This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

04 January 2011

Meteoritics & Planetary Science: October/November 2010 (Multiple Articles on Asteroid 2008 TC3 and Output Science Results)

The October/November 2010 (Volume 45, Issue 10-11, Pages 1553–1845) issue of the journal Meteoritics & Planetary Science has multiple articles on the recovered asteroid 2008 TC3. A NASA Goddard press release a contains more information on the implications of some of the science results, specifically on finding amino acids in samples of the 2008 TC3 asteroid.

A summary of the recovery of 2008TC3 follows from one of the journal articles:

On October 7, 2008, asteroid 2008 TC3 impacted Earth and fragmented at 37 km altitude above the Nubian Desert in northern Sudan. The area surrounding the asteroid’s approach path was searched, resulting in the first recovery of meteorites from an asteroid observed in space. This was also the first recovery of remains from a fragile “cometary” PE = IIIa/b type fireball. In subsequent searches, over 600 mostly small 0.2–379 g meteorites (named “Almahata Sitta”) with a total mass 10.7 kg were recovered from a 30 × 7 km area. Meteorites fell along the track at 1.3 kg km−1, nearly independent of mass between 1 and 400 g, with a total fallen mass of 39 ± 6 kg. The strewn field was shifted nearly 1.8 km south from the calculated approach path. The influence of winds on the distribution of the meteorites, and on the motion of the dust train, is investigated. The majority of meteorites are ureilites with densities around 2.8 g cm−3, some of an anomalous (porous, high in carbon) polymict ureilite variety with densities as low as 1.5 g cm−3. In addition, an estimated 20–30% (in mass) of recovered meteorites were ordinary, enstatite, and carbonaceous chondrites. Their fresh look and matching distribution of fragments in the strewn field imply that they were part of 2008 TC3. For that reason, they are all referred to as “Almahata Sitta.” No ureilite meteorites were found that still held foreign clasts, suggesting that the asteroid’s clasts were only loosely bound.

Source: The recovery of asteroid 2008 TC3, Muawia H. SHADDAD1, Peter JENNISKENS2,*, Diyaa NUMAN1, Ayman M. KUDODA1, Saadia ELSIR3, Ihab F. RIYAD1, Awad Elkareem ALI4, Mohammed ALAMEEN1, Nada M. ALAMEEN1, Omer EID1, Ahmed T. OSMAN1, Mohamed I. AbuBAKER1, Mohamed YOUSIF1, Steven R. CHESLEY5, Paul W. CHODAS5, Jim ALBERS2, Wayne N. EDWARDS6,7, Peter G. BROWN6, Jacob KUIPER8, Jon M. FRIEDRICH9,10, Article first published online: 14 DEC 2010, Meteoritics & Planetary Science
Volume 45, Issue 10-11, pages 1557–1589, October/November 2010.

Selections from a National Geographic article on some of the research presented in the journal follow:

Hot on the heels of finding arsenic-loving life-forms, NASA astronomers have uncovered amino acids—the fundamental foundation for life—in a place where they shouldn't be.

The acids—precursors of proteins—have been unexpectedly found inside fragments of previously superheated meteorites that landed in northern Sudan in 2008, a new study says.

Amino acids have already been found in a variety of carbon-rich meteorites formed under relatively cool conditions. (See asteroid and comet pictures.)

But this is the first time the substances have been found in meteorites that had been naturally heated to 2,000 degrees Fahrenheit (1,100 degrees Celsius). That extreme temperature which should have destroyed any hint of organic material inside, said study leader Daniel Glavin, an astrobiologist at NASA's Goddard Space Flight Center in Maryland.

"Previously, we thought the simplest way to make amino acids in an asteroid was at cooler temperatures in the presence of liquid water," Glavin said in a statement. "This meteorite suggests there's another way involving reactions in gases as a very hot asteroid cools down."

The discovery also "provides additional support for the theory that life's ingredients were delivered to the Earth by asteroids," he said.

The meteorites came from a 13-foot-wide (4-meter-wide) parent asteroid that entered an Earth-crossing orbit in 2008.

A collision about 15 million years ago sent the 59-ton asteroid closer to Earth—and provided scientists the first opportunity to observe a celestial object before it entered our atmosphere in October 2008.

During desert treks, scientists later recovered nearly 600 meteorite fragments from the meteor shower.

"Finding evidence for the extraterrestrial amino acids in this meteorite is a big deal," Glavin said, "since we can learn about the chemistry that took place in space prior to the origin of life on Earth."

Likewise, "these meteorites would have contributed to the amino acid inventory of the early Earth and other planets in our solar system, including Mars."

This may mean that organic compounds such as amino acids—delivered via asteroids—may have been much more pervasive throughout the solar system than thought, he said.

Link: Meteoritics & Planetary Science, October/November 2010, Volume 45, Issue 10-11, Pages 1553–1845

Link: NASA Goddard Press Release ("Building Blocks of Life Created in "Impossible" Place")

Link: Article ("Life Ingredients Found in Superhot Meteorites—A First")

Link: Astrobiology Magazine Article ("More than One Way to Make Amino Acids")
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