?
The Mollusk Shell
▪ Seashells look fragile, but they are usually difficult to break. “I’d have to hit some of them with a hammer to get a piece off,” says engineer Kenneth Vecchio, reflecting on his childhood days. The toughness of the seashell is especially evident in the shell of mollusks. *
Consider: The inner layer of the shell of mollusks (called nacre, or mother-of-pearl) has microscopic scales that are just nanometers, or billionths of a meter, apart. “The complexity we have observed in nacre at the nanoscale is quite amazing and seems likely to be a critical determinant of the toughness of the material,” says Christine Ortiz, associate professor of the Department of Materials Science and Engineering at the Massachusetts Institute of Technology, U.S.A.
Science writer Charles Petit describes a magnified view of nacre as “astonishingly orderly.” He explains: “A microscopic cross section looks like brickwork, with flat, hexagonal tablets of a crystalline, calcium carbonate mineral stacked in neat layers. Mortaring them is a flexible protein-rich gum originally secreted by the shellfish.”
Scientists believe that the secrets of the mollusk’s shell have broad applications—tougher armor systems, auto panels, and airplane wings, to name a few. “Nature uses nanoscale structural design principles to produce materials with superior mechanical properties,” says Ortiz. “In many aspects, human engineers have yet to achieve the same skill.”
What do you think? Did the shell of the mollusk with its amazing strength come about by chance? Or was it designed?
^ par. 3 Mollusks are soft-bodied, boneless animals. Sea mollusks include clams, mussels, oysters, scallops, octopuses and squid.
[Picture on page 25]
Enlarged cross-section of the inner layer of a mollusk shell
Inset: © Eye of Science/Photo Researchers, Inc.