Even after some 200 years of discovery and exploration, the Antarctic continent still contains many secrets. One of them, the “Blood Falls” discovered by Scott’s Terra Nova expedition in the Dry Valleys of East Antarctica, has now been solved thanks to latest analytical methods.
Not red algae, not bacteria or other microorganisms, and not simply dissolved iron forms the rust-like reddish color of the water masses pouring down from about 100 meters into the dry valley below. Rather, amorphous nanospheres, which are enormously rich in chlorine and iron and are oxidized by aerial oxygen, are responsible for the phenomenon of the blood-red color. That is the conclusion of a study by a U.S. research team with first author Dr. Elizabeth Sklute of the Planetary Science Institute in Tucson. The results were published in the journal Frontiers in Astronomy and Space Sciences.
The research team discovered the tiny spheres when they examined various samples from the water and surrounding soil. They used new methods, previously used elsewhere, to find the components of the samples. Various types of spectroscopy and investigations with different electron microscopes were used by the team for analyses.
The results of the studies surprised the research team as it dispelled a previous assumption. It is not crystalline structures containing iron that are responsible for the coloration, but amorphous nanospheres that are very rich in chlorine and iron and also consist of other minerals. “As soon as I looked at the microscope images, I realized that there were these little nanospheres and they were rich in iron, and they had a lot of different elements besides iron: silicon, calcium, aluminum, sodium, and they all varied,” explains Dr. Ken Livi of John Hopkins University, who had analyzed the samples.
The team also examined the material composition of the samples and discovered that they consist primarily of calcite and aragonite plus quartz, feldspar and clay minerals. These minerals then provide the other elements that, together with the iron, form the spheres by oxidation. However, this process only occurs when the material dissolved in the water gets in ccontact with air, i.e. at the spilling point at the glacier.
The question of whether this means that the theory of microorganisms coloring the water is off the table, however, can be clearly answered no by the team. Earlier studies have shown that beneath the 56-kilometer-long glacier lies an entire network of rivers and small lakes in which microorganisms can only live through chemical processes – chemosynthesis instead of photosynthesis. The mineral-rich environment and the water strongly support this process. The research team’s analyses show that the organisms contribute at least some of the color and thrive there. “Potentially, these microorganisms could have existed there for millions of years,” Professor Livi continues.cor
These results not only impact the view of biology and geology of the Dry Valleys in Antarctica. They literally go much further, into planetary research, especially on Mars. For they show that the previous analytical methods performed by the Mars rovers are not enough to get a better picture of the environment. “To really understand the nature of the surfaces of rocky planets, a transmission electron microscope would be required,” claims researcher Livi. But at least for the time being, this demand will remain just fantasy.
Dr Michael Wenger, PolarJournal
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