NASA Scientist’s Claim of Extraterrestrial Life Kicks Hornets Nest of Criticism

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Last week, NASA scientist Richard Hoover at the Marshall Space Flight Center near Huntsville, Alabama, published a paper in the Journal of Cosmology claiming that fragments collected from the Orgueil meteorite and two similar meteorites contain fossilised bacteria. Hoover made nearly identical claims in 2004 and again in 2007. In his paper, he contrasts photos of tubular and ribbon-like squiggles on the inner surface of the space rocks and pictures of bacteria found on Earth.


In addition to this shape-based evidence, Hoover described chemical evidence, arguing that the squiggles contain more carbon than the meteorite matrix in which they are suspended, suggesting they were once alive.

The world's science community is currently debating whether there is enough evidence to accept that the filamentous structures inside the meteorites are, as Hoover claims, biological organisms from outer space, whether they are in fact terrestrial bacteria that wormed their way into the meteorite after it crashed or whether the squiggle lines are nothing more than naturally occurring mineral structures that, to Hoover's eye, may very well look like bacteria.

Here's a seminal critique of Hoover's claims from Rosie Redfield's RRResearch Blog. Redfield , professor of zoology at the University of British Columbia, gained fame for her brilliant critique of the paper on the NASA-funded discovery at Mono Lake called:  "A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus":

Is this claim of bacteria in a meteorite any better than the 1996 one?

"A new paper from a NASA scientist claims to present evidence for bacteria-like organisms in some meteorites.  (Richard Hoover, 2011, Fossils of cyanobacteria in C11 carbonaceous meteorites. Journal of Cosmology 2011, vol 13.)

"I don't know much about meteorites, but here's my evaluation:

What the author did:

"He fractured tiny comet-derived meteorites (0.1 – 0.6 g) from two events and examined the freshly broken surfaces.  He claims to have observed structures that are remnants of cyanobacteria.

"These meteorites are of a special very rare type (only 9 are known).  They are about 20% water, and soft enough to cut with a knife.  They mainly consist of minerals cemented together with magnesium sulfate ('Epsom salts'). They come from asteroids and comets, not planets like the Alan Hills meteorite from Mars.  Hooper's reasoning that they come mainly from comets seems reasonable to me.

"They contain quite a bit of organic (carbon-based) material, but I don't know if this differs significantly from the polycyclic aromatic hydrocarbons known to be present in comets.  It's true that PAHs found on Earth are usually biological in origin (think of the tarry crud that accumulates on your barbeque grill), but that doesn't mean that PAHs from space have biological origins.

"An important concern with this kind of study is contamination with terrestrial organisms before examination.  He doesn't say how the meteorites have been stored before he obtained them, nor how the surfaces of the meteorites were treated before being fractured and examined.  He doesn't say how they were fractured — might they have been cut with a scalpel blade or just pressed on until they crumbled?  He says that the tools were flame-sterilized, but not what the tools were or how they were used. 

"He used two examination techniques.  FESEM is field emission scanning electron microscopy — this seems to be a higher-resolution form of scanning electron microscopy (SEM), with the usual risks of artefacts.  The fractured surfaces were not coated with anything before being analyzed. I don't know what effect this might have.  The other technique is energy-dispersive X-ray analysis – I gather that this is an add-on to SEM that can scan a specimen and report on the abundance of specific atoms at different positions.  Its results can be reported as the distribution of atoms at a particular position or as an image of the specimen, shaded to show the varying density of a particular atom.

Results:

"He shows an image and analysis of one filament from the Ivuna meteorite.  It has more carbon than the surrounding material but no detectable nitrogen or phosphorus. 

"He bolsters his claim that it's a bacterium by showing an image of the giant bacterium Titanospirillum and an image of another filament from the meteorite.  His claim that the sulfur granules in this second   filament are like those of Titanospirillum is weakened by the very high sulfur in the surrounding material.  And although this filament is similar in size and shape to Titanospirillum (upper images), the other filament is about 15 times smaller (bottom images, adjusted to approximately the same scale).

M-1 pix

M-1 scaled

"The image he shows of an inner surface of the Orgueil meteorite has more filaments (no attempt is made at quantitation).  These are more complex in structure and fairly similar to each other, suggesting that they were formed by a single kind of process.

"The atomic analysis is not at all convincing.  He claims that different parts of the filament have different composition, but doesn't present any control analysis of the variability of the measurements or of the background values for positions away from the filaments.  He claims that the atom-density scans show enrichment of carbon and oxygen in the filaments, but this looks very weak to me — the only strong signals are for magnesium and sulfur.  Again there is no detectable nitrogen or phosphorus.

"He spends a lot of text discussing the morphological similarities of these filaments to cyanobacteria, but I don't regard these similarities as worth anything.  Filamentous bacteria are very morphologically diverse, and additional variations in appearance are likely to result from inconsistent preparation for electron microscopy.  It's probably pretty easy to find a bacterial image that resembles any fibrous structure.  In the absence of any statistical evidence to the contrary, it's prudent to assume that such similarities are purely coincidental.

"The author tacks on quite a bit of other less-than-compelling information intended to support his claim that life from space is plausible.  For example, he shows photos of colonies of coloured microorganisms to support his argument that the colours seen on the surfaces of Europa and Enceladus are biological in origin.

Bottom line:

"The Ivuna meteorite sample showed a couple of micron-scale squiggles, one of which contained about 2.5-fold more carbon than the background.  One of the five Orguil samples had at least one patch of clustered fibers; these contained more sulfur and magnesium than the background, and less silicon.  As evidence for life this is pathetic, no better than that presented by McKay's group for the ALH84001 Martian meteorite in 1996.

The Daily Galaxy via newscientist.com and Rosie Refield Blog

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