Life from the Abyss
Nigel Mason is director of research at the Centre of Molecular and Optical Science at the Open University in the UK. One of the Centre’s main focuses of study is on Astrobiology, specifically on determining how simple molecules such as methane, ammonia or water found in the interstellar medium can be transformed into the building blocks of biochemistry.
In this interview with Astrobiology Magazine, Mason explains how molecules formed in space might eventually lead to life, and describes what scientists are doing to better understand this process.
Astrobiology Magazine (AM): Carl Sagan famously said, “We are all made of star stuff.” Most people today, however, wouldn’t think of astrochemistry and stellar evolution as being relevant to the origin of life. How does your research bridge this gap in understanding?
Nigel Mason (NM): Our research tries to address two basic questions. First — where did the molecules that are necessary for the formation of biological molecules like DNA come from? Where were they formed? And second, are those molecules prevalent anywhere in the universe?
There are two possible answers to the question of the origin of life. There may be something special about the Earth, and the molecules of life only formed here because of the special conditions we have of being in a solar system with the sun at the right size and at a certain distance. On the other hand, it may be possible to form the molecules of life around a star system anywhere. If that’s the case, life would be much more common, indeed maybe the most likely system to occur on any planet.
We’re trying to recall the chemistry behind these possible scenarios. For instance, investigating how the building block molecules like amino acids and peptides are made. In order to probe these questions we use a combination of experiment, observation, and modeling. We want to develop a model that takes us from the Big Bang through to now.
So we start with how the first matter in the universe was made and follow it through to when you start to have chemistry, which is about 1,000 seconds into the history of the universe. Then you try and follow that chemistry through to the formation of a planet and to the molecules in the planet. From there you try to see how those molecules may be assembled to create self-replicating, life-giving molecules.
AM: Don’t these molecules have to pass through the stage of being a star first, and then be processed in a supernova in order to be formed?
NM: That’s possible, but the main dark area of space, what we call the interstellar medium, is full of large, dark, cold regions of dust. We believe many molecules are made there, and those are exactly the same regions where the stars and the planets are born. These clouds collapse under gravity, and when they collapse they can form the star. The other bits of material that don’t go into forming the star can then form the planets.
At the same time it’s possible that many of the molecules that are needed for life are already made. All the leftover bits of the planetary system, such as comets or Kuiper belt objects, could be an assemblage of the early molecules that were made in these interstellar regions. That means all the chemistry for life begins with the formation of those dusty clouds. That gets us to the idea that, potentially, life could have formed there.
We don’t know how those building blocks are assembled. We also don’t know all the molecules that are there, and the reason we don’t know that is because the bigger and more complicated the molecule, the more difficult it is to identify with spectroscopy. Some people believe you can have amino acids in these clouds, but those molecules are almost impossible to detect with the satellites and telescopes we have now.
However, in the next few years we have the exciting prospect of big new telescopes like ALMA, a microwave array which will look with much more detail into these dark regions. These instruments will be so sensitive to small concentrations that we might be able to see if some of the biological precursors are there. We know from comets that they are there. But whether those were made in the early dust clouds, or whether they were processed and formed during the formation of the planets and the stars, we don’t know.
AM: What are some of the ESA missions that support this research?
NM: Recent missions going to a comet, such as Rosetta and Gaia, are interesting, because they’ll tell us what this primordial material looks like. At the moment it’s all guesswork. Some of the astronomical observations suggest much of the material is either silicate or carbonaceous-based material. But to really know what it looks like and what form it is in, we have to go get some of it.
The missions to investigate comets can give us a close-up view and also tell us what sort of chemistry is going on. We’ve now got quite a different picture of what a comet looks like. We used to think it was a rather fluffy object with a core of ice, but now we’re getting a different picture, a much more grainy picture of these black conglomerates of dust. It’s like taking your vacuum cleaner and hoovering up the carpet. When you look afterward you see all this dust that falls apart very easily. That’s perhaps what the interstellar dust looks like. The Stardust mission collected some comet dust and brought it back, and scientists are now analyzing that.
Unfortunately we can’t send a mission far enough to get the dust from the interstellar medium. We can only look at the dust that is around our solar system. But if you want to know what interstellar dust grains look like, get a McDonald’s hamburger and look through a microscope at the soot on the meat patty. That’s what we think these grains look like.
AM: Perhaps then the new slogan of the 21st century is “We are all made from McDonald’s hamburgers…?”
NM: If you’ve eaten one you might think so. (laughs)
We believe that there’s nothing very special about our star. Therefore the sort of dust in the cometary material in the Kuiper belt objects – which is almost primeval material — is probably similar to what is around other stars. Of course there are different types of stars and the dust might be slightly different. We won’t know for sure because we’ll probably never be able to send a probe that far away. We’re only going to be able to look at our solar system, but we believe the chemistry is universal.
AM: Are you saying that the possibility for the basis of life is ubiquitous?
NG: If you’ve got the building blocks, then the next question is, “How do they get assembled?” It could be that if all the molecules are made in the interstellar medium, then when the planet forms they get parachuted down onto the planet’s surface. That’s an idea of Panspermia: all the material arrives on the surface and then finds some way to assemble. The early formation of planets like the Earth is so volcanically violent that probably all the water evaporates. So water needs to somehow get parachuted in later, because we need water for life.
It’s also possible that when the planet has formed and has volcanic activity and the atmosphere forms and so on, you might make some of the compounds on the planet. The chemistry might switch on because of atmospheric effects or lightning. The Miller-Urey experiments demonstrate that if you have an atmosphere and you put an electrical charge through it you can make many of the molecules of life. But probably the answer is a mixture of both. Some of the material comes from meteorites and lands on the planet, and some is made when the planet’s atmosphere forms.
We don’t know how the first DNA molecule was made. In fact DNA probably wasn’t the first information molecule, we probably had something like RNA, which is simpler. The holy grail of astrochemistry and astrobiology is figuring out how DNA or RNA formed. Also, how did the first cell form? Once you know how the cell formed, then you can really start to talk about chemistry.
We can work out how to make an amino acid or a peptide in the lab. We can argue about whether the chemistry occurs on the mineral surface, or in the atmosphere, or in the ocean. We can make all the components of DNA. Several groups around the world now, particularly in Europe, are trying to come up with experiments that try and put together these molecules. They think of ways in which the molecules might have been assembled on the early Earth and try to form what we call the proto-cell, into which we can then try to do biochemistry. There are many speculations of how it’s done. All I can say at the moment is that nobody has made a proto-cell, and we’re all waiting to be first.
AM: If I’m not mistaken, didn’t a NASA lab claim to have done exactly that a couple of years ago?
NM: NASA Ames reported results from experiments about three years ago. They took some comet-like material they’d created in the lab, dumped it in water, and it formed something they called a vesicle, which is meant to be a proto-cell. I know of at least two other people who have tried to replicate that experiment and they have not gotten it to work.
AM: Is it a case of “cold fusion” then, where the results couldn’t be replicated and the experiment was shown to be flawed?
NM: No, I think the problem is that the conditions of these experiments are very sensitive. If we don’t have control over which ingredients are used, then the results could be due to statistical differences. It could be that they had exactly the right combination but they didn’t know it, and everybody else has done it allegedly under the same conditions that were in fact slightly different. So they could have just been lucky that they got the right combination and the others didn’t.
Not only do you need to have all the ingredients in the right place, but statistically there’s a chance that they’ll assemble in the right orientation – or that they won’t. One of the final questions is if you start to put the molecules together, is it certain they will always find the best combination and the best energy configuration that leads to life? Or does life require something special? It’s like baking a cake. Even though you may have all the ingredients there, you might not get a perfect cake. It might just be a mess if you don’t know what you’re doing and you don’t stir it properly.
AM: Sounds like you need to be a good cook to follow nature’s recipe for life.
NM: People have run computer programs to work out what exactly is the recipe, what is each stage of life being formed, what’s the chance for getting the right number of ingredients or the planets in the right place around the right star. If you do all those statistics, which have huge error bars, you can prove on the merit of those models that there is no life in the universe — that we don’t exist — or alternatively you can prove that life is teaming across the universe! It just shows that we don’t know the statistics yet. We have to do the experiments, because each time we do an experiment we prove that this leads to that, and we reduce the error bars. And then ultimately we might be able to say, “That’s how it works.” I suspect one day we will make DNA or a proto-cell and people will say it was blindingly obvious that it worked that way. The trouble is that until it is blindingly obvious, we can’t see it. So you’ve got to work your way to it by throwing all the ideas up in the air and trying different things.
AM: That’s a lot of permutations to get through isn’t it? It’s cosmic natural selection.
NM: Yes. It could be that life is a statistical fluke. But alternatively there might be laws or patterns which, once we know what they are, become fairly obvious. I suspect that nature is more clever than we realize. Think about the human body and all the things that have to happen for cell biology to work. Some say there is a lot of junk and redundant material in the cell, but the more people look into it the more they realize that most of that redundant junk does have a purpose, but we just aren’t clever enough to understand it. So we’ve probably evolved in a particularly good pattern, and I suspect that the origin of life evolved in the same way, but we just don’t know the chemistry yet. Hopefully sometime in the next ten or fifteen years there will be a Eureka moment.