Shock waves could force amino-acid forming chemistry.

Striking a glancing blow to a planet could create the perfect conditions in a comet's icy core to create amino acids — molecules that are vital to forming life on Earth.

This shock-compression theory for making amino acids has been developed by Nir Goldman and his colleagues at the Lawrence Livermore National Laboratory in Livermore, California. Goldman presented their results on 24 March at the American Chemical Society meeting in San Francisco, California.

The researchers wanted to find out what chemical events might occur in an ice grain trapped inside a comet glancing off a planet. They used around one million computer hours on the powerful Atlas computer cluster at Lawrence Livermore to simulate the possible chemical processes occurring in a single ice grain during such an impact. In particular, they were looking for amino acids — markers of potential life.

Previous theories for how amino acids on Earth might have come into being include lightning strikes on a primordial soup of simple molecules or the ultraviolet irradiation of interstellar dust grains, but none of the theories proposed so far is definitive.

Goldman's simulations included 210 molecules: a mixture of water, methanol, ammonia, carbon dioxide and carbon monoxide. This mix is commonly used by scientists to represent ice in comets.

First impact
When a comet strikes a planet, a shock wave travels through it as it comes to a sudden halt. This, Goldman explains, compresses the comet, and the compression wave travels through the comet faster than the speed of sound. As a result, the molecules inside deform and bonds break.

Goldman's group based its models on the impact that a comet travelling at 29 kilometres per second would be likely to experience. The impact had to be a side-on blow because a head-on impact would probably destroy everything inside.

To unpick the chemistry going on inside the ice, the researchers used density functional theory simulations, a quantum mechanical treatment of the electrons in a molecule. In the model, if the electrons around the atoms come close enough to those around other atoms a bond will form.

The first and weakest shock compression that Goldman and his colleagues modelled had a pressure of 10 gigapascals and reached a temperature of 700 kelvin. The grain was compressed by 40%. The team noticed that molecules with carbon–nitrogen bonds were forming, including an unstable molecule called carbamide. This was a hint that amino-acid-forming processes were possible. "Under these sorts of conditions everything's very reactive, so if you have one sort of morsel that has an essential component like a C–N bond you can imagine more carbons adding to it and getting a complicated amino acid," says Goldman.

In further simulations, in which the pressures and temperatures were higher, the scientists saw more chemistry. They focused on a simulation at 47 gigapascals and a temperature of 3,141 kelvin for the first 20 picoseconds of the impact. They saw many complex molecules forming, including large molecules with carbon–nitrogen bonds. (...)

Nautilidae wrote:Wow, this sheds much light on panspermia! Thank you for the post.

RichardPrins wrote:Comet crash creates potential for life

Shock waves could force amino-acid forming chemistry.

Striking a glancing blow to a planet could create the perfect conditions in a comet's icy core to create amino acids — molecules that are vital to forming life on Earth.

This shock-compression theory for making amino acids has been developed by Nir Goldman and his colleagues at the Lawrence Livermore National Laboratory in Livermore, California. Goldman presented their results on 24 March at the American Chemical Society meeting in San Francisco, California.

The researchers wanted to find out what chemical events might occur in an ice grain trapped inside a comet glancing off a planet. They used around one million computer hours on the powerful Atlas computer cluster at Lawrence Livermore to simulate the possible chemical processes occurring in a single ice grain during such an impact. In particular, they were looking for amino acids — markers of potential life.

Previous theories for how amino acids on Earth might have come into being include lightning strikes on a primordial soup of simple molecules or the ultraviolet irradiation of interstellar dust grains, but none of the theories proposed so far is definitive.

Goldman's simulations included 210 molecules: a mixture of water, methanol, ammonia, carbon dioxide and carbon monoxide. This mix is commonly used by scientists to represent ice in comets.

First impact
When a comet strikes a planet, a shock wave travels through it as it comes to a sudden halt. This, Goldman explains, compresses the comet, and the compression wave travels through the comet faster than the speed of sound. As a result, the molecules inside deform and bonds break.

Goldman's group based its models on the impact that a comet travelling at 29 kilometres per second would be likely to experience. The impact had to be a side-on blow because a head-on impact would probably destroy everything inside.

To unpick the chemistry going on inside the ice, the researchers used density functional theory simulations, a quantum mechanical treatment of the electrons in a molecule. In the model, if the electrons around the atoms come close enough to those around other atoms a bond will form.

The first and weakest shock compression that Goldman and his colleagues modelled had a pressure of 10 gigapascals and reached a temperature of 700 kelvin. The grain was compressed by 40%. The team noticed that molecules with carbon–nitrogen bonds were forming, including an unstable molecule called carbamide. This was a hint that amino-acid-forming processes were possible. "Under these sorts of conditions everything's very reactive, so if you have one sort of morsel that has an essential component like a C–N bond you can imagine more carbons adding to it and getting a complicated amino acid," says Goldman.

In further simulations, in which the pressures and temperatures were higher, the scientists saw more chemistry. They focused on a simulation at 47 gigapascals and a temperature of 3,141 kelvin for the first 20 picoseconds of the impact. They saw many complex molecules forming, including large molecules with carbon–nitrogen bonds. (...)

jaydot wrote::coffee:

rainbow wrote:

jaydot wrote::coffee:

...yet strangely, I get accused of evading questions.

Lazar wrote:

rainbow wrote:

jaydot wrote::coffee:

...yet strangely, I get accused of evading questions.

the symbol is usually used to indicate someone is bookmarking the discussion so they can find it again easily in their "your posts" tab.

amino acids — molecules that are vital to forming life on Earth.

rainbow wrote:

Lazar wrote:

rainbow wrote:

jaydot wrote::coffee:

...yet strangely, I get accused of evading questions.

the symbol is usually used to indicate someone is bookmarking the discussion so they can find it again easily in their "your posts" tab.

...as I am.
I will patiently wait for someone to explain the statement:

amino acids — molecules that are vital to forming life on Earth.

Lazar wrote:

rainbow wrote:

Lazar wrote:

rainbow wrote:

jaydot wrote::coffee:

...yet strangely, I get accused of evading questions.

the symbol is usually used to indicate someone is bookmarking the discussion so they can find it again easily in their "your posts" tab.

...as I am.
I will patiently wait for someone to explain the statement:

amino acids — molecules that are vital to forming life on Earth.

So you bookmark by accusing other bookmarking posters of evading questions. Interesting strategy .

Lazar wrote:What irony would that be?

Rumraket wrote:I actually agree with Rainbow on this one, to a certain extend. It seems to me in contemporary origin of life hypotheses, the presence of amino acids on earth are not initially important for the formation of the first protocells.

That is not to say that they are completely irrelevant for the evolution of life, once it has taken hold. As I understand it, once the protocells have formed with their primitive fatty acid membrane and whatever genetic material was present, having amino acids readily available in the environment, could potentially subject that lifeform to a selective pressure for incorporating those amino-acids in it's internal chemistry... and so they could be relevant for subsequent evolution of life.

Going further, if these lifeforms evolve to incorporate these aminoacids in their internal metabolism, it seems reasonable that at some point, the lakes or oceans where these organisms live will eventually, although slowly and gradually, run out of free amino acids and will therefore be under a selective pressure to evolve it's own amino-acids synthesizing machinery.

So, I guess a case could be made that the most primitive form of life could come about without the aid of amino-acids, but further evolution could largely rely on it. I think the title of the article would be better as "Comet crash creates potential for evolution of complex life".