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ToSeek
2004-May-05, 04:06 PM
Study May Cast Doubt on Some 1996 NASA Evidence of Past Life on Mars (http://www.spaceref.com/news/viewpr.html?pid=14162)


The new paper reports that magnetite, an iron-bearing mineral found in Martian meteorite ALH84001, was likely caused by inorganic processes, and that those same processes can be recreated in the laboratory, forming magnetite identical to that found in the Mars meteorite.

Irishman
2004-May-05, 07:52 PM
These findings do place doubt on the previous findings. Dr. McKay does make a good point that the data must be evaluated as a whole, and not on any one line item. However, they're conclusion of life being the cause was founded on all four premised cummulatively. Any one line of evidence presented was very questionable and alternative explanations available. The conclusion was based on taking all four lines together and showing how as a whole that conclusion was stronger. Finding specific flaws in one line weakens the overall conclusion. Given that alternatives exist on each line, it comes down to accepting the alternatives in each case were fortuitously combining in such a way to duplicate the results from life. It becomes a knife fight with Occam's razors. Which is the simplest explanation?

Interesting side note: I used to lunch with McKay, Everett, and some others from their office. They're pretty sensible and very bright guys. I also once met Kathie Keprta-Thomas in line at a grocery store. Same store I have seen from time to time Gene Kranz. Yep, these folks are real people with real lives. And no, I didn't memorize the contents of their shopping carts. ;)

Bubblecar
2004-May-06, 12:00 PM
It's taking them a surprisingly long time to resolve the question of these Martian fossils, & the whole "nanobacteria" debate in general. Life, or not life? You'd think in this DNA age, these questions would be easier to settle...

Irishman
2004-May-06, 03:14 PM
You can't get DNA from this kind of fossil. It is a mineral replacement type, like petrification. There's no DNA to sequence.

The answers are really tied up in chasing down each line to show the assumptions and methods are sound and try to rule out the alternatives.

harlequin
2004-May-06, 08:18 PM
It's taking them a surprisingly long time to resolve the question of these Martian fossils, & the whole "nanobacteria" debate in general. Life, or not life? You'd think in this DNA age, these questions would be easier to settle...

As has already been mention, it would be extremely unlikely that DNA could survive in such a rock with its history. Indeed it is very rare for fossils to have verifiable "fossil" DNA at all. I also would also point out that Martain life might not have DNA.

But those things been said, that meteorite in question has fossilized life has been an extreme minority position since shortly after the initial announcement. Any new evidence against it is just another nail in the coffin unless and until those who advocate that it is life come up with far better evidence.