StarDust Dust

[smita]

Pardon me for a non-APOD question. But this is the only place I know where someone may have the answer.

Just heard on the news that the scientists discovered proteins critical to life in StarDust dust. And that may be a comet similar to that would have brought life to Earth.

Well, my question is why do we think that some extra-terrestrial object would have brought these life-critical chemicals to our great planet? In other words, why do we think that these proteins could not be native to Earth?After all, Earth does seem to have all the necessary ingredients of the recipe. Even if some disaster (cosmic or earth-based) destroyed all life on earth, I doubt the small organisms would have been destroyed, specially given that now we know there are creatures that can survive in all kinds of environs.

Thanks much.
Smita

[neufer]

Just heard on the news that the scientists discovered proteins critical to life in StarDust dust. And that may be a comet similar to that would have brought life to Earth. Well, my question is why do we think that some extra-terrestrial object would have brought these life-critical chemicals to our great planet? In other words, why do we think that these proteins could not be native to Earth? After all, Earth does seem to have all the necessary ingredients of the recipe. Even if some disaster (cosmic or earth-based) destroyed all life on earth, I doubt the small organisms would have been destroyed, specially given that now we know there are creatures that can survive in all kinds of environs.

I think that all options are on the table in this regard.

Cometary impacts are especially nice, however, since they provide their own water source.

The discovery of amino acids in cometary dust bolsters the idea that amino acids are actually quite easy to generate naturally and they should be fairly ubiquitous in the universe.
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<<The Murchison meteorite that fell near Murchison, Victoria, Australia in 1969 was found to contain over 90 different amino acids, nineteen of which are found in Earth life.>>

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<<In 2008, a group of scientists examined 11 vials left over from Miller's experiments of the early 1950s. In addition to the classic experiment, reminiscent of Charles Darwin's envisioned "warm little pond", Miller had also performed more experiments, including one with conditions similar to those of volcanic eruptions. This experiment had a nozzle spraying a jet of steam at the spark discharge. By using high-performance liquid chromatography and mass spectrometry, the group found more organic molecules than Miller had. Interestingly, they found that the volcano-like experiment had produced the most organic molecules, 22 amino acids, 5 amines and many hydroxylated molecules, which could have been formed by hydroxyl radicals produced by the electrified steam. The group suggested that volcanic island systems became rich in organic molecules in this way, and that the presence of carbonyl sulfide there could have helped these molecules form peptides.>>

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<<New analysis of tiny particles captured by the Stardust comet-chasing probe has revealed for the first time the presence of traces of an amino acid called glycine, a basic component of proteins without which life as we know it could not exist. The discovery, by Nasa scientists, supports a theory that the raw material from which life began first formed in space, and was carried to Earth by comets that crashed into the planet. It also means that other planets are likely to have been seeded with amino acids from comets in a similar fashion, suggesting that extraterrestrial life may well have evolved elsewhere in the Universe and could even be common.

“Glycine is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet,” said Jamie Elsila, of Nasa’s Goddard Space Flight Centre in Maryland, who led the research. “Our discovery supports the theory that some of life’s ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts.”

Carl Pilcher, director of the Nasa Astrobiology Institute, said: “The discovery of glycine in a comet supports the idea that the fundamental building blocks of life are prevalent in space, and strengthens the argument that life in the Universe may be common rather than rare.” The discovery is the latest to come from Nasa’s unmanned Stardust mission, which flew through the cloud of dust and debris trailing the Wild 2 comet on January 2, 2004. Millions of tiny particles from the comet’s tail were captured by a grid filled with aerogel, a super-light, sponge-like material sometimes nicknamed “frozen smoke” because 99 per cent of its volume is empty space. A capsule containing the collection grid detached from the spacecraft soon after its close encounter with Wild 2 and returned to Earth, where it parachuted to the surface on January 15, 2006. Scientists have since been examining the contents of the capsule for clues about the early solar system.

All forms of life on Earth rely on proteins, which drive chemical reactions in their cells and form many of the structural elements around which organisms are built. This huge variety of proteins are all made up of chains of 20 amino acids. The origin of amino acids has long been debated among scientists, with some favouring the view that they emerged in the primordial soup of the planet’s youth, and others proposing that they formed in space and came here on comets and meteorites.

The discovery of glycine in the Stardust samples points towards an extraterrestrial origin for at least one of the 20 amino acids.

Dr Elsila’s team first identified traces of glycine last year, in particles removed both from the aerogel and aluminium foil around it. As glycine is also present on Earth, however, the scientists had to confirm that it originated from space. The team used isotopic analysis to examine the chemical composition of the glycine. Many elements occur in different isotopes, or versions, which have different masses. “We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet,” Dr Elsisa said.>>

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<<Glycine (abbreviated as Gly or G) is the organic compound with the formula NH2CH2COOH. It is the smallest of the 20 amino acids commonly found in proteins, coded by codons GGU, GGC, GGA and GGG. Glycine is unique among the proteinogenic amino acids in that it is not chiral. Most proteins incorporate only small quantities of glycine. A notable exception is collagen, which contains about 35% glycine. Solid glycine is a colourless, sweet-tasting crystalline material.>>

[Chris Peterson]

Just heard on the news that the scientists discovered proteins critical to life in StarDust dust. And that may be a comet similar to that would have brought life to Earth.

Well, my question is why do we think that some extra-terrestrial object would have brought these life-critical chemicals to our great planet? In other words, why do we think that these proteins could not be native to Earth?After all, Earth does seem to have all the necessary ingredients of the recipe. Even if some disaster (cosmic or earth-based) destroyed all life on earth, I doubt the small organisms would have been destroyed, specially given that now we know there are creatures that can survive in all kinds of environs.

The fact that amino acids are found in meteorites, and now in comets, doesn't necessarily suggest that these important organic molecules came to Earth from space (although it certainly seems that some material did). The important lesson is that these chemicals do not require the conditions found only on Earth in order to form. Knowing that they are apparently ubiquitous in extraterrestrial material provides support for the idea there may be life elsewhere in the Solar System, and that the building blocks of life are easily formed under conditions probably found all over the Universe- not just on Earth-like planets.

[harry]

G'day

There are various theories as to the origin and evolution of life on Earth.

Earth a few billion years ago was like Venus unable to sustain life.

We know that complex carbon molecules can be formed here on Earth and "Out There".

When the Earth started to cool down these complex carbon molecules started mixing within the pasta soup, evolving and changing and given enough time evolved into complex living things.

So in a way we can think that the seeds for life can be found out there.

We are part of the "OUT THERE".

[bystander]

NASA Researchers Make First Discovery of Life's Building Block in Comet
NASA Mission News - Stardust-NExT - 08.17.09

NASA scientists have discovered glycine, a fundamental building block of life, in samples of comet Wild 2 returned by NASA's Stardust spacecraft.

"Glycine is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet," said Dr. Jamie Elsila of NASA's Goddard Space Flight Center in Greenbelt, Md. "Our discovery supports the theory that some of life's ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts."
...
"The discovery of glycine in a comet supports the idea that the fundamental building blocks of life are prevalent in space, and strengthens the argument that life in the universe may be common rather than rare," said Dr. Carl Pilcher, Director of the NASA Astrobiology Institute which co-funded the research. ...

http://stardustnext.jpl.nasa.gov/
http://www.nasa.gov/mission_pages/stard ... index.html

[neufer]

There are various theories as to the origin and evolution of life on Earth.

Earth a few billion years ago was like Venus unable to sustain life.

Earth a few billion years ago was like Australia : unable to sustain sophisticated life.

Stromatolites at Lake Thetis, Western Australia


<<Stromatolites (from Greek στρώμα, strōma, mattress, bed, stratum, and λιθος, lithos, rock) are layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria (commonly known as blue-green algae). They include some of the most ancient records of life on Earth. A variety of stromatolite morphologies exist including conical, stratiform, branching, domal,[1] and columnar types. Stromatolites occur widely in the fossil record of the Precambrian, but are rare today. Very few ancient stromatolites contain fossilized microbes. While features of some stromatolites are suggestive of biological activity, others possess features that are more consistent with abiotic (non-organic) precipitation. Finding reliable ways to distinguish between biologically-formed and abiotic (non-biological) stromatolites is an active area of research in geology.

Stromatolites were much more abundant on the planet in Precambrian times. While older, Archean fossil remains are presumed to be colonies of single-celled blue-green bacteria, younger (that is, Proterozoic) fossils may be primordial forms of the eukaryote chlorophytes (that is, green algae). One genus of stromatolite very common in the geologic record is Collenia. The earliest stromatolite of confirmed microbial origin dates to 2,724 million years ago. A recent discovery provides strong evidence of microbical stromatolites extending as far back as 3,450 million years ago.

Stromatolites are a major constituent of the fossil record for about the first 3.5 billion years of life on earth, with their abundance[verification needed] peaking about 1,250 million years ago. They subsequently declined in abundance and diversity, which by the start of the Cambrian had fallen to 20% of their peak. The most widely-supported explanation is that stromatolite builders fell victims to grazing creatures (the Cambrian substrate revolution), implying that sufficiently complex organisms were common over 1 billion years ago. The connection between grazer and stromatolite abundance is well documented in the younger Ordovician evolutionary radiation; stromatolite abundance also increased after the end-Ordovician and end-Permian extinctions decimated marine animals, falling back to earlier levels as marine animals recovered.

While prokaryotic cyanobacteria themselves reproduce asexually through cell division, they were instrumental in priming the environment for the evolutionary development of more complex eukaryotic organisms. Cyanobacteria are thought to be largely responsible for increasing the amount of oxygen in the primeval earth's atmosphere through their continuing photosynthesis. Cyanobacteria use water, carbon dioxide, and sunlight to create their food. The byproducts of this process are oxygen and calcium carbonate (lime). A layer of mucus often forms over mats of cyanobacterial cells. In modern microbial mats, debris from the surrounding habitat can become trapped within the mucus, which can be cemented together by the calcium carbonate to grow thin laminations of limestone. These laminations can accrete over time, resulting in the banded pattern common to stromatolites. The domal morphology of biological stromatolites is the result of the vertical growth necessary for the continued infiltration of sunlight to the organisms for photosynthesis.

Modern stromatolites are mostly found in hypersaline lakes and marine lagoons where extreme conditions due to high saline levels exclude animal grazing. One such location is Hamelin Pool Marine Nature Reserve, Shark Bay in Western Australia where excellent specimens are observed today, and another is Lagoa Salgada, state of Rio de Janeiro, Brazil, where modern stromatolites can be observed as bioherm (domal type) and beds. Inland stromatolites can also be found in saline waters in Cuatro Ciénegas, a unique ecosystem in the Mexican desert. Modern stromatolites are only known to prosper in an open marine environment in the Exuma Cays in the Bahamas.>>

[bystander]

NAI Research Reveals Major Insight into Evolution of Life on Earth
NASA Astrobiology Institute - 2009 August 19

Humans might not be walking on Earth today if not for the ancient fusing of two microscopic, single-celled organisms called prokaryotes, NASA-funded research has found.

By comparing proteins present in more than 3000 different prokaryotes – a type of single-celled organism without a nucleus – molecular biologist James A. Lake ... showed that two major classes of relatively simple microbes fused together more than 2.5 billion years ago. Lake’s research reveals a new pathway for the evolution of life on Earth. ...

This endosymbiosis, or merging of two cells, enabled the evolution of a highly stable and successful organism with the capacity to use energy from sunlight via photosynthesis. Further evolution led to photosynthetic organisms producing oxygen as a byproduct. The resulting oxygenation of Earth’s atmosphere profoundly affected the evolution of life, leading to more complex organisms that consumed oxygen, which were the ancestors of modern oxygen-breathing creatures including humans.

“Higher life would not have happened without this event,” Lake said. “These are very important organisms. At the time these two early prokaryotes were evolving, there was no oxygen in the Earth’s atmosphere. Humans could not live. No oxygen-breathing organisms could live.” ...

[apodman]

So did plant life and animal life both evolve from the same line of cellular life, or did conditions and predecessor organisms produce two separate lines? Is there any genetic correlation between plant DNA and animal DNA?

the cells of all plants and all animals contain DNA in the same shape – the famous “double helix” that looks like a twisted ladder. What’s more, all DNA molecules – in both plants and animals – are made from the same four chemical building blocks – called nucleotides.

What is different is how these four nucleotides in DNA are arranged. It’s their sequence that determines which proteins will be made. The way the nucleotides are arranged, and the information they encode, decides whether the organism will produce scales or leaves – legs or a stalk

[NoelC]

This is a trivial logic problem.

Given the virtually infinite (or astronomically large) universe, life is either... Impossible or inevitable.

I vote for the latter.

-Noel

[harry]

G'day

We know life is "Out There", its not probable it's definite.

or else I would not be saying G'day.

[Qev]

So did plant life and animal life both evolve from the same line of cellular life, or did conditions and predecessor organisms produce two separate lines? Is there any genetic correlation between plant DNA and animal DNA?

Plants, animals, and fungi are all pretty closely related, as these things go. I daresay their mutual last common ancestor was quite a while back, but they're all eukaryotes and almost certainly share ancestry. We're certainly closer to plants and fungi than we are to things like the prokaryotes or the archaea.

[harry]

G'day from the land of ozzzzzzz

Evolution of Prokaryotes
http://en.wikipedia.org/wiki/Prokaryote

The current model of the evolution of the first living organisms is that these were some form of prokaryotes, which may have evolved out of protobionts. The eukaryotes are generally thought to have evolved later in the history of life.[15] However, some authors have questioned this conclusion, arguing that the current set of prokaryotic species may have evolved from more complex eukaryotic ancestors through a process of simplification.[16][17][18] Others have argued that the three domains of life arose simultaneously, from a set of varied cells that formed a single a gene pool.[19] This controversy was summarized in 2005:[20]

There is no consensus among biologists concerning the position of the eukaryotes in the overall scheme of cell evolution. Current opinions on the origin and position of eukaryotes span a broad spectrum including the views that eukaryotes arose first in evolution and that prokaryotes descend from them, that eukaryotes arose contemporaneously with eubacteria and archeabacteria and hence represent a primary line of descent of equal age and rank as the prokaryotes, that eukaryotes arose through a symbiotic event entailing an endosymbiotic origin of the nucleus, that eukaryotes arose without endosymbiosis, and that eukaryotes arose through a symbiotic event entailing a simultaneous endosymbiotic origin of the flagellum and the nucleus, in addition to many other models, which have been reviewed and summarized elsewhere.

The oldest known fossilized prokaryotes were laid down approximately 3.5 billion years ago, only about 1 billion years after the formation of the Earth's crust. Even today, prokaryotes are perhaps the most successful and abundant life forms. Eukaryotes only appear in the fossil record later, and may have formed from endosymbiosis of multiple prokaryote ancestors. The oldest known fossil eukaryotes are about 1.7 billion years old. However, some genetic evidence suggests eukaryotes appeared as early as 3 billion years ago.[21

It seems there is a logical start with Prokaryotes evolving into Eukaryotes and other branches of life.

[neufer]

The presence of steranes in Australian shales indicates that eukaryotes [started evolving] about 2.7 billion years ago.

Steranes are a class of 4-cyclic compounds derived from steroids or sterols via diagenetic and catagenetic degradation and saturation. They are sometimes used as biomarkers for the presence of eukaryotic cells. The sterane structure constitutes the core of all sterols and steroids.

Eukaryotes are more closely related to Archaea than Bacteria, at least in terms of nuclear DNA and genetic machinery, and one controversial idea is to place them with Archaea in the clade Neomura.

It seems there is a logical start with Prokaryotes evolving into Eukaryotes and other branches of life.

• Friends and Family
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Most eukaryotes are now included in one of the following supergroups:

Code: Select all

Opisthokonts 	Animals, fungi, choanoflagellates, etc.

Amoebozoa 	Most lobose amoeboids and slime moulds

Rhizaria 	Foraminifera, Radiolaria, and various other amoeboid protozoa

Excavates 	Various flagellate protozoa

Archaeplastida (or Primoplantae) 	Land plants, green algae, red algae, and glaucophytes

Chromalveolates 	Heterokonts, Haptophytes, Cryptomonads, and Alveolates.

[apodman]

Man, this is like a foreign language. I need a dictionary and an encyclopedia to get through a sentence. I hope non-astronomers and non-physicists don't feel quite this bad when they read our astronomy and physics banter.

[neufer]

Man, this is like a foreign language. I need a dictionary and an encyclopedia to get through a sentence. I hope non-astronomers and non-physicists don't feel quite this bad when they read our astronomy and physics banter.

Not to flagellate you on this issue, apodman, but one needs always to be a sophisticate opisthokont.

The opisthokonts (Greek: ὀπίσθω- (opisthō-) = "rear, posterior" + κοντός (kontos) = "pole" i.e. flagellum) are a broad group of eukaryotes, including both the animal and fungus kingdoms, together with the phylum Choanozoa and Mesomycetozoa of the protist "kingdom". Both genetic and ultrastructural studies strongly support that opisthokonts form a monophyletic group.

One common characteristic is that flagellate cells, such as most animal sperm and chytrid spores, propel themselves with a single posterior flagellum. This gives the groups its name. In contrast, flagellate cells in other eukaryote groups propel themselves with one or more anterior flagella.

The close relationship between animals and fungi was suggested by Cavalier-Smith in 1987, who used the informal name opisthokonta (the formal name has been used for the chytrids), and was confirmed by later genetic studies.

Cavalier-Smith and Stechmann argue that the uniciliate eukaryotes such as opisthokonts and Amoebozoa, collectively called unikonts, split off from the other biciliate eukaryotes, called bikonts, shortly after they evolved.>>

[bystander]

In the days of the comet
University of Leicester - 28 May 2010

Eleven years ago, NASA launched Stardust, a mission to collect material from a comet and return it to Earth. And now some of that precious material is at the University of Leicester.

What are comets made of? Well, dust and ice mostly – hence the common description of a comet as a ‘dirty snowball’. But what sort of dust? And indeed, what sort of ice? Researchers in our Space Research Centre are finding out.

Stardust was launched in 1999 and orbited the sun twice before, in 2004, flying right through comet Wild 2. Two years later, Stardust returned to Earth carrying the only material ever retrieved from a comet. A very few select labs around the world have been allowed to study these minute specks of dust, the value of which is incalculable because, frankly, we’re not likely to get hold of any more any time soon. And a few of those specks of dust came to Leicester.

A team led by Dr John Bridges have been examining a few tiny bits of comet using the massive Diamond Light Source synchrotron in Oxfordshire. The synchrotron is a particle accelerator which produced intensely focussed beams that can reveal the composition and structure of the comet particles.

This study revealed the presence of iron oxide grains – ‘rust’ to you and me – some of which formed at very low temperatures. Given that the comet originated way out in the Kuiper belt (around about the orbit of Pluto) this is not surprising, but other iron oxide grains seem to have formed at high temperature and this is a surprise. Further research, as the saying goes, is needed…

Post-mortem of a Comet
University of Leicester - 28 May 2010

Scientists put the Comet Wild 2 under the microscope

Researchers at the University of Leicester are examining extraterrestrial material from a comet to assess the origins of our Solar System.

For the first time ever, material samples from a comet were collected in the Stardust Mission. It was the first mission since the Apollo landings to have successfully returned extraterrestrial material for scientists to study in the laboratory. At the University of Leicester’s Space Research Centre and at Diamond Light Source, the UK’s national synchrotron facility – a series of super microscopes – scientists are currently finding out what a comet is really made of.

The Stardust probe travelled 3.2 billion km in space, and flew through the coma of Comet Wild2 collecting tiny grains of dust, returning them back to Earth in 2006. They are being dissected at NASA and the University of California and being sent to a few laboratories around the world, with the University of Leicester being one of them.

By developing micro manipulation techniques, researchers at the University of Leicester have further dissected the tiny samples to study the comet to atomic precision under a Transmission Electron Microscope. This ‘post-mortem’ of Comet Wild2 has revealed for the first time the true composition of a comet.
...
The researchers are obtaining unprecedented chemical information about the smallest grains of the comet, with sizes less than 1/10th the width of a human hair. The Diamond synchrotron is an electron particle accelerator that produces highly intense X-ray beams which can be used to delve deep into matter and materials to reveal information on the atomic and molecular scale. These X-rays were used to probe Stardust to the highest sensitivity.
...
Using a globally unique technique at Diamond which enables the mapping of the widest range of elements, the group found X-ray signatures of iron oxides. Further research at Leicester has shown that the small grains of iron oxide contained in the Stardust samples may have formed by low temperature aqueous activity on Wild2. However, other grains formed at very high temperature – around 2000 degree Celsius which is not what was expected from this icy comet that would have formed in the coldest, outermost reaches of the Solar System. This unexpected discovery has raised new questions about how these ‘dustbins’ of the early Solar System really formed.

http://asterisk.apod.com/vie ... 31&t=18403
http://asterisk.apod.com/vie ... 31&t=19061

APOD: Help Search for Interstellar Dust (2006 Oct 25)
Stardust@Home