Discovery Adds Mystery to Earth's Genesis

Mike Wall, SPACE.com Senior Writer

Earth and the other rocky planets aren't made out of the solar system's original starting material, two new studies reveal.

Scientists examined solar particles snagged in space by NASA's Genesis probe, whose return capsule crash-landed on Earth in 2004. These salvaged samples show that the sun's basic building blocks differ significantly from those of Earth, the moon and other denizens of the inner solar system, researchers said.

Nearly 4.6 billion years ago, the results suggest, some process altered many of the tiny pieces that eventually coalesced into the rocky planets, after the sun had already formed.

"From any kind of consensus view, or longer historical view, this is a surprising result," said Kevin McKeegan of UCLA, lead author of one of the studies. "And it's just one more example of how the Earth is not the center of everything." [The Solar System To Scale (Infographic)]

Salvaging the samples

The Genesis spacecraft launched in 2001 and set up shop about 900,000 miles (1.5 million kilometers) from Earth. It spent more than two years grabbing bits of the solar wind, the million-mph stream of charged particles blowing from the sun.

The idea was to give scientists an in-depth look at the sun's composition, which in turn could help them better understand the formation and evolution of the solar system.

To that end, Genesis sent its sample-loaded return capsule back to Earth in September 2004. But things didn't go well; the capsule's parachute failed to deploy, and it smashed into the Utah dirt at 190 mph (306 kph).

While some of Genesis' samples were destroyed in the crash, others were salvageable, as the two new studies show. Two different research teams looked at the solar wind particles' oxygen and nitrogen — the most abundant elements found in Earth's crust and atmosphere, respectively.

And they did so with a great deal of care, knowing that the crash had limited their supplies of pristine solar material.

"The stakes were raised on the samples that did survive well," McKeegan told SPACE.com. "There wasn't as much to go around."

Analzying oxygen

McKeegan and his team measured the abundance of solar wind oxygen isotopes. Isotopes are versions of an element that have different numbers of neutrons in their atomic nuclei. Oxygen has three stable isotopes: oxygen-16 (eight neutrons), oxygen-17 (nine neutrons) and oxygen-18 (ten neutrons).

The researchers found that the sun has significantly more oxygen-16, relative to the other two isotopes, than Earth. Some process enriched the stuff that formed our planet — and the other rocky bodies in the inner solar system — with oxygen-17 and oxygen-18 by about 7 percent. [Amazing New Sun Photos From Space]

While scientists don't yet know for sure how this happened, they have some ideas. The leading contender, McKeegan said, may be a process called "isotopic self-shielding."

About 4.6 billion years ago, the planets had not yet coalesced out of the solar nebula, a thick cloud of dust and gas. Much of the oxygen in this cloud was probably bound up in gaseous carbon monoxide (CO) molecules.

But the oxygen didn't stay bound up forever. High-energy ultraviolet light from the newly formed sun (or nearby stars) blasted into the cloud, breaking apart the CO. The liberated oxygen quickly glommed onto other atoms, forming molecues that eventually became the rocky building blocks of planets.

Photons of slightly different energy were required to chop up the CO molecules, depending on which oxygen isotope they contained. Oxygen-16 is far more common than either of the other two, so there would have been much more of this substance throughout the solar nebula, researchers said.

The result, the self-shielding theory goes, is that many of the photons needed to break up the oxygen-16 CO were "used up," or absorbed, on the edges of the solar nebula, leaving much of the stuff in the cloud's interior intact.

By contrast, relatively more of the photons that could strip out oxygen-17 and oxygen-18 got through to the inner parts of the cloud, freeing these isotopes, which were eventually incorporated into the rocky planets. And that, according to the theory, is why the sun and Earth's oxygen isotope abundances are so different.

"The result that we're publishing this week gives support to the self-shielding idea," McKeegan said. "But we don't know the answer yet."

Nitrogen, too

In a separate study, another research team led by Bernard Marty of Nancy University in France analyzed the nitrogen isotopes in Genesis' samples. (Nitrogen has two stable isotopes: nitrogen-14, which has seven neutrons, and nitrogen-15, which has eight.)

Marty and his colleagues found an even more dramatic difference than McKeegan's group did: The solar wind has about 40 percent less nitrogen-15 (compared to nitrogen-14) than do samples taken from Earth's atmosphere.

Previous studies had hinted that the sun's nitrogen might be very different from that of Earth, Mars and other rocky bodies in the inner solar system, Marty said. But the new study establishes this firmly.

"Before Genesis and the present measurement of the N isotopic composition of the solar wind and by extension of the sun, it was not possible to understand the logic of such variations," Marty told SPACE.com in an email interview. "Now we understand that the starting composition, the solar nebula, was poor in 15N, so that variations among solar system objects are the result of mixing with a 15N-rich end-member."

As to how this enrichment of nitrogen-15 could have happened, Marty as well suggests some type of self-shielding as a possible mechanism. But it's not a certainty.

"This is a scenario that is consistent with present-day observations," he said. "We cannot eliminate yet the possibility that these 15N-rich compounds were imported from outer space as dust in the solar system."

The new results also suggest that most nanodiamonds — tiny carbon specks that are a major component of stardust — likely formed in our own solar system, because they share similar nitrogen isotope ratios with the sun. Some scientists have regarded nanodiamonds as being primarily presolar, thinking they were ejected from other stellar systems by supernova explosions.

Both studies appear in the June 23 issue of the journal Science.

Genesis' legacy

The two new studies should help scientists get a better understanding of the solar system's early days, researchers said.

And the results should help rehabilitate the reputation of the $264 million Genesis mission, showing that the capsule crash didn't render it a failure, McKeegan said.

"We managed to accomplish all the science that we set out to do, all the important stuff," he said. "The enduring image in everybody's mind — the picture of the crashed spacecraft in the desert — will be more of a footnote instead of the primary thing that people remember. That's my hope, anyway."

You can follow SPACE.com senior writer Mike Wall on Twitter: @michaeldwall. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

• Top 10 Extreme Planet Facts 
• Spectacular Photos of Nebulas in Deep Space 
• How Planets in Alien Solar Systems Stack Up (Infographic) 
• VIDEO: Genesis Probe Crash Down to Earth 

http://news.yahoo.com/s/space/20110623/sc_space/discoveryaddsmysterytoearthsgenesis

Galaxies formed sooner after Big Bang than thought

PARIS (AFP) – Astronomers said on Tuesday they believed the first galaxies formed just 200 million years after the Big Bang, a finding that challenges assumptions of how the Universe grew from infancy into childhood.

Their evidence comes from a remote galaxy whose glimmer of light was teased open to reveal the presence of truly ancient stars.

"We have discovered a distant galaxy that began forming stars just 200 million years after the Big Bang," said lead author Johan Richard, an astrophysicist at the Lyon Observatory, southeastern France.

"This challenges theories of how soon galaxies formed and evolved in the first years of the Universe. It could even help solve the mystery of how the hydrogen fog that filled the early Universe was cleared."

The oldest galaxy previously detected and confirmed was created some 480 million years after the Big Bang.

To all appearances, the new finding could lay a claim on being the record-beater.

But no such claims are being made because the discovery was made indirectly, rather than through direct observation, Richard told AFP.

Richard's team used a technique called gravitational lensing.

Under this, the light from the galaxy was observed by the Hubble and Spitzer orbital telescopes after it had been amplified by the gravitational pull of a second galaxy that, by sheer chance, lay on a direct line with Earth.

Without this gravitational amplification, the light from the distant galaxy would have been undetectable because it was so faint.

Using the Keck II spectroscopic telescope in Hawaii to analyse the light, the team found that the galaxy's redness -- a telltale of age -- gave a reading of 6.027.

In layman's terms, this says the light arriving here today was emitted when the Universe was 950 million years old. By comparison, the earliest known galaxy, reported in January, had a whopping "redshift" of 10.3.

However, hidden in the bundle of infrared data from Spitzer were signs that many stars in the galaxy were surprisingly old and relatively faint.

"This told us that the galaxy was made up of stars already nearly 750 million years old -- pushing back the epoch of its formation to about 200 million years after the Big Bang, much further than we had expected," said Eiichi Egami of the University of Arizona.

Under the Big Bang theory, the Universe originated in a superheated flash around 13.7 billion years ago and started to expand.

After the nascent cosmos cooled a little, electrons and protons teamed up to form hydrogen, the most primitive element, and for hundreds of millions of years, this gas filled the Universe.

How the fog lifted is one of the big mysteries.

One idea is that radiation from galaxies ionised the gas. But this would have been impossible as there were clearly not enough galaxies available to do so.

The answer, in fact, could be simple, said Jean-Paul Kneib, a Marseille-based astrophysicst with France's National Centre for Scientific Research (CNRS).

"It seems probable that there are in fact far more galaxies out there in the early Universe than we previously estimated -- it's just that many galaxies are older and fainter, like the one we have just discovered," he said in a press release.

"If this unseen army of faint, elderly galaxies is indeed out there, they could provide the missing radiation that made the Universe transparent to ultraviolet light."

http://news.yahoo.com/s/afp/20110412/sc_afp/spaceastronomygalaxy

Astronomers claim earliest galaxy yet from Hubble

Seth Borenstein, Ap Science Writer

WASHINGTON – An international team of astronomers say they've glimpsed the earliest galaxy yet, a smudge of light from nearly 13.2 billion years ago — a time when the cosmos was a far lonelier place.

The research hasn't been confirmed, and some astronomers are skeptical. The new findings are based on an image from the Hubble Space Telescope and are published in Thursday's issue of the journal Nature. The scientists calculate the new-found galaxy dates to just 480 million years after the Big Bang.

That would trump last fall's announcement by a French team who said they found a galaxy from about 600 million years after the Big Bang. That discovery also is not universally accepted and one of the skeptics is the co-author of the latest paper.

Even more interesting than the advanced age of the newly discovered galaxy is the absence of other similarly aged bright galaxies. That indicates that star formation during that point in the universe's early childhood was happening at a rate 10 times slower than it was millions of years later, said study co-author Garth Illingworth of the University of California Santa Cruz.

Illingworth described what the cosmos might look like at that time period when the universe was smaller and the stars bluer and dimmer.

"It wouldn't be nearly as interesting — a blob here, a blob there," he said in a phone interview.

But other astronomers have their doubts about this discovery.

Richard Ellis at the California Institute of Technology is troubled because Illingworth's team originally found three 13.2 billion-year-old galaxies and then withdrew their original study. The authors then came up with an entirely different galaxy, so all that switching "makes it difficult to believe," he said.

Illingworth said originally he and colleagues confused what may have been real light from billions of years ago and background "noise" from the process of looking so far away, so they re-did the study. He said they then found the new galaxy and saw that it was more likely to be real than the previous ones.

"We made a mistake and luckily we had ways to catch it before we went out and it was formally published," said Illingworth whose co-authors included astronomers from the Netherlands and Switzerland.

Ellis and Henry Ferguson of the Space Telescope Science Institute said they were also worried that the Illingworth team only used one of several telescope filters to find this galaxy. They speculated that they might have found an object that's much nearer.

Illingworth acknowledged in his paper that there is a 20 percent chance that the smudge they found is contamination, but "we're pretty sure it's a real object."

Ferguson said Illingworth did "a very good job of making that detection convincing."

The vaunted 20-year-old Hubble telescope has progressively produced images of older and more distant objects. Peering earlier into space will require the more advanced cameras of NASA's new James Webb Space Telescope, Illingworth said. However, it isn't likely to launch until at least 2015.

The farther away a galaxy, the longer it takes for light from it to travel, so seeing the most distant galaxies is like looking back in time. If the new research is correct, light from the newly found galaxy would have traveled 13.2 billion light years to be seen by Hubble.

Online:

Nature: www.nature.com/nature 

Online:

http://www.nature.com/nature

http://news.yahoo.com/s/ap/20110127/ap_on_sc/us_sci_oldest_galaxy