February 28, 2013

The Origins of Life: Did Life Get Started by Asteroids?

(Disclaimer: Origins of life research is a new area of study for me. I’m not an expert on this topic and writing this post may be somewhat premature on my part. Please feel free to correct me if you see something that is incorrect, since I am going on limited research.)

For decades scientists have been searching for answers about the origins of life. How did life get started on Earth? How did the first cell form? Today, many scientists are convinced they are closer than ever to an answer—an answer that does not include God. Life, they say, was jumpstarted by asteroids bearing organic compounds; furthermore, they believe they have found such asteroids dating to the early years of our solar system. The organic material in these asteroids is compelling evidence, they believe, that primitive life got started by a natural process. However, they fail to recognize that there is a perfectly good alternative answer to why organic compounds have been found on asteroids which has everything to do with design.

The Discoveries

First, let’s take a quick look at the types of organic molecules that have been found in asteroids since the 1960s. These include: two of the four building blocks of DNA (guanine and adenine), a few of the amino acids that are used to build proteins, and amphiphilic compounds which are used in building cell membranes. Notably, two of the four building blocks have not been reported to have been found, as best I can tell. These molecules are all built of common organic elements: carbon (C), hydrogen (H), oxygen (O), and nitrogen (N).

Chirality

I should also discuss chirality. To save time let me boil it down to the best of my limited knowledge. Amino acids and various other molecules can be in two forms—what are called left-handed and right-handed forms. Most of life uses left-handed forms of amino acids and proteins. All proteins need to be constructed of 100% left- or right-handed amino acids[5]. Also, life’s DNA and RNA chains use exclusively right-handed sugars in the backbones. Asteroids and comets have contained 60% or less of left-handed forms of amino acids. Even the 18% excess of left-handed acids in one meteorite[2] is thought to be statistically insufficient to accidentally produce a useful protein (with 50+ amino acids) or enough right-handed sugars to directly form and facilitate the perpetuation of a self-replicating strand of typical RNA.

Even one molecule of the wrong type of handedness in a protein or an RNA strand would destroy its biological activity, it appears. Thus, even a small percentage of either left-handed or right-handed molecules mixed with the other would present problems for life’s eventual formation. No known natural means exists to produce nearly 100% of one handedness in such a way as to allow an ongoing random mixing of organic compounds—a condition that would seem to be necessary for the emergence of life.

An Abundance of Organic Elements

Now, the primary point of this blog post is to point out that there is a perfectly good reason why one kind of asteroid has amino acids and, more significantly, nucleic acids. If an alien race that reproduced asexually were to come to earth and see two brothers who are identical twins they might jump to the conclusion that one brother came from the other brother. But they certainly would be wrong. Though the aliens’ assumption might seem logical, there is another perfectly sound answer: the identical humans had a common origin. The materials of asteroids and the planet Earth have had a common origin, which is the sun. Moreover, the Earth’s atmosphere may have been formed partly from asteroid and comet bombardment. Because of the common origin for these things, it would stand to reason that their chemical compositions might have some similarities.

God wanted to form life from certain elements, and these elements (e.g. carbon [C], Hydrogen [H], Oxygen [O], & Nitrogen [N]) needed then to be common in the universe and more importantly on earth. If you look at the relative abundance of elements in the universe you will see that these are the top seven: H, He, O, C, Ne, Fe, and N, with the abundance of Ne, Fe, and N being nearly the same. Notice that the “organic elements” C, H, O, & N are all highly abundant in the entire universe. If you look at the earth, you will see that in the atmosphere these are the top five elements by number of atoms: H, He, O, C, & N. Again, the organic elements are the most common (excluding the inert noble gas He which does not bond with other atoms). The sun was used to produce these organic elements in the early solar system. Is it any surprise that some asteroids contain high levels of the organic elements? 75% of asteroids are C-type, which contain significant levels of carbon. These carbonaceous asteroids are rich in H, O, C, & N[1]—not to say that they have no other elements. What might seem more surprising is that roughly 20% of asteroids do not contain high levels of carbon, considering that C is a common element in the universe. The earth’s crust also contains high levels of C, H, & O, though N is much rarer there, probably because it mostly formed N2 gas early in the Earth’s formation making it get expelled into the atmosphere. (Nitrogen is also very stable in the atmosphere and has built up over the eons.)

Organic life requires organic elements. Our environment needed to be filled with these elements to allow for life to thrive. The sun that formed the Earth also formed asteroids, and asteroids were likely used to help form the Earth and its atmosphere[3]. So, the four most common organic elements needed to be abundantly generated by the sun. Again, it would be likely that most asteroids would be rich in these organic elements, considering the design purposes of God. (Aside: this argument only really works for an old earth.)

The Reason Some Organic Molecules Are Common

Now, just because it makes sense that there would be asteroids abundant in organic elements does not mean that you would necessarily expect to see organic compounds, like the four DNA nucleobases (viz. the molecules generally represented as G, A, T, C). But here’s the deal: C-type asteroids contain a wide range of molecules composed of C, H, O, & N, including acids not typically found in life on earth. The nucleobases are relatively un-complex molecules composed of anywhere from 12 to 16 atoms. Because God undoubtedly wanted to form living creatures using simple, stable compounds (which is the only thing that makes sense), that implies these building blocks of DNA should be chemically stable compared with many other similar molecules. This leads us to the conclusion that it would be fairly likely that asteroids containing the organic elements would contain the stable and relatively un-complex organic building blocks of life.

Summary

So, in case I have made the logic hard to follow here, the summary is that a wise and intelligent Creator who wanted to make C, H, O, & N based organisms would probably make those elements abundant in the universe and would make the organic components stable and thus more likely to be found in Nature in places unrelated to life’s formation. This means we should expect to find organic compounds to be quite common elsewhere in the universe, even in other solar systems, and there still be no life in any of those other places.

(Aside: this also is the same type of logic I would use to explain why Earth-sized planets may be abundant in the universe.)


Closing Arguments

There are two other things to address, though. One is an argument in favor of life forming through natural means, and the other argument is against it. The argument in favor relates to the 18% excess of left-handed amino acids found in an asteroid. Why would there just happen to be this left-handed excess in asteroids and also in living organisms, if life did not get jumpstarted by these meteorites? There are several possible answers. One, it could be coincidence and nothing more. Remember, 18% excess does almost nothing to solve the origin of life problem; we need very close to 100% of one form. Two, it could be from contamination, as some scientists have acknowledged[4]. Three, it could be that those left-handed acids are even more stable such that Nature sometimes generates those forms in greater abundance, and God designed and used the most stable form of the molecules for life. (It is important to note here that news reports seemed not to mention anything about finding an excess of right-handed sugars used to form the backbone of DNA/RNA, which might have been more interesting.)

The second important argument is that two of the four DNA/RNA building blocks, the T (or U for RNA) and C, appear to have not been found naturally occurring in meteorites—not to mention most of the other bioactive amino acids. This may be highly problematic to those trying to find the origins of life. How did the other organic compounds form? They are either relatively rare in the solar system or they are nonexistent apart from life. Either way, it is not especially good news for those looking for a naturalistic answer to the origins of life. Will these other two nucleic acids turn up sometime? I imagine they will, but that may be the least of the problems facing the origins of life researchers.

How life got started is still very much a mystery for Darwinian evolutionists. There are a number of hypotheses, but none of them are validated by observational evidence. None of them have been shown to be probable paths to how life began. Purely theoretically, could God have used “natural means” to form life? Even if there are countless Earth-like worlds, the probability of it happening naturally still seem slim, but perhaps so. Nevertheless, the evidence is lacking. Finding organic material in asteroids may well mean nothing more than that the whole universe was designed with Earth’s organic life in mind.

EDIT: After posting this, it was reported in the news that organic compounds were found in a galactic cloud here in our galaxy.[6] This new discovery actually helps validate what I've been saying in this post: organic elements and compounds are likely to be common in the whole universe.

[1]
http://en.wikipedia.org/wiki/CHON
[2]
http://www.cbc.ca/technology/technology-blog/2009/03/did_lifes_bias_come_from_space.html
[3]
http://www.universetoday.com/47331/earths-atmosphere-came-from-outer-space/
[4]
http://news.sciencemag.org/sciencenow/2009/03/16-02.html
[5]
http://www.reasons.org/articles/homochirality-and-the-origin-of-life
[6] http://news.discovery.com/space/astronomy/icy-clues-for-lifes-origins-130307.htm#mkcpgn=rssnws1

2 comments:

  1. As far as origins of life are concerned, Michael Prescott recommended this book in his Subversive interview with Jime Sayaka on the Subversive Thinking Blog:

    http://www.amazon.com/Origins-Skeptics-Guide-Creation-Earth/dp/0553343556/ref=sr_1_1?ie=UTF8&qid=1362501117&sr=8-1&keywords=Robert+Shapiro+Origins

    ReplyDelete
  2. Also, check this out:

    http://ncu9nc.blogspot.com/2013/03/top-five-problems-with-current-origin.html

    ReplyDelete