PEPSci
Planetary
and Exoplanetary
Science
Netherlands Organisation for Scientific Research
PEPSci
Planetary and Exoplanetary Science
Over the last two decades, we have witnessed a revolution in astronomy that is
shaking up our views of the Universe and completes the Copernican revolution
started some 450 years ago. We now know that planetary systems are bountiful
and almost every star has an associated planetary system. Planets range from
gas-rich super Jupiters, to gas-giant Neptunes, to super-Earth, to Earth-analog
planets. Planets are truly widespread and diverse. While our understanding of
the architecture of extrasolar planetary systems is still in its infancy and our
measure of the inventory is greatly limited by selection effects, we have already
started to ponder the conditions on these planets and their moons. In addition,
recent exploration missions have revolutionised our knowledge of the formation,
evolution, and present-day properties of many bodies in our solar system.
Potentially habitable zones have been identified and characterised on Mars and
in the interiors of icy moons. New ground-based opportunities and space-based
missions are actively being developed to pursue these aspects. In the end,
this will lead us to address the biggest questions of them all; indeed the
questions that define humanity: ‘What is our connection to the Universe?’ and
‘Are we alone?’ As these questions have gotten more and more impetus over the
last decade, the field of astrobiology has emerged from our great interest
to understand the chemical evolution in the Universe from simple to complex
molecules, especially those with biogenic potential and the roles they may play
as primordial seeds in the origin of life on habitable worlds. Much more detailed
characterisations of planets and exoplanets will become possible in the next
decade and a plethora of biomarkers have been proposed and studied.
New missions are in preparation and the European Extremely Large Telescope
(E-ELT) will make it possible to obtain the first direct images of rocky exoplanets.
The Dutch Planetary and Exoplanetary Programme
The interpretation and understanding of this wealth of data requires the
development of new, highly interdisciplinary research approaches. Astronomical
observations need to be combined with knowledge from the fields of earth
sciences, biology and chemistry to provide a coherent framework to understand
planetary system formation and evolution. The goal of the Planetary and
Exoplanetary Programme is to understand the origin, structure and evolution
of rocky planets and to identify the best approaches to detect biosignatures
and organics in planetary systems. This goal will be reached through a highly
integrated and coherent programme of experiments, numerical simulations,
and astronomical observations. Two research themes have been identified that
best match the current national expertise in (exo)planetary science and that
will significantly advance the (exo)planetary science field: (1) Detection of
extraterrestrial biosignatures and organics and (2) Formation, structure and
evolution of rocky exoplanets. For each theme, four projects were selected by
an international jury.
The Network
In addition to the scientific goals, this cross-disciplinary NWO research programme
also aims at establishing a long-term, cross-disciplinary network of excellent
scientists in the Netherlands who are well established in their respective fields:
earth sciences, biology, chemistry, and astronomy. The close proximity of the
relevant research groups, and their willingness to cross traditional research
area boundaries, can be expected to rapidly advance the field. The resulting
community will work towards a well-integrated, world-leading planetary and
exoplanetary research team in the next decade. The key to success for this
network is a close collaboration between the individual teams at the working
level to ensure true cross-fertilisation between the disciplines.
[Project 1]
Shining light on bio-molecular evolution: complex organics and comets
Prof. Harold Linnartz (Leiden University)
Dr. Inge Loes ten Kate (Utrecht University)
[Project 2]
Delivery of organics and water through asteroid impacts
Dr. Frank Helmich (SRON)
Dr. Michael Müller (SRON)
[Project 3]
How do (exo)planetary environments affect chemistry & spectra
of (supposed) biomarkers and geochemical processes?
Prof. Matthias Bickelhaupt (VU University Amsterdam)
[Project 4]
Photosynthesis in extreme environments on Earth as proxy for remote
detection of extraterrestrial life
Dr. Wilfred Röling (VU University Amsterdam)
[Project 5]
Formation, structure and evolution of rocky exoplanets
Prof. Carsten Dominik (University of Amsterdam)
Prof. Wim van Westrenen (VU University Amsterdam)
[Project 6]
Exoplanet geology; gas and dust from hot, rocky exoplanets
Prof. Ignas Snellen (Leiden University)
Prof. Christoph Keller (Leiden University)
[Project 7]
Observing the atmospheres of super-Earths and rocky exoplanets
Prof. Ignas Snellen (Leiden University)
Dr. Remco de Kok (SRON)
[Project 8]
Detecting conditions for life and biosignatures on rocky exoplanets
Dr. Daphne Stam (Delft University of Technology)
Planetary and Exoplanetary Science
Theme 1
Projects
Towards the Detection of Extraterrestrial
Biosignatures and Organics
Three complementary projects [1, 2, 4] focus on
A major driver for (exo)planetary science is the
in space, to characterise the conditions that allow
search for habitability and the detection of life
preserving COMs formed in space, or that are
elsewhere in the universe. This is spurred by the
needed to establish life on (exo)planets, and to
finding that many stars harbour rocky planets in the
describe the possible pathways for the evolution of
habitable zone, the zone in which it is theoretically
life. This requires both laboratory and theory based
possible for a planet to maintain liquid water on its
research (calculations, modelling, and observations)
surface. Complementary to the direct observation
– with origins both in astronomy and life sciences.
of exoplanets, therefore, are studies that aim at
A backbone project [3] puts the relevant processes
characterising (exo)planetary atmospheres and the
in a theoretical chemical picture.
improving our understanding on what to search for
detection of signatures that hint for habitability and
the potential presence of life. To correctly interpret
Deliverables
such signatures, it is necessary to understand the
The research will provide the information needed to
astronomical, geological and physical-chemical
quantitatively characterise processes that are directly
processes that determine the presence of life on
linked to life elsewhere and are aligned along direct
other celestial bodies, in our own solar system and
observables. What are the conditions under which
around other stars.
COMs can be delivered to (exo)planets and how
Biosignatures comprise molecules relevant to life
do they survive and react to form biologically
– water and complex organic molecules (COMs) –
relevant species as the planet evolves? What are
and are characterised by molecule-specific properties
the dominating physical-chemical properties that
that reflect intrinsic properties, such as homo-
govern at the microscopic level? How does life
chirality. Studying the possibility of extra-terrestrial
adapt to a changing habitat? Questions like these
life at a molecular level encompasses everything
are addressed by the leading specialists in the
from the formation and preservation of COMs,
Netherlands, through combining expertise in
including the processes involved and the optimum
laboratory astrophysics, experimental geochemistry,
conditions, the evolutionary trail during planet
microbiology astrochemical modelling, astronomical
formation, potential delivery on planetary surfaces,
instrumentation, planetary modelling and physical-
the interaction with (geo)chemical conditions on
chemical simulations. Moreover, observations from
these planets, to the adaptation of living systems to
Earth and space-based telescopes provide detailed
changing conditions in their habitats. The study and
information on the chemical inventory of matter
modelling of these processes and the challenges and
in space.
requirements for their remote detection are the
topic of this network theme.
Theme 2
Projects
The Formation, Structure, and Evolution
of Rocky Exoplanets
The physical properties of rocky exoplanets are
As far as we know, life requires a solid or liquid
and astronomers. The four research projects [5-8]
surface to develop and evolve. Hence, the search for
address the formation and evolution of planets,
habitability and extraterrestrial life focuses on small,
by constraining the chemical compositions in the
rocky planets and exoplanets rather than on the
innermost regions of planetary disks. The influence of
large, gaseous or icy ones. The vast majority of the
this chemical composition on the planetary internal
exoplanets known today are gas giants, because
composition and evolution will be studied, and the
usually, the bigger the planet, the easier it is to detect.
resulting mass-radius ratios of rocky planets will
However, thanks to improved instrumentation, data
be compared against observations. There will also
analysis methods, and dedicated space telescopes such
be focus on the evolution of the atmospheres and
as Corot and in particular Kepler, the number of
surfaces of close-in, rocky exoplanets that are strongly
confirmed rocky exoplanets has increased such
irradiated by their parent star. The spectroscopic
that we can safely assume that they are common
traces of the evolution of an atmosphere and surface
occurrences around stars in our Galaxy.
will be predicted and searched for in observations.
The currently known rocky exoplanets show a
Finally, a study into the evolution of the surfaces and
huge diversity in their sizes and masses. Especially
atmospheres, in particular clouds, of rocky exoplanets
interesting is the wide range in their densities,
in the habitable zone of their parent star will provide
as derived from their masses and radii. This wide
not only observable fluxes but also the state of
range indicates that there is a variation in internal
polarisation of the planetary signals.
being investigated, bringing together geoscientists
composition and structure, and therefore probably
also in the external geological and surface conditions.
Deliverables
Based on our knowledge of the rocky planets and
The research within this network will combine the
moons in the Solar System, we can also expect a wide
national strengths in research from the geoscience
range in the properties, such as thickness and
and astronomy communities, and will enable
composition of their atmospheres. The surface and
the Dutch science community to take maximum
atmosphere properties are thought to be crucial for
scientific advantage of the future observations. In the
a planet’s habitability. This type of research forges
Netherlands alone, METIS (Mid-Infrared E-ELT Imager
a natural connection between geoscientists and
and Spectrograph, Dutch PI-led) and EPICS (ExoPlanet
astronomers. Making this connection is the aim of the
Imager for E-ELT) are instruments planned for the
network theme ‘Formation, Structure and Evolution
E-ELT that will provide data unparalleled in sensitivity,
of Rocky Exoplanets’.
wavelength coverage and angular resolution.
Netherlands Organisation for Scientific Research (NWO)
Visiting address: Laan van Nieuw Oost-Indië 300, The Hague, the Netherlands
Postal address: PO Box 93138, 2509 AC The Hague, the Netherlands
Telephone: +31 70 344 06 40
[email protected]
www.nwo.nl/exo-planetary-science
Photocredits: ESO, ESA, NASA, Sterrewacht Leiden, Shutterstock
Netherlands Organisation for Scientific Research