(1) Executive Summary


Life continues to appear in the unusual and extreme locations from hot vents on the seafloor to ice covered hypersaline lakes in Antarctica (Priscu et al., 1998).

 

The subglacial environment represents one of the most oligotrophic environments on earth, an environment with low nutrient levels and low standing stocks of viable organisms. It is also one of the least accessible habitats.

 

Recently the significance of understanding subglacial communities has been highlighted by discoveries including the thriving bacterial communities beneath alpine glaciers (Sharp et al., 1999), to the evidence from African stratigraphy for a Neoproterozoic snowball earth (Hoffman et al., 1998a, Kirschvink, 1992) to the compelling ice images from Europa, the icy moon of Jupiter.

 

If life thrives in these environments it may have to depend on alternative energy sources and survival strategies. Identifying these strategies will provide new insights into the energy balance of life.


The identification of significant subglacial bacterial action (Sharp et al., 1999) as well the work on permafrost communities (i.e. Gilichinsky et al., 1995) suggests that life can survive and possibly thrive at low temperatures. Neither the alpine subglacial environment nor the permafrost environment is as extreme as the environment found beneath a continent-wide ice sheet as Antarctica today.

 

The alpine subglacial environment has a continual high level of flux of nutrients from surface crevasses. The Antarctic subglacial environment lacks a rapid flux of surface meltwater and subsequently is more isolated. In addition to being more isolated, the Antarctic subglacial environment is a high pressure region due to the overburden of ice.


The Antarctic subglacial environment may be similar to the environment beneath the widespread ice sheets in the Neoproterozoic, a time period from about 750 to 543 million years ago. It has been suggested that during this period the earth experienced a number of massive glaciations - covering much of the planet for approximately 10 million years at a time. The evidence for an ancient ice covered planet comes from thick widespread sedimentary sequences deposited at the base of large ice bodies.

 

These glacial units alternate with thick carbonates units-warm shallow water sedimentary deposits.

 

These paired sequences have been interpreted as representing a long period when the earth alternated between from an extremely cold, completely ice covered planet (the snowball earth) and a hothouse planet (Hoffman et al, 1998b). Some speculate that the extremes of these climates introduced an intense “environmental filter”, possibly linked to a metazoan radiation prior to the final glaciation and an Ediacaran radiation (Hofmann et al., 1990; Knoll, 1992).

 

Portions of the Antarctic continental subglacial environment today, which have been isolated from free exchange with the atmosphere for at least 10 million years, are similar to the environment in this ancient global environment. Understanding the environmental stresses and the response of the microbes in a modern extreme subglacial environment will help us decipher the processes which lead to the post-glacial evolutionary radiation over 500 million years ago.


The third important analogue for modern Antarctic subglacial environments is from the outer reaches of the solar system, the ice moon of Jupiter, Europa.

 

Recent images resembling sea ice, combined with the very high albedo of this moon has lead to the interpretation that this moon is ice covered. Beneath the ice covering Europa is believed to be an ocean. The thick cover of ice over a liquid ocean may be a fertile site for life (Chyba, 1996; Williams et al., 1997). The Antarctica subglacial lakes have similar basic boundary conditions to Europa.


An investigation of Antarctic subglacial environments should target the unique role these lakes may have in terms of the triggers for rapid evolutionary radiation, for understanding the global carbon cycle through major glaciations and as an analogue for major planetary bodies.


Lake Vostok is a large (10,000 km2) water body located beneath ~4 km of glacial ice at 77oS, 105oE within the East Antarctica Precambrian craton (Kapitsa et al., 1996). Based on limited geophysical data, it has been suggested that the Lake occupies a structural depression, perhaps a tectonically active rift.

 

The water depth varies from approximately 500 m beneath Vostok Station to a few 10’s of meters at the northern end of the Lake; the ice sheet thickness also varies by nearly 400 m and is thickest in the north (4,150 m).

 

Ice motion across the lake, freezing and melting at the base of the ice sheet and geothermal heating could establish density-driven flows, large scale circulation and geochemical gradients in Lake Vostok.

 

Figure 1:

ERS-1 Surface Altimetry indicating location of Lake Vostok

 


The existence of this lake, and at least 76 others like it, has been documented by extensive airborne 60 MHz radio-echo sounding records that provide coarse sampling coverage of approximately half of the Antarctic ice sheet (Siegert et al., 1996). The majority of sub-glacial lakes are near ice divides at Dome C and Ridge B, East Antarctica.

 

More recently, the European Research Satellite-1 (ERS-1, Figure 1) has provided radar altimeter data which provide unprecedented detail of ice surface elevations. These data have been used to define the physical dimensions of the lake, its drainage basin, and predict lake water density (Kapitsa et al., 1996).
 
The water body appears to be fresh. Based on considerations of temperature and pressure fields, most of the dissolved gases in the lake would be present as hydrates, which may be segregated in density layers. The unique geochemical setting of Lake Vostok may present an opportunity and a challenge for the development of novel life forms.

 

Lake Vostok, due to its size, is the lake which is most likely to have remained liquid during changes in the Antarctic ice sheet volume and therefore most likely to provide new insights into these subglacial environments.

 

We understand much more about the subglacial processes such as accretion and melting within Lake Vostok than any other lake, and we have a solid local climate record for the last 400,000 years from the overlying ice core (Petit et al., 1999).

 

Figure 2:

Location of subglacial lakes in Antarctica determined from the NSF/SPRI airborne radar program.

The radar flight lines are shown in the inset on the lower left. (adapted from Siegert et al., 1996)

 

An international team of scientists and engineers has been drilling the ice sheet above Lake Vostok to obtain a detailed record of the past climate on earth.

 

This ice-core program, started in 1989, recently terminated drilling at a 3,623 m depth (approximately 120 m above the ice-water interface at this location). This is the deepest ice core ever recovered.

 

The ice core corresponds to an approximately 400,000 year environmental record, including four complete ice age climate cycles. Below 3,538 m there is morphological and physical evidence that basal ice is comprised of re-frozen Lake Vostok water.


Throughout most of the ice core, even to depths of 2,400 m, viable microorganisms are present (Abyzov, 1993). Previous sampling of ice in the interior of the Antarctic continent has repeatedly demonstrated that microorganisms characteristic of atmospheric microflora are present. Air-to-land deposition and accumulation is indicated, rather than in situ growth in the ice (Lacy et al., 1970; Cameron et al., 1972).

 

Cameron and Morelli (1974) also studied 1 million year old Antarctic permafrost and recovered viable microorganisms. Prolonged preservation of viable microorganisms may be prevalent in Antarctic ice-bound habitats. Consequently, it is possible that microorganisms may be present in Lake Vostok and other Antarctic subglacial lakes. However, isolation from exogenous sources of carbon and solar energy, and the known or suspected extreme physical and geochemical characteristics, may have precluded the development of a functional ecosystem in Lake Vostok.

 

In fact, subglacial lakes may be among the most oligotrophic (low nutrient and low standing stocks of viable organisms) habitats on earth. Although “hotspots” of geothermal activity could provide local sources of energy and growth-favorable temperatures, in a manner that is analogous to environmental conditions surrounding deep sea hydrothermal vents (Karl, 1995), it is important to emphasize that without direct measurements, the possible presence of fossil or living microorganisms in these habitats isolated from external input for nearly 500,000 years is speculation.


Lake Vostok may represent an unique region for detailed scientific investigation for the following reasons:

  • it may be an active tectonic rift which would alter our understanding of the East Antarctic geologic terrains

  • it may contain a sedimentary record of earth’s climate, especially critical information about the initiation of Antarctic glaciation

  • it may be an undescribed extreme earth habitat with unique geochemical characteristics

  • it may contain novel, previously undescribed, relic or fossil microorganisms with unique adaptive strategies for life

  • it may be a useful earth-based analogue and technology “test-bed” to guide the design of unmanned, planetary missions to recently discovered ice-covered seas on the Jovian moon, Europa.

These diverse characteristics and potential opportunities have captivated the public and motivated an interdisciplinary group of scientists to begin planning a more comprehensive investigation of these unusual subglacial habitats.

 

As part of this overall planning effort, a NSF-sponsored workshop was held in Washington, D.C. (7-8 Nov. 1998) to evaluate whether Lake Vostok is a curiosity or a focal point for sustained, interdisciplinary scientific investigation.

 

Because Lake Vostok is located in one of the most remote locations on earth and is covered by a thick blanket of ice, study of the lake itself that includes in situ measurements and sample return would require a substantive investment in logistical support, and, hence financial resources.

 

Over a period of two days, a spirited debate was held on the relative merits of such an investment of intellectual and fiscal resources in the study of Lake Vostok. The major recommendations of this workshop were:

  • To broaden the scientific community knowledgeable of Lake Vostok by publicizing the scientific findings highlighted at this workshop.

  • To initiate work on sampling, measurement and contamination control technologies so that the Lake can be realistically and safely sampled.

  • Both NASA and NSF should prepare separate, or a joint, announcement of opportunity for the study of Lake Vostok, possibly through the LExEn program.

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(2) Introduction


The goal of the workshop was to stimulate discussion within the U.S. science community on Lake Vostok, specifically addressing the question:

“Is Lake Vostok a natural curiosity or an opportunity for uniquely posed interdisciplinary scientific programs?”

The workshop was designed to outline an interdisciplinary science plan for studies of the lake. The structure of the workshop was a series of background talks on subjects including:

  • Review of Lake Vostok Studies - Robin E. Bell

  • The Overlying Ice: Melting and Freezing - Martin Siegert

  • Evidence from the Vostok Ice Core Studies - Jean Robert Petit

  • Tectonic Setting of Lake Vostok - Ian Dalziel

  • Biodiversity and Extreme Niches for Life - Jim Tiedje

  • Lake Vostok Planetary Analogs - Frank Carsey

  • Identification of Life - David White

  • Mircrobial Contamination Control - Roger Kern

A summary of each of these background talks is presented in this report Section (4) entitled:

“Lake Vostok: Background Information.”

Following these talks each workshop participant presented a 3 minute, one overhead presentation of why, from their perspective, Lake Vostok was more than a curiosity, and warranted significant effort to study.

 

These presentations ranged from discussion of helium emerging from the mantle, to the unique temperature and density structure which might develop in such an isolated high pressure, fresh water environment as Lake Vostok. Written summaries of these presentations and key illustrations are included in Appendix 1 entitled “Why Lake Vostok?”.


Next, the workshop participants as a large group, identified the fundamental aspects of a research program across Lake Vostok with each participant presenting five key ideas. These ideas were synthesized into 6 major themes which became the subject of working groups.

 

The working groups and their members were:

  1. Geochemistry-Mahlon C. Kennicutt II, Berry Lyons, Jean Robert Petit, Todd Sowers

  2. Biodiversity-Dave Emerson, Cynan Ellis-Evans, Roger Kern, José de la Torre, Diane McKnight, Roger Olsen

  3. Sediment Characterization - Luanne Becker, Peter Doran, David Karl, Kate Moran, Kim Tiedje, Mary Voytek

  4. Modeling - David Holland, Christina Hulbe

  5. Site Survey - Robin Bell, Ron Kwok, Martin Siegert, Brent Turrin

  6. Technology Development - Eddy Carmack, Frank Carsey, Mark Lupisella, Steve Platt, Frank Rack, David White

Each group was tasked with developing: a) justification for a Lake Vostok effort; b) the goals of a research effort; c) a strategy to meet the goals; and d) a time-frame for the effort. In addition, the groups were tasked with presenting the single most compelling scientific justification for studying Lake Vostok.

 

The groups worked through the morning of the second day preparing draft presentations. The draft reports were presented in plenary at the conclusion of the workshop. The reports from the working groups are found in Section 6, “Group Reports”. The workshop participants debated the justifications and the major obstacles to studying Lake Vostok.


The discussion of the major obstacle to advancing a well developed scientific justification and plan to study Lake Vostok hinged on several major factors including:

  • the exploratory nature of the program coupled with the paucity of data about this unknown region making development of a detailed scientific justification difficult

  • the need for technological developments to ensure contamination control and sample retrieval, recognizing that Lake Vostok is a unique system whose pristine nature must be preserved

  • the need for a strong consensus within the U.S. science community that Lake Vostok represents an important system to study, and recognition that international collaboration is a necessary component of any study

  • the recognition that the logistical impact of a Lake Vostok program will be significant and that the scientific justification must compete solidly with other ongoing and emerging programs

  • that the lack of understanding of the present state of knowledge of the Lake as a system within the U.S. science community remains a difficulty in building community support and momentum for such a large program.

These obstacles were addressed in workshop discussions and are specifically addressed in the report recommendations, the draft science plan and the proposed timeline.

 

The preliminary science plan and timeline was based on working group reports and is presented below in Section (3) "Preliminary Science Plan and Timeline ".
 

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(3) Preliminary Science Plan and Timeline


This preliminary science plan is based on a synthesis of working group reports.

 

The overarching goal of the science plan is to understand the history and dynamics of the Lake Vostok as the culmination of a unique suite of geological and glaciological factors.

 

These factors may have produced an unusual ecological niche isolated from major external inputs. The system structure may be uniquely developed due to stratification of gas hydrates.

 

Specific scientific targets to accomplish this goal include:

  • determine the geologic origin of Lake Vostok within the framework of an improved understanding of the East Antarctic continent as related to boundary conditions for a Lake Vostok ecosystem

  • develop an improved understanding of the glaciological history of the lake including the flux of water, sediment, nutrients and microbes into a Lake Vostok ecosystem

  • characterize the structure of the lake’s water column, to evaluate the possibility of density driven circulation associated with melting/freezing processes or geothermal heat, the potential presence of stratified gas hydrates, and the origin and cycling of organic carbon

  • establish the structure and functional diversity of any Lake Vostok biota, an isolated ecosystem which may be an analogue for planetary environments

  • recover and identify extant microbial communities and a paleoenvironmental record extending beyond the available ice core record by sampling the stratigraphic record of gas hydrates and sediments deposited within the Lake

  • ensure the development of appropriate technologies to support the proposed experiments without contaminating the Lake.


 

Timeline

1999 (99-00)

Planning Year

Modeling studies
Develop international collaboration
SCAR Lake Vostok workshop
Begin technology development

2000 (00-01)

Site Survey Year I
Joint NSF/NASA LExEn Call for Lake Vostok Proposals
Airborne site survey
Preliminary ground based measurements
Preliminary identification of observatory sites

2001 (01-02)

Site Identification and Site Survey Year II
Ground based site surveys
Complete airborne survey if necessary
Test access/contamination control technology at a site on the Ross Ice Shelf
Finalize selection of observatory sites

2002 (02-03)

In Situ Measurement Year
Drill access hole for in situ measurements
Attempt in situ detection systems to demonstrate presence of microbial life
Install long term observatory
Acquire vertical profile of water column
Acquire microscale profiles within surface sediments
Conduct interface survey (ice/water and water/sediment)
International planning workshop (including exchange workshop)

2003 (03-04)

Sample Retrieval Year
Acquire samples of basal ice
Acquire samples of water and gas hydrates
Acquire samples of surface sediments
Stage logistics for second observatory
International planning workshop (including data exchange)

2004 (04-05)

Installation of Second Long Term Observatory
Installation of second long term observatory
Analysis of data
Build new models
International planning workshop (including data exchange)

2005 (05-06)

Core Acquisition Year
Begin acquisition of long core
International planning workshop (including data exchange)

In order for this science plan and timetable to be realized, several coordination issues must be addressed including inter-agency and international collaboration, refinement of the scientific objectives, rigorous selection of the observatory and sample locations, and identification of the critical observations.

 

The development of three major groups is envisioned including,

(1) an interagency working group to identify the relative interests and potential roles in a Lake Vostok program

(2) an international working group focused on scientific and logistical coordination for studies of Lake Vostok

(3) a Lake Vostok Science Working group to address refinement of science objectives, site selection and determination of primary objectives

 

Inter-agency Working Group:

The study of the Lake Vostok system is relevant to the mandate of several agencies, most notably NASA, NSF and the USGS. Active coordination between these agencies will be key to a successful science program focused on Lake Vostok.

 

Other agencies or industrial partners might be sought as well. Due to their role as stewards of Antarctica and providers of logistical support, NSF would be the preferred lead U.S. agency for any Lake Vostok mission.


 

International Working Group:

To date, our understanding of Lake Vostok is the result of integration of diverse data sets from the international research community. A successful exploration of Lake Vostok will require ongoing international collaboration with significant contributions from all participants.

 

International collaboration will broaden the scope of the Lake Vostok studies. The SCAR workshop in 1999 is an excellent venue for developing an international Lake Vostok Working Group.


 
 Science Working Group:

Before implementation of the science plan can begin, scientific objectives must be refined, the site selection process defined, and the critical observations defined. Careful review of these issues would best be accomplished by a small team of scientists, engineers, and logistics experts.

 

The creation of this group is a key first step. This group will be tasked with addressing issues such as site selection and development of an observation and sampling strategy.

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