Solar System may be 2 million years older than we thought

August 24, 2010

Timescales of early Solar System processes rely on precise, accurate and consistent ages obtained with radiometric dating. However, recent advances in instrumentation now allow scientists to make more precise measurements, some of which are revealing inconsistencies in the ages of samples. Seeking better constraints on the age of the Solar System, Arizona State University researchers Audrey Bouvier and Meenakshi Wadhwa analyzed meteorite Northwest Africa (NWA) 2364 and found that the age of the Solar System predates previous estimates by up to 1.9 million years.

By using a dating technique known as lead-lead dating, Bouvier and Wadhwa were able to calculate the age of a calcium-aluminum-rich inclusion (CAI) contained within the Northwest Africa 2364 chondritic meteorite. These CAIs are thought to be the first solids to condense from the cooling protoplanetary disk during the birth of the Solar System. Download Full Image

The study’s findings, published online on August 22 in Nature Geoscience, fix the age of the Solar System at 4.5682 billion years old, between 0.3 and 1.9 million years older than previous estimates. This relatively small revision to the currently accepted age of about 4.56 billion years is significant since some of the most important events that shaped the Solar System occurred within the first ~10 million years of its formation.

“This relatively small age adjustment means that there was as much as twice the amount of iron-60, a certain short-lived isotope of iron, in the early Solar System than previously determined. This higher initial abundance of this isotope in the Solar System can only be explained by supernova injection,” said Bouvier, a faculty research associate in the School of Earth and Space Exploration (SESE) in ASU’s College of Liberal Arts and Sciences. “This supernova event, and possibly others, could have triggered the formation of the Solar System. By studying meteorites and their isotopic characteristics, we bring new clues about the stellar environment of our Sun at birth.”

According to Meenakshi Wadhwa, professor in SESE and director of the Center for Meteorite Studies, “This work also helps to resolve some long-standing inconsistencies in early Solar System time scales as obtained by different high-resolution chronometers. However, there is certainly room for future studies. In particular, it will be important to conduct high precision chronologic investigations of CAIs from other pristine meteorites. We also need to understand the reasons for why the CAIs measured previously from two other chondritic meteorites, Allende and Efremovka, have yielded younger ages.”

One significant aspect of this study is that it is the first published lead-lead isotopic investigation that takes into account the possible variation of the uranium isotope composition. Earlier work conducted in Wadhwa’s laboratory by ASU graduate student Gregory Brennecka, in collaboration with SESE professor Ariel Anbar, has shown that the uranium isotope composition of CAIs, long assumed to be constant, can in fact be highly variable and this has important implications for the calculation of the precise lead-lead ages of these objects.

Using the relationship demonstrated by Brennecka and colleagues between the uranium isotope composition and other geochemical indicators in CAIs, Bouvier and Wadhwa inferred a uranium isotope composition for the CAI for which they reported the lead-lead age. Future work at ASU will focus on development of analytical techniques for the direct measurement of the precise uranium isotope composition of CAIs for which lead-lead isotopic investigations are being conducted.

“Our work can help researchers better understand the sequence of events that took place within the first few million years of the Solar system formation, such as the accretion and melting of planetary bodies,” Bouvier said. ”All these processes happened extremely rapidly, and only by reaching such a precision on isotopic measurements and chronology can we find out about these processes of planetary formation.”

Nikki Cassis

marketing and communications director, School of Earth and Space Exploration

Tryouts for Sun Devil track & field team set

August 24, 2010

Current Arizona State University students that are interested in trying out for the Sun Devil track & field squad will have their opportunity on September 8-9 at Sun Angel Stadium, Greg">">Greg Kraft, Director of Track & Field for ASU, announced today. The tryouts will begin at 4 p.m. on both days at the facility located on Packard Drive between the Whiteman Tennis Center and Packard Stadium.

In order to try out for the team, students must first stop by the Sun Devil track & field office to pick up a purple form that is hanging on the front door. The form must be filled out completely and one copy of the form returned to the coaching staff NO LATER than 4:00 p.m. on Tuesday, September 7. The office is located on the second floor of the Carson Student-Athlete Center on the south side of Sun Devil Stadium (football stadium). Download Full Image

One of the requirements of the form is a physical and sickle cell test, both of which must be completed before the final signature may be obtained by the Office of Compliance. Physicals and sickle cell testing can be done anywhere, including the Student Health Center on campus. NOTE: it takes 48 hours to receive your sickle cell test results, so plan to get your tests done early before you begin the tryout process.

On September 8 and 9, each athlete trying out should be warmed-up and ready to go at 4 p.m. sharp at the common start-finish line on the track at Sun Angel Stadium. Starting at 4 p.m., each athlete will do the following:

September 8:
- Test #1: standing long jump (3 trials)
- Test #2: 30-meter sprint from a stand (2 trials)
- Test #3: 30-meter sprint with a 20-meter fly (2 trials)

September 9:
- Test #4: 45 second run (run as far as you can in 45 seconds)
- Test #5 (throwers only): javelin (softball throw), shot put (throw shot), discus (throw discus)

Following the two-day tryout period, the Sun Devil coaches will determine those that will join the program and will then post the list of accepted athletes on the Sun Devil Track & Field office door no later than noon on September 13.

For more information and to begin the tryout process, please stop by the track & field office or contact Coach Kenny">">K... McDaniel at (480) 965-2528.