Advertisement - Click to support our sponsors.

UH team IDs
first material in
solar system

Metal grains dating to the
solar system's formation are
found in a meteorite

By Helen Altonn
Star-Bulletin

University of Hawaii researchers have identified the first materials formed in the solar system 4.56 billion years ago, which may ultimately reveal how the system was formed.

The discoverers: Klaus Keil, UH Institute of Geophysics and Planetology director; postdoctoral fellow Anders Meibom; and assistant researcher Alexander Krot, with collaborators at Harvard University, NASA-Ames and Lancaster University, United Kingdom.

The team found metal grains in a primitive meteorite collected from the Antarctic ice sheet in 1991. Krot participated in the search expedition.

The iron and nickel grains represent the first solids found in the solar system, Meibom said from Stanford University.

"That gives us a window into the disk of gas we call the solar nebula," said Meibom, key investigator for the project.

The planets formed in that pancake-shape disk are lying in the same plane today, he noted.

He said the challenge for planetary scientists is to determine how the first solid materials formed and how the material clumped together to form larger bodies that became the nine planets.

The composition and texture of most components of ancient meteorites have been altered or destroyed, but the metal grains "look today as they looked five minutes after they formed," Meibom said.

"It's kind of miraculous that we have material that primitive."

The scientists now can look back into the solar nebula to see what it was like when the solar system formed, Meibom said.

The team believes the metals were formed within the solar nebula by a gas-solid condensation process, where atoms clump together into solid particles.

Studying the composition, temperature and pressure of the solar nebula gas and how fast the grains grew, the researchers determined that they formed at a "phenomenally fast cooling rate for a system as large as the solar nebula," Meibom said.

"We see a picture of extremely dynamic, almost violently fast-moving gas that is transporting these particles around."

Keil said the discovery, reported in the May 5 issue of Science, is one of the most exciting new developments in cosmochemistry, involving the study of extraterrestrial materials.

With the detection of materials dating back to the solar system's formation, Keil said, scientists can test astrophysical models based on theories.

"By being able to identify in these primitive meteorites materials which formed by condensation from a solar nebula, and by being able to determine the rate at which they cooled, we are coming up with boundary conditions for models on the origin of stars and solar systems," Keil said.

Somehow, astrophysical models will have to account for moving nebula gas from hot to cold rapidly, he said.

Keil recently received a $343,000 NASA grant to continue studies at the HIGP on the "Origin of Meteorite Parent Bodies and the Moon."

Krot said discovery of the preserved 4.56 billion-year-old grains is "very exciting," particularly since they were in a primitive meteorite he helped to locate.

He said he is primarily interested in the first 10 million years of solar system formation.

It is believed that some isotopes in meteorites existed only in that period, but they may be detected by looking at products of the decay, and isotopes produced by that decay, he said.

That requires sophisticated equipment that UH does not have but is available at Stanford, he said. He is continuing to work with Meibom on several projects, he said.

---

Ka Leo O Hawaii