Cruise support for Dr Christopher Smith-Duque, shipboard petrologist on IODP Expedition 329

The world's oceans and the seafloor are the most poorly explored regions of Earth. Despite covering over 70% of the Earth's surface, only a few hundred drilled holes and dredge sites currently represent the entirety of our sampling of the sub-seafloor. More so than any other region on Earth there remains a dearth of sampling in the South Pacific Gyre, the world's largest ocean current system. The last scientific expedition to systematically recover material from the ocean floor in this region of the South Pacific Ocean was over 130 years ago during the HMS Challenger Expedition (1872-1876).

Integrated Ocean Drilling Program (IODP) Expedition 329 represents a unique opportunity to discover the nature and extent of life below the seafloor and to understand the geological processes that have operated for over 100 million years in one of the largest, most poorly explored regions of the Earth. The JOIDES Resolution's transect, will cover 11,000 km of ocean over a period of 66 days from Papeete, Tahiti to Auckland, New Zealand and will collect sediment cores from 7 sites and drill into the basalts of the oceanic crust at 3.

Aboard ship, I will be part of an international team of scientists using a multi-disciplinary approach to characterise the geological and biological nature of seafloor sediments and the underlying volcanic rocks that formed at the East Pacific Rise mid-ocean ridges. The South Pacific Gyre is of particular interest because this has been a region of extremely low biological activity within the oceans for many millions of years.

IODP Expedition 329 will determine:

1) What, if any, life occurs beneath the sea floor within the gyre and in what habitats and conditions does life occur;
2) The role the ocean plays in controlling habitats beneath the seafloor across a transect from the centre to the edge of the gyre. For example, how does the accumulation of dead biomass from near the surface affect life in the ocean floor;
3) The extent of life within sea floor sediment and basement that is independent of the photosynthetic process, and
4) How the geology of sub-seafloor rocks, and the evolving thermally driven seawater/rock chemical interactions affect the habitability of the seafloor and distribution of life.

My role as the sole petrologist sailing on Expedition 329 will be to describe and characterise the volcanic rocks that occur beneath the sediments. These basaltic lavas formed during eruptions of magma at the southern East Pacific Rise, the mid-ocean ridges that has formed much of the Pacific Ocean basement. These lavas have since cooled and the sites moved over millions of years away from the active ridge to their present locations. Describing and analysing the rocks during Expedition 329 will allow me to infer the styles of lava eruptions and classify the rock types.

My role will also include describing and interpreting how seawater interacts with oceanic basement and the conditions of seawater-basalt thermal and chemical exchange. New minerals are formed by thermally driven chemical process known as hydrothermal alteration that exchanges elements and compounds between seawater and rock. These new minerals form in voids between fragments of rock, in cooling fractures and within bubbles known as vesicles that were once occupied by gases escaping from the magmas during eruption. Volcanic glass formed by the very rapid quenching of magma by seawater can also be replaced as can the igneous minerals that were formed during the slower cooling of the lava. Many of the reactions between seawater and basalts release chemicals and energy that create potential habitats for primitive microbial sub-seafloor life. Describing these alteration features will be imperative for understanding the biological colonization and potential extent of life within oceanic basement.

Participation as a petrologist aboard JOIDES Resolution during IODP Expedition 329 South Pacifc Gyre (SPG) Sub-Seafloor Life will benefit my immediate shipboard research partners as well as a broad range of researchers across several disciplines worldwide. Specifically my work will provide detailed information for the SPG expedition regarding the volcano-stratigraphic make up of the basaltic igneous basement, the nature and extent of hydrothermal alteration, and the geochemical and thermal setting in which alteration took place.

Benefits to: IODP
Our work addresses one of the fundamental objectives outlined in the Initial Science Plan of the IODP, namely 'defining the physical and chemical limits of sub-seafloor microbial communities'. In addition, 'The aging of the ocean crust' is a key objective in the ISP.
Benefits to: Academic Researchers
Our work will have significant impact in a wide range of disciplines concerned with trying to understand the subseafloor processes and the interaction between seawater and basement. Microbiologists interested in understanding basement habitability and diversity of biomass, igneous and metamorphic petrologists who research basement alteration processes and ocean crust aging, geochemists who investigate fluid rock interactions in sub-seafloor hydrothermal systems, and physical properties experts who are interested in characterising the evolving physical properties of ocean crust will all draw upon the petrographic research obtained during Expedition 329.
Benefits to: Public
Expedition 329 joins a long list of highly successful endeavours by scientific ocean drilling and places IODP at the forefront public interest in geosciences, with strong linkages to school teachers, journalists, and museums.

How does my participation generate impact?
By documenting the nature and extent of oxidative alteration, crustal structure, and making inferences on the thermal regime within the upper oceanic crust during Exp 329 I will create a reference frame which the microbiology community will utilize to assess basement habitability, the availability of electron donors (food), and the diversity of microbial life present within the basement. Our sampling and description of basement across the SPG will allow microbiologists to assess the nature of the subbasement biosphere across the entire range of the gyre, and at differing crustal ages, sediment thicknesses and basement rocktypes.
IODP Expedition 329 will be the first time the South Pacific Gyre has been drilled and it is the first expedition designed specifically to address the nature of subseafloor biomass within an ocean gyre. Ocean Gyres are the largest ocean current systems and they are areas of ultra-low productivity. Collectively make up the vast majority of the worlds oceans, and our research on Expedition 329 is of critical importance to anyone trying to understand the nature and extent of subseafloor biosphere.
Expedition 329 is a prime example of cutting edge science that IODP makes possible in some of the least explored and remote regions on Earth. My petrographic observations will give insight into the nature life beneath the sea floor and they will feed into our understanding of the seafloor hydrothermal processes that affect the environment in which we live. There is broad public interest in the origins and extremes of life.
Pathways to Impact
Researchers benefit from our research as all the shipboard results are publicly available in the 'Proceedings of the Integrated Ocean Drilling Program'. As part of our commitment to high quality output a summary of our shipboard research will be submitted to Science (achieved 03/2011). To address the public outreach component of Expedition 329 shipboard scientists will engage with the Teacher at Sea programme that inform and encourage younger generations to consider careers in science.