Were fossils from Mars found on Earth?
I remember the widespread media coverage regarding the Martian meteorite ALH84001, back in 1996. Researchers were suggesting that certain features in there resembled micro-fossils - i.e. evidence for life on Mars. For some time it was possible to follow the debate back and forth, but it is a long time ago now and it has all gone quiet. Was there ever a conclusion to this debate?
Tamela - Yes. I think people can be forgiven for being a bit inconclusive about this because it's just disappeared. So, Derek has got a nice background to this story. So basically in 1996, there is this paper that was published by a NASA scientist and he had found these sort of nanometre scale, chain-like structures on top of this meteorite maybe slightly embedded as well and interpreted it as fossils of bacteria. One of the first criticisms, well, these are a much smaller scale than any kind of bacteria that we see here on Earth. So, how can they possibly exist on these nanoscale things and maybe that's got around by the fact that Mars has a very different sort of chemistry or something exotic like that. It created a lot of excitement particularly because they thought that this meteorite formed on Mars during the period when water existed on Mars. We have a lot of evidence to suggest that this is true, that there were liquid oceans or rivers or something on Mars at some point, but ages ago, 4 billion years ago or so. This is particularly interesting because it was with water and now, it's here, maybe some evidence of fossils. Maybe we found life and I think even Bill Clinton at this time eluded to it and was a huge discovery. Today, there's no consensus that this is actually definitive evidence of life and unfortunately, we don't have that evidence of any kind of life outside of planet Earth past or present. I think one of the main arguments against it was, there's these magnetite crystals that have formed and at the time, we only knew of these being formed by biological processes from little microorganisms that deposit these minerals. But in the early 2000, they were able to replicate these crystals in a lab study without any kind of organic input. As soon as you can do that, people are inconclusive. So sadly, we're withholding judgment until further data comes along.