Wednesday, October 19, 2011

Tonight: Nova on Finding Life Beyond Earth

by Salman Hameed

The new NOVA episode is on tonight. Its on Finding Life Beyond Earth. Here is the preview, but I think full episode will also be available online. In any case, I will post it on Irtiqa this coming Saturday.

This is perfect timing as I'm co-teaching Astrobiology this semester with biochemist Jason Tor from Hampshire College and planetary geologist Darby Dyar from Mount Holyoke College. It has been a fun class so far. Just this past week we had a fascinating discussion over the work on the origins of life versus what we know about Last Universal Common Ancestor (LUCA). What is fascinating is that the date for LUCA can be estimated from what we know about genes, and is now estimated to be between 3.9-4.1 billion years. Still, we don't have much idea about the path (and perhaps some dead-ends too) between the first life form and LUCA. Absolutely fascinating!

While on the subject, here is a bit from a NYT interview with the 2009 chemistry Nobel Laureate, Jack W. Szostak. He is currently working on the problem of origins of life. Here are the relevant parts of the interview and it will give you a flavor of how researchers think about these issues:

What do you study now? 
The origins of life. In my lab, we’re interested in the transition from chemistry to early biology on the early earth. Let’s go back to the early earth — let’s say probably some time within the first 500 million years. And let’s say the right chemistry that would make the building blocks of life has happened and you have the right molecules with which you can spark life. How did those chemicals get together and act something like a cell? You want something that can grow and divide and, most importantly, exhibit Darwinian evolution. The way that we study that is by trying to make it happen in the lab. We take simple chemicals and put them together in the right way. And we’re trying to build a very, very simple cell that might look like something that might have developed spontaneously on the early earth.
How far have you gotten?
Maybe I can say we’re halfway there.
We think that a primitive cell has to have two parts. First, it has to have a cell membrane that can be a boundary between itself and the rest of the earth. And then there has to be some genetic material, which has to perform some function that’s useful for the cell and get replicated to be inherited. The part we’ve come to understand reasonably well is the membrane part. The genetic material is the harder problem; the chemistry is just more complicated. The puzzle has been understanding how a molecule like RNA can get replicated before there were enzymes and all this fancy biological stuff, protein machinery, that we have now in our cells.
You’ve now been working on this problem for a quarter of a century. Do you ever grow weary of it?
No. No. Because this isn’t a monolithic question where there’s nothing interesting until you get to the end. In fact, the question breaks down into maybe a dozen smaller questions. Each has interesting parts. Eventually it will all fit together.
For instance, we’ve made progress on the question of how you make a primitive cell membrane. Others had showed how a common clay mineral, montmorillonite, might have played a role in helping to make RNA. Our lab showed how it could help membranes to form and bring the RNA into the membrane.


Asad M said...
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Asad M said...

I saw this Nova documentary last night and thought that it was an old one because there was not much new in it; maybe I was confusing it with some other BBC or Discovery Channel documentaries which have covered the same topic. So I googled it and out came this blog. I am a Pakistani myself and am glad to find that there are at least some of our countrymen who are passionate about science and making a significant contribution to the propagation of science and reason.

Now on the topic on hand, is the date (3.9 - 4.1B yrs) for the LUCA determined using the very reliable rate of mutations in the genes? Is the same technique (i.e. using the rate of genetic mutations) that links us humans to a common ancestor of modern-day apes some 6 to 7M yrs ago? Anyways, the 3.9-4.1B yrs date for the LUCA seems to corroborate well with the geological date of the rocks found in West Greenland that are dated to 3.8B yrs old and believed to contain the earliest signatures of carbon based life-forms (or micro-fossils of single-celled organisms). More confirmation comes from the over 3.5B yrs old Stromatolites (made from layer upon layer of tiny microbes) found in Western Australia that are also one of the earliest living creatures.

I may be going off-topic here but just giving my perspective here in appreciation of this blog. I struggle to find friends or people to discuss science (esp. astronomy & the origins of the universe/solar system, evolution/humans origins, origins of life). Mostly people try to connect science to religion in some way or are simply more interested (and therefore more knowledgeable) about religion because of their upbringing and the increasing bigoted society that we are becoming.

At the local town mosque I know a person who is a Professor of Immunology & Parasitology (a Ph.D. of course) at a local University and tried to elicit his opinion on Evolution in general and human evolution in particular. He accepted and supported ‘natural selection’ as the basis for the evolution of all animals & plants but when it came to humans he turned out to be a Creationist and quoted the story of Adam & Eve from the Quran. I wasn’t shocked at all because my sister (a practicing physician – M.D. in the States) does not even believe in Darwin’s theory at all.

I will read more of the blogs here but have to go now.

Salman Hameed said...

Dear Asad,

Yes, the LUCA estimate is based on gene mutation rates (though I don't know the specific details). It is considered quite reliable and we had another discussion in the class about what if it had come out to be 6 billion years or so, i.e. older than the age of the Earth. This is an interesting question as then it would have pointed to panspermia - the idea that life was formed elsewhere and then got transported here (possibly via interstellar debris). However, that is not the case, and LUCA estimates are coincide more or less with the end of the late age of bombardment, and yes, it is also consistent with the ages of oldest rocks etc. But then how long between LUCA and the origin if life? Don't know. Another interesting question.

We have a talk coming up on November 3rd by Robert Hazen. I will post the announcement on the blog shortly. It is all about the scientific quest for life's origins, and I will post the video a few weeks after.

Thanks for your kind words about the blog - and hope you become a regular here.

Atif Khan said...

Welcome aboard Asad.

Glad to see more people.. I would rather say rational people around who one can debate with in a creative and open manner.


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