Research Themes

CPS Research themes and their coordinators:

Astrobiology

Coordinator: Ian Crawford
Astrobiology - Crusader, Mars. Credit: NASA

Atmospheres and magnetospheres

Coordinators: Geraint Jones and Nick Achilleos
Atmospheres & Magnetospheres - Saturn. Credit: C. Arridge

Exoplanets

Coordinator: Giovanna Tinetti
Exoplanets - Detection. Credit: G. Tinetti

Interiors

Coordinator: Lidunka Vocadlo
Interiors - Ganymede. Credit: D. Fortes

Surfaces

Coordinator: Pete Grindrod
Surfaces - Moon. Credit: R. Bugiolacchi
 
Coordinator: Ian Crawford

Astrobiology is a new field of science, investigating the possibility of life beyond the Earth. Astrobiology is a deeply interdisciplinary field, with biochemists, microbiologists, geologists, planetary scientists, physicists and astronomers all working together on this search for extraterrestrial life. Within the CPS, researchers focus on a variety of different topics:

What are the hardiest lifeforms on Earth that could survive on other planetary bodies? 

Iceland. Credit: L. Dartnell

Ultra-hardy lifeforms, known as extremophiles, thrive in some of the most hostile environments on Earth and teach us a lot about what sort of environments on other planets and moons could be habitable. CPS researchers are working on microorganisms we have isolated from inhospitable environments including the Dry Valleys of Antarctica, the volcanic icefields of Iceland, and the very salty and alkaline soda lakes of East Africa. By studying the locations, characteristics and survival of these organisms we can understand better the broad range of conditions and environments that can support life, and therefore where best to search for life beyond Earth.

What signs of life to look for on Mars?

Mars - Crusader. Credit: NASA

Evidence of microbial life on the surface of Mars will be tricky to find. Signs of organisms may be detectable by reflectance spectroscopy, Raman spectrometry, or fluorescence. In particular, CPS researchers are involved in the design of the PanCam camera system for the ExoMars probe and the WALI spectrofluorescent enhancement. Crucial considerations include how these different biosignatures are degraded by the harsh martian environment, including the unshielded solar ultraviolet light and ionising radiation from cosmic rays.

Life in icy satellites

The outer solar system is host to many icy planetary bodies. These have rocky cores overlain by several hundred kilometres of ice, and can harbour deep global oceans of liquid water beneath brittle icy crusts as much as 100-200 km thick. These subsurface oceans in icy satellites represent possibly the largest habitable volume in the solar system, and perhaps the universe, and are an exciting target for astrobiological study - both by remote and in situ instrumentation, and by study of terrestrial analogues (e.g., Lakes Vostok and Ellsworth, under the Antarctic ice sheet). Furthermore, studies of bacterial growth in ice - either in natural glaciers or in high-pressure laboratory apparatus - lead us to believe that ecosystems may pervade the entire high-pressure ice shell of the largest outer solar system satellites. Saturn's largest icy moon, Titan, also stands out because of its thick nitrogen-methane atmosphere, the presence of liquid methane-ethane seas on its surface, and the generation of complex hydrocarbons and nitriles in the upper atmosphere. Whilst it is thought by many that these processes will aid in understanding prebiotic chemistry on the early Earth, others consider it plausible that life began (and persists) in the liquid methane on Titan's surface, living in reverse versions of the membranes used by cells on Earth.

Astrobiology and the Moon

Although the Moon has, almost certainly, never supported any life of its own, lunar exploration will nevertheless reveal much of astrobiological interest. As the Earth's closest celestial neighbour it retains a unique record on the inner Solar System environment under which life evolved on our planet. CPS researchers are involved in projects related to a number of aspects of lunar astrobiology, including the survivability and detectability of terrestrial meteorites on the Moon, and the potential of ancient lunar regolith deposits to record the changing galactic environment of the Solar System and its astrobiological consequences.

Researchers directly involved with Astrobiology research

Coordinators: Geraint Jones and Nick Achilleos

Magnetospheres are found across the Universe from Mercury, Earth, the giant planets of our Solar System, to exoplanets, pulsars and even the galaxy. Magnetospheres are regions surround celestial bodies that are dominated by electromagnetic forces. The magnetosphere around Earth has been studied for over 50 years and we have a very detailed understanding of its three-dimensional structure and variability. It is significantly affected by the Sun producing the phenomenon of Space Weather.

Saturn

CPS planetary scientists at MSSL and UCL study magnetospheres beyond the Earth, from the magnetospheres surrounding Venus and Mars, to those of the giant planets. These magnetospheres are often driven by very different energy sources and have different sources of particles to populate the magnetosphere. Jupiter's magnetosphere is the largest physical structure in the Solar System. It could easily swallow the Sun and if it were visible to the naked eye it would appear twice as big as the Moon in the night sky even though it is 2000 times further away! The image on the right shows an artist's impression of the inner regions of Saturn's magnetosphere.

Our instruments return data about these magnetospheres to answer questions such as:

  • How do the magnetospheres of other planets interact with the Sun?
  • What are the sources of energy for particles in the magnetosphere?
  • How do moons and ring systems interact with magnetospheres?
  • How are auroral emissions produced on the giant planets?

Further information

Coordinator: Giovanna Tinetti

Our group works on many areas related to exoplanetology including detection, atmospheric characterisation and modelling, the development of novel detection techniques, the modelling of radial velocity curves and instrumentation. Please see the Extrasolar Planets website for more information.

Detection and Observation

The detection and continued observation of extrasolar planet is one the key research goals of the group.  Although the group's expertise has traditionally been in modelling, we are increasingly finding success in this highly competitive arena.

Radial velocity plot

UCL has its own observatory at Mill Hill known as the University of London Observatory (ULO) which possesses several small to medium sized telescopes. Most recently, Dr. Steve Fossey used the Celestron 14-inch telescope at ULO to discover the first ever transit of a planet known as HD 80606b.  ‘606, as it is affectionately known, has both the highest orbital eccentricity and longest orbital period out of any planet yet found in transit.  This makes it one of the most exciting discoveries yet seen.

UCL is actively studying both this target and several others in follow-up programmes currently underway, including the world’s first ever dedicated search for an extrasolar moon. 

Atmospheric characterisation

Exoplanet atmosphere

As more and more exoplanets continue to be discovered, scientists are becoming increasingly interested in characterisation of these worlds.  Just knowing a name like HD 209458b tells us nothing about what this world is really like. 

UCL CPS researchers are very active in this exciting field, with particular emphasis on the use of the “transit method”.  When a planet passes in front of its parent star it causes the starlight to appear dimmer for a short period of time. The magnitude of this dip in light allows us to infer the radius of the planet. By repeating this measurement at different wavelengths of light one can see the planet seemingly change size. This apparent change in planetary radius is actually the effect of the exoplanet atmosphere absorbing and emitting light at the different wavelengths.  By studying these changes very carefully we can infer the temperature, pressure and even the chemical composition of the atmosphere.

As an example, Dr. Giovanna Tinetti used the method to make the first discovery of water vapour in the atmosphere of an exoplanet in 2007.  Since then, further studies have seen methane, carbon dioxide and carbon monoxide discovered.  It is this work which could one day allow astronomers to detect signs of life ("bio-signatures") in the chemical make-up of an exoplanet's atmosphere.

To this end, UCL is currently leading the proposal of a new space mission, the Exoplanet Characterisation Observatory (EChO). This is one of the ESA M3 class missions currently being assessed for launch in 2022, and it will provide dedicated high-resolution observations of exoplanetary atmospheres, enabling us to address some of the fundamental questions concerning planetary system formation and evolution, and the emergence of life itself.

Molecular Linelists

When spectra of exoplanets are retrieved, we must compare the observations to that of models in order to understand what we are seeing.  To do this, we use the Quantemol programme suites (developed here at UCL) to generate the spectra expected from various molecules at different temperatures.

The generation of these molecular line lists is led by Prof. Jonathan Tennyson of the Atomic, Molecular, Optical and Positron Physics (AMOPP) Group.  The recent comprehensive line list of water, BT2, was used in the detection of water in the exoplanet HD 189733b and is being used widely in a number of astronomical and non-astronomical studies.  

Atmospheric Modelling

Exoplanet models

In order to physically interpret the observations of exoplanet atmospheres, we must compare observations with theoretical predictions. To do this, we have produced highly sophisticated models of the atmospheres, allowing us to better understand the physical nature of the world in question.

UCL’s Atmospheric Physics Laboratory (APL) is dedicated to developing the most accurate and sophisticated models of atmospheres possible.  These models have been used extensively in studying the atmosphere of the Earth, Venus, Mars, Jupiter and Saturn and are now being applied to the myriad of extrasolar worlds being found. 

In addition to the GCMs in use by the APL, we use various transmission and emission models to look at the transfer of radiation through planetary atmospheres as they transit their parent stars. Results from these studies have been used to reveal the sometimes extreme conditions (e.g. compositions and temperatures) of atmospheres of hot-Jupiter-type planets orbiting close in to their stars.

Coordinator: Lidunka Vocadlo

Recent space missions have revealed that our solar system displays a rich variety of bodies, each with a complex and diverse evolutionary history. Understanding the evolution of the planets and moons presents one of the major challenges in Earth and planetary sciences. Critical understanding of the basic physical processes that govern planetary interiors is now possible because the solar system is accessible to highly-detailed remote-sensing and a variety of unique in-situ measurements. Observations of surface morphologies, such as volcanic and tectonic features, and impact craters, provide the surface expression of processes occurring deep in planetary interiors. The last decade has also seen rapid advances in the techniques and facilities necessary to investigate both the materials from which the planets and their moons are composed, and the structure, dynamics and evolution of these bodies. For example, parallel computing techniques now allow simulation at length-scales from the atomic to planetary, while experiments using in situ probes (particularly synchrotron- and neutron-source based techniques) allow us to measure a wide range of hitherto undetermined physical properties under the relevant conditions of pressure and temperature. At the same time, ever-more detailed data are being returned from current (and future) space missions. Materials' properties, obtained through a combination of theory and experiment, coupled with numerical dynamic computer modelling enable further understanding of the formation and evolution of planets, satellites and small bodies in the Solar System.

The door is now wide open for combining observations, experiments and computer simulations with dynamical modelling to tackle some of the fundamental problems concerning the interiors of the planets and moons of our solar system. This theme aims to address major unresolved problems such as:

  • why does Mercury have such a large iron core (~0.75 the radius of the planet compared to ~0.5 for Venus, Earth and Mars), and does the presence of a weak magnetic field mean it has a liquid outer core (required from dynamo theory), a layered outer core, or even a double-snow state;


    Models of Mercury's core

Schematic illustrations of the likely states of Mercury's core at the present time. In the double-snow state, the core consists of two distinct zones (red bands) where iron snow (yellow squares) forms, a thick liquid outer shell (pink) and a small solid inner core that is less than about 1200 km in radius (yellow). The iron snow sinking towards the center (indicated by arrows) leads to a compositional gradient in the liquid, with sulfur enriched immediately above the snow boundaries (red) and depleted in the bottom layer (light pink). The middle layer (dark pink) has an intermediate sulfur concentration; it receives iron snow from above and sulfur-rich liquid from below. In the Ganymede-like state, the core has a single snow zone in a liquid outer shell, and a solid inner core. The radius of the inner core is determined by the core's sulfur content and temperature. From Chen et al., 2008.

  • why does Venus have no magnetic field at all? Being much hotter than the Earth, it is likely that Venus has a metallic liquid outer core, but is unlikely to be convecting. Is there no inner core to drive convection? Or is the core in a steady hot state, i.e., no cooling? Or is a reversal currently occurring (magnetic steady-state);
  • although Mars does not have a magnetic field, significant magnetisation of the crustal rocks suggest that a dynamo existed in the past and has since ceased operation. Was this due to the cooling and solidification of the convecting liquid or perhaps some other process involving a change in the dominant heat transfer mechanism;
  • why are the interiors of Jupiter’s Io and Saturn’s Enceladus unusually active;
  • even within the confines of the moons of Jupiter, distinctively different evolutionary pathways have occurred, ranging from highly differentiated (Ganymede) to well-mixed (Callisto). How can moons in apparently similar local environments have such radically different histories;

    Internal structure of the Jovian moon Ganymede. Credit: Dominic Fortes

Internal structure of the Jovian moon Ganymede, one of the largest icy satellites in the solar system. Ganymede has a deep icy mantle with a subsurface water ocean, a dense rocky mantle, and a partially molten iron core. Both the ocean and core contribute to the intrinsic and induced magnetic field of Ganymede, which modifies the plasma flow around the body.



  • the data from the Cassini-Huygens mission to Titan have revealed features suggesting a dynamic world with a young surface continually modified by cryovolcanism dominated by methane and are now providing the means to assess many questions such as: where did Titan form - in Saturn orbit or elsewhere? – how fast did it form? – when and how fast did it differentiate, if at all? – when did the current atmosphere form? Where is this methane coming from, how is it being degassed (steady state vs. periodic), is it primordial or is it being formed within Titan by reduction or serpentinisation reactions. Very recent gravity data suggest that traditional view of Titan’s interior (a partially differentiated anhydrous rock + ice core) may have to be replaced since the evidence suggests something different - that Titan has a large low-density core comprised primarily of hydrous silicates, as shown in the figure below.


    Titan's interior. Credit: D. Fortes

New model of Titan’s internal structure proposed by Dominic Fortes.

Underpinning the planetary interiors theme are established groups, such as the Crystallography and Mineral Physics Group (CMP) and the Planetary Ices Group (PIG). We have infrastructural equipment support including X-ray diffractometers, large-volume presses, uniaxial and triaxial creep rigs. Computer calculations are supported by the Mineral Physics computer consortium which gains regular access to national supercomputing facilities. The combination of theoretical and experimental techniques, combined with dynamical modelling and, of course, observations allow us to interrogate the interiors of planets and moons to better understand their origin and evolution.

Coordinator: Pete Grindrod

Planetary surfaces record geological events. These events are a combination of internally and externally driven phenomena, which together define the origin and evolution of a planetary body and to a certain extent the wider solar system. Externally driven forces are dominated by impact cratering (across an eleven order-of-magnitude spatial scale), but also includes electromagnetic and particle irradiation on airless bodies ('space weathering') and 'traditional' fluid-mediated weathering on bodies with atmospheres. Internally driven forces are dominated by volcanism and tectonics, although in the case of smaller bodies, such as Io, Europa, Enceladus, and Triton, the ultimate power source is the external gravity field of their primary.

Artist's impression of an erupting ice volcano on the surface of Titan. Credit: Dominic Fortes



Artist's impression of an erupting ice volcano on the surface of Titan, which may be driven by the rapid decomposition of methane clathrate crystals entrained in the rising cryomagma. Such features may be responsible for resurfacing Titan with water-based lavas and pumping methane gas into the atmosphere. Image courtesy Dominic Fortes.

Driven both by internally and externally generated power, life is an extremely significant force in the Earth's geological record, and may play, or have played, a role in the evolution of Mars, Europa and Titan, for example.The record is often a complex palimpsest; transcription and interpretation of this multilayered geological record written on a planetary surface requires a combination of techniques; Mapping, Measurement, and Modelling:

  • Mapping of geological structures and rock units using remotely sensed data.
  • Measurement of chemical and mineralogical properties both in situ (on landers and rovers) and ex situ (using returned samples).
  • Modelling (both theoretical and experimental) of geological processes based on terrestrial analogues.

On the Moon, for example, we use visible-light images to map crater-size distributions and establish age relationships between mapped units. These are combined with elemental abundance maps from orbital remote sensing to learn about changes in the composition of erupted lavas with time, and to study the chemistry of deeper crustal units exposed in impact basins and crater walls. Detailed petrological analysis of returned rock samples and lunar meteorites are then slotted into this broader context to provide detailed clues to understanding the Moon's thermal evolution. Solar wind ions implanted in the lunar soil also yield a record of the Sun's evolution. In turn, this process guides our development of instruments and of observing strategies for future lunar studies.

False colour image of the southern Imbrium Basin on the Moon. Credit: Roberto Bugiolacchi


False colour image of the southern Imbrium Basin on the Moon - composed from multispectral Clementine Orbiter data and Lunar Orbiter IV photographs. Colours indicates differences in surface mineralogy, allowing for lithological units (e.g., lava flows) to be distinguished. Image courtesy Roberto Bugiolacchi.

Rapidly increasing computer power allows synthesis of imaging and spectroscopic data sets to extract global shape and local topographic data, as well as mapping of compositional variations. Combining image-based digital data with topography, gravity and magnetic field data can help to resolve difficult problems, such as the Martian hemispheric dichotomy and the existence of a putative northern ocean shoreline.

The UCL/Birkbeck Centre for Planetary Sciences has the ability to do world-class research in all three of these areas, and the work done within this theme provides not only the input for work across the other three themes, but the evidence for discriminating between hypotheses generated by modelling in these other areas.

Researchers directly involved with surfaces research

Page last modified on 28 jun 12 15:39 by Marianne Smith