San Francisco – Microscopic bits of dust from the tail of a comet are squashing widely held beliefs about the solar system and giving scientists an unprecedented look at the building blocks of life.
The tiny grains, captured by a spacecraft and hurled back to Earth in a capsule in January, contain clues to how the sun and planets formed from a giant gaseous cloud more than 4 billion years ago.
“It has really shaken up the common dogma of the early solar system,” said physicist John Bradley of Lawrence Livermore Laboratory, one of more than 200 scientists studying the comet dust from NASA’s $212 million Stardust project.
The dust is the first sample of material from beyond the giant planets ever to be collected. Bradley and eight other Livermore lab scientists have been analyzing the makeup of the dust particles using a one-of-a-kind atomic-resolution electron microscope.
“We’re looking at material that’s at least 4.6 billion years old.
That gives you goose bumps,” Bradley said. “The plain facts are, you’re looking at your atomic and molecular ancestors. It’s an eerie feeling.”
Some of the early results from the project were presented last week at the American Geophysical Union meeting in San Francisco, and published in the journal Science on Friday.
One of the biggest surprises is that the comet contained a mineral called osbornite that forms at extremely high temperatures – nearly 5,000 degrees – and must have come from near the sun.
This means that the solar system couldn’t have formed as was previously thought, from a slowly inward condensing cloud known as a solar nebula. Because the comet formed near the cold outer edges of the solar system, there must have been a great deal of mixing in the cloud. Material wasn’t moving only inward; some was moving outward.
“The last thing we expected to find was material from the inner solar system,” Bradley said. “Now it looks like the early solar nebula was much more dynamic and perhaps much more violent than we thought.”
Several theories about how mixing could occur in the solar nebula had previously been proposed, but no one took them seriously.
“Now we have to take them seriously,” astronomer Donald Brownlee of the University of Washington in Seattle said Thursday at the meeting. “We now have evidence that there was this mixing.”
Scientists are also busy studying organic matter found in the dust, something that wasn’t expected to survive the collection process and make it back to Earth intact.
And the organics that did make it are a far more diverse set than has been found in a meteorite.
“Some of it is new. It’s not like anything we’ve ever seen before,” said Scott Sandford of NASA Ames Research Center at Moffett Field.
The organic material, older than the solar system, could reveal clues about the origin of life and whether it exists elsewhere in the universe. Because there was some sort of mechanism that spread matter from the inner solar system to the outermost area where comets were formed, the same stuff must have been sprinkled on all the other comets and planets in the solar system.
“So if you need some magic ingredient, some pixie dust to get life to pop up somewhere, we have a mechanism to sprinkle it around,” Brownlee said.
