Life Origins: Here or There?

[Arne Saknussemm]

Excuse me for starting a whole new thread on this topic. I realize there has recently been one on this very topic, among other aspects of life's origins. I wish, however, to focus on this one question:

Why is it thought that life (i.e. organic molecules) originated on comets rather than on Earth?

I know that comets may have first brought water to the Earth, but is not the Earth a more ambient, friendly sort of place to foster life rather than some ice-ball that is sometimes too close, often too far from the Sun?

Why is the comet origin theory so prevalent? Please explain to those of us who are interested - the pros and cons of this view, as well as the reasons it may be more likely that the Earth is the origin of life as we know it.

I hardly need to point out, I think, that if comets are supposed to have carried life here from another planet: where would that planet be? And why should we suppose that planet is more likely to have been the origin than this one? How could organic matter have survived in space for any length of time?

Earth seems as likely a place as any, more likely even, to be where life (as we know it) sprang up. Why is this not the prevailing view?

 

[spidergoat]

Because amino acids are found on them. At one point in the early Earth it was not friendly to life, so we can imagine these building blocks landing constantly on Earth and only eventually finding a suitable environment in which to flourish as it cooled.

 

[Arne Saknussemm]

Thanks. Good answer. It sounds like a silly question, I know: Why would there be amino acids on comets? Do they often exist elsewhere as well?

 

[paddoboy]

Why is it thought that life (i.e. organic molecules) originated on comets rather than on Earth?

We don't know that it did.
It may have originated on Earth.
It may have been brought to Earth via a comet or Asteroid.
It may have been both.

 

[Arne Saknussemm]

We don't know that it did.
It may have originated on Earth.
It may have been brought to Earth via a comet or Asteroid.
It may have been both.

The key phrase to my question is "why is it thought" I realize that noting is known for certain on this topic. I am asking why the comet-origin theory is so prevalent. Spider had a good answer, but as you can see, I had a pair of follow-up questions. (Why would there be amino acids on comets? Do they often exist elsewhere as well?)

 

[paddoboy]

I am asking why the comet-origin theory is so prevalent. Spider had a good answer, but as you can see, I had a pair of follow-up questions. (Why would there be amino acids on comets? Do they often exist elsewhere as well?)

I'm not sure it is prevalent. Panspermia is just one of the possibilities.
Why do they carry amino acids. I doubt they all do, but some asteroids are ejected by planetary collisions.
Comets in general are thought to be the left over from stellar/planetary formation.
I would also hazard a guess and say that the same processes of creating amino acids that occurred on Earth, can also occur in space...carbon, water, energy.
Amino acids have also been detected in interstellar space.
That's about all I can add.

 

[Arne Saknussemm]

I never knew before that amino acids could be found in interstellar space. Do you mean not even associated with a comet or asteroid? if that's so, well then, hell! You are probably correct to surmise as you often do that life is abundant throughout the universe. The intriguing thing now is to learn what it is like. Does it always evolve into proteins and DNA-based organisms or something quite different? Fascinating.

 

[paddoboy]

I never knew before that amino acids could be found in interstellar space. Do you mean not even associated with a comet or asteroid? if that's so, well then, hell! You are probably correct to surmise as you often do that life is abundant throughout the universe. The intriguing thing now is to learn what it is like. Does it always evolve into proteins and DNA-based organisms or something quite different? Fascinating.

August 2009
An amino acid has been found on a comet for the first time, a new analysis of samples from NASA's Stardust mission reveals. The discovery confirms that some of the building blocks of life were delivered to the early Earth from space.

Amino acids are crucial to life because they form the basis of proteins, the molecules that run cells. The acids form when organic, carbon-containing compounds and water are zapped with a source of energy, such as photons – a process that can take place on Earth or in space.

Previously, researchers have found amino acids in space rocks that fell to Earth as meteorites, and tentative evidence for the compounds has been detected in interstellar space. Now, an amino acid called glycine has been definitively traced to an icy comet for the first time.

"It's not necessarily surprising, but it's very satisfying to find it there because it hasn't been observed before," says Jamie Elsila of NASA's Goddard Space Flight Center, lead author of the new study. "It's been looked for [on comets] spectroscopically with telescopes but the content seems so low you can't see it that way."
http://www.newscientist.com/article/dn17628-found-first-amino-acid-on-a-comet.html#.U9hdreOSxZ8

 

[tashja]

I never knew before that amino acids could be found in interstellar space.

I heard an astronomer on a youtube lecture that there are even clouds made of alcohol in space. The kind you drink. Yeah.

 

[Arne Saknussemm]

I heard an astronomer on a youtube lecture that there are even clouds made of alcohol in space. The kind you drink. Yeah.

Is this the same astronomer who observed that in space no one can hear ice cream?

 

[C C]

I never knew before that amino acids could be found in interstellar space.

In that domain, pre-biotic molecules may originally develop on dirty ice grains that provide a quasi-hospitable surface. With gaseous nebulae serving as the greater environmental incubator for synthesizing them over time. Any infant or proto- star formations in such interstellar clouds provide the energy source. Polarizing EM radiation from the latter may also contribute to "discrimination" in the chirality department.

“There’s nothing to prevent life from developing from right-handed amino acids, it just happened that on our planet the left-handed amino acids were what was available.” --Mindy Levine; 2008

 

[Fraggle Rocker]

Amino acids are crucial to life because they form the basis of proteins, the molecules that run cells. The acids form when organic, carbon-containing compounds and water are zapped with a source of energy, such as photons – a process that can take place on Earth or in space.

We only know this about the kinds of living things that exist on our planet. There's no reason to assume that all life, everywhere in the universe, has the same blueprint as ours.

When we finally develop the transportation technology to visit other solar systems, it's quite possible that on some distant planet there will be so many living things that we walk all over them without realizing what they are, because they are so different from terrestrial life.

Most of the elements in the definition of "life" in Wikipedia are simply features that all Earth life has:

• 1. Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.
• 2. Organization: Being structurally composed of one or more cells — the basic units of life.
• 3. Metabolism: Transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
• 4. Growth: Maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
• 5. Adaptation: The ability to change over time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity, diet, and external factors.
• 6. Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion; for example, the leaves of a plant turning toward the sun (phototropism), and chemotaxis.
• 7. Reproduction: The ability to produce new individual organisms, either asexually from a single parent organism, or sexually from two parent organisms.

For each of these elements, it's not too difficult to imagine a lifeform on another planet (or for that matter a red giant star or in interstellar space) that doesn't have it.

Perhaps there is an environment in which abiogenesis occurs constantly, so there's no need for living things to reproduce.

Perhaps there's an environment in which it's unnecessary for living things to grow once they pop into existence. For that matter, right here on this planet, single-cell living things don't exactly grow. They simply split in two to become two new cells.

 

[paddoboy]

We only know this about the kinds of living things that exist on our planet. There's no reason to assume that all life, everywhere in the universe, has the same blueprint as ours.

I don't believe I did infer that.
In fact I have mentioned in a few posts, of the possibility of "Life as we don't know it"
Perhaps I should have said amino acids are crucial to life as we do know it.

When we finally develop the transportation technology to visit other solar systems, it's quite possible that on some distant planet there will be so many living things that we walk all over them without realizing what they are, because they are so different from terrestrial life.

You won't get any argument from me on that score.

 

[paddoboy]

I heard an astronomer on a youtube lecture that there are even clouds made of alcohol in space. The kind you drink. Yeah.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
There are Giant Clouds of Alcohol Floating in Space

Ten thousand light years from earth in a constellation far, far away, there is massive cloud of alcohol. It’s space booze.

Discovered in 1995 near the constellation Aquila, the cloud is 1000 times larger than the diameter of our solar system. It contains enough ethyl alcohol to fill 400 trillion trillion pints of beer. To down that much alcohol, every person on earth would have to drink 300,000 pints each day—for one billion years.

Sadly, for those of you planning an interstellar pub crawl, the cloud is 58 quadrillion miles away. It’s also a cocktail of 32 compounds, some of them as nasty as carbon monoxide, hydrogen cyanide, and ammonia.
more at....
http://mentalfloss.com/article/51271/there-are-giant-clouds-alcohol-floating-space
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

[youreyes]

current mission to Ceres might answer the question on probability of life originating from the comets.

 

[paddoboy]

Astronomers find alcohol cloud spanning 288 billion mile:
Apr 04, 2006
Astronomers based at Jodrell Bank Observatory have discovered a giant bridge of methyl alcohol, spanning approximately 288 billion miles, wrapped around a stellar nursery. The gas cloud could help our understanding of how the most massive stars in our galaxy are formed.

Read more at: http://phys.org/news63346824.html#jCp
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

 

[tashja]

Haha. Thanks, Paddo. I thought I probably misheard that lol. :cheers:

 

[Aqueous Id]

In that domain, pre-biotic molecules may originally develop on dirty ice grains that provide a quasi-hospitable surface. With gaseous nebulae serving as the greater environmental incubator for synthesizing them over time. Any infant or proto- star formations in such interstellar clouds provide the energy source. Polarizing EM radiation from the latter may also contribute to "discrimination" in the chirality department.

“There’s nothing to prevent life from developing from right-handed amino acids, it just happened that on our planet the left-handed amino acids were what was available.” --Mindy Levine; 2008

This post reminded me of Chinglu's argument against abiogenesis (in the thread "Cytosine", Biology & Genetics) in which he presumes that life could not have formed on Earth by spontaneous chemical reaction from mineral sources. He will (after 100 posts of beating around the bush) eventually tell us that, for one reason, the environment was too hot. Since the comets that orbit the Sun cycle in temperature we might relate this to the conditions of, say, volcanism on Earth before there were any greenhouse gases to speak of, and therefore it was a frozen rock with some hot spots, possibly similar to a comet as far as temp extremes. Interestingly, there is a small school of biologists and chemists that believe such conditions were favorable to the natural evolution of nucleotides out of a primordial soup, in an ambient of fire and ice. As you brought this to mind, it takes me to the position that maybe the Panspermia advocates might someday come to this same conclusion, that it's the presence of both temperature extremes which leads to abiogenesis. Also, there is a school that advocates for clay as sort of catalyst--that is, it assists in organizing monomers into polymers. Supposing a similar substance could be found on the particular comets that host amino acids--then there is another possible reason for marrying these ideas together.

Of course now I forgot what I was talking about since I had to watch your new sequence art from beginning to end. Gawd you're good. There's more content in one of your gifs than in half of these threads. Oh but that line "Travel to far away places" was also on the T-shirts preceded by "Join the Military" and followed by "Meet Interesting People" and then "And Kill Them". But your 50s genre kicks butt. If you're really that old and this lucid I would sure like to get a transfusion from you. Whatever you're doing is remarkably good for the synaptic pads. Probably a lot of RNA in your diet. Whatever it is, you really should bottle the stuff and at least put it up on craigslist. Too bad I'm a dolt in philosophy. *Sigh* Now next time I'm on here from a PC at a local library, heavily visited by residents of an adjacent retirement community, I'm going to be posting here, then looking up at whoever is on the machine next to me and wondering: Is that CC ? Of course you're probably out rollerblading or catching a football while your former classmates are calling for bedpans. All that RNA and all. Anyway there is a lot of vitality in your art which is tucked into a niche that just can't be accessed since I can find no venue. I would open a thread trying to do it justice, but the last thing I would want to do is to steal your mojo. Recognizing of course that I steal my own by slobbering on the keyboard like this. So hey there anyway.

 

[exchemist]

I never knew before that amino acids could be found in interstellar space. Do you mean not even associated with a comet or asteroid? if that's so, well then, hell! You are probably correct to surmise as you often do that life is abundant throughout the universe. The intriguing thing now is to learn what it is like. Does it always evolve into proteins and DNA-based organisms or something quite different? Fascinating.

It may be a rather obvious point, but amino acids do not mean "life". They are just one of the prerequisite building blocks.

I presume the idea is that comets, being cold, but subject to periodic excursions to zones of higher energy due to their highly elliptical orbits, are the sort of environment in which complex molecules can (a) be created and (b) then be stable for long periods of time. It is perhaps seldom not appreciated how much of the environment in the universe is hostile to the creation and persistence of molecules with more than say 2 or 3 atoms. Chemistry itself is a bit of an exception.

 

[wellwisher]

The Miller experiment, from the early 1950's, showed that animo acids could be created beginning with simple gases and water using an electrical spark to simulate a stormy young earth. With water the second most abundant molecule in the universe, and comets often containing water, amino acids should be able to form under many conditions from comets to earth. It is not one or the other.

The experiment used water (H2O), methane (CH4), ammonia (NH3), and hydrogen (H2). The chemicals were all sealed inside a sterile array of glass flasks and flasks connected in a loop, with one flask half-full of liquid water and another flask containing a pair of electrodes. The liquid water was heated to induce evaporation, sparks were fired between the electrodes to simulate lightning through the atmosphere and water vapor, and then the atmosphere was cooled again so that the water could condense and trickle back into the first flask in a continuous cycle.

Within a day, the mixture had turned pink in colour,[9] and at the end of two weeks of continuous operation, Miller and Urey observed that as much as 10–15% of the carbon within the system was now in the form of organic compounds. Two percent of the carbon had formed amino acids that are used to make proteins in living cells, with glycine as the most abundant. Sugars were also formed.[10] Nucleic acids were not formed within the reaction. 18% of the methane-molecules became bio-molecules. The rest turned into hydrocarbons like bitumen.

The bitumen is interesting because Miller and Urey showed one could form an oily substance, found in "fossil fuels", without life being present. The current theory is fossil fuels required life, but Miller's expedient showed that life was not necessary to form bitumen.