A Scientist's Life: James Day

James Day is a geologist and geochemist at Scripps Institution of Oceanography at UC San Diego. He received his bachelor’s degree in geology in 2000 and his PhD in geology in 2004 from Durham University in the United Kingdom. He joined Scripps in 2011 and teaches as part of the geosciences program.

explorations now: What do you do for a living?

James Day: I study how planets form and how they evolve with time to their present-day states. These include the earth, the moon, Mars, and other planetary bodies that we have access to.

We have several field programs. On Earth, we're interested in the study of volcanic rocks because they tell us about the interior of the Earth and hence where elements and compounds like water ultimately come from. We're working on ocean islands as well as on basaltic volcanism in the Columbia River in Washington, for example. We're also working on Apollo mission samples as well as meteorites from Mars and asteroids. We're getting more and more involved in converting the physical understanding we have of the rocks to what we actually observe on those planets from remote sensing.

en: What are some of the tools you use in your research?

JD: We do field work, obviously on Earth, but I've collected meteorites in the Antarctic and use everything from microscopy to mass spectrometry to study the materials that come from different planetary bodies.

Meteorites land everywhere on the planet roughly equally, but in the Antarctic you have a great difference. The dark meteorites standout against a light background and they're well preserved because the Antarctic is a desert. We take those rocks that are very fresh and have come from space and we're able to understand a wide variety of planetary processes because they're sourced from asteroids, from Mars, and even from the moon. These meteorites are an amazing treasure trove.

en: What are some of the main questions in your field?

JD: The big question that motivates me is where did Earth and other planets get their water from? Did that water arrive very early as the planet was forming, known as accreting, or did it come from additions much later after the planet formed, by a process called late accretion? What effect would this different timing have on planetary habitability?

These processes may not affect us on a daily basis, but it is important to know how planets formed and why we have the climate conditions we have on our planet today. The answers will also tell us about other planetary bodies such as planets orbiting other stars (exoplanets). They can give us some indication of whether there are other planets harboring life.

There are other questions that drive my research. For example, how quickly is the earth losing heat from its interior? That's important for all life on the planet because we want to know how long our optimal conditions will persist. I'm also interested in processes of subduction, which is when rocks descend into the earth’s interior, and how they affect the system that we have today. One of the things that's important to emphasize is that the earth, the solid earth, the ocean and the atmosphere, they're all interlinked. In order to understand, for example, atmospheric changes, we really need to understand how the atmosphere interacts with the ocean and the solid earth.

en: What made you want to work at Scripps Oceanography?

JD: Scripps is pretty unique in the diversity of research being carried out, and the clustering of people so close together who do it. It enables people with very diverse backgrounds to come together and to come up with new ideas and challenges that they can research and understand.

Scripps is renowned for the study of the earth, ocean and atmosphere. Since I study planets and how they formed, and one of those planets is the earth, I thought it was a very natural place for me to come to. I don't see [studies of Earth and other planets] as being separate. I see them as being interlinked. Take for instance, Venus, which is of a similar size to the earth, but has a much denser atmosphere and very high temperatures on its surface. What makes the two bodies so different? I think Scripps allows us to study that because of our deep knowledge of the earth. That's where we base much of our planetary knowledge. We use it as our foundation, if you will.

One of the wonderful things about Scripps is that it’s right on a beach where we have some amazing geology. You don't need to go very far to teach people about these wonderful rocks. The sediments supporting the Scripps campus were formed around 49 to 47 million years ago. But the volcanic dike along its beach was formed about 14 million years ago. It was actually formed next to rocks that are now somewhere in the middle of Baja California, Mexico. We've moved northward on the Pacific plate and Baja has moved southward on the American plate. This tells us a great deal about processes that have been acting geologically over the last 40 million years or so.

en: Where do you think your interest in geology came from?

JD: Since I was a child, I've loved anything to do with nature and I find studying nature to be one of the most motivating things you could ever do. I find interest in everything I see around me. I spent a lot of time in Scotland as a child around the rivers picking up pebbles and saying, where did they come from? That is really what motivated me and got me started as a three-year-old, four-year-old child. It's been a lifelong passion.