Antarctica – Australian Science

Lake Vostok: life beneath the ice

Kevin Orrman-Rossiter — Fri, 26 Jul 2013 00:09:44 +0000

Imagine, Lake Vostok is covered by more than 3,700 metres of Antarctic ice. Devoid of sunlight, it lies far below sea level in a depression that formed 60 million years ago, when the continental plates shifted and cracked. Few nutrients are available. Yet scientist, led by Scott Rogers, a Bowling Green State University professor of biological sciences, have found a surprising variety of life forms living and reproducing in this extreme environment. A paper published June 26 in PLOS ONE details the thousands of species they identified through DNA and RNA sequencing.

What lies sealed beneath the glacial ice?

Antarctica, 35 million years ago, had a temperate climate and was inhabited by a diverse plants and animals. About 34 million years ago, a huge drop in temperature occurred and ice covered the lake, when it was probably still connected to the Southern Ocean. This lowered the sea level by about 100 metres, which could have cut off Lake Vostok from the ocean. The ice cover was intermittent until a second big plunge in temperature took place 14 million years ago, and sea level dropped even farther.

As the ice crept across the lake, it plunged the lake into total darkness and isolated it from the atmosphere, and led to increasing pressure in the lake from the weight of the glacier. While many species probably disappeared from the lake, as indicated by Rogers’ results, some seem to have survived.

Rogers and his colleagues examined core sections from the ice above Lake Vostok that were extracted in 1998. At the time, no one had reached the actual lake, a feat that was achieved only last year. But the drilling had gone deep enough to reach a layer of ice at the bottom of the sheet that formed as lake water froze onto the bottom of the glacier where it meets the lake. The team sampled cores from two areas of the lake, the southern main basin and near an embayment on the southwestern end of the lake. The embayment appears to contain much of the biological activity in the lake.

By sequencing the DNA and RNA from the ice samples, the team identified thousands of bacteria, including some that are commonly found in the digestive systems of fish, crustaceans and annelid worms, in addition to fungi and two species of archaea, or single-celled organisms that tend to live in extreme environments. Other species they identified are associated with habitats of lake or ocean sediments. Psychrophiles, or organisms that live in extreme cold, were found, along with heat-loving thermophiles, which suggests the presence of hydrothermal vents deep in the lake. Rogers said the presence of marine and freshwater species supports the hypothesis that the lake once was connected to the ocean, and that the freshwater was deposited in the lake by the overriding glacier.

These results, however, are not without controversy.

Other claims and other lakes

Long before he began using these techniques to study the ice, Rogers and his team had developed a method to ensure purity. Sections of core ice were immersed in a sodium hypochlorite (bleach) solution, then rinsed three times with sterile water, removing an outer layer. Under strict sterile conditions, the remaining core ice was then melted, filtered and refrozen.

Sergey Bulat has doubts about the results, despite the careful sample preparation. Bulat, a Lake Vostok expert at the Petersburg Nuclear Physics Institute in Gatchina, Russia, is quoted as saying, “that it is very probably that the samples are heavily contaminated with tissue and microbes from the outside world.”

Quirin Schiermeier has noted in Nature News:

Bulat and Rogers have both studied Vostok ice samples taken in the 1990s by a consortium of Russian, French and US Antarctic researchers. In the past, the pair pondered a close collaboration. But their scientific relationship broke over enduring disagreement about the level of contamination of samples.

In March, Bulat himself faced criticism over an unknown species of bacterium his team had discovered in a Lake Vostok ice core drilled last year. Sceptics said that this finding was due to contamination from drilling fluid.

The two researchers’ claims are probably the first in what will no doubt be an interesting period of discovery in Lake Vostok and other Antarctic lakes. The first samples of water from Lake Vostok itself, collected in early 2013 are currently being analysed. The Russian team has said that it hopes to have results within the next year. Bacteria, of known species, have been recovered from the smaller Antarctic Lakes, Whillans and Vida. Lake Vida has been sealed off for around 2,800 years. Ice cores drilled in 2005 and 2010 have recently revealed life, but at about one-tenth of the abundance usually found in freshwater lakes in moderate climate zones. Similarly in Lake Whillans the bacteria levels were roughly one-tenth the abundance of microbes in the oceans.

These results are glimpses into the the sub-glacial world of Antarctica. Glimpses that may change how we not only view this continent but also providing clues to how extra terrestrial life may exist on icy moons such as Jupiter’s Europa and Saturn’s Enceladus.

Cite this article:
Orrman-Rossiter K (2013-07-26 00:09:44). Lake Vostok: life beneath the ice. Australian Science. Retrieved: May 03, 2024, from http://australianscience.com.au/science-2/lake-vostok-life-beneath-the-ice/

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Does my science look big in this? The astrobiology edition

Kevin Orrman-Rossiter — Fri, 09 Nov 2012 00:07:51 +0000

During the 20th century a powerful new idea gradually entered our consciousness and culture: cosmic evolution. We are all par of a huge narrative: a cosmos billions of years old and billions of light years in extent. It is this idea that caught my attention this month via the proceedings of the Sao Paulo Advanced School of Astrobiology SPASA 2011, published in the October International Journal of Astrobiology.

Although the question of extraterrestrial life is very old, the concept of full-blown cosmic evolution – the connected evolution of planets, stars galaxies and life on Earth and beyond – is much younger. In a rather breathtaking paper, Steven Dick formerly of the Aerospace History at the National Air & Space Museum places his arguments for cosmic evolution. Dick traces the idea from its roots in the 19th century theories of Pierre-Simon Laplace and Robert Chambers through its philosophical, astronomical, and biological upbringing to the present day. He examines evolution, the worldview that it had become in the 1950s and 1960s and how it had permeated culture in numerous ways and different cultures in diverse ways. Dick cautions us though noting “we need to remember that ‘culture’ is not monolithic and that ‘impact’ is a notoriously vague term.”

Cosmic evolution. Image credit: Harvard University.

In addition to the impact of our new understanding on culture, cosmic evolution also provides a window on long-term human destiny, asserts Dick. He presents this idea via three scenarios, the: the physical , biological, and postbiological universe. Life is unique to earth in the physical universe scenario, and the options flow from this situation – think of Isaac Asimov’s Foundation series. We will certainly interact with extraterrestrials in the biological universe – here cosmic evolution commonly ends in life, mind and intelligence. Cultural evolution in a biological universe may replace biologicals with artificial intelligence creating what Dick calls a postbiological universe. We do not know yet, which of these is our reality, that is one of the challenges of astrobiology, maintains Dick.

In a second ‘big-picture’ paper Marcelo Gleiser presents his four ages of astrobiology. For Gleiser the influx of astrophysical data, particularly on the prevalence of exoplanets “indicates that there are plenty of potentially life-bearing platforms within our galaxy.” He then presents the ‘history’ of life in the universe in terms of the steps needed for matter to have sequentially self-organised into more and more complex structures. His sequence is best viewed as a prelude to the physical or biological universe scenarios of Dick. Gleiser’s fourth age, the Cognitive Age (the age of thinking biomolecules), really addresses whether we are unique or not i.e. which of Dick’s two scenarios, the physical or biological are reality. Gleiser’s first three ages: physical, the creation of stars and planets from atomic nuclei; chemical, in which elements organise into biomolecules; and thirdly biological, in which living creatures of growing complexity form from biomolecules. the papers by Dick and Gleiser are both papers heady and exhilarating conceptual reads.

Jorge Horvath and Douglas Galante accept the premiss that life exists, and then argue we need to take high-energy astrophysical events seriously. Scientists and the public account for meteor impacts in both academic studies, science-fiction writing and film – not so for events such as supernovae, gamma-ray bursts and flares. They show that these events are more frequent than asteroid strikes and that the effects are non-negligible (academic speak for potentially fatal to planet based species). They conclude that just because we have not yet been wiped out by such events can be seen as either a measure of earthlife’s resilience or a threat we are statistically yet to encounter.

My attention was captured by two other papers from the proceedings. Martin Brasier and David Wacey address the problem of studying life in deep space – comparing it to study of life remote in time. This view is pertinent, as it is non-trivial for scientists to determine what is a viable signal of extinct life. The authors develop a set of protocols and then apply these to earth samples, of varying ages. They do this to show how we could interpret similar samples, where much of the desirable information (the context) has been filtered out during the process of transmission (either physical or data) across vast distances of space, or time or both (as is likely on Mars). Even 10 years ago these questions were moot, but we have learned much over the recent past about metabolic pathways and living microbial systems. Brasier and Wacey conclude that there is still work required on pseudo-fossils, structures that arise naturally within complex physico-chemical systems, so that we can confidently agree on signs of life that are remote in space and time.

The Dry Valleys in Antarctica. Photo credit: NASA

My final pick is an experimental paper that looks at the ExoMars mission. The European Space Agency and (initially NASA ) ExoMars mission is scheduled for launch in 2018 – specifically to detect life signatures on the surface and subsurface of Mars. This probe will carry, for the first time, a Raman spectrometer, a technique with proven ability to determine the spectral signals of key biochemicals. The authors support these assertions by assessing samples acquired from Arctic and Antarctic cold deserts and a meteorite crater. These terrestrial environments are similar to those found on Mars. The experimental results presented in this paper demonstrate that it will be possible using this technique to assess and detect spectral signals of extra-terrestrial (Mars in this case) extremophilic life signatures.

Cite this article:
Orrman-Rossiter K (2012-11-09 00:07:51). Does my science look big in this? The astrobiology edition. Australian Science. Retrieved: May 03, 2024, from http://australianscience.com.au/biology/does-my-science-look-big-in-this-the-astrobiology-edition/

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