Exolife: Why it would be similar to earth life.

There has always been the underlying theme, among most alien encounters, of humanoids who look remarkably like us. Body configurations similar to us externally, as well as some obvious communication similarities (i.e. Language) have also been reported. Now, for the sake of argument, let us say that we know life does exist near us in the galaxy. And let us also say that it has visited us either recently or in the distant past. If this is the case, and our account of aliens appearing to be extremely similar to us is accurate, than how can this be possible?

Well I intend to show there exists a distinct possibility that life near us in the universe would have an extremely high chance of being similar to us, and also show that the further we get from our region of space, the less likely life will be like terran life. Please note that I will be using the word ‘Life’ to indicate the existence of any organism on a planet with single or multi-cellular function. When talking about a sentient species like us, I will refer to them as ‘conscious life’.

I will start with some background information for ease of the reader and to create a starting point.

[atsimg]http://files.abovetopsecret.com/images/member/3818561fbe61.jpg[/atsimg]

The formation and evolution of the Solar System is estimated to have begun 4.55 to 4.56 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. Most of the collapsing mass collected in the centre, forming the Sun, while the rest flattened into a protoplanetary disc out of which the planets, moons, asteroids, and other small Solar System bodies formed.

This is where I incorporate my model:

The “...giant molecular cloud...” mentioned in the above paragraph (Wiki) is quite an amazing thing. Wikipedia has some interesting information about this cloud here, particularly, “A molecular cloud, sometimes called a stellar nursery if star formation is occurring within, is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen (H2).”

What I find most intriguing is that, our solar formation used but a small portion the initial giant molecular cloud (henceforth referred to as GMC), that spawned us. I cannot accurately guess how much was consumed, but based on the GMC’s observed by our telescopes, it must have been a very small percentage given the size of the clouds. Also, since we were formed we can be assured that our GNC was also in the category of a Stellar Nursery

Therefore the extra matter, one could reason, formed other stars within the nursery. Stars that formed under similar conditions, with similar building blocks. Our planet itself was formed from the same matter that formed all other regional planets. Subject to the same fundamental principles of formation and composition, system layout etc.

When the terrestrial planets were forming, they remained immersed in a disk of gas and dust. The gas was partially supported by pressure and so did not orbit the Sun as rapidly as the planets. The resulting drag caused a transfer of angular momentum, and as a result the planets gradually migrated to new orbits. Models show that temperature variations in the disk governed this rate of migration, but the net trend was for the inner planets to migrate inward as the disk dissipated, leaving the planets in their current orbits.

See here for more info, scroll to the section entitled “Formation of planets".

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Vast assemblages of molecular gas with masses of 104–106 times the mass of the sun are called Giant molecular clouds (GMC). The clouds can reach tens of parsecs in diameter and have an average density of 10²–10³ particles per cubic centimetre (the average density in the solar vicinity is one particle per cubic centimetre).

GMCs are so large that "local" ones can cover a significant fraction of a constellation such that they are often referred to by the name of that constellation, e.g. the Orion Molecular Cloud (OMC) or the Taurus Molecular Cloud (TMC). These local GMCs are arrayed in a ring in the neighborhood of the sun coinciding with the Gould Belt. The most massive collection of molecular clouds in the galaxy, the Sagittarius B2 complex, forms a ring around the galactic centre at a radius of 120 parsec. The Sagittarius region is chemically rich and is often used as an exemplar by astronomers searching for new molecules in interstellar space.

Having established that these clouds are big, and don't create single stars, we can assume then that, it would be strange to find things were not extremely similar. Couple this with the idea of panspermia, which has been brought up several times recently by very rational and intelligent people, and you have an interesting possibility.

ATS Post on recent news & Another news source on a different perspective of panspermia.

This possibility is that, within the same nursery that created our sun, the building blocks of life were also formed. So, you have the possibility that basic life is created externally and eventually rains down on a forming planet like the rest of the matter. If this is the case, which it appears there may be reason to believe it is, than we should assume that planets, formed from the same basic building blocks (essentially H2), as life. That being said, if another planet in our vicinity was seeded, and life successfully took root, it would be subject to evolution similar in nature to earth.

Even on earth we have examples of convergent evolution. Where several different species will find different means to the same end, for instance, flight. So, one could assume that, if another conscious lifeform arose, and it was near enough to us to have visited, we may well find that this life is very much like us. Subject to the same requirements for sentience as us. Probably bipedal in order to elevate the brain, standing upright to avoid overheating, with limbs and sense organs etc. Not to say that biologically they wouldn't have taken a very different route. It is highly unlikely we will find any planets that are EXACTLY like earth.

This however should not discourage the possibility of nearby life, as we have life in the darkest coldest most inhospitable places of the planet. The trouble life has is starting, it can survive just fine. If the new insight into panspermia theory proves correct, and we truly are descendant from microbes carried by comets, than we most certainly weren't the only planet lucky enough to be seeded. The comet was part of a certainly larger cluster, perhaps the same cluster that brought our water.

Nonetheless, at least in my opinion, we cannot rule out the fact there is the possibility for earth-like life of all types to exist near us, and that life further away, formed from different GMC's would yield different results.

[atsimg]http://files.abovetopsecret.com/images/member/bc2e63d22962.jpg[/atsimg]

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[edit on 6-2-2010 by JunoJive]

I would also like to add, that even if life doesn't arise through panspermia, we would still find that regionally life would be similar to ours, due solely to the fact that the compounds forming the planets and oceans of a planet would be similar to our own. Perhaps oceans of methane like Europa. The initial life would adapt to the fundamental difference and go from there. So we cannot rule it out entirely.

Thanks very much for your time and I look forward to your comments, I will modify and expand this if necessary!

Another good read is The feasibility of greys

Note for mod: please move thread if you feel its more appropriate in a different category


[edit on 6-2-2010 by JunoJive]

Great thread. Even at the biochemical level, organisms would have to be near the same. Certain things only match up with certain things, and if some of them are missing, that could either create no life, or incredibly different life.

What would an organism living off of methane look like?

www.titanexploration.com...

This discusses what life on Titan would be like. They theorize that it would be perfect for large birds to do it's very low gravity.

reply to post by Phlynx


Interesting stuff, if you get a chance there is a Scientific American (Jan 2010 vol. 302 #1) that explores the possibility of life supporting universes which have only three of the four (known) fundamental laws. I believed they removed torsion. The universe, as a result, had different types of stars, and only one type of supernova, however the other laws compensated for the adjustment. And that to me is a key realization people need to make, that our 'constants' can be adjusted provided there are compensations from the other laws.

In the case of the universe with only three of the laws, the habitable zone for our star would be near Venus. Also another point made that I feel is relevant, is that they mention that some of our most common elements would appear in only small quantities in that universe. Basically not easily occurring in nature. What I find important is that, in this 'hypothetical' universe, the element itself would have a different weight etc. For instance Titanium (22, Ti 47.867) might appear in the place of Neptunium (93, Np 237), and perhaps their more common elements would appear as 'fringe' elements on our table. Nonetheless interesting reading, of that there is little doubt.

Thanks for the post.



[edit on 7-2-2010 by JunoJive]