Has Peru's mysterious illness been explained? Seems like. The New York Times is reporting that a meteor did, in fact, hit the ground, but rather than alien microbes taking a ride through space, or radiation poisoning, it seems like arsenic from the ground water is actually the culprit. The theory is that when the hot meteor hit, it dug far enough into the ground that the local ground water, and everything it's contaminated with, steamed up in a big cloud which made the locals sick. Until I hear a better story, I'll buy it.

I read two articles this morning that really seemed to tie into each other and are part of the continuing search for the origins of life here on Earth.

Previously I've written about the red rain in India and how it seems to suggest that bacteria are quite well adapted for space travel. Today one of the articles I read, on National Geographic's website, talked about a meteorite that landed in Canada's Tagish Lake which seems to contain organic material older than our Sun. Most of the organic material was actually approximately the same age as our Sun, but one tenth of one percent was deemed to be older, and the organic material looks like it formed at very cold temperatures; approximately absolute zero, in fact. It is entirely likely that the Earth has been bombarded with this type of organic material since it formed, and that the basic building blocks of life didn't form here on Earth, but instead formed elsewhere in the universe.

Then I read an article from a professor at my alma mater, the University of Colorado. Carol Cleland was an associate professor while I was there, but she's a full professor now and her article for Astrobiology Magazine provides some interesting insights into the origins of life as well. She discusses the possibility that amino acids used to form proteins could have combined differently than what we're used to seeing, and if it did, how would we know and how would we look for it? One part of her article which I found very interesting based on what I was already thinking about was this:

So why does life as we know it on Earth today use its particular combinations of molecular building blocks? The best explanation is that they are the result of conditions on the early Earth. This is true not only for proteins and nucleic acids, but also for ribosomes. Because they physically realize the translation of hereditary information into functioning, self-maintaining organisms, ribosomes lie at the very heart of the molecular architecture of familiar life. Their unique characteristics are almost certainly the product of historical contingencies. So it is unlikely that the ribosomes found in the cells of familiar life represent the only possibility for translating hereditary information stored on nucleic acids into proteins, let alone the original mechanism utilized by the first proto-cells. Had circumstances on the early Earth been different, familiar life would also have been different.

This opens up a provocative possibility. It is commonly assumed that life originated only once on Earth. But if the emergence of life is highly probable under certain physical and chemical circumstances that were present on the early Earth, then there could have been multiple cradles of life. There must have been natural variations in the collections of organic molecules available in different regions on the early Earth. Assuming that life did originate on Earth and was not transported here from elsewhere, then it is unlikely that the first forms of Earth life were all built from exactly the same molecular building blocks.

But what if the building blocks for life as we know it did come from elsewhere? I would imagine that it would be just as possible that "life" did not originate from one particular spot elsewhere, either, which leads to the same possibilities that she discusses in the article. If life, in some other form, were present here on Earth, or being bombarded upon us from the universe, how would we know it? It's an interesting question that there's not an easy answer to. Just the fact that we seem to know that life can come from elsewhere is already a major revelation. The idea that we might not be able to even recognize it should be a cause for concern to anyone whose job it is to explore the possibilities of life here and elsewhere. Or, as Carol Cleland puts it:

The lesson should be clear. Because microbiologists are working under a paradigm that says there is only one form of life on Earth today, it is unlikely that they would recognize the significance of traces of an alternative form of microbial life even if they encountered them.

While we don’t know how different life could be from life as we know it, there are good reasons for thinking that life on Earth could have been at least modestly different in its molecular architecture and building blocks. A dedicated search for shadow microbes ought to be seriously considered. The obvious place to begin is with known puzzling phenomena, such as desert varnish, that are difficult to explain in terms of familiar life and yet also difficult to explain in terms of abiotic processes.