From chemical fingerprints preserved in primitive meteorites, scientists at the University of California, San Diego have determined that the collapsing gas cloud that eventually became our sun was glowing brightly during the formation of the first material in solar system more than 4.5 billion years ago.

Their discovery, detailed in a paper that appears in the August 12 issue of Science, provides the first conclusive evidence that this "protosun" played a major role in chemically shaping the solar system by emitting enough ultraviolet energy to catalyze the formation of organic compounds, water and other compounds necessary for the evolution of life on Earth. Scientists have long argued whether the chemical compounds created in the early solar system were produced with the help of the energy of the early sun or were formed by other means.

"The basic question was, Was the sun on or was it off?" says Mark H. Thiemens, Dean of UCSD's Division of Physical Sciences and chemistry professor who headed the research team that conducted the study. "There is nothing in the geological record before 4.55 billion years ago that could answer this."

...

"This measurement tells us for the first time that the sun was on, that there was enough ultraviolet light to do photochemistry," says Thiemens. "Knowing that this was the case is a huge help in understanding the processes that formed compounds in the early solar system."

Astronomers believe the solar nebula began to form about 5 billion years ago when a cloud of interstellar gas and dust was disturbed, possibly by the shock wave of a large exploding star, and collapsed under its own gravity. As the nebula's spinning pancake-like disk grew thinner and thinner, whirlpools of clumps began to form and grow larger, eventually forming the planets, moons and asteroids. The protosun, meanwhile, continued to contract under its own gravity and grew hotter, developing into a young star. That star, our sun, emanated a hot wind of electrically charged atoms that blew most of the gas and dust that remained from the nebula out of the solar system.

Planets, moons and many asteroids have been heated and had their material reprocessed since the formation of the solar nebula. As a result, they have had little to offer scientists seeking clues about the development of the solar nebula into the solar system. However, some primitive meteorites contain material that has remained unchanged since the protosun spewed this material from the center of the solar nebula more than 4.5 billion years ago.

Thiemens says the technique his team used to determine that the protosun was glowing brightly also can be applied to estimate when and where various compounds originated in the hot wind spewed out by the protosun.

"That will be the next goal," he says. "We can look mineral by mineral and perhaps say here's what happened step by step."

More: http://ucsdnews.ucsd.edu/newsrel/science/mcmeteorite.asp
1:13:25 PM    comment []  

Nothing trying. Just a walk across the road, up the track, and along the top of the low western ridge to my old sitting rock.

The last time I came here everything was green and bursting into bloom, or about to, and the ground was still soft from snowmelt and spring rain. Now it's hard and dry, waffled bootprints from my spring hikes appear chased into stone alongside the deep mated teardrops of impressed deer hoofs. Almost all the herbaceous plants and grasses are dead-dry, long gone to seed. Here and there I see an artemisia or rabbitbrush, still green and tender, who love the hot months best. Next largest, the purshias--bitterbrush--shoulder-high old men of the slopes, beloved of antelope and rabbit, the pale green-white blooms that frothed them over months ago gone brown now at the tips of their black scraggly limbs.

Those perfumers the junipers celebrate summer. These so-called "trash" trees stand jewelled with fat brilliant blue new berries. I close my eyes, lean into their bright rigid green, and inhale. The sun-warmed scaly needles give off an incense to rival even autumn-rain-on-sagebrush.

A good sound silence this morning: hiss of dry grasses moving in the heated air. Rhythms of a distant quail's repetitive call. At acceptable intervals you can hear the crunch of vehicle wheels in gravel, the creaks and squeaks of a livestock trailer rattling over the bad dirt roads. An intermittant clack and rattle of locusts against the erect dead leaves of May's balsamroot, which clatter anyway when they knock together in a breeze. The horse people across the way recently built a new small stable and corral, and so whinnies, nickers, and snorts insert themselves into the local music.

I hear an elder goat's throaty maaa from somewhere nearby. My downstream neighbor's dozen-and-a-half meat goats defeat all his fences, and so they roam by day in a tight herd grazing up and down these hills and ridges and dirt roads, and trot home to their enclosures every night. I enjoy watching them from a distance, but it sends a chill when I think what they could do to my unfenced herb garden. I'm a good half-mile south and east, at least, though, and they haven't found me yet, and I imagine the dogs discourage them when they get too close.

Due east, Bald Mountain lies revealed between the low shoulders of its companions. Few peaks at this (northernmost) end of the Warner Mountains actually "stand"; it's a youthful range. It would be easy in fact to think of it as Bald Hill were it not for its 8000+-foot elevation. In July a year ago it was still snowcovered, but this year it's been bare of snow since mid-May, and now I see even its green is retreating downslope into folds and crevices ahead of the brown of its drying crown.

The air is good, moving in little puffs around the stones, and so is the forbearing forenoon light. Even the heat is good. I knew it would be.
1:07:24 PM    comment []  

"HHMI researchers have harnessed a mobile gene from the cabbage looper moth and modified it for routine use to determine the function of genes in mice and other vertebrates.

"If the new tool works as they expect, it will speed understanding of genes involved in human biology and disease and accelerate the search for effective new therapies."

Research published in the August 12, 2005, issue of Cell.

For the full story, go to http://www.hhmi.org//news/xu4.html

[Photo borrowed from http://ccvipmp.ucdavis.edu/insects/worms.html.]
10:38:25 AM    comment []