Six months ago, somewhere in the tropical waters off the coast of Mexico, scientists began drilling into one of the most iconic geological features on Earth: the Chicxulub crater; the 66 million year old remnants of a deadly asteroid impact, thought to have contributed to the demise of dinosaurs and most other forms of life which inhabited the Earth at the time.
Today we speak to Sonia Tikoo, Assistant Professor of Planetary Sciences, Department of Earth and Planetary Sciences, Rutgers University, and one of the researchers part of an international team which is currently trying to decipher the secrets held by the rocks of the Chicxulub crater at a core repository in Bremen.
First, could you introduce yourself and tell our readers a little more about your career path so far?
In general, my work involves using the magnetism recorded within rocks to understand problems in the planetary sciences. I started doing research in palaeomagnetism during college but I really wanted to work in something involving space so I transitioned into planetary science during graduate school. During my PhD at MIT, I worked on studying the palaeomagnetism of lunar rocks from the Apollo missions to understand the history of the now-extinct lunar dynamo magnetic field. It was really cool to explore the different ways that small planetary bodies could also generate long-lived magnetic fields lasting a billion years or more. I subsequently started studying how shock and impact cratering events affect magnetic records within rocks during my postdoc at UC Berkeley, and that experience eventually led me to the work on Chicxulub that I’m doing right now!
For those readers who may not be so familiar with the project, could you give us a whistle-stop tour of aims of the research and why it’s important?
In addition to being the crater linked to the demise of the dinosaurs (cool in and of itself!), Chicxulub is also the best-preserved impact structure on Earth and it is the only crater with an intact and well-defined peak ring (a ring of elevated topography within the crater that forms during the collapse stage of crater modification). As part of IODP/ICDP Expedition 364, we are planning to address a lot of questions regarding this crater, including: (1) how peak rings (stay tuned for our paper on that which is coming out very soon!), (2) how rocks are damaged or weakened by impact shock, (3) how much hydrothermal circulation occurs after the impact, and how long it lasts, and (4) how life recovered within and above the crater following the impact and Cretaceous-Paleogene extinction?
In terms of my specific job…studying the palaeomagnetism of rocks from the crater can be used as a powerful tool to answer some of the aforementioned questions because the magnetizations within rocks can be modified by high temperatures and pressures, and new magnetic minerals can form via hydrothermal activity. All of these things happen during large impacts on Earth and on other bodies as well, and we see these effects in the crustal magnetism of planetary surfaces. The entire Science Party is going to be quite busy working on these problems over the next couple years. What we learn here is not only going to tell us about Chicxulub but also about peak-ring basins across the solar system, and as a planetary scientist I find that angle to be particularly exciting.
What is your role specific role in the project?
I’m serving as a palaeomagnetist on the expedition. There are two groups of scientists associated with Expedition 364 – the Offshore Science Party (the team that recovered the core at sea) and the Onshore Science Party (the team that conducts sampling and preliminary analyses here in Bremen). There wasn’t a magnetometer on the drilling vessel, so I became a member of the Onshore Science Party. My job here is to collect samples and develop a first-pass dataset of measurements that characterizes the magnetization of the various rock units in the core, spanning both the post-impact sediments and the underlying impactite rocks. The sediment data will eventually be used for magnetostratigraphy and to develop an age model for the post-impact period, and the impactite data gives us a sneak peek at what we will be working with in much greater detail during our post-expedition research as we try to understand the different types of magnetization present in the crater’s peak ring.
So, the experiments are taking place right as we speak?! Can you tell us more about what it is like working at the core repository?
Yes, they are running right now! Working on an IODP/ICDP expedition is a totally intense, totally rewarding experience! The Onshore Science Party here in Bremen involves around 45 members of the Onshore Science Party and a team of IODP scientists and technicians working together continuously for a month.
First, one team splits the large drill core into halves. The core halves then get passed onto teams that do detailed visual descriptions of the cores and some physical properties measurements.
Then the core goes to the sampling room, where we collect specimens for both the immediate measurements we are conducting here in Bremen as well as for the post-expedition research that the Science Party members will be conducting at their home institutions.
Starting bright and early at 7:30 every morning, I drill and prepare sample plugs for moisture and density, P-wave, and paleomagnetic analyses. In the afternoons, I usually shift over to processing magnetic data and writing reports while another paleomagnetist, William Zylberman, conducts measurements in the lab.
Of course, every other team like physical properties, petrology, biostratigraphy, or geochemistry is doing the same kind of fast-paced work in their own way and we’re always comparing notes and taking advantage of our built-in collaborations. Some scientists have been working on Chicxulub or the K-Pg boundary for decades and others of us (like me!) are first-timers.
There is a fantastic energy associated with having so many talented scientists with all these different avenues of expertise working closely together (and trying to get everything done before our month here is over)!
If you want to learn more about the IODP Expedition and associated research, you’ll find some resources here:
- IODP Expedition 364 blog: https://esoexpedition364chicxulubimpactcrater.wordpress.com/
- IODP Expedition 364 website (inc. downloadable prospectus): http://www.ecord.org/expedition364/
- Chicxulub ‘dinosaur crater’ investigation begins in earnest (October, 2016, BBC Science News)
- Scientists hit pay dirt in drilling of dinosaur-killing impact crater (May, 2016, Science Magazine)
Geotalk is a regular feature highlighting early career researchers and their work.