Space rocks Wadhwa's world at meteorite center

January 29, 2007

It was a piece of Mars that set ASU geology professor Meenakshi “Mini” Wadhwa on a career investigating meteorites. At the time, Wadhwa, who directs the Center for Meteorite Studies in the School of Earth and Space Exploration, was a graduate student at Washington University in St. Louis and newly arrived from India.

“I had come from a terrestrial geology background, and I wanted to study other planets,” she says. “I knew about the lunar material from the Apollo program, but not about any other extraterrestrial rocks.” Download Full Image

Then one of her professors told her about the meteorites from Mars." alt="Meenakshi “Mini” Wadhwa" hspace="5" vspace="5" width="288" height="191" align="right" />Incredulous at first that pieces of Mars were here on Earth, Wadhwa knew immediately what direction her career would go. It soon broadened to include all kinds of meteorites.

“Meteorites are rocky pieces from the first solid bodies to form when our solar system was born,” she says.

They include the oldest rocks known, which have an age of more than 4.5 billion years. This age is greater than the oldest rocks native to Earth, and it defines the age of the solar system.

“One of my research programs is to resolve in detail the timeline for the formation of these bodies,” Wadhwa says.

Meteorites arrive on Earth through a haphazard process that begins in a collision between rocky bodies in space called asteroids. These range in size from perhaps a dozen yards across up to hundreds of miles in diameter. As rocky fragments fly after the collision, some escape the gravity of the parent object and sail off into space.

After drifting around the sun for perhaps millions of years, a rock fragment may collide with Earth. If the fragment is larger than an inch or so across – and if it escapes falling into the ocean – it will land on the ground. (Space rocks smaller than an inch mostly burn up as they pass through the atmosphere.) With luck, someone may find the meteorite and let scientists examine it.

Because a meteorite doesn't arrive with a return-address label, scientists first determine what kind of space rock it is. From that, they draw a preliminary conclusion about its birthplace.

Most meteorites are primitive, rocky objects that formed in the same cloud of gas and dust from which the sun and planets formed. Other meteorites are made of mostly nickel-iron: These include the famous Cañon Diablo meteorite that blasted Meteor Crater in northern Arizona some 49,000 years ago.

But scientists found other meteorites that didn't fit into existing categories. One of these oddball space rocks landed in the village of Chassigny, France, in 1815. Another fell on Shergotty, India, in 1865, and a third landed at Nakhla, Egypt, in 1911. Taken together, these meteorites somewhat resembled each other, and scientists took to calling them the SNC meteorites, for Shergotty-Nakhla-Chassigny. The SNCs (or “snicks” for short) are now known to be fragments of the planet Mars.

“If you just look at a Mars meteorite, you'd be hard-pressed to tell it from an ordinary Earth rock,” Wadhwa says.

Scientists finally identified these as coming from Mars by noting that they contain trapped gases. As she explains, these “have a composition matching the Martian atmosphere, as detected by the Viking landers in the mid-1970s. That cinched a Martian origin.”

Likewise, careful analysis showed that other oddball meteorites were pieces of the moon. They were chemically similar to rock samples brought back from the moon by Apollo astronauts. To date, about 40 lunar meteorites and 36 Martian ones are known.

Housed at the Center for Meteorite Studies, ASU's meteorite collection numbers more than 1,500 – including several Mars meteorites and two from the moon. It's the largest meteorite collection at any university in the world.

“We have such an incredible resource to work with,” says Wadhwa, adding that it was part of what drew her to ASU from the Field Museum in Chicago, where she was the curator of meteorites.

“For me, as an analytical geochemist, there are wonderful facilities here,” she says.

Adding to the facilities will be a new, state-of-the-art mass spectrometer, one of the tools for studying chemical elements within meteorites.

Besides meteorites, Wadhwa's research involves developing new methods for investigating tiny amounts of extraterrestrial materials, such as those returned by the recent spacecraft missions Genesis and Stardust. Wadhwa received the prestigious Guggenheim Fellowship in 2005 in support of her work on the solar wind sample returned by NASA's Genesis spacecraft. She also is a science team member of OSIRIS, a sample-return mission to an asteroid; it is one of three Discovery-class missions NASA is considering.

ASU welcomes new Regents' Professors

January 29, 2007

Four exceptional professors have been named to the university's most prestigious ranks as ASU Regents' Professors for 2007. The selection was ratified Jan. 23 by the Arizona Board of Regents.

The honorees are: Download Full Image

• Laurie Chassin, professor of psychology.

• Robert Denhardt, director of the School of Public Affairs.

• Subhash Mahajan, director of the School of Materials.

• Richard Rogerson, Rondthaler chair of economics.

Regents' Professors stand out for their accomplishments in many areas, including excellence in teaching, exceptional achievements in research or other creative activities, and national and international distinction in their fields. They serve as advisers to the university president and take on a broader role as consultants and teachers throughout the university.

“The four individuals chosen this year to be Regents' Professors exemplify the university's ideal for professors,” says Elizabeth D. Capaldi, ASU's executive vice president and university provost. “They are superb scholars, excellent teachers, and university and discipline citizens who build programs and work with students while changing the world through their own research. We are very happy they are here, and that we can recognize their achievements.”

Nominations for Regents' Professorships are made by faculty members and are submitted to a nominating committee in the fall. The prestigious honor includes an increase of $5,000 to the faculty member's base salary, as well as an annual grant of $5,000 to support their scholarly endeavors.

Below is a brief description of the honorees' accomplishments:

• Chassin's research in child clinical psychology has earned her a multitude of leadership positions in the field, as well as continuous funding from the National Institute of Health. As a principal investigator of a prevention-training grant and author of more than 140 publications, Chassin has been a leader in developing and conducting longitudinal studies of children and families at risk for substance abuse and associated mental health disorders.

• Denhardt, an author of 17 books and more than 60 journal articles, has earned national acclaim for his research and developments in organizational studies. He is a winner of the American Society of Public Administration's lifetime achievement award, and he has produced research in phenomenology and critical theory that helped redefine the field of public administration.

• Mahajan, a leader in electronic materials, has been recognized for his international contributions to materials science. His extensive publishing career as editor of a leading journal in the field and an author of an undergraduate textbook, coupled with his pioneering work on semiconductors, led to his being elected to the National Academy of Engineering in 2005.

• Rogerson's macroeconomic research and well-published work have made him a leading expert in labor economics and an important consultant to four Federal Reserve banks. His transformative papers on such issues as labor supply have appeared in the renowned economic journals Review of Economic Dynamics and the American Economic Review , for which he serves as co-editor.

Britt Lewis

Communications Specialist, ASU Library