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geardrops
03-06-2011, 09:27 AM
Maybe?

http://news.yahoo.com/s/digitaltrends/nasascientistfindsevidenceofalienlife


That astonishingly awesome claim comes from Dr. Richard B. Hoover, an astrobiologist at NASA’s Marshall Space Flight Center, who says he has found conclusive evidence of alien life — fossils of bacteria found in an extremely rare class of meteorite called CI1 carbonaceous chondrites. (There are only nine such meteorites on planet Earth.) Hoover’s findings were published late Friday night in the Journal of Cosmology, a peer-reviewed scientific journal.

So, yeah. There you go. Smarter folk than I can dissect this.

Astronomer
03-06-2011, 07:54 PM
To be fair, Dr. Hoover doesn't claim that his evidence is conclusive -- only that it is "interesting" and warrants further investigation.

It is important to note that he found structures within a meteorite that do not appear to have arisen from a non-biotic process. The structures are indeed strange, strikingly organic-looking, and not something you'd expect to find inside a rock.

It's is also important to note that no amino or nucleic acids have been found. Dr. Hoover is going only by the appearance of the structures he discovered, and not by any chemical or DNA analysis.

Though some structures do not resemble anything found on Earth, many actually do, which suggests that the meteorite may have been infiltrated by terrestrial microbes some time after impact. Dr. Hoover doubts that local infiltration occurred, but it is the most mundane explanation.

On one side, the unidentifiable structures could just be terrestrial microbes that have been "mangled" into unrecognizable form during the fossilization process. (Let a Jello cube completely dry out and see to what extent it resembles its former self.)

On the other side, the meteorite microbes may be extraterrestrial, but bear a passing resemblance to local microbes only coincidentally, and may, in fact, be completely different genetically and internally -- though such evidence of any internal differences (or similarities) is not likely to be found.

Or they may be non-biotic structures that arose from a heretofore unknown process.

More data!

RobJ
03-06-2011, 07:56 PM
There's another thread running on this:

http://www.absolutewrite.com/forums/showthread.php?t=206922

geardrops
03-06-2011, 11:51 PM
More data!

Exactly my thought :)

Pthom
03-07-2011, 02:41 AM
There's another thread running on this:

http://www.absolutewrite.com/forums/showthread.php?t=206922
True enough. Let's be sure we don't get the two of them mixed up. This forum is for discussions of scientific facts. The forum where the other thread exists is for those who wish to discuss anything else about the phenomenon.

GeorgeK
03-07-2011, 01:41 PM
Assume for the moment that this actually is evidence of extraterrestrial bacteria. How could one prove the point of origin?

movieman
03-07-2011, 08:12 PM
Assume for the moment that this actually is evidence of extraterrestrial bacteria. How could one prove the point of origin?

That's difficult. If the bacteria is genetically linked to some other Earth creatures then the odds are high that it came from Earth. If it's clearly using something we've never seen on Earth (e.g. not DNA-based or using a completely different DNA symbol set) then the odds of being alien are reasonable but not certain.

We could then guess where the meteorite came from by looking at the geology, but we would still be hard-pressed to say with great certainty because we don't have much detailed information about anywhere other than Earth. If we knew when it landed we might be able to improve the guesswork by seeing whether a reasonable post-ejection orbit could have coincided with Earth's at that time.

Either way these claims seem to come up every few years and then vanish, so I wouldn't hold out too many hopes. It sounds worth investigating though.

Astronomer
03-08-2011, 06:52 AM
That's difficult. If the bacteria is genetically linked to some other Earth creatures then the odds are high that it came from Earth.
No genetics, unfortunately. Just a bunch of tube-shaped voids and hairy fissures in the rock. And proving the existence of life based on amorphous shapes is difficult -- as it should be.


If we knew when it landed we might be able to improve the guesswork by seeing whether a reasonable post-ejection orbit could have coincided with Earth's at that time.
The meteorite landed in France in 1864. Your orbital mechanics analysis proposal is a clever idea, but there's no guarantee that the rock didn't take millions of years (or longer) to fall here after it was ejected from its planet of origin, which would broaden the number of possible post-ejection orbits pretty much to infinity.

Drat.

I wonder if the person who found it washed his hands before picking it up?

geardrops
03-08-2011, 06:58 AM
http://news.discovery.com/space/nasa-refutes-alien-discovery-claim-110307.html

screenscope
03-08-2011, 07:26 AM
I suspect that when - and if - we do finally get hold of some genuine alien DNA, it will actually be related to us anyway. The stuff of the universe and all that.

small axe
03-12-2011, 01:37 PM
The stuff of the universe and all that

Let's imagine that Life has originated on planet Earth more than the one time leading up to Us / life-as-we-know-it.

So it might be utterly different from any now-living earth life.

Would it necessarily have some characteristic that would demonstrate that, however different from us, it was still EARTH-originated life?

Or how might extraterrestrial life have something that clearly identifies it as being not just different from current Earth lifeforms ... but in fact something living that could not have possibly originated here?

Astronomer
03-13-2011, 03:13 AM
Let's imagine that Life has originated on planet Earth more than the one time leading up to Us / life-as-we-know-it.

So it might be utterly different from any now-living earth life.

Would it necessarily have some characteristic that would demonstrate that, however different from us, it was still EARTH-originated life?
If the first go-around were wiped out completely, then I think the only properties that could prove its Earthly origins would be isotope-based instead of genetic-based. But if anything of the first go-around were to survive well enough to be analyzed, then it would be difficult to rule out the possibility that it played some role in forming the basis for the second go-around.


Or how might extraterrestrial life have something that clearly identifies it as being not just different from current Earth lifeforms ... but in fact something living that could not have possibly originated here?Because we all emerged from the same primordial soup and evolved in the same environment, over 80% of our human DNA is shared with a housefly, and over 15% with a milkweed. Though DNA-based life could emerge elsewhere, I wouldn't expect it to have any overlap with the terrestrial gene pool. ERV structure in the genome is purely stochastic (unlike the more purposeful genes), and the probability of an alien genome coincidentally matching even one percent of the ERV structures shared by humans and houseflies is less than one in 10^50.

So if we are ever able to obtain alien DNA, it should be readily apparent that it's not from Earth.

Of course, life that has emerged elsewhere need not necessarily be nucleic acid-based at all, though no one is sure what form such life would take.

veinglory
03-13-2011, 03:29 AM
Also if there is link to earth bacteria, the argument is they possibly came from it. So it will not be utterly different from what is here. (Keep in mind this rock hit Earth when life on earth was in the early stages or didn't exist.)

screenscope
03-14-2011, 06:16 AM
Endlessly fascinating stuff!

lpetrich
04-06-2011, 12:04 PM
PZ Myers slammed this claim very hard: Did scientists discover bacteria in meteorites? (http://scienceblogs.com/pharyngula/2011/03/did_scientists_discover_bacter.php)

He started off by noting that the story was first reported by Fox News, and he then went on to describe the Journal of Cosmology as a publication of some crackpots who believe that Earth life is derived from organisms that had lived in outer space. Not exactly a big-name journal.

Turning to the "paper" itself, Fossils of Cyanobacteria in CI1 Carbonaceous Meteorites: Implications to Life on Comets, Europa, and Enceladus (http://journalofcosmology.com/Life100.html), he discovered that the title in it links to a page at Amazon for a book (!) Not exactly a "proper" paper.

It was poorly written; much of it was an assortment of odds and ends about carbonaceous chondrites, a kind of meteorite. There were some pictures of what looked like real bacteria, but they were all of Earth organisms. Seeing bacteria in the meteorite pictures seemed like pareidolia to him, like seeing shapes in clouds. They did not even have some subset with consistent shapes.

Mineral content? Lots of C, Mg, Si, and S, but no N -- rather odd for an organism.

lpetrich
04-06-2011, 07:59 PM
Because we all emerged from the same primordial soup and evolved in the same environment, over 80% of our human DNA is shared with a housefly, and over 15% with a milkweed.
There hasn't been much genetic research done on houseflies (Musca domestica) or milkweeds (Asclepias spp.). But there's been a LOT on fruit flies (Drosophila melanogaster) and a little plant called Arabidopsis.

So where did those numbers come from? Some popularization that was extrapolating from fruit flies to houseflies and Arabidopsis plants to milkweed plants? Those extrapolations are likely legitimate, but they are extrapolations none the less.

I did some testing on my own, looking in PubMed (http://www.pubmed.org). I used elongation factor 1-alpha [Homo sapiens] - Protein result (http://www.ncbi.nlm.nih.gov/protein/AAK95378.1), GenBank AAK95378.1, as a reference -- it's involved in assembling proteins using nucleic-acid sequences. I then used BLAST: Basic Local Alignment Search Tool (http://blast.ncbi.nlm.nih.gov/Blast.cgi) to look for the amount of match in different species.

Human protein database entries: 1534433 (PubMed hits; some of them for other species' proteins)
Best BLAST score: 1000
Zebrafish (Danio rerio): 905 (DB: 70885)

Fruit fly (Drosophila melanogaster): 850 (DB: 152358)
Housefly (Musca domestica): only a few matches, the best being 591 (DB: 908)

Brewers' Yeast (Saccharomyces cerevisiae): 760 (DB: 222049)

Arabidopsis thaliana: 715 (DB: 464911)
Milkweed (Asclepias spp.): only a few fragmentary matches, the best being 23 (DB: 190)

The low-quality matches for houseflies and milkweed is a consequence of their having much less gene sequencing.

Astronomer
04-06-2011, 10:50 PM
There hasn't been much genetic research done on houseflies (Musca domestica) or milkweeds (Asclepias spp.). But there's been a LOT on fruit flies (Drosophila melanogaster) and a little plant called Arabidopsis.

So where did those numbers come from?I got those numbers from a handout at a science and nature museum exhibit. Not being a biologist or geneticist, I relied solely on the handout's authority in my post above.