Expedition 364 is being implemented by ESO (European Consortium for Ocean Research Drilling (ECORD) Science Operator) on behalf of the International Ocean Discovery Program (IODP) and the Inter Continental Scientific Drilling Program (ICDP). The path to getting a proposal funded and ultimately drilled, can be a long one. Co-Chief Scientist Sean Gulick explains the background to Expedition 364.
Years go into the planning of a scientific drilling expedition. Proposals have to be written for collection of the geophysical data that create images we can interpret to identify the best location to drill. Workshops are held to discuss these images and the hypotheses that could be addressed if you were to gain rock cores from one spot versus another. Scientific drilling proposals; sometimes many versions, have to be written to gain approval by your scientific peers. Following this funding is sought from international programs, in order have enough resources to finally mount an expedition. Once selected, additional work must be done to ensure safety at the drill site. Getting the right team to participate is also important. A call is put out the Scientists to apply to be part of the expedition. Eventually you and your team of Scientists get to sail and sample the part of the Earth you selected as being important many years earlier, and then spend years analysing and interpreting these hard won samples.
In the case of the offshore drilling into the Chicxulub impact crater, the first geophysical images of the crater were collected in 1996 and the first drilling proposal for the offshore was written 1998. In 1999 an onshore site near the crater rim was successfully drilled by the International Continental Drilling Project. However, offshore drilling was always truly the ultimate goal because the seismic images are so much better offshore. The area is dominated by underground caves and waterfilled sinkholes that make imaging the subsurface onshore very challenging. It’s critical to have clear images of the buried crater to allow careful selection of exactly where to drill.
I joined my now Co-Chief Scientist, Joanna Morgan, in 2002, when together with colleagues from the US, UK and Mexico, we wrote both a revision to the drilling proposal. In addition, we wrote a proposal to collect a full grid of seismic images and conduct a 3D experiment to study the crater’s physical properties (in this case the speed of sound through the craters rock layers). We successfully got the seismic study funded and acquired the new subsurface images in 2005. With these new data and the 1996 data we continued writing proposals to both the IODP and the ICDP. We also had a workshop in Germany to pour over the new data with impact crater specialists from around the world. Here we made the decision that if we only could drill at one site then it should be the peak ring. This ring of mountains surrounds the crater center, and is now buried by a few hundred meters of limestone. Drilling in this location has the potential to answer the most hypotheses of any single location within the crater. Finally in 2012, proposing a simplified plan to drill a single site in this peak ring, we were selected to have our expedition to the Chicxulub impact crater drilled. In 2013 we collected images of the seafloor at the proposed drilling site and in 2015 selected the Science Party of ~30 other Scientists from around the world to be a part of the team. Finally in 2016, we are here drilling into the Chicxulub peak ring.
Our goals are;
- to study the recovery of life at ground zero after the impact,
- to core the boundary layer of the impact itself to help understand kill mechanisms that caused 75% of life to go extinct (including the dinosaurs) 66 million years ago,
- to recover for the first time peak ring rocks to understand how fundamentally impacts deform planetary surfaces, and;
- to study whether impacts can provide a habit for life in the deep subsurface biosphere.
It is literally a dream that is years in the making…