You know the metaphor. Somebody’s looking for something, perhaps their keys, in the dark. There’s a lamp-post somewhere, spreading a circle of light. They confine their search to the circle of light, where they can see. Of course, the keys can be anywhere, not just under the light, and so this search has a seriously limited scope.
Well, a lot of research is like that, somewhat inevitably. Often with the additional limitation that you’re not sure what you’re looking for, either. You’re just hoping you’ll know it when you see it. This happens in all fields.
One place where I -as an outsider- always feel somewhat frustrated by the discussions is in the search for life elswhere in the universe. NASA makes some announcement about this sort of thing from time to time and it is always phrased in terms of looking for water. (See e.g., Saturn’s moon, Enceladus (right) where a water geyser was identified recently.) I find that a bit annoying, since they never mention other possibilities. I understand how crucial water can be for life as we know it, but is that really the only sign we should be looking for? And what if it is a red herring?
And what about life as we don’t know it? How do we know we’re not missing huge deposts of life on those objects in the solar system that we’ve ignored because they don’t have water? And one can go to some extremes with this, and have some fun. One thing I especially love to do is speculate about life existing in conditions that are so extremely different than ours that pretty much everything we can imagine about their experiences would be incredibly alien to us. How about creatures that live on the surface of the sun, for example, or in the accretion disc of a black hole, while it sucks the life out of its neighbouring star? What about vast gaseous creatures the size of several star systems, incredibly long-lived and slow to move – but alive, nonetheless. I could go on, but you can have more fun making up your own examples, I’m sure. The problem with most of them is – how would be able to find and recognize them as life?
Coming back to the lamp-post, or at least near it, I was pleased to see an article by Britt Peterson on Seed’s website about two colleagues of mine, USC professors Douglas Capone and Kenneth Nealson. It was about taking a different focus in the current searches for life.
Incidentally, I’d never really known what exactly “Astrobiology” was before this semester, nor met a real practicioner of the craft. Then Douglas approached me at a reception one day and asked me to come and teach a guest lecture to their Astrobiology class on the origins and evolution of the universe, right up to the formation of the Solar System. I was delighted to do it, of course, and in fact invited my colleague from Astronomy, Ed Rhodes, to do the second half of the presentation, focusing on the formation of the solar system, the search for extrasolar planets, etc, topics about which he has much more knowledge than I. We had a great time (and from the questions, possibly the students too), and may well do our double act again next year. (Perhaps even polish it up, get a manager, and take it on the road….)
The article refers to an opinion piece my colleagues wrote in the journal Science. They talk about focusing on Nitrogen. Here are some extracts:
“Water just provides the context for life as we know it,” said Douglas Capone, an environmental biologist at USC and a co-author of the opinion piece, along with Earth scientist Kenneth Nealson. “If we wanted to look for really solid evidence that life had ever existed, organic nitrogen deposits would be good things to look for.”
The article quotes him further…
“They can go all over the place looking for evidence of past water formation, or even finding water deposits maybe down deeper in the geological strata,” he said. “It’s still not going to answer the fundamental question of whether there ever had been life on Mars.”
Nitrogen, on the other hand, is an ingredient of life, one of the building blocks in the protein and nucleic acids from which all life on Earth is made. Its appearance on a planet is difficult to explain if life similar to ours is not also present, the authors said.
“At least on a body that has had a separation of continental and oceanic components, the existence of nitrogen on continents is not easy to explain without special life-supplied chemistry”
Lifting further from the Seed article:
Currently, nitrogen has not been discovered in great quantities on Mars, but evidence suggests it may have been present in the ancient past of the red planet. While Capone said that he is unconvinced that life ever existed on Mars, in the article he and his colleagues argued for a greater emphasis on assessing nitrogen levels there, while still keeping track of the aquatic evidence.
“Our recommended approach might be to search for the nitrogen, characterize and quantify it,” the authors suggest in their paper. If its abundance and chemistry cannot be explained by abiotic processes, do not leave until it is explained and when it comes to sample return, bring back anything that is enriched in nitrogen!”
Actually I find this really very interesting, and would like to know more about the whole Astrobiology field. Are there any among our readers who can tell us a bit about the sorts of signatures that people have thought about? And who gets to call the shots about what instrumentation goes up on the various spacecraft we send to our neighbouring heavenly bodies? There’s a limit to payload sizes, so prioritization must be done. What thoughts go into this? What about ground-based searches? Is spectroscopy, etc, still an active tool in this field, or is it long since had its day?
I like this nitrogen discussion. Of course, it is not really going as far as looking beyond the lamp-post, but rather (to stretch the analogy rather poorly) making sure one is at least using colour vision in one’s search in the circle of light. How one really goes out there and looks for life patterned according to a truly different blueprint is anyone’s guess. It would probably be a very lucky shot in the dark to find and identify something truly different, given our current understanding.