Blood Falls

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Coordinates: 77 ° 43 ′ 0 ″  S , 162 ° 16 ′ 0 ″  E

Relief Map: Antarctica
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Blood Falls​
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Antarctic
Satellite image of the area

Blood Falls (also known as blood falls or blood stream) is the name of an outflow from a plume of salt water enriched with iron oxide , which flows from the tongue of the Taylor Glacier onto the ice-covered surface of western Bonney Lake in the Taylor Valley , one of the Antarctic dry valleys in Victorialand , Antarctica .

Iron-containing hypersaline water sporadically escapes through small cracks in the ice cascade. The source of the brine is a subglacial lake of unknown size, overlaid by about 400 meters of ice, several kilometers away from the small outlet at the Bloodfalls.

The reddish deposit was found in 1911 by the Australian geologist Griffith Taylor , a participant in the Terra Nova expedition . He was the first to explore the valley that bears his name. The first pioneers of Antarctica attributed the red color to red algae . However, it was later proven that it was iron oxides.

geochemistry

These are sparingly soluble, water-containing iron oxides (Fe 2 O 3 ), which are deposited on the surface of the ice after the iron ions in the thawed salt water are oxidized on contact with the atmosphere ( oxygen ) . Old seawater that is trapped in a subglacial pocket releases iron ions from the rock. It originated in the Antarctic Ocean when a fjord was isolated by the glacier at the end of the Miocene (about 5 million years ago) when sea levels were higher than they are today.

Unlike most Antarctic glaciers, Taylor Glacier is not frozen to the bottom , probably because of the presence of the salts that remain in solution when the ancient seawater trapped beneath it freezes out . The salt- cryo-concentration of the remaining (relict) sea water is due to the fact that pure ice crystallized, displaced the dissolved salts and the remaining liquid cooled because of the heat exchange with the enormous ice masses of the glacier. As a result, the enclosed water was concentrated to a brine with a salt content of two to three times that of sea water.

Hypersaline fluids that leaked through a crack in the ice and were randomly sampled were free of oxygen and rich in iron (II) sulfate . Sulphate is a lagging geochemical signature of marine conditions, while soluble divalent iron was likely released from the minerals of the subglacial foundation through microbial activity under reducing conditions.

Microbial ecosystem

This schematic cross-section of the bloodfalls shows how subglacial microbial communities survived in the cold, darkness, and absence of oxygen for a million years in salt water under the Taylor Glacier . Credit: US National Science Foundation (NSF)

The chemical and microbial analyzes indicate that a rare subglacial ecosystem of autotrophic bacteria has developed that metabolizes sulfates and iron ions. According to Jill Mikucki, a geomicrobiologist at Dartmouth College , the water samples from the bloodfalls contain at least 17 different types of microbes and almost no oxygen. One explanation could be that the microbes breathe sulfate as a catalyst with ferric ions and metabolize the microscopic amounts of organic matter that is trapped with them down there. Such a metabolic process had never been observed in nature before.

A puzzling observation is the coexistence of Fe 2+ and SO 4 2− ions under anoxic conditions. In fact, no hydrogen sulfide (HS - ) anions were found in the system. This suggests that there is a complex and poorly understood interaction between the biochemical sulfur and iron cycles.

Effects on the “snowball earth” hypothesis

According to Mikucki et al. (2009), the now inaccessible, subglacial lake was sealed off 1.5 to 2 million years ago and transformed into a kind of "time capsule". This isolated the microbial populations for a long enough time to develop independently from other, similar marine organisms. It could explain how other microorganisms could have survived before, according to the snowball earth hypothesis, the whole earth could have been frozen.

In fact, ice-covered seas may have been the only refuge for microbial ecosystems when the earth was covered by glaciers, possibly as far as tropical latitudes, during the Proterozoic ( aeon about 650-750 million years ago).

Consequences for astrobiology

This unusual location offers scientists a unique opportunity to study deep microbial life under extreme conditions without having to drill deep into the polar ice cap , combined with the risk of contaminating the fragile and still intact ecosystem.

Studying the harsh environments on earth is useful in understanding the range of conditions to which life can adapt; and to estimate the possibility of life in other parts of the solar system (→ extraterrestrial life ) - in places like Mars or Europe , an ice-covered moon of Jupiter . Scientists at the NASA Astrobiology Institute speculate that these worlds could house subglacial liquid water (→ extraterrestrial ocean ). These would be favorable conditions for elementary forms of life, which would be better protected from UV and cosmic radiation in the depths than on the surface.

Photo gallery

  • Blood Falls 2474051 e40871ef30 o.jpg
  • Blood Falls 1834170 166fdf53a6 o.jpg

See also

Individual evidence

  1. ^ Ohio State University: Explanation offered for Antarctica's 'Blood Falls' . In: ScienceDaily (Nov. 5, 2003) . November 5, 2003. Retrieved April 18, 2009.
  2. ↑ Juske Horita: Isotopic evolution of saline lakes in the low-latitude and polar regions . In: Aquatic Geochemistry . 15, No. 1, 2009, pp. 43-69. doi : 10.1007 / s10498-008-9050-3 .
  3. ↑ a b c Jackie Grom: Ancient ecosystem discovered beneath antarctic glacier . In: Science . News post . April 16, 2009. Retrieved April 17, 2009.
  4. ↑ Jill A. Mikucki, Ann Pearson, David T. Johnston, Alexandra V. Turchyn, James Farquhar, Daniel P. Schrag, Ariel D. Anbar, John C. Priscu, Peter A. Lee: A contemporary microbially maintained subglacial ferrous “ocean ” . In: Science . 324, No. 5925, 2009, pp. 397-400. doi : 10.1126 / science.1167350 . Retrieved April 17, 2009.
  5. ↑ Mars: Life on Mars? . In: Nasa Mars Exploration Program . October 5, 2005. Archived from the original on April 24, 2009. Retrieved on April 20, 2009.
  6. ^ The case of the missing Mars water . In: Nasa Science Portal . January 5, 2001. Retrieved April 20, 2009.
  7. ↑ Mars: Follow the Water… . In: Nasa Mars Exploration Program . February 15, 2006. Archived from the original on April 13, 2009. Retrieved on April 20, 2009.

further reading

  • Abraham Lerman, GW Luther III (ed.): Special Issue: Saline Lakes and Global Change . In: Springer (Ed.): Aquatic Geochemistry . 15, No. 1-2, February 1, 2009, pp. 1-348. ISSN  1573-1421 .
  • William Green, W. Lyons: The saline lakes of the McMurdo Dry Valleys, Antarctica . In: Aquatic Geochemistry . 15, No. 1, 2009, pp. 321-348. doi : 10.1007 / s10498-008-9052-1 .

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