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Sudan Meteorites Offer Look at Early Solar System


Jon Friedrich, Ph.D., has published on the composition of Almahata Sitta in the March 2009 issue of Nature.
Photo by Janet Sassi

In a small laboratory in John Mulcahy Hall, Jon Friedrich, Ph.D., and Julianne Troiano have opened a window that looks 4.5 billion years into the past.

That window is Almahata Sitta—fragments of a rare, carbon-rich type of meteorite called an ureilite deposited in northern Sudan in 2008, when asteroid 2008 TC3 slammed into Earth’s atmosphere and exploded 37 kilometers above the ground.

Friedrich is an assistant professor of chemistry; Troiano is a senior in Fordham College at Rose Hill, majoring in chemistry. The window they’ve opened doesn’t look like much—a tiny speck of material that resembles a black breadcrumb—but the insights gleaned from it already have changed the way we think about the composition of matter in the early solar system.

“The great thing about this is that it allows us to see what the early solar system was like without having to back-calculate the effect of terrestrial contamination,” Friedrich said.

“There’s a chemical signature that occurs in most ureilites known to date, and that chemical signature was not present in Almahata Sitta. We were actually able to say that, okay, Almahata Sitta does not contain that signature, so other meteorites of this class may be actually somewhat contaminated.”

Friedrich said the chemical composition of Almahata Sitta is intriguing because it is so atypical. The most common type of asteroid in the asteroid belt (a vast collection of small objects between the orbits of Mars and Jupiter) is something called an s-type asteroid. If you held a part of one in your hand, it would be heaver than a ureilite of the same size because the s-type would probably contain 10 to 15 percent metal—particularly nickel iron, or nickel metal, and it would be gray.

“We have the samples, and they’re pretty small—probably the size of a pinky nail,” Troiano said. “We grind the samples so it’s easier to dissolve them, then we mix them with nitric acid and hydrofluoric acid and we put them in a microwave digestion system that heats them up and increases the pressure so the samples can dissolve in the acid. Then they dry down and they sort of just look like goo.”

The goo is mixed into a 50-milliliter solution and put into a mass spectrometer, which tells the researchers which elements are present and in what amounts. The results are then fed into Excel spreadsheets for analysis.

FCRH senior Julianne Troiano, a Clare Booth Luce scholar, sits at the mass spectrometer.

“One of the things that came out of all of the work that’s been done by people all around the world is that we know the 2008 TC3 asteroid that produced the Almahata Sitta meteorite was a very un-homogenous chunk of rock,” Friedrich said. “Julianne and I focused on the pieces that were ureilitic in nature, which is the majority of Almahata Sitta and the TC3 asteroid. But what we did find was that if you’re a geologist and you had an asteroid and you grabbed pieces of rock, they’d look a little different.”

He said it seems that different pieces of the asteroid did have different internal chemistry, to some extent, perhaps because different parts were formed under different temperatures.

Analysis of Almahata Sitta tells us that not everything in the asteroid belt is of the same composition, which has implications for how these objects should be dealt with should they be nudged into an Earth-crossing orbit. Should an object of sufficient size be on a collision course with Earth, the results could be catastrophic.

Though so-called “slate wiper” impacts are rare (perhaps once every hundred million years), they are a real threat. NASA has created the Near Earth Object Program to track possible impactors and devise defenses, most likely nudging those objects out of their Earth-crossing orbits long before they reach us. How the objects get nudged away depends on their composition.

“What we’re learning is that asteroids aren’t necessarily big, giant rocks in the sky that are one big piece,” Friedrich said. “Sometimes, they can be made up of lots of little pieces sort of weakly held together. Trying to destroy or alter the course of asteroids with these two different properties will take different tactics.”

Friedrich’s research is supported in part by a Fordham Faculty Research Grant. He has published on the composition of Almahata Sitta before, including in the March 2009 issue of Nature. He and Troiano have published several papers on the meteorite in the peer-reviewed journals Meteoritics & Planetary Science and Geochimica et Cosmochimica Acta—a somewhat unusual honor for an undergraduate researcher.

Troiano, a Clare Booth Luce Scholar, has made the Dean’s List for the last two years. She is a cheerleader, a member of the Expressions Dance Alliance, and a member of the American Chemical Society and American Geophysical Union.


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