Is Astrobiology a Legitimate Scientific Field?

[Widdekind]

Oh my! Well, I now see that the "link" that I promised to check out earlier is not in fact a link at all, but merely the title of a source (properly underlined as per MLA referencing). However, given the position stated above, I would have to question the legitimacy of this source. What is the energy source that initiated this "fission"? How is it sustained over millions of years? Why is the comet not blown apart by the fission reaction?

Fission reactions — aka "Radioactive Decay" — in the interiors of Comets is essentially the same as that which occurs in the Cores of larger, planetary bodies. Lord Kelvin famously showed, that the Earth should have radiated its heat from formation (~ G M² / R) in roughly 50-100 million years... but the Earth's interior has remained molten for 4-5 billion years (up to 100x longer than expected). This is the result of Fission reactions (Radioactive Decay) in the Earth's interior. These reactions are not explosive, like a run-away chain reaction in a bomb. Rather, they are slow and steady, much like a heat-generating Nuclear Reactor.

Thus, even as the Earth is not "blown apart by the fission reaction", neither would Comets explode either. And, just as on Earth, where all the heat pouring out of the Core (from these Fission reactions) ultimately provides the energy source for Chemosynthetic Life to thrive upon — eg. at Black Smokers & Geothermal Vent systems along spreading Mid-Ocean Ridges, whose Plate Tectonics are powered by the motions of the Mantle, whose Convection cells are driven by the heat pouring out of the Earth's radioactive Core — so, too, the same might be said for Comets.

I may have missed, or mis-understood, some things, but I think the argument is something like this:

Radioactive Decay --> Heat --> Comet Core becomes a "gooey" mess of Organic Compounds --> Primordial "soup" of first Life​

 

[Chronos]

Water is a natural search target. It is the only substance necessary for life as we know it. There may be other options that work, but, we do not know of any at present. So, it makes perfect sense to look for water as an indicator of life elsewhere in the universe. We also have reason to believe water is abundant in the universe. I'm still not buying the radioactive comet thing, Why would such heavy elements exist in abundance in the Oort cloud? It makes much more sense for them to be concentrated near the sun.

 

[Widdekind]

Why would such heavy elements exist in abundance in the Oort cloud? It makes much more sense for them to be concentrated near the sun.

Wouldn't the "collapsing cloud" of the proto-Solar Nebula be chemically well-mixed ? Couldn't a clump create a comet, containing many 'metals', even far from the proto-core of the collapsing cloud ?

Are you saying, that proto-stellar nebulae undergo Gravitational Differentiation, as in planetesimals, where all the heavy metals migrate to the center of mass ?

 

[Widdekind]

According to Wikipedia, the Oxygen-binding organo-chemicals, in the "blood" of both Arthropods (Hemocyanin) and Mammals (Hemoglobin), have closely comparable coefficients (Hill Coefficients) for binding Oxygen:

In some hemocyanins of horseshoe crabs and some other species of arthropods, cooperative binding is observed, with Hill Coefficients of 1.6 - 3.0. Hill constants vary depending on species and laboratory measurement settings. Hemoglobin, for comparison, has a Hill Coefficient of usually 2.8 - 3.0.​

Thus, the best binders of Oxygen, anywhere in the Animal kingdom, appear to asymptote towards a Hill Coefficient of ~3. Applying this (cautiously, of course) to the Cosmos, might this mean, that (Oxygen metabolizing) Exo-fauna might "max out" at comparable coefficients ?

 

[Widdekind]

Would (Oxygen-metabolizing) Exo-fauna have blue "blood" ??

Arthropods' "blood" contains Hemocyanin, to transport Oxygen. And, "Oxygenation causes a color change between the colorless Cu(I) deoxygenated form and the blue Cu(II) oxygenated form".

Likewise, it is well-known, that Oxygenated Hemoglobin is blue.

And, it is well-known, that the sky appears blue, b/c atmospheric Oxygen (& Nitrogen) preferentially scatter shorter (bluer) wavelengths of light.

QUESTION: Does all this imply, that "Oxygen is just plain blue" in appearance (since it scatters shorter wavelength light) ??

And, if so, would that mean, that any hypothetical Oxygen-binding compound, appearing in the "blood" (equivalent) of Exofauna, be likely to be blue in appearance (when Oxygenated) ??

 

[Chronos]

Uniformly mix heavy and light elemenst in solution. Add a central 'attractor to draw them in, then 'shock' the media [like a star igniting]. Do the heavy elements tend to collect nearer or more distant to the star?

 

[Widdekind]

I don't know how to answer that. Don't pre-Main Sequence, proto-stellar nebulae, take many millions of years to form ? That might make plenty of time for gravitational differentiation, or it might mean that the cloud's collapse is so slow, and quasi-static, such that such differentiation doesn't proceed apace.

What about stars forming in clusters, and nearby Supernova explosions "polluting" proto-stellar collapsing clouds w/ more metals -- such a process would preferentially populate the periphery of the collapsing cloud w/ the most metals.

According to the PBS documentary Exploring Space -- The Quest for Life (DVD), "comet & asteroid" impacts, upon this planet, have produced copious quantities of heavy metals mostly found only in Earth's core. For one example, the Vredefort Crater in S.Africa has produced fully 40% of all Earth's mined gold, and the narrator listed a long list of other craters, yielding copper, coal, and hydrocarbons. This strongly suggests, that "comets & asteroids" contain copious quantities of many metals -- but, perhaps, all the coal comes from carbonaceous comets, and all the metals from meteorites (?).

 

[LURCH]

Are you saying, that proto-stellar nebulae undergo Gravitational Differentiation, as in planetesimals, where all the heavy metals migrate to the center of mass ?

That is one model (one to which I happen to subscribe). It is based on the composition of planets in our own solar system, with rocky planets near the center, and the gas giants toward the outside. Of course, this model has problems, not the slightest of which is the overwhelming central mass of the sun, which is almost entirely hydrogen and helium.

Likewise, it is well-known, that Oxygenated Hemoglobin is blue.

I thought hemoglobin was only blue when it is depleted of oxygen. Oxygenated hemoglobin is red, is it not?

 

[qraal]

Comets and asteroids in the protoplanetary nebula would have been efficiently heated by Aluminium-26 decay.

 

[Vanadium 50]

Likewise, it is well-known, that Oxygenated Hemoglobin is blue.

No, it's not. It's red.

 

[LURCH]

Comets and asteroids in the protoplanetary nebula would have been efficiently heated by Aluminium-26 decay.

But that heating should only last a few million years at most, as I understand.

 

[qraal]

But that heating should only last a few million years at most, as I understand.

According to Wickramasinghe's thermal modelling the comets of sufficient size efficiently retain heat from the initial decay spike to remain liquid for far longer. Don't forget the Sun's energy input would have been significant too. Once the comets were scattered into the Opik-Oort Cloud they would've preserved any biomolecules created, perhaps even concentrating them sufficiently for Life to begin. Biogenesis gurus Leslie Orgel & Stanley Miller independently concluded that proto-life biochemistry would have been accelerated by freezing the medium, due to the concentrating action of the way water freezes especially when full of solutes.

 

[qraal]

Here’s a very good treatment of why our favorite molecules are the ones that won the “biology lottery” and some insight into the wanta be’s:
http://books.nap.edu/catalog.php?record_id=11919#toc

A very good reference and FREE!

 

[planethunter]

Given the shear unimaginable size of the universe, the question is not whether there is intelligent life outside of earth, but instead how much life?

Look into Drake's equation for an interesting discussion of this assertion.

Given the biology of some of the known exoplanets, life similar to life on Earth is not probable. However, we are bound to find an Earth size planet in its sun's habitable zone that will give us the best change of life elsewhere in the universe.

 

[Chronos]

Agreed. Once you establish that planets are common [which has been done], the existence of extrasolar life is a certainty. Are any such life forms intelligent [as in human like intelligence] - that is unknown at present. My guess is there must be at least a half dozen human-like civilizations scattered across the galaxy at present. The real problem is traversing the vast distances of space between stars, imo. I doubt any civilization has yet mastered that feat. The energy costs are just too enormous. Perhaps a civilization a million years ahead of our own could accomplish this feat. I suspect they are too busy exploring their own neighborhoods for resources and potential relocation sites to give much thought to traveling here.

 

[LURCH]

But drake's equation is nothing but a string of complete unknowns. It does not give us any idea about the likelyhood of extrasolar life, nor do I believe Drake intended it to. It merely gives us a formalism by which that likelyhood could be calculated at some point in the future, when some of the variables can be filled in.

As for intelligent life; look into Fermi's Paradox.

 

[cosmolojosh]

Somebody found amino acid on a comet

 

[planethunter]

Somebody found amino acid on a comet

I am aware of NASA supposedly finding some kind of organic material on a martian meteorite some time ago, which according to them ended up being because it had been contaminated.

Where did you hear the story about the amino acid on a comet?

 

[cosmolojosh]

Planethunter, go to science.discoery.com. It is the website of the science channel. Go to brink. Then go to videos and watch proof of alien life.

 

[Chronos]

Find ozone in an exoplanet atmosphere and you have found the smoking gun for life. That study is already underway.

 

[cosmolojosh]

There is 2 problems with seti anyway. 1. it would take a human like species. There is also a million and 1 other explamaations for what seti is looking for.

 

[JerryClower]

Does astrobiology imply that life exists elsewhere in the Universe besides earth?

 

[qraal]

Does astrobiology imply that life exists elsewhere in the Universe besides earth?

That's what it means, though of course it might all be related to Life here by panspermia.