Convenor: Pat Irwin
Talks: LG09N, Wed 2 April, 16:00-17:30
Posters: Whitla Annexe
This session will review the UK's current planetary science activities, covering ground-based observations, spacecraft missions such as Cassini, Huygens, Venus Express and Mars Reconnaissance Orbiter, and also future plans.
P15/202 - The climate on Venus investigated by Venus Express - submitted 22/02/2008
Presented by: Fred Taylor (University of Oxford)
Status: Accepted as talk. 16:00-16:15
Abstract: Venus Express is the first European mission to Venus. It has been in a polar orbit around the planet since April 2006 and is scheduled to operate until May 2009. One of the main goals is to understand why the climate on the planet differs so much from early expectations, and to place such an understanding in a common physical and meteorological framework that includes the other terrestrial planets with atmospheres, Earth and Mars. Results to date and progress towards this objective will be presented.
P15/381 - Recent studies at Saturn and Venus with Cassini and Venus Express - submitted 29/02/2008
Presented by: Christopher S. Arridge (Mullard Space Science Laboratory, UCL; Centre for Planetary Sciences, UCL)
Co-authors: Andrew J. Coates, Geraint H. Jones, Sandrine Grimald, Sheila Kanani, Sharon Tsang, Anne Wellbrock
Status: Accepted as talk. 16:15-16:30
Abstract: In this talk we review recent studies of Saturn and Venus using data primarily from electron spectrometers on the Cassini and Venus Express spacecraft respectively. Using Cassini data we: a) describe ring spokes and present a model for their formation and evolution, b) review attempts to understand the production of periodicities in the kronian magnetosphere and the quest to find Saturn's sidereal rotation period, c) discuss the interaction of icy satellites with Saturn's magnetosphere, d) discuss Titan's background environment and its variability due to solar wind dynamic pressure variations and rotational asymmetries inside Saturn's magnetosphere and e) describe the detection of very heavy negative ions in Titan's ionosphere and discuss the production of Tholins at Titan. We also use Cassini data to discuss plasma escape from Titan driven by ambipolar electric fields. We relate this to observations of atmospheric escape at Venus and use Venus Express data to discuss ionospheric electrons.
P15/376 - X-ray emission from Jupiter and Saturn - submitted 29/02/2008
Presented by: Graziella Branduardi-Raymont (University College London, Mullard Space Science Laboratory)
Status: Accepted as talk. 16:30-16:40
Abstract: In recent years X-ray observations with XMM-Newton and Chandra have offered a novel way of furthering the study of planets in our solar system and have provided a wealth of information about the physical processes taking place on them, and especially about those leading to the production of aurorae. This presentation will give an up-to-date review of what we have discovered about Jupiter and Saturn.
Jupiter's X-ray emission has been found to separate into two components: a polar, auroral one and a low-latitude, disk component. Auroral soft X-rays are most likely being produced by energetic heavy ions precipitating in the planet's atmosphere and producing X-rays by charge exchange. At energies above ~3 keV bremsstrahlung by energetic electrons has also been detected from the Jovian aurorae, and there is clear evidence that these same electrons are responsible for the auroral oval FUV emission as well. X-rays from Jupiter's disk are mostly due to scattering of solar X-rays in the planet's atmosphere, and as such are controlled by the X-ray output of the Sun. Saturn, on the other hand, has only shown (so far) scattered, disk X-ray emission, with no evidence for X-ray aurorae (unlike in the FUV). In addition, an atomic oxygen X-ray emission line has been detected from its rings, and has been associated with fluorescent scattering of solar X-rays from the icy ring material.
P15/141 - SuperWASP Observations of the Outburst of Comet 17P/Holmes - submitted 16/02/2008
Presented by: Henry H. Hsieh (Queens University Belfast)
Co-authors: Alan Fitzsimmons, Don L. Pollacco
Status: Accepted as talk. 16:40-16:50
Abstract: Comet 17P/Holmes, a seemingly typical Jupiter-family comet, underwent a substantial outburst on 24 Oct 2007. Over the span of two days it underwent a million-fold increase in brightness that is unprecedented for a comet, brightening from m(V)~17 to m(V)~2 between 23 Oct and 25 Oct. In subsequent weeks, 17P/Holmes' coma steadily expanded, eventually growing larger than the Sun. The progression of this outburst was serendipitously observed by the SuperWASP-North telescope on La Palma over several weeks, including the night of the initial outburst, providing a unique record of the onset and evolution of 17P/Holmes' dramatic transformation. While the exact cause of the outburst remains obscure, we find that the light curve of the comet on the first night of the outburst can be fit by a square law, consistent with a linearly-expanding, optically thick coma, and implying a start date for the outburst of Oct 23.8 UT. By measuring the diameter of the coma on successive nights from 31 Oct through 23 Nov, we find a best-fit linear expansion rate of the coma of 0.430±0.01 km/s and an implied outburst date of Oct 20.3 UT. This outburst date differs substantially from the true outburst date, implying that the rate of coma expansion in the days immediately following the outburst must have been higher than the rate we measure from 31 Oct onward. We will discuss possible origins and implications of the deceleration of 17P/Holmes' expanding coma, and also present wide-field images of the comet and discuss its evolving morphology.
P15/123 - Cometary populations and the Oort cloud - submitted 08/02/2008
Presented by: David Asher (Armagh Observatory)
Co-authors: Mark Bailey, Vacheslav Emel'yanenko (South Ural University)
Status: Accepted as talk. 16:50-17:00
Abstract: We use large scale dynamical simulations to show that the various observed cometary populations entering the planetary system are consistent with injection from the Oort cloud. In addition to the near-parabolic flux with perihelion within the planetary region, these populations include high eccentricity trans-Neptunian objects, Centaurs, and Jupiter family and Halley type comets. The orbital characteristics of the Centaur population are a useful constraint in distinguishing whether the proximate origin of Centaurs is primarily the Oort cloud or the near-Neptune high eccentricity region. Although the Edgeworth-Kuiper belt contributes to short period comets, this work demonstrates the importance of the Oort cloud as a cometary source.
P15/119 - Deducing the dust properties near comet ary nuclei from meteor showers - submitted 07/02/2008
Presented by: Iwan Williams, Queen Mary, University of London
Status: Accepted as talk. 17:00-17:10
Abstract: With the Rosetta mission now well under way, knowledge of the dust properties close to the nucleus is vital. Remote observations can give global averages, but in meteor showers, each meteor represents the ablation of a single dust grain. Hence by studying meteor showers we obtain the properties of individual grains. Some measured meteors are of centimetre size, large enough to cause problems for the Rosetta lander. Hence knowing where on the orbit these are ejected and in what numbers is vital information. The talk will summarise what is known.
P15/129 - Reflectance Properties of Low Tj Objects in the Near Earth Population - submitted 11/02/2008
Presented by: Sam Duddy (Queen's University, Belfast)
Co-authors: Alan Fitzsimmons, Stephen Lowry (Jet Propulsion Laboratory, NASA)
Status: Accepted as talk. 17:10-17:20
Abstract: Studying the Near Earth Object (NEO) population provides an insight into the mechanisms at work during the evolution of the solar system. Dynamical studies imply that 94% of objects originate in the Main Asteroid Belt while the remaining 6% could be extinct comets, having their origins in the outer solar system (Bottke et al 2002; Icarus 156, 399). SUSI2 and SOFI on the NTT were used to obtain quasi-simultaneous optical and near infrared images of a sample of the NEO population which have a Tisserand value of 2
P15/112 - Present and future observations of a meteor shower in the Martian atmosphere - submitted 01/02/2008
Presented by: Apostolos Christou (Armagh Observatory)
Co-authors: Jeremie Vaubaillon (1), Paul Withers (2); 1 - Spitzer Science Center, CalTech/ IMCCE, Paris; 2 - Center for Space Physics, Boston
Status: Accepted as talk. 17:20-17:30
Abstract: Mars, like the Earth, intersects cometary meteoroid streams, an as-yet-unquantified source of exogenous material, including organics, coming to the Martian atmosphere and surface. By simulating numerically the dynamical evolution of trails of meteoroids ejected from several Jupiter-family and Halley-type comets, we have obtained quantitative, testable predictions for Martian meteor activity. These will enable the planning and execution of in situ observations of meteor activity on planets other than the Earth.
In this talk we will concentrate on the meteoroid stream of comet 79P/du-Toit-Hartley, a relatively poorly-known member of the Jupiter-Family type of comets. We show that meteoroids ejected from this comet during past perihelion passages do find their way to the Martian atmosphere at specific times during the 20th and 21st centuries and should have measurable effects on the planetary environment. On two of these occasions, in April 2003 and March 2005, we have examined archived ionospheric profile data obtained by the Mars Global Surveyor (MGS) Radio Science experiment. In the 2003 case we see a statistically significant feature that is consistent in time, location and altitude with our predictions while in 2005 no such signature was detected (Christou et al., A&A 471, 321–329, 2007). We discuss these observations, how they relate to our knowledge of the cometary properties and highlight the need for observational characterisation of the Mars-crossing comet population with Earth-based facilities. Finally, we issue predictions for exceptional 79P-related meteor activity that should be similarly observable by in-situ instrumentation during the next decade of Mars exploration.
P15/239 - Retrieval of Uranus' vertical cloud structure from UKIRT/UIST observations - submitted 26/02/2008
Presented by: Patrick Irwin (University of Oxford)
Co-authors: Nicholas Teanby, Gary Davis(Joint Astronomy Centre)
Status: Accepted as poster
Abstract: Since Uranus has a very high obliquity of 98 degrees and a very small amount of residual internal heat left over from its formation, the circulation of its atmosphere is strongly affected by seasonal changes in solar irradiation. Uranus reached its northern spring equinox in December 2007 and at the planet’s last equinox in 1965 there were indications of a substantial change in the planet’s appearance. Ground-based instrumentation has improved dramatically since 1965 and thus there is great international interest in monitoring the cloud structure of Uranus through this equinox period to monitor any rapid variations that may occur this time.
New near-infrared spectra of Uranus were observed in August/September 2006 and in June 2007 using the UIST instrument on the United Kingdom Infrared Telescope (UKIRT). Spectra (in Long Slit mode) were recorded between 1 and 2.5 microns with the slit aligned with the planet’s central meridian to determine any north-south variations of Uranus’ cloud structure. In addition, context images were also recorded to note the position of discrete mid-latitude clouds to ensure that these were not confused with any general latitudinal variation. We here present retrievals of the latitudinal variation of Uranus' vertical cloud structure from these data using an optimal estimation retrieval model, NEMESIS, together with new methane absorption coefficients and a Matrix Operator multiple scattering model. We currently find that the data are best fitted with two cloud layers, one at ~3 bar and, curiously, a deeper cloud layer at 8 - 12 bars. We also note some changes in Uranus' cloud structure between 2006 and 2007, which should be confirmed by new UKIRT observations scheduled for July 2008.
P15/241 - Ion build up by species and energy in the Venusian upper atmosphere - submitted 26/02/2008
Presented by: Ian Whittaker (Aberystwyth University)
Co-authors: Manuel Grande, Gemma Guymer
Status: Accepted as poster
Abstract: An investigation is launched into the global scale dynamics of individual ion species and where they cluster. The work is carried out by analysis of the IMA mass spectrometer onboard Venus-Express. By careful bin packing of the data, ion maps can be built up and compared. We examine the location of different populations relative to boundaries. Maps of average cases will be presented, and case study events compared to this baseline.
P15/512 - The 2007 Aurigid Outburst - submitted 02/03/2008
Presented by: Prakash Atreya, Armagh Observatory
Co-authors: Apostolos Christou
Status: Accepted as poster
Abstract: A rare outburst of the Aurigid meteor shower was predicted to occur 11:36±20 min UT on the 1st of September 2007 due to Earth's encounter with the 1-revolution dust trail of long period comet C/1911 N1 (Kiess). The outburst was predicted to last ~1.5 hours with a peak Zenith Hourly Rate of ~200/h, which is ~20 times higher compared to annual Aurigid. The meteors, traveling at the speed of 67 km/s, would emanate from a Radiant at R.A.= 92°, Dec.= +39° (J2000) in the constellation Auriga. The prediction was made using a complete simulation of the evolution of the comet's dust stream ejected 2000 years ago. Three members of Armagh Observatory observed this outburst from San-Francisco, USA, where the shower was anticipated to be best seen. Observed radiant, velocity and peak time were as predicted within the error bars, whereas the Zenith Hourly Rate was lower than expected. We present here some of our results for double station meteors (meteors observed simultaneously from two different locations to triangulate trajectory precisely), and compare their orbital parameters with that of their parent comet C/1911 N1 (Kiess).
P15/566 - An Investigation of Oxygen and Helium ions inside Earth’s Magnetoshphere using Data taken by the MICS instrument on CRRES during 1991 - submitted 06/03/2008
Presented by: David Forster, Institute of Physics, Aberystwyth University
Co-authors: M Grande, C H Perry, J A Davies
Status: Accepted as poster
Abstract: Ionic number density data, taken by the MICS (Magnetospheric Ion Composition Spectrometer) instrument on CRRES (Combined Release and Radiation Effects Satellite), is used to investigate the behaviour of singly charged Oxygen ions and Alpha Particles while under both quiet and storm-time conditions. Mean time lags between DST and ion populations are also used to investigate the development of the enhanced ring current during storm time. The results of this investigation show clearly an enhancement of oxygen in the outer radiation belts during times of highly negative DST, and are in agreement with previous work (Grande et al, 1996, 2004) and existing theories.
P15/584 - Study of Stellar Variability and Exoplanetary Transits using STEREO-Heliosperic Imager - submitted 06/03/2008
Presented by: Vinothini Sangaralingam (University of Birmingham)
Status: Accepted as poster
Abstract: In addition to studying solar wind phenomena, the Heliospheric Imager (HI) instruments onboard the two STEREO (Solar TErrestrial RElations Observatory) spacecraft provides an excellent opportunity for space-based stellar photometry. The HI instruments provide wide area coverage (20×20 degrees for the 2 HI-1 instruments and 70×70 degrees for the two HI-2 instruments, and long continuous periods of observations.
We will describe the data analysis pipeline for the HI instruments and some early stellar results, and describe the prospects for using STEREO to study such phenomena as eclipsing binaries, pulsating and flare stars and transiting extrasolar planets.
P15/587 - Mapping the dynamics and stability of Jovian Irregular Satellites - submitted 06/03/2008
Presented by: Tobias C. Hinse (Armagh Observatory, UK, NI)
Co-authors: Apostolos A. Christou
Status: Accepted as poster
Abstract: An application of the 3-body problem to the real solar system is the dynamics of irregular satellites. Since 1997 an ever increasing population of these bodies has been discovered, increasing the tally of known objects from roughly 10 to 100. As a result, strong evidence of structure in their orbital distribution has now become apparent. The currently-favoured formation model is that irregular satellites are objects captured from original heliocentric orbits. The new observations allow new tests of this hypothesis and provide a unique window in to the early environmental conditions of giant planet and solar system formation.
Here we apply the so-called MEGNO technique to study the phase space within which Jovian irregular satellite orbits exist. The MEGNO factor is a fast indicator revealing and distinguishing the presence of chaotic and quasi-periodic dynamics. Initial tests revealed this technique to be a powerful tool in studying the present day dynamics of irregular satellite orbits and, in particular, sources of instability that may have an observable signature in their dynamical evolution. A complete mapping in the semimajor-axis-, eccentricity- and inclination space have been performed revealing interesting dynamical features. The MEGNO maps show the fine-structure locations of mean motion resonances and identifies the presence of Kozai cycles at near-polar orbits. In addition the MEGNO maps clearly divide phase space into stable and unstable regions revealing an dynamical asymmetry between the prograde and retrograde satellite orbits. This work can help on-going and future ground-based observing surveys to constrain and limit sky regions within Jupiter's Hill sphere revealing stable orbit configurations of the irregular satellite population.
P15/591 - An Outer Solar System High Ecliptic Latitude Survey - submitted 06/03/2008
Presented by: Eamonn Ansbro (Open University)
Co-authors: Simon Green, John Murray, Apostolos Christou (Armagh Observatory)
Status: Accepted as poster
Abstract: Edgeworth Kuiper Belt Objects (EKBOs) orbit beyond Neptune and offer important clues about the formation of our solar system. Far from resembling an accretion disk leftover, the discovery of some EKBOs with inclinations as high as 40 degrees demonstrates that the full latitudinal extent of the EK belt must be large. Ascertaining the true extent of the transneptunian objects (TNO) inclination distribution is important for planning TNO surveys. It is important for determining the total number of TNOs and the past and present mass contained in the EKB. It will also provide data that may confirm or alter our understanding of solar system formation. Past surveys of TNOs are probably a poor representatiion of the true distribution of EKBO inclinations because most were found in surveys centred on the ecliptic. Such surveys were biased towards finding low inclination objects which spend the majority of their orbit close to the ecliptic.
A 0.9 metre telescope at Kingsland Observatory, County Roscommon, Ireland has been carrying out a two year statistical survey by imaging a range of ecliptic latitudes that are equidistant from each other and measuring the density of EKBOs found at each latitude. Imaging sets of fields spaced uniformly North of the ecliptic will determine the resonance structure imposed on the belt by the gravitational effects of Neptune. At each longitude, fields at several ecliptic latitudes have mapped the inclination distribution of the belt, testing competing theories for the formation and orbital evolution of the giant planets. The survey also includes a search for a hypothetical ninth planet beyond the EKB as a follow up survey of some 'suspected planets'. The follow up survey will attempt to detect whether or not this planet exists based on the targets located by prior research.
P15/592 - 0.9 Metre Robotic Survey Telescope at Kingsland Observatory - submitted 06/03/2008
Presented by: Eamonn Ansbro (Open University)
Co-authors: Simon Green, John Murray, Apostolos Christou (Armagh Observatory)
Status: Accepted as poster
Abstract: The 0.9m telescope at Kingsland Observatory is a custom made, advanced technology, wide field imaging system, designed for sky survey applications. All functions are automatically controlled by the Observatory Control Software called ACP. ACP provides the automation hub for the observatory. It sequences the observations and controls the telescope, CCD imager, filter wheel, autoguider, focuser and RORO observatory. The observatory operations may work unattended from dusk to dawn. It may be operated locally at the control centre or remotely over the internet. The present two year survey involves an outer solar system search for EKBOs at high latitudes.
P15/626 - Atmospheric erosion by small scale magnetic structures at Venus - submitted 07/03/2008
Presented by: Gemma Guymer (Aberystwyth University)
Co-authors: Manuel Grande, Ian Whittaker, Hanying Wei (1), Teilong Zhang (2) & the ASPERA team ; 1 - UCLA, 2 - Austrian Academy of Science
Status: Accepted as poster
Abstract: An investigation into the role which small scale magnetic structures play in the erosion of the Venusian atmosphere is underway. Initial studies have indicated that the flow of planetary ions may be associated with these structures. Details of the interactions will be explored. Data from the ion mass analyzer (IMA) instrument and magnetometers onboard the Venus Express are analyzed to confirm that the structures are of the correct scale and then attempts are made to correlate the direction of these structures to signatures in the ion composition data.
