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RE: [escepticos] nuevas evidencias de vida en Marte



Si os interesa... os copio el press release original de la NASA sobre
estos nuevos análisis del ALH84001.
¿Mi opinión? Que es agosto. Recordemos que la noticia original del
análisis del equipo de McCay sobre ese meteorito se lanzó al mundo un 8
de agosto, creo recordar que en 1996, así que estamos de cumpleaños. Y
siendo agosto y teniendo aniversario, qué mejor que volver a marear una
vez más la perdiz... Alguien podría preguntarse, por otro lado, por qué
solamente los análisis de equipos que trabajan para (o con) la NASA
siguen apostando por la interpretación biótica (y marciana) de las
características del ALHetc. 

Saludos

javier armentia
http://javarm.blogalia.com

THE FOLLOWING RELEASE WAS RECEIVED FROM NASA HEADQUARTERS, IN
WASHINGTON, 
DC, AND IS FORWARDED FOR YOUR INFORMATION. 
RELEASE: 02-150
RESEARCHERS PUBLISH LATEST RESULTS 
IN CONTINUING SEARCH FOR ANCIENT MARTIAN LIFE
In the latest study of a 4.5 billion-year-old Martian 
meteorite, researchers have presented new evidence confirming 
that 25 percent of the magnetic material in the meteorite was 
produced by ancient bacteria on Mars. These latest results 
were published in the journal Applied and Environmental 
Microbiology.
The researchers used six physical properties they refer to as 
the Magnetite Assay for Biogenicity (MAB) to compare all the 
magnetic material found in the ancient meteorite -- using the 
MAB as a biosignature. A biosignature is a physical and/or 
chemical marker of life that does not occur through random 
processes or human intervention. 
"No non-biologic magnetite population, whether produced by 
nature or in the laboratory, has ever met the MAB criteria," 
said Kathie Thomas-Keprta, an astrobiologist at NASA's 
Johnson Space Center (JSC) in Houston and the lead researcher 
on the study. "This means that one-quarter of the magnetite 
crystals embedded in the carbonates in Martian meteorite 
ALH84001 require the intervention of biology to explain their 
presence."
Magnetotactic bacteria, which occur in aquatic habitats on 
Earth, arrange magnetite crystals in chains within their 
cells to make compasses, which help the bacteria locate 
sources of food and energy. Magnetite (Fe3O4) is produced 
inorganically on Earth, but the magnetite crystals produced 
by magnetotactic bacteria are very different -- they are 
chemically pure and defect-free, with distinct sizes and 
shapes.
Four of the MAB biosignature properties relate to the 
external physical structure of the magnetite crystals, while 
another refers to their internal structure and another to 
their chemical composition.
In their earlier studies, the researchers found that 
approximately one-quarter of the nanometer-sized magnetite 
crystals in ALH84001 had remarkable physical and chemical 
similarities to magnetite particles produced by a bacteria 
strain on Earth called MV-1. This is the first time, however, 
that any researcher has used the full MAB range of 
biosignature properties to compare the proposed bacteria-
produced crystals in Mars meteorite ALH84001with the 
bacteria-produced crystals from Earth and with the other 
magnetites in the meteorite. 
The comparison between the proposed bacteria-produced 
crystals in the meteorite and crystals known to be produced 
by Earth-bacteria MV-1 is striking and provides strong 
evidence that these crystals were made by bacteria on Mars.
The fact that Mars Global Surveyor data suggest that early 
Mars had a magnetic field is consistent with a reason why 
Mars would have magnetotactic bacteria. "Our best working 
hypothesis is that early Mars supported the evolution of 
bacteria that share several traits with magnetotactic 
bacteria on Earth, most notably the MV-1 group," said Simon 
Clemett, a coauthor of the paper at Johnson.
Mars has long been understood to provide the sources of light 
and chemical energy sufficient to support life, but in 2001 
the Mars Global Surveyor spacecraft observed magnetized 
stripes in the crust of Mars, which showed that a strong 
magnetic field existed in the planet's early history, about 
the same time as the carbonate containing the unique 
magnetites in ALH84001 was formed. 
In June, researchers using the Mars Odyssey spacecraft 
announced that they had found water ice under the surface of 
Mars. These attributes, coupled with a carbon dioxide-rich 
atmosphere, would have provided the necessary environment for 
the evolution of microbes similar to the fossils found in 
ALH84001. 
"We believe this latest study proves that the magnetites in 
ALH84001 can be best explained as the products of multiple 
biogenic and inorganic processes that operated on early 
Mars," Thomas-Keprta said. 
An international team of nine researchers collaborated on the 
three-year study. The team, led by Thomas-Keprta of Lockheed 
Martin at Johnson Space Center, was funded by the NASA 
Astrobiology Institute. Co-authors of the study are Clemett 
and Susan Wentworth of Lockheed Martin at JSC; Dennis 
Bazylinski of Iowa State University (funded by the National 
Science Foundation); Joseph Kirschvink of the California 
Institute of Technology in Pasadena; David McKay and Everett 
Gibson of JSC; Hojatollah Vali of McGill University in 
Canada; and Christopher Romanek of the Savannah River Ecology 
Laboratory. 
For a more technical discussion of this latest publication 
please visit the following Web site:
http://ares.jsc.nasa.gov/astrobiology/biomarkers/recentnews.html


-----Mensaje original-----
De: owner-escepticos en dis.ulpgc.es [mailto:owner-escepticos en dis.ulpgc.es]
En nombre de Ismael
Enviado el: jueves, 08 de agosto de 2002 19:47
Para: escepticos en dis.ulpgc.es
Asunto: [escepticos] nuevas evidencias de vida en Marte


Bueno esto lo he encontrado en 100cia.com, ¿que opinan?

Con un nuevo estudio realizado sobre una muestra del meteorito ALH84001,
los investigadores del Johnson Space Center de la NASA han llegado a la
conclusión de que al menos el 25% de la magnetita encontrada en el
meteorito tiene un origen biológico. Los investigadores han realizado un
informe donde detallan las seis propiedades que debería tener un
compuesto de magnetita que tuviese un origen biológico y que lo
diferenciase de uno que no lo fuera. Tomando esto como referencia,
analizaron por completo la muestra y han llegado a la conclusión de que
al menos una cuarta parte de la magnetita que encontraron coincidía
plenamente con el patrón que marcaron para deducir su origen biológico. 

Según los científicos, la magnetita encontrada jamás llegaría a
producirse en la naturaleza de forma casual ni es reproducible tampoco
en un laboratorio, por lo que esa cuarta parte ha requerido la presencia
de seres vivos para su formación. 
En la Tierra, las bacterias magnetostáticas viven en medios acuosos y
ordenan los cristales de magnetita en cadenas a modo de brújulas, lo que
les ayuda a localizar alimento y energía. La magnetita (Fe3O4), se
produce de manera inorgánica en nuestro planeta, pero los producidos por
las bacterias tienen una pureza mayor y tienen distintos tamaños y
formas. 

En estudios anteriores, los investigadores llegaron a la conclusión de
que un cuarto de la magnetita del meteorito tenían unas propiedades
físicas y químicas similares a las producidas por bacterias en nuestro
planeta, sin embargo es la primera vez que los científicos han usado
seis de las características de la magnetita y han comprobado que son
idénticas a las encontradas en la Tierra. 

De hecho, este resultado concuerda con los datos obtenidos por la sonda
Mars Global Surveyor referentes a que en el pasado Marte tuvo un campo
magnético propio al encontrar franjas en la corteza que aún lo
mantienen, ya que ese hecho permitiría orientarse a las bacterias a la
hora de fabricar las cadenas. Además en junio de este año, los técnicos
de la NASA anunciaron la presencia de agua bajo la superficie de Marte,
lo que junto con la abundancia de CO2 permite el desarrollo de
bacterias. 



Un saludo a todos
Ismael.

Lo que se afirma sin pruebas,puede también ser negado sin pruebas.
Euclides.