Tuesday, May 08, 2007

Is there anybody out there?

This piece in November promised a lot more and I have failed to deliver on my promise so far. This is my first attempt to catch up with what I had promised. This post will deal with the chemicals that one finds in asteroids that land on Earth and with it questions the possibility that the raw materials for life on Earth could have started by the availability of these chemicals and also discuss the possibility of panspermia.

First, I will start with astronomical spectroscopy. This is the method by which chemists identify the compounds present in space. When light or any electromagnetic radiation is passed through a sample, the sample absorbs and emits certain wavelengths of light better than others and the wavelengths that are emitted and absorbed can be used as a fingerprint analysis of the chemical nature of the compound itself. Unfortunately, the science is not as simple* as I mention here but will suffice for the discussion that follows.

There have been many meteors that have hit the Earth's surface and some of these impacts have been seen as the reason for major climate change in the Earth. The interest in astronomical spectroscopy was purely to understand the physical and chemical nature of the universe around us. But as soon as astronomical spectroscopy developed into a reliable science, it stood to reason that it could lead us to understand how life on Earth originated and whether there are traces of life elsewhere in the universe. Afterall, if life evolved on Earth, the chemicals responsible for life should have been present on Earth before that (and possibly elsewhere) and hence the chemical nature of these meteors became important to biology as well, but all these studies have not been localized to the meteors alone.

The interstellar medium is divided into the dense and diffuse kind. The diffuse interstellar medium is cold and icy material that is not too dense and is made up of neutral and charged ions of compounds of C, H, and N, and also contain compounds such as naphthalene, which are aromatic compounds. In the dense interstellar compounds, the temperature is close to 10K to 200K (freezing point is 273K) important compounds such as hydrogen gas, carbon monooxide, water, carbon dioxide, methane, methanol, ammonia and hydrogen disulfide were found among others. That is, it has a source for H, C, N, O, and S. Later, in some clouds they have also found organic acids and higher alcohols such as ethanol (pure delight!).

The meteorites that have hit close to home were found to be quite rich in the lower and higher organic compounds of the classes mentioned above but were also found to have trace quantities of natural as well as unnatural amino acids (natural defined as biologically natural), purines, and pyrimidines (the base compound in DNA and RNA). In addition trace quantities of phosphonates and other P containing compounds were also found (also found in DNA and RNA). What was also interesting is that some of these amino acids was found to be chiral in nature (like in biological systems). In other words, there is a way in space to make optically active compounds and not synthsize all the isomers in equal quantities. It is actively debated whether these meteors were contaminated by biologically active components on their way to the ground even though there is evidence that says that it was not contaminated.

To summarize, the raw materials for life to start could be found in meteors and other components of space and indeed, these compounds under the right condition could lead to life anywhere. I will deal later with attempts by scientist these days to understand how life started from these raw materials.

I would like to end with panspermia and I think wikipedia has a good definition - Panspermia is the hypothesis that "seeds" of life exist already in the Universe, that life on Earth may have originated through these "seeds", and that they may deliver or have delivered life to other habitable bodies.

It is kind of a whacky theory and people either do not believe it or do not want to believe it because it is a theory like intelligent design - once you have said it, there is no way to prove it right or wrong. It is a theory which is unscientific in nature. But one of the leading scientists believing in the theory was none other than the Nobel Laurette - Francis Crick. Finding these organic chemicals in space has only led to more evidence for this hypothesis.

* Before one performs spectroscopy of a sample, one has to attempt to purify all the compounds present in the sample which is not an easy job because the chemical nature of the substance is an unknown at the beginning. A variety of chromatographic techniques are used for this. In addition, even after the spectroscopy of the individual samples are performed, it does take some time to realize the exact chemical nature of the substance being examined.

References:
Wikipedia as usual - on Origin of life and Astronomical Spectroscopy and Panspermia.

Extraterrestrial Organic Matter: A review - William M. Irvine - Origins of Life and Evolution of Biospheres - Volume 28, 1998, 365-383.**
** I can provide the pdf of this document on request.

13 comments:

Sakshi said...

Is the assumption then that only lifeforms similar to us will be found else where?

Born a Libran said...

Not neccessarily... That is one of the reasons that people can not come up with a single broad enough defn of life. Rather, finding chemicals that are neccessary for life here in space has sent out the signal that life similar to us could have evolved elsewhere too...

Tarun said...

Hmmm interesting.

One would like to read the "Urey-Millers" experiment.

Read it is school way back.

Prasoon said...

A enlightening post..

Pass over the pd btw - shall give it a read anyways.

Just recently, Ministry of Defense in Britain said that it'll soon grant access to all its UFO files. just yest Discovery had scientists speak on the issue of UFOs and many of them concluded that there is life beyond Earth - only that its too tough for letting everyone realize because once done, people will definitely panic.

Prasoon said...

The link to the news - wo to dena bhool hi gaya.

Its very good to see people post on science - am wondering if I could contribute but then, tech is not something that is out here in full flare. :S

Born a Libran said...

@tarun: Those experiments will be discussed in the next post.

@prasoon: Thank you from all of us. I will send the pdf to you within the next couple of days. Thanks for the URL. You are welcome to contribute. There were a couple of initial posts on how digital cameras work. So we do take on tech articles as well.

Tarun said...

Next post awaited.

:)

Ashutosh said...

One recent paper provided possible support for panspermia by investigating the bacterium Dienococus radiodurans, which can withstand ungodly measures of radiation. The hypothesis is that at no time in the history of the earth were radiation levels so high that the bacterum actually needed to evolve such radiation resistance. Thus, one plausible hypothesis to support this observation could be that Dienococcus evolved on Mars and was transported to earth.

Francis Crick was a man who was known for being unusally prescient and right. So who knows if...

Also, let me suggest an excellent recent book on origins of life:
Astrobiology- A brief introduction by Kevin Plaxco. Quite detailed, but very accessible.

Born a Libran said...

@ashutosh: One factor that may have come into play for this is that D.radiodurans might not have evolved to resist radiation but some other factor that produces the same effect as radiation.

For example, I quote from a news and views article from Nature "his extreme radiation resistance is but a by-product of its selection for resistance to desiccation." Both desiccation and radiation break D. radiodurans's chromosomes into short DNA fragments. Radman and his colleagues blasted the microbe with one megarad of gamma radiation, enough to sterilize food but well below D. radiodurans's resistance threshold. Nevertheless, its chromosomes broke down into short strands of DNA. For the next hour and a half, the cells appeared dead, but by the end of three hours the chromosomes of D. radiodurans were reassembled and fully functioning.

Well, that is the thing with panspermia. Any scientific fact can then be re-engineered to sound like it is made up to support panspermia or vice versa.

Ashutosh said...

Born a libran: Actually this is exactly the hypothesis that the recent paper challenges; that radiation resistance was a byproduct of dessication resistance. They believe there are multiple inconsistencies with this scenario, one of them being the fact that radiation resistance is not induced in bacteria that have undergone cycles of dessication. But instead of iterating their arguments, I will give you the reference:

ANATOLY K. PAVLOV,1 VITALY L. KALININ,2,* ALEXEI N. KONSTANTINOV,2
VLADIMIR N. SHELEGEDIN,2 and ALEXANDER A. PAVLOV3

ASTROBIOLOGY
Volume 6, Number 6, 2006

write my term paper said...

It was very interesting to read your article. But my opinion is that there is nobody out there, except small bacteria. This is the biggest we can find there.

Suncorp Internet Banking said...

I can't wait to meet the Others. What's funny is that all biologists will immediately jump ship to study them, despite not even having completed the libraries of our own planet.

Nedbank internet banking said...

I'll be pissed if we don't find something cool soon.