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Friday, 28 October 2011

Stars create complex organic molecules

Complex organic molecules like those on which life is based exist throughout the universe and can be made naturally by stars, European Space Agency data has revealed.
Professor Sun Kwok and Dr Yong Zhang of the University of Hong Kong say they've found compounds so complex that their chemical structures resemble those of coal and petroleum.
The find suggests that complex organic compounds can be synthesized in space without the presence of life forms.
"Our work has shown that stars have no problem making complex organic compounds under near-vacuum conditions," says Kwok. "Theoretically, this is impossible, but observationally we can see it happening."
The researchers were investigating a set of infrared emissions detected in stars, interstellar space and galaxies, and known as Unidentified Infrared Emission features.
These signatures were believed to have come from simple organic molecules made of carbon and hydrogen atoms, called polycyclic aromatic hydrocarbon (PAH) molecules.
But, using the Infrared Space Observatory and the Spitzer Space Telescope, Kwok and Zhang discovered that the spectra have features that can't be explained by PAH molecules.
Instead, they say, the substances generating these infrared emissions have chemical structures that are much more complex.
Analysis of the spectra of star dust formed in novae shows that stars are making these complex organic compounds in a matter of weeks, and then ejecting it into the general interstellar space.
Interestingly, this organic star dust is similar in structure to the complex organic compounds found in meteorites, and could form their source. Thus, it's possible that life on Earth developed from this organic star dust

Battered asteroid Lutetia revealed as ancient baby planet that never fully formed

A battered, pockmarked object floating in the asteroid belt between Mars and Jupiter has been revealed as an ancient fledging planet, formed when Earth was in its infancy.
The European Space Agency’s comet-hunting probe Rosetta flew past the asteroid Lutetia last year and studied it with thermal and spectroscopic sensors.
What it discovered is that Lutetia is no ordinary asteroid – but actually a primitive ‘mini-world’ that used to be round and may even have tried to grow a metal heart like a fully formed planet.
For the crater good: Lutetia has been revealed as a fledgling planet containing huge amounts of iron that was around when Earth was born
For the crater good: Lutetia has been revealed as a fledgling planet containing huge amounts of iron that was around when Earth was born
Astronomers believe that Lutetia should really be described as a planetesimal, a body formed from clumps of cosmic grains.

These have the potential to grow into planets, because once they reach around 3,000 feet in width they develop gravity that can attract other masses.
Asteroids, on the other hand, are formed from collisions between planets and other asteroids.
Rosetta flew past Lutetia on 10 July 2010 at a speed of nine miles a second and came within 1,969 miles of it.
Heavenly body: The ESA's Rosetta probe analysed Lutetia with thermal and spectroscopic sensors to reveal that it is no ordinary floating rock
Heavenly body: The ESA's Rosetta probe analysed Lutetia with thermal and spectroscopic sensors to reveal that it is no ordinary floating rock
At the time, the 80-mile-long asteroid was the largest encountered by a spacecraft.
Images from Rosetta’s instruments reveal that parts of Lutetia’s surface are around 3.6billion years old.
Other parts are young by astronomical standards, at 50 to 80million years old.
Astronomers estimate the age of airless planets, moons, and asteroids by counting craters.
Each bowl-shaped depression on the surface is made by an impact. The older the surface, the more impacts it will have accumulated.
Exploration: An artist's rendition shows the Rosetta orbiter, top, and lander, which it uses to reach the surface of comets
Exploration: An artist's rendition shows the Rosetta orbiter, top, and lander, which it uses to reach the surface of comets
Some parts of Lutetia are heavily cratered, implying that it is very old.
On the other hand, the youngest areas of Lutetia are landslides, probably triggered by the vibrations from particularly jarring nearby impacts.
Debris resulting from these many impacts now lies across the surface as a 3,000ft-thick layer of pulverised rock.
There are also boulders strewn across the surface: some are 1,300-feet across, or about half the size of Ayers Rock, in Australia.
Some impacts must have been so large that they broke off whole chunks of Lutetia, gradually sculpting it into the battered wreck we see today.
‘We don’t think Lutetia was born looking like this,’ says Holger Sierks, Max-Planck-Institut für Sonnensystemforschung, Lindau, Germany. ‘It was probably round when it formed.’
Rosetta also let scientists investigate beneath the asteroid’s surface.
It appears that Lutetia tried to grow an iron core like a bona-fide planet when it formed.
Ready for take-off: Rosetta was launched on board the Ariane-5 launcher from the European Spaceport in Kourou, French Guiana, in 2004
Ready for take-off: Rosetta was launched on board the Ariane-5 launcher from the European Spaceport in Kourou, French Guiana, in 2004
During the encounter, Lutetia’s weak gravity tugged on Rosetta. The slight change in Rosetta’s path was reflected in radio signals received back at Earth, indicating a mass of 1.7 million billion tons.
This was a surprise.
‘The mass was lower than expected. Ground-based observations had suggested much higher values,’ says Martin Pätzold, Universität zu Köln, Germany, leader of the radio science team.
Nevertheless, when combined with its volume, Lutetia still turns out to have one of the highest densities of any known asteroid: 3400 kg per cubic meter.
The density implies that Lutetia contains significant quantities of iron, but not necessarily in a fully formed core.
To form an iron core, Lutetia would have had to melt as a result of heat released by radioactive isotopes in its rocks. The dense iron would then sink to the centre and the rocky material would float to the top.
However, Lutetia’s spectrometer indicates that the body’s surface composition remains entirely primordial, displaying none of the rocky material expected to form during such a molten phase.
The only explanation appears to be that Lutetia was subjected to some internal heating early in its history but did not melt completely and so did not end up with a well-defined iron core.
These results, all gathered during just a short flyby, make Lutetia a unique asteroid and an invaluable postcard from the past, at a time when Earth was forming.
‘We picked a most important member of the asteroid belt,’ said Rita Schulz, ESA’s Rosetta Project Scientist. ‘All the asteroids encountered so far were different from each other, but Lutetia is the only one in which both primordial and differentiation features have been found.
‘These unexpected results clearly show that there is still much more to investigate before we understand the belt fully.’
Having now left Lutetia far behind, Rosetta is in hibernation and en route to its 2014 rendezvous with comet Churyumov-Gerasimenko.