How do we make an X-ray scan of Earth’s oceanic crust?

Similar to X-rays used in medicine to scan human bodies, to understand the characteristics of the oceanic crust that covers >70% of our planet, marine geophysicists conduct controlled source seismic experiments at sea on research vessels. We produce tiny earthquakes using compressed air, which travel through the subsurface built of different rock types; the differences in the rocks introduce changes in the propagated waves, which are registered by an array of receptors and then processed to produce seismic images. However, this field of research is not commonly known by school students or the general public. To bridge this gap, we designed a seismic atelier to expose the less-known but marvelous world of marine geophysics and show it as a possible career path. The atelier includes a presentation of our work at sea supported by pictures and videos, presentation of the Ocean Bottom Seismometer (OBS) developed and designed internally at IPGP, and model that simulates seismic data acquisition. For this model, we obtained the EGU Public Engagement Award in 2023. The elements that constitute the model:

• 400 l water tank, floating LEGO ship
• three 3-D printed OBSs connected to an electromagnetic mechanism that simulate deployment and recovery of the instruments
• ballons that are perforated under the water to mimic the seismic source
• hydrophone connected to a laptop for signal recording

The experiment is accompanied by a 5-question quiz tailored to correspond to the age of the participants; all the topics concerning the questions were covered in the presentations. The quiz is conducted before and after the atelier, which helps us to evaluate the impact of outreach activity. All the questions were designed as a multiple-choice. For example, for the age 11-15 years, one question is: What is the temperature of the deep ocean?, with the offered responses: a) 0-3º, b) 23-25ºC, and c) 0 -10 ºC.

We have already run the atelier on two occasions, and the results are promising. The first time was during the Fête de la Science (Open House event in France) at IPGP in early October 2024, during which we presented our atelier to four groups, 10-12 participants (9-12 years old) in each group. The second session was organized with 30 high-school students (~15 years old). The quizzes' analyses clearly show that the number of correct answers increases by up to 50% after the conducted atelier, demonstrating the positive impact of the activity on student knowledge. The results also show that some questions were tackling less-known topics. For instance, the question we gave as an example above was consistently answered incorrectly by ~80% of students before the atelier; in contrast, after the atelier, the situation was reversed, and >90% of the participants gave the correct answer. Overall, the impressions of the students after participating in the atelier, especially the youngest ones, are highly positive, and we hope they will develop a certain level of passion for marine sciences. The next stage for our project would be to film it and make it available online in different languages to reach students internationally.