new hot papers - 2010
March 2010 (Commentary added in March 2010 for January 2010 late entry.)

Qingzhu Yin talks with ScienceWatch.com and answers a few questions about this month's New Hot Paper in the field of Geosciences.
	Article Title: Al-26-Mg-26 and Pb-207-Pb-206 systematics of Allende CAIs: Canonical solar initial Al-26/Al-27 ratio reinstated Authors: Jacobsen, B;Yin, QZ;Moynier, F;Amelin, Y;Krot, AN;Nagashima, K;Hutcheon, ID;Palme, H Journal: EARTH PLANET SCI LETT, Volume: 272, Issue: 1-2, Page: 353-364, Year: JUL 30 2008 * Univ Calif Davis, Dept Geol, Davis, CA 95616 USA. * Univ Calif Davis, Dept Geol, Davis, CA 95616 USA. * Geol Survey Canada, Ottawa, ON K1A 0E8, Canada. (addresses have been truncated.)

  Why do you think your paper is highly cited?

The existence of the short-lived radioactive nuclide ²⁶Al (half-life 0.73 million years, Myr) at the beginning of the solar system 4.567 billion years (Gyr) ago, has been known since the mid-1970s. Recently, the amount of radioactive ²⁶Al relative to the stable ²⁷Al in the early solar system was revised upwards by about 10% or more, as described in papers that appeared in the prominent journals like Science (2005) and Nature (2004, 2005), respectively. Our paper shows that this upward revision is not warranted.

  Does it describe a new discovery, methodology, or synthesis of knowledge?

"I consider isotopes to be the "DNA" of physical science. Natural abundance variation of isotopes will continue to serve us well, as these are the most important tracers of physicochemical processes which exist in nature."

Our paper described the most detailed investigation, using modern technology, of the initial inventory of ²⁶Al in the oldest object in the solar system, a solid material called Ca-Al-rich inclusions in the "Allende" meteorite, one of the most primitive meteorites known as carbonaceous chondrites ever found on Earth.

These carbonaceous chondrites are cosmic sediments, which witnessed the birth of our solar system. They remained intact in the cold storage of asteroid belts for the past 4.567 Gyr, and then were delivered to Earth by natural forces in 1969 to Allende, Mexico, in a "free sample return" as meteorites, in the same year when the Apollo program astronauts returned to Earth with the first lunar samples.

  Would you summarize the significance of your paper in layman's terms?

A precise knowledge of the initial inventory of radioactive nuclides, such as ²⁶Al, at the beginning of the solar system provides crucial pieces of information for the time zero age-anchor and the initial heat budgets from radioactivities for early planetary differentiation and evolution.

It also provides important information about the environment in which our solar system was born 4.567 Gyr ago. The paper describes the very first solid object in our solar system, which was precisely dated with an uncertainty of 20 Kyr. On a human scale, this is equivalent to uncovering a memory of the first 1.7 hours of birth for a 45-year-old person.

  How did you become involved in this research, and were there any problems along the way?

Like many discoveries in science, I got involved in this research serendipitously. I gave my student (the first author Benjamin Jacobsen) a project to develop Mg chemical separation procedures for other applications.

Purely as a way of self-consistency to check whether the protocols developed by us work properly or not, I gave the meteoritic materials to the student to reproduce the literature value, as outlined in the most recent Science and Nature results. To our surprise, the more we worked on the material, the more we became convinced that there was nothing wrong with our own procedures.

  Where do you see your research leading in the future?

I consider isotopes to be the "DNA" of physical science. Natural abundance variation of isotopes will continue to serve us well, as these are the most important tracers of physicochemical processes which exist in nature.

Qing-zhu Yin, Ph.D.
Professor
Department of Geology
University of California, Davis
Davis, CA
Web

KEYWORDS: EARLY SOLAR SYSTEM CHRONOLOGY; SHORT-LIVED RADIOACTIVITY; ALLENDE METEORITE; CA-AL RICH INCLUSIONS; U-PB AGE; AL-26/AL-27 RATIO; REFRACTORY INCLUSIONS; ISOTOPE FRACTIONATION; PLANET FORMATION; AL-26; METEORITES; CHONDRULES; URANIUM; ORIGIN; LEAD; MG.