NASA planetary scientists say they have found evidence of past water movement throughout a Martian meteorite.
This SEM image shows spheroidal features embedded in a layer of iddingsite, a mineral formed by action of water, in the Martian meteorite Yamato 000593: an area with the spheres, circled in red, was found to have about twice as much carbon present as an area without the spheres, circled in blue. The scale bar at lower left is 1 micron. Image credit: White LM et al.
The 13.7-kg meteorite, dubbed Yamato 000593, was found on the Yamato Glacier in Antarctica by the Japanese researchers in 2000. It was classified as a nakhlite, a subgroup of Martian meteorites.
Martian meteoritic material is distinguished from other meteorites and materials from Earth and the moon by the composition of the oxygen atoms within the silicate minerals and trapped Martian atmospheric gases.
Analyses show that Yamato 000593 was formed about 1.3 billion years ago from a lava flow on Mars.
Around 12 million years ago, an impact occurred on Mars which ejected it from the Red Planet’s surface.
The meteorite traveled through space until it fell in Antarctica about 50,000 years ago.
In a new study, reported in the journal Astrobiology, NASA scientists focused on structures within Yamato 000593.
These structures suggest biological processes might have been at work on Mars hundreds of millions of years ago.
The team found two distinctive sets of features associated with Martian-derived clay.
They found tunnel and micro-tunnel structures that thread their way throughout the meteorite.
The observed micro-tunnels display curved, undulating shapes consistent with bio-alteration textures observed in terrestrial basaltic glasses, previously reported by researchers who study interactions of bacteria with basaltic materials on Earth.
This SEM image shows spherulitic features encased in both an upper, false-colored orange, and lower layer of iddingsite. Image credit: White LM et al.
The second set of features consists of nanometer- to-micrometer-sized spherules that are sandwiched between layers within the rock and are distinct from carbonate and the underlying silicate layer.
Similar spherical features have been previously seen in the Martian meteorite Nakhla that fell in 1911 in Egypt. Composition measurements of the Yamato 000593 spherules show that they are significantly enriched in carbon compared to the nearby surrounding iddingsite layers.
A striking observation is that these two sets of features in Yamato 000593, recovered from Antarctica after about 50,000 years residence time, are similar to features found in Nakhla, an observed fall collected shortly after landing.
The scientists said that “they cannot exclude the possibility that the carbon-rich regions in both sets of features may be the product of abiotic mechanisms: however, textural and compositional similarities to features in terrestrial samples, which have been interpreted as biogenic, imply the intriguing possibility that the Martian features were formed by biotic activity.”
“The unique features displayed within the Martian meteorite Yamato 000593 are evidence of aqueous alterations as seen in the clay minerals and the presence of carbonaceous matter associated with the clay phases which show that Mars has been a very active body in its past. The planet is revealing the presence of an active water reservoir that may also have a significant carbon component,” said study co-author Dr Everett Gibson of NASA Johnson Space Center in Houston, Texas.
“The nature and distribution of Martian carbon is one of the major goals of the Mars Exploration Program.”
“Since we have found indigenous carbon in several Mars meteorites, we cannot overstate the importance of having Martian samples available to study in earth-based laboratories.”
“Furthermore, the small sizes of the carbonaceous features within the Yamato 000593 meteorite present major challenges to any analyses attempted by remote techniques on Mars.”
“This is no smoking gun. We can never eliminate the possibility of contamination in any meteorite. But these features are nonetheless interesting and show that further studies of these meteorites should continue,” said lead author Dr Lauren White from the Jet Propulsion Laboratory in Pasadena, California.
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White LM et al. 2014. Putative Indigenous Carbon-Bearing Alteration Features in Martian Meteorite Yamato 000593. Astrobiology 14 (2): 170-181; doi: 10.1089/ast.2011.0733
