Almahata Sitta meteorite could come from triple asteroid mash-up

ScienceDaily (Oct. 11, 2011) — Analysis of fragments of the Almahata Sitta meteorite, which landed in Sudan in 2008, has shown that the parent asteroid was probably formed through collisions of three different types of asteroids. The meteorites are of particular interest because they contain material both primitive and evolved types of asteroids.

The results are being presented at the EPSC-DPS Joint Meeting 2011 in Nantes, France, by Dr Julie Gayon-Markt.

The meteorites are fragments of the asteroid 2008 TC3, which impacted Earth exactly three years ago on 7th October 2008. More than 600 fragments were collected from the Nubian Desert in Sudan. They are collectively known as Almahata Sitta, which is Arabic for "Station Six," a train station between Wadi Halfa and Khartoum near where the fragments were found. The impact was historic because it was the first time that an asteroid was observed in space and tracked as it descended through Earth's atmosphere.

"Because falls of meteorites of different types are rare, the question of the origin of an asteroid harbouring both primitive and evolved characteristics is a challenging and intriguing problem," said Gayon-Markt. "Our recent studies of the dynamics and spectroscopy of asteroids in the main asteroid belt shed light on the origin of the Almahata Sitta fragments. We show that the Nysa-Polana asteroid family, located in the inner Main Belt is a very good candidate for the origin of 2008TC3."

Primitive asteroids, which are relatively unchanged since the birth of the Solar System, contain high proportions of hydrated minerals and organic materials. However, many other asteroids have undergone heating at some point, probably through the decay of radioactive materials, and the molten magma has separated into an iron core surrounded by a rocky mantle.

The Nysa-Polana family is divided into three different types: relatively rare B-type asteroids, which are primitive remnants of the early Solar System, stony S-type asteroids and intermediate X-type asteroids. Both S-type and X-type asteroids have undergone thermal evolution in their past. The spectral characteristics of all these three types are found in the Almahata Sitta fragments. The Nysa-Polana family is located in the inner Main Asteroid Belt and has a low orbital inclination relative to the ecliptic plane, which corresponds to the low-inclination of 2008TC3 during its journey to Earth.

The study led by Gayon-Markt suggests that 2008TC3 formed from the impact of an S-type object in the inner Main Asteroid belt with a B-type object from the Nysa-Polana family, followed by a second impact with an X-type asteroid of the Nysa-Polana.

"Around seventy to eighty percent of the Almahata Sitta fragments are what we call ureilites. Although ureilites show both primitive and evolved characteristics, their spectra in visible light are very similar to B-type primitive objects. The remaining twenty to thirty percent of the Almahata Sitta fragments gather two other kinds of meteorites which are linked to S-type and X-type asteroids. A workable explanation for how asteroid 2008TC3 could have formed involves low velocity collisions between these asteroid fragments of very different mineralogies," said Gayon-Markt.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Europlanet Media Centre, via AlphaGalileo.

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Meteorite holds clues to organic chemistry of early Earth

ScienceDaily (June 9, 2011) — Carbonaceous chondrites are a type of organic-rich meteorite that contain samples of the materials that took part in the creation of our planets nearly 4.6 billion years ago, including materials that were likely formed before our Solar System was created and may have been crucial to the formation of life on Earth. The complex suite of organic materials found in carbonaceous chondrites can vary substantially from meteorite to meteorite.

New research from Carnegie's Department of Terrestrial Magnetism and Geophysical Laboratory, published June 10 in Science, shows that most of these variations are the result of hydrothermal activity that took place within a few million years of the formation of the Solar System, when the meteorites were still part of larger parent bodies, likely asteroids.

Organic material in carbonaceous chondrites shares many characteristics with organic matter found in other primitive samples, including interplanetary dust particles, comet 81P/Wild-2, and Antarctic micrometeorites. It has been argued by some that this similarity indicates that organic material throughout the Solar System largely originated from a common source, possibly the interstellar medium.

A test of this common-source hypothesis stems from its requirement that the organic diversity within and among meteorites be due primarily to chemical and thermal processing that took place while the meteorites were parts of their parent bodies. In other words, there should be a relationship between the extent of hydrothermal alteration that a meteorite experienced and the chemistry of the organic material it contains.

If--as many have speculated--the organic material in meteorites had a role to play in the origin of life on Earth, the attraction of the common-source hypothesis is that the same organic material would have been delivered to all bodies in the Solar System. If the common source was the interstellar medium, then similar material would also be delivered to any forming planetary system.

The research team -- led by Christopher Herd of the University of Alberta, Canada, and including Carnegie's Conel Alexander, Larry Nittler, Frank Gyngard, George Cody, Marilyn Fogel, and Yoko Kebukawa -- studied four meteorite specimens from the shower of stones, produced by the breakup of a meteoroid as it entered the atmosphere, that fell on Tagish Lake in northern Canada in January 2000. The samples are considered very pristine, because they fell on a frozen lake, were collected without hand contact within a few days of landing and have remained frozen ever since.

The samples were processed and analyzed on the microscopic level using a variety of sophisticated techniques. Examination of their inorganic components indicated that the specimens had experienced large differences in the extent of hydrothermal alteration, prompting an in-depth examination of their organic material. The team demonstrated that the insoluble organic matter found in the samples has properties that span nearly the entire range found in all carbonaceous chondrites and that those properties correlate with other measures of the extent of parent body alteration. Their finding confirms that the diversity of this material is due to processing of a common precursor material in the asteroidal parent bodies.

The team found large concentrations of monocarboxylic acids, or MCAs, which are essential to biochemistry, in their Tagish Lake samples. They attributed the high level of these acids to the pristine nature of the samples, which have been preserved below zero degrees Celsius since they were recovered. There was variety in the types of MCAs, which they determined could also be due to alterations that took place on the parent bodies.

The samples also contained amino acids -- the essential-for-life organic building blocks used to create proteins. The types and abundances of amino acids contained in the samples are consistent with an extraterrestrial origin, and were clearly also influenced, albeit in a complex way, by the alteration histories of their host meteorites.

"Taken together these results indicate that the chemical and thermal processing common to the Tagish Lake meteorites likely occurred when the samples were part of a larger parent body that was created from the same raw materials that formed our Solar System," said Larry Nittler of Carnegie's DTM. "These samples can also provide important clues to the source of organic material, and life, on Earth."

Funding was provided by Natural Sciences and Engineering Research Council of Canada, Alberta Innovates, NASA (Astrobiology, including NASA Astrobiology Institute teams at the Carnegie Institution and the Goddard Center for Astrobiology; Origins of Solar Systems; Cosmochemistry and Postdoctoral Programs), the U.S. Office of Naval Research, Carnegie Institution for Science, Grant MacEwan University, and the Carnegie Institution of Canada. Some data was acquired at Advanced Light Source, which is supported by the Director of the Office of Science, Department of Energy, and by a W.M. Keck Foundation grant to the Carnegie Institution for Science.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Carnegie Institution, via EurekAlert!, a service of AAAS.

Journal Reference:

Christopher D. K. Herd, Alexandra Blinova, Danielle N. Simkus, Yongsong Huang, Rafael Tarozo, Conel M. O’D. Alexander, Frank Gyngard, Larry R. Nittler, George D. Cody, Marilyn L. Fogel, Yoko Kebukawa, A. L. David Kilcoyne, Robert W. Hilts, Greg F. Slater, Daniel P. Glavin, Jason P. Dworkin, Michael P. Callahan, Jamie E. Elsila, Bradley T. De Gregorio, Rhonda M. Stroud. Origin and Evolution of Prebiotic Organic Matter As Inferred from the Tagish Lake Meteorite. Science, 2011; 332 (6035): 1304-1307 DOI: 10.1126/science.1203290

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Meteorite holds clues to organic chemistry of early Earth

ScienceDaily (June 9, 2011) — Carbonaceous chondrites are a type of organic-rich meteorite that contain samples of the materials that took part in the creation of our planets nearly 4.6 billion years ago, including materials that were likely formed before our Solar System was created and may have been crucial to the formation of life on Earth. The complex suite of organic materials found in carbonaceous chondrites can vary substantially from meteorite to meteorite.

New research from Carnegie's Department of Terrestrial Magnetism and Geophysical Laboratory, published June 10 in Science, shows that most of these variations are the result of hydrothermal activity that took place within a few million years of the formation of the Solar System, when the meteorites were still part of larger parent bodies, likely asteroids.

Organic material in carbonaceous chondrites shares many characteristics with organic matter found in other primitive samples, including interplanetary dust particles, comet 81P/Wild-2, and Antarctic micrometeorites. It has been argued by some that this similarity indicates that organic material throughout the Solar System largely originated from a common source, possibly the interstellar medium.

A test of this common-source hypothesis stems from its requirement that the organic diversity within and among meteorites be due primarily to chemical and thermal processing that took place while the meteorites were parts of their parent bodies. In other words, there should be a relationship between the extent of hydrothermal alteration that a meteorite experienced and the chemistry of the organic material it contains.

If--as many have speculated--the organic material in meteorites had a role to play in the origin of life on Earth, the attraction of the common-source hypothesis is that the same organic material would have been delivered to all bodies in the Solar System. If the common source was the interstellar medium, then similar material would also be delivered to any forming planetary system.

The research team -- led by Christopher Herd of the University of Alberta, Canada, and including Carnegie's Conel Alexander, Larry Nittler, Frank Gyngard, George Cody, Marilyn Fogel, and Yoko Kebukawa -- studied four meteorite specimens from the shower of stones, produced by the breakup of a meteoroid as it entered the atmosphere, that fell on Tagish Lake in northern Canada in January 2000. The samples are considered very pristine, because they fell on a frozen lake, were collected without hand contact within a few days of landing and have remained frozen ever since.

The samples were processed and analyzed on the microscopic level using a variety of sophisticated techniques. Examination of their inorganic components indicated that the specimens had experienced large differences in the extent of hydrothermal alteration, prompting an in-depth examination of their organic material. The team demonstrated that the insoluble organic matter found in the samples has properties that span nearly the entire range found in all carbonaceous chondrites and that those properties correlate with other measures of the extent of parent body alteration. Their finding confirms that the diversity of this material is due to processing of a common precursor material in the asteroidal parent bodies.

The team found large concentrations of monocarboxylic acids, or MCAs, which are essential to biochemistry, in their Tagish Lake samples. They attributed the high level of these acids to the pristine nature of the samples, which have been preserved below zero degrees Celsius since they were recovered. There was variety in the types of MCAs, which they determined could also be due to alterations that took place on the parent bodies.

The samples also contained amino acids -- the essential-for-life organic building blocks used to create proteins. The types and abundances of amino acids contained in the samples are consistent with an extraterrestrial origin, and were clearly also influenced, albeit in a complex way, by the alteration histories of their host meteorites.

"Taken together these results indicate that the chemical and thermal processing common to the Tagish Lake meteorites likely occurred when the samples were part of a larger parent body that was created from the same raw materials that formed our Solar System," said Larry Nittler of Carnegie's DTM. "These samples can also provide important clues to the source of organic material, and life, on Earth."

Funding was provided by Natural Sciences and Engineering Research Council of Canada, Alberta Innovates, NASA (Astrobiology, including NASA Astrobiology Institute teams at the Carnegie Institution and the Goddard Center for Astrobiology; Origins of Solar Systems; Cosmochemistry and Postdoctoral Programs), the U.S. Office of Naval Research, Carnegie Institution for Science, Grant MacEwan University, and the Carnegie Institution of Canada. Some data was acquired at Advanced Light Source, which is supported by the Director of the Office of Science, Department of Energy, and by a W.M. Keck Foundation grant to the Carnegie Institution for Science.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Carnegie Institution, via EurekAlert!, a service of AAAS.

Journal Reference:

Christopher D. K. Herd, Alexandra Blinova, Danielle N. Simkus, Yongsong Huang, Rafael Tarozo, Conel M. O’D. Alexander, Frank Gyngard, Larry R. Nittler, George D. Cody, Marilyn L. Fogel, Yoko Kebukawa, A. L. David Kilcoyne, Robert W. Hilts, Greg F. Slater, Daniel P. Glavin, Jason P. Dworkin, Michael P. Callahan, Jamie E. Elsila, Bradley T. De Gregorio, Rhonda M. Stroud. Origin and Evolution of Prebiotic Organic Matter As Inferred from the Tagish Lake Meteorite. Science, 2011; 332 (6035): 1304-1307 DOI: 10.1126/science.1203290

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here