Jan. 9, 2012

The mystery of how a highly unusual material found in a rock from a Russian mountain could have been created naturally on Earth may have been answered: It didn’t. A new study by scientists from Princeton University suggests that the material, called a quasicrystal, came from outer space in a meteorite. Moreover, the meteorite may be older than Earth itself. The finding indicates that materials that could never form naturally on Earth can form in space–which has scientists wondering what other materials are out there.

In a crystal, atoms are arranged in an orderly manner, with a regularly repeating pattern. The atoms in a quasicrystal also have an orderly arrangement, but they do not have a regularly repeating pattern. Scientists once thought that quasicrystals were an impossibility. In fact, when Daniel Shechtman, an Israeli engineer, reported his discovery of quasicrystals in 1982, the scientific community dismissed his findings completely. (In 2011, Shechtman won the Nobel Prize in chemistry for his discovery.) Several years after his discovery, other scientists made more quasicrystals in various arrangements. Then in 2009, scientists reported finding a naturally occurring quasicrystal in a rock from Russia’s Koryak Mountains.

Now Princeton scientists have reported that the Koryak quasicrystal appears not to have formed naturally on Earth after all. The rock apparently is the remains of a meteorite that formed 4.5 billion years ago, even before Earth had taken shape in the early solar system. In the rock sample, the scientists found a tiny grain of a mineral called stishovite, which occurs only at the kind of high pressure achieved in meteorite impacts and collisions. The quasicrystal was encased in the stishovite.

Both quasicrystals and crystals, such as these salt crystals, contain atoms that are arranged in an orderly pattern. But the atoms in quasicrystals do not follow the kind of repeating pattern found in crystals. (c) Charles Falco, Science Source from Photo Researchers

Many quasicrystals have practical uses. Certain quasicrystals can be particularly strong and hard. They are mixed with such metals as aluminum and steel and other alloys (mixture of metals) to increase a metal’s strength and hardness. Quasicrystals may also exhibit nonstick abilities, such as those found in the nonstick coatings on cookware.

Additional World Book articles:

• Mineral
• Symmetry

Jan. 3, 2012

Did Earth once have two moons? Does the moon have an iron core? Where should astronauts or unpiloted probes land for future missions to the moon? Information gathered by two new NASA probes orbiting Earth’s single natural satellite may soon help scientists answer these questions and several more. Launched on Sept. 10, 2011, the twin spacecraft of the GRAIL mission (Gravity Recovery and Interior Laboratory) went into orbit around the moon on December 31, and Jan. 1, 2012. Their mission is to create the most detailed map of the moon’s gravitational field ever made.

GRAIL-A and GRAIL-B were to spend the next two months gradually orbiting closer and closer to the surface until they are flying in formation at an altitude of only about 34 miles (55 kilometers). Then in March, instruments on-board the probes will start measuring the distance between them to within a few microns–the width of a human blood cell. That distance will vary as differences in the gravitation field caused by mountains, craters, and other surface features as well as features belowground cause the probes to speed up or slow down slightly. The probes will then radio this information to scientists at the Jet Propulsion Laboratory in Pasadena, California.

A tremendous collision between Earth and a smaller object led to the birth of the moon. Debris from the impact went into orbit in a ring around Earth, then gathered together to form the moon.        © William K. Hartmann

The second-moon theory is one explanation for the startling differences between the smoother near side and higher, more-mountainous far side of the moon. Scientists believe that the moon formed as a result of a collision 4.6 billion years ago between Earth and an object roughly the size of the planet Mars. Vaporized rock from Earth’s surface blasted into orbit around Earth then gradually cooled into solid bodies that gathered together. Some scientists believe that a second, much-smaller moon formed at the same time. They have theorized that after 10 million to 100 million years, the smaller moon collided with its larger companion. During the impact, the smaller moon flattened itself against the far side of the moon, creating the elevated highlands there. The gravitational map should show evidence of this impact, if it occurred, along with the answers to many other questions.

Additional World Book articles

• Armstrong, Neil
• Galileo (Mature scientific career)
• How the Moon Was Born (A Special Report)
• Space exploration (Lunar probes)

The fossils of single-celled organisms found in Australia may be the oldest evidence of life on Earth. The fossils are 3.4 billion years old, only about 1 billion years younger than Earth itself, according to a report by a team of scientists from Australia and the United Kingdom. The team was headed by David Wacey of the University of Western Australia and Martin Brasier of the University of Oxford.

Scientists search for fossils. © Ken Abbott, University of Colorado at Boulder

Wacey and Brasier reported finding the microfossils in rock formed from sand that once covered an ancient beach in what is now Western Australia. The beach lay at the edge of what may have been one of the first sections of solid land to form.  At that time, most of Earth was covered by water.

Previously, what were believed to be the oldest known fossils, also found in Western Australia, were dated to 3.465 billion years ago. But a number of scientists have expressed doubts that these structures are fossils from that early in Earth’s history. Similarly, some scientists argued for more research to confirm that the structures presented by Wacey and Brasier actually represent ancient organisms and were not created by nonbiological processes.