Smithsonian Science » rocks & minerals

Smithsonian volcanologist Rick Wunderman talks about volcanos and the recent eruptions in Iceland

John Barrat — Fri, 30 Apr 2010 00:11:41 +0000

Keeper Tracey Barnes talks about the National Zoo’s Andean bear, Billie Jean, and her two new cubs

Book Review: Planetary Tectonics examines otherworldly landforms

John Barrat — Mon, 05 Apr 2010 15:06:19 +0000

In recent decades, manned and unmanned spacecraft have taken hundreds of thousands of detailed photographs of the terrestrial planets in our solar system, the distant outer planets and various asteroids, comets and planetary satellites. Much of the geology that has emerged from the study of these photographs is spelled out in the new book Planetary Tectonics, edited by Thomas Watters, senior scientist at the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum, and Richard Schultz, Professor of Geological Engineering and Geomechanics at the University of Nevada.

Image right: A moasic photo of part of the Moon’s southern Mare Serenitatis showing wrinkle ridges.

This new book is a primer on the many different surface features that exist on the planets in our solar system, the internal and external forces that created these features and what they reveal about the conditions on the planets where they are found. From the wrinkle ridges of the moon, to the surface grooves of an asteroid or the fracture belts of Venus, Planetary Tectonics is a studious look at the complex interplay of powerful forces that act upon planetary crusts and the mechanical properties of the crusts themselves.

The number and diversity of tectonic landforms in our solar system “is truly remarkable,” Watters and Schultz write in the preface of their book. Photographs of these structures have stimulated a range of scholarly investigations, “from the characterization and modeling of individual classes of tectonic landforms to the assessment of regional and global tectonic systems,” the scientists write. Planetary Tectonics is an overview of the major themes of this research as they relate to each planet and small body. The book contains methods for mapping and analyzing planetary tectonic features and is illustrated with many diagrams and spectacular images. Planetary Tectonics, which is extensively referenced, provides a springboard to other sources of information, and is an essential reference for researchers and students alike. Published by Cambridge University Press, additional information about this new volume can be accessed at the Web address: www.cambridge.org/catalogue/catalogue.asp?isbn=9780521765732

Meteorite that fell in Lorton, Va., identified by Smithsonian scientists

John Barrat — Mon, 25 Jan 2010 18:59:20 +0000

A meteorite that crashed through the roof of a Lorton, Va., doctors’ office on Monday, Jan. 18, 2010 was recently identified by scientists in the Division of Mineral Sciences at the Smithsonian’s National Museum of Natural History. Local newspapers reported that thousands of people from southern New Jersey to southwestern Virginia witnessed the meteorite streak through the sky in a colorful fireball and break apart as it passed through the atmosphere.

A local television news crew brought the meteorite to the Smithsonian for verification and Natural History Museum Collections Manager Linda Welzenbach identified it as a stony chrondite meteorite weighing about two-thirds of a pound. “It’s ordinary because 85 to 90 percent of everything that falls is this type of meteorite,” Welzenbach told the Baltimore Sun newspaper. “It has a light gray interior with little, tiny iron, nickel metal particles.” The meteorite is covered with a black fusion crust that was created as its exterior melted from the heat generated by friction with the Earth’s atmosphere.

Bombarded with ultraviolet light, the blue Hope diamond glows red

John Barrat — Wed, 19 Aug 2009 12:17:53 +0000

Some research is best done behind heavy, locked doors.

When geologist Jeffrey Post recently embarked on an experiment involving the Hope Diamond, at 45.52 carats, the world’s largest deep-blue diamond and one of the most famous and valuable museum objects on earth, he and his colleagues locked themselves and the diamond inside a large vault in the depths of the Smithsonian’s National Museum of Natural History.

Photo: The 45.52 carat, deep-blue Hope Diamond is shown here inside its surrounding pendant of 16 pear- and cushion-cut white diamonds. (Photo by Chip Clark)

Post was investigating a phenomenon that the millions of museum visitors who gaze at the diamond on its rotating pedestal behind bulletproof glass will never see—the mysterious red phosphorescent glow the stone emits when exposed to ultraviolet light.

The Hope Diamond’s red glow has long been considered a unique property of that stone. Most blue diamonds produce a bluish-white phosphorescence if exposed to ultraviolet light. The few other diamonds known to emit red phosphorescence were commonly assumed to have been from the even larger original stone from which the Hope was cut.

“It is something that always intrigued people,” says Post, curator of the Smithsonian’s National Gem and Mineral Collection. “For people who like the whole idea of a curse and that kind of story, the fact that this thing phosphoresces a bloody red color is just too good to be true.”

Photo: The Hope Diamond, right, without its white-diamond pendant, and the 30.62 carat Blue Hart Diamond.

Post timed his research to occur in the hours after the museum closed for the evening and before it reopened the next day. With guards standing by, the diamond was removed from its pedestal in the Harry Winston Gallery.

“We had a local jeweler come in and take it out of its setting for us,” Post says. (The jeweler returned early the following morning to reset the stone.) Next, Post and fellow diamond investigators from the U.S. Naval Research Laboratory, Ocean Optics Co. and Pennsylvania State University locked themselves in the vault with the diamond and a portable spectrometer.

“The clock was running,” Post says, and the scientists got to work. The diamond was positioned on a piece of clay inside a box that could be sealed to keep out ambient light. A fiber-optic cable connected to an ultraviolet light source was extended into the box and “pushed up against the top face of the Hope Diamond,” Post says. Then the diamond was exposed to ultraviolet light for several seconds.

When the light source was turned off, the diamond began to emit its characteristic red glow, a phenomenon that lasts several minutes. A second fiber-optic cable in the box channeled phosphorescent light from the diamond to the spectrometer.

Photo: The Hope Diamond emits a red phosphorescence after being bombarded with ultraviolet light. (Photo by John Nels Hatleberg)

Spectrometers measure wavelengths of light, and the display on a laptop computer hooked to the spectrometer revealed the Hope Diamond’s red light was more than just red. “That was the first time we had been able to see a display of what the phosphorescence spectrum looked like for the Hope Diamond,” Post says.

“We saw two strong peaks in the spectrum,” Post explains. One was in the red portion of the spectrum, “but the second peak, interestingly, was in the green portion of the spectrum.”

In the vault that night, the scientists also collected spectrum readings from other diamonds, including the second largest known deep-blue diamond, the 30.62 carat Blue Heart, also in the Smithsonian’s gem collection.

Later, Post and his colleagues hauled their portable spectrometer to New York City’s Diamond District, an area of Manhattan that is a center of the world diamond industry. A dealer known to Post granted the researchers access to dozens of valuable blue diamonds in his safe for further spectrum measurements.

The scientists learned that all blue diamonds show red and green peaks in their phosphorescence spectrum. But the relative intensity of those peaks and the rate at which they decay varies from diamond to diamond, leading to differences in the phosphorescent glow seen by the naked eye.

Diamonds are composed of carbon, and impurities in the carbon give rise to an individual stone’s color. Blue diamonds have relatively high levels of boron impurities but low levels of nitrogen. Post believes that the red phosphorescence emitted to some degree by all blue diamonds is likely due to interaction between those two elements. To test that possibility, he is continuing his study of blue diamonds, using a different kind of instrument that lets him measure the amount of boron and nitrogen in individual stones “and then correlate that with the particular spectra that we’re getting off those diamonds.”

Photo: Photographed through the thick protective glass of the Hope Diamond’s exhibition case, Jeffrey Post returns the diamond to its pedestal in the Harry Winston Gallery of The Janet Annenberg Hooker Hall of Geology, Gems, and Minerals in the Smithsonian’s National Museum of Natural History. (Photos by Chip Clark)

Post’s work has already yielded knowledge of interest not just to scientists but to diamond sellers and their customers. Because the relative intensity of the blue and red components of each blue diamond’s phosphorescence is unique, the same sort of analysis that the researchers did in the museum vault might be used to fingerprint individual blue diamonds and to distinguish natural stones from man-made ones.

No stranger to spectacular gems, Post still gets a thrill from working with the Hope Diamond. “Every time I look at it I kind of go, ‘My gosh!,’” he says, noting that it is impossible to overlook the stone’s “human history, the curse and the kings, the queens, the thefts.”

However, the scientist believes that his recent research underscores the famous diamond’s importance as “a unique natural history object.”

Fossils Show Prehistoric Global Warming

John Barrat — Fri, 22 May 2009 12:52:32 +0000

The Past as Prologue
For those who think that global warming is a 21st-century phenomenon, Scott Wing, a scientist at the Smithsonian’s National Museum of Natural History, has news about the past.

Wing headed an international team of scientists whose discovery of plant fossils in the Bighorn Basin of northwestern Wyoming helps document the consequences of a sudden global warming, called the Paleocene-Eocene Thermal Maximum (PETM), 55 million years ago.

Experts believe the PETM, which was caused by a massive release of carbon into the atmosphere, may be an analogue for what is happening today as humans burn increasing amounts of fossil fuel and release large amounts of carbon dioxide.

Plant Movement Signals Global Warming
For nearly 15 years, Wing and his team dug through sediments deposited during uplift of the Rocky Mountains, looking for fossils of the right age and condition. Their discoveries proved that warming caused major shifts in the distribution of plants, allowing southern-dwelling trees and shrubs, related to poinsettia, sumac, and paw-paw, to move some 1,000 miles north in less than 10,000 years. These subtropical invaders flourished for about 100,000 years in what we now know as Wyoming. As carbon dioxide levels dropped and temperatures cooled again, plants related to birches and bald cypress came to dominate the vegetation.

The study and interpretation of this fossil record helps other scientists project future changes in plant life that may result from global warming induced by human activity.