Before getting his PhD in Astronomy and Planetary Science at the University of Aix-Marseille, Sebastien Besse studied Natural Sciences, but gradually he specialized in the geology of the bodies of the Solar System and in spectroscopy. After working in the University of Maryland (EEUU) and the headquarters of the European Space Agency (ESA) in The Hague (The Netherlands), he continues investigating his favorite subjects: the Moon, Mercury, minor bodies, spectroscopy and geology of the Solar System... Since last year, he is in the European Center for Space Astronomy (ESAC), ESA headquarters in Madrid, in charge of the Planetary Science Archive, where millions of data obtained in space missions are conserved. Besse will share his experience as a “space documentarian” in the XXVIII Canary Islands Winter School of Astrophysics, organized by the Instituto de Astrofísica de Canarias (IAC).

By Elena Mora (IAC)

“In the past decade, computers performances have greatly improved the understanding of our Solar System by performing very complex simulations of its formation and evolution. Space missions are absolutely needed to confront these models to the reality, and gain considerable knowledge.”

“A mission like Rosetta has at the same time confirmed that comets are among the best candidates to host and bring life to Earth, in particular because the have key component for life: organics, water, etc.”

“Analyzing the mineralogical variability of and object with spectroscopy tells you how evolved, and allows you to go back to the initial stage of formation when materials were accreted from the proto-planetary disk to form the planet.”

Question: You describe yourself as geologist and spectroscopist of the Solar System in your personal profile on ESA website. What do you mean with that?

Answer: What I mean is that I have a science background, which is geology, and a more technical expertise, which is spectroscopy. I studied geology for years, and during my master degree, I specialized in the geology of Solar System objects. There are multiple ways you can use your knowledge of geology whether it is in the field, in the laboratory or on your computer, and all of them with different approaches and techniques.

I use remote sensing and spectroscopy to analyze geological features on various objects of the Solar System and in particular their mineralogical composition.  World experts have trained me with spectroscopy; I loved it so much that I keep doing it.

I could describe myself as a planetary scientist studying the variability of the Solar System, but I believe this will be incomplete, and geology together with spectroscopy is what makes me a planetary scientists.

Q: Currently, you are working with another researcher who is also participating in this Winter School of Astrophysics, Michael Küppers. What is this collaboration about?

A: With Dr. Kuppers, we work together on the analysis of images of comets and asteroids. Today, we continue our collaboration in analyzing the images of the comet 67P/Churyumov-Gerasimenko in the context of the Rosetta mission and the OSIRIS instruments for which we are both part of the science team.

Few years ago, we combined our expertise in geology and small bodies to understand the lineaments we see on the surface of the asteroid (21) Lutetia, an asteroid observed by the Rosetta mission. We have shown that there is probably a huge impact crater on the side not observed during the flyby of Rosetta, a crater so big that he modified the geology of the opposite hemisphere.  And since we can never be 100% sure, we named the crater “Suspicio” because we really believe there is something there.

Q: You are one of the scientists working on the Planetary Science Archive, which sounds like being a space documentarian. What is this archive and what are your duties there?

A: At the European Space Astronomy Centre (ESAC) in Madrid, I am the scientific leader of the Planetary Science Archive. The Planetary Science Archive (PSA) is the repository for all scientific observations done by instruments onboard ESA’s missions that explore the Solar System. We ensure the long preservation of the scientific observations, the preservation of knowledge.

At the PSA, we ensure that our database is complete, in a good shape and accessible. Similarly to a library and a documentarian, we ensure that the collection of books we have is complete, with no missing pages, and we make sure that the library is open 24/7 to anybody that needs to look at it.

Within this, my specific task is to facilitate, improve the accessibility of the scientific observations. Currently, the PSA host more then 8 millions products, and we have to facilitate the access of this too big library. I am here to make the life of scientists (include mine) easier. Therefore, my duty is to guide the development of the PSA according to the needs of the scientists. I collect inputs from numerous scientists and group of experts; I prioritize all of this and communicate this to the Archive Engineers to improve the services we are providing to the scientific community, the media, the teachers and the public.

My reward, our reward, is to see new discoveries with scientific observations easily accessible and well preserved in the PSA.

Q: Asteroids and comets are bodies whose original composition allows to study the origin of the Solar System and clarify how life arose on Earth. After space missions, probes, surveys and thousands of images and data, are we closer to know this origin?

A: Science has this unique capacity to always bring you closer to the answer, and at the same time stimulate more questions and discoveries. Are we closer to know the origin of the Solar System, I strongly believe that the answer is yes. However, at the same time we also realize the specificity of our Solar System and how unique it might be.

In the past decade, computers performances have greatly improved the understanding of our Solar System by performing very complex simulations of its formation and evolution. Space missions are absolutely needed to confront these models to the reality, and gain considerable knowledge into the formation and evolution of the Solar System.

A mission like Rosetta for instance has at the same time confirmed that comets are among the best candidates to host and bring life to Earth in particular because the have key component for life (e.g., organics, water, etc..). Nonetheless, the same mission has also shown that the fundamental ingredient water is not necessarily the same between this comet and Earth.

Thus yes, we are getting closer, but it is now evident that there are no single answers to the question.

Q: You are also interested in volcanic activity in objects like the Moon and Mercury. Why? Is it common that activity among planets and asteroids?

A: Volcanism is a key aspect of the evolution of Earth, it is also described as key in the formation and development of life on Earth. Therefore when I started to hear about volcanism on other planets, I absolutely wanted to investigate this.

Of course, volcanism on the Moon and Mercury is not linked to life. However, volcanism is a unique approach to understand the interior of an object, and its evolution through time. Analyzing its mineralogical variability (with spectroscopy) tells you how the planet evolved, and allows you to go back to the initial stage of formation when materials were accreted from the proto-planetary disk to form the planet.

Did you know that you have volcanoes on the Moon? Volcanic flows, like we can see on Earth are visible on the Moon and Mercury. We even have samples of volcanic material from the Moon brought back by the astronauts. Volcanism is present also on Venus and Mars. I focus more on Mercury and the Moon because the lack of atmosphere help the preservation of the mineralogical signature, and it ultimately helps you to go back further in time to understand the early stage of a planet.

Volcanism strictly speaking is not present on asteroids, mostly because their limited sizes do not allow retaining sufficient radiogenic material to heat up the interior and start volcanism. In fact, if an object is large enough to start melting its interior, it usually falls into the category of dwarf planets. The asteroid Vesta is a good example of this, it is an asteroid but you could also consider it as a dwarf planet with its volcanism.

And you should also considered cryovolcanism, where the only difference is that you melt ices instead of rocks to expulse material on the surface. Cryovolcanism is present on numerous satellites of Saturn and Jupiter, and comets. Thus volcanism and cryovolcanism together cover the entire Solar System, it is a probe to the interior of planetary objects and their evolution through time. It is a fundamental process to understand the Solar System, I tasted it and I am now addicted to this field of research.