We present a method for inferring the relative molar abundance of constituents of a liquid mixture, in this case methane, ethane, nitrogen and argon, from a measurement of a set of physical ...properties of the mixture. This problem is of interest in the context of the Huygens Surface Science Package, SSP, equipped to measure several physical properties of a liquid in case of a liquid landing on Saturn's moon Titan. While previous models emphasized the possibility of verifying a certain model proposed by atmospheric composition and equations of state, we use an inverse approach to the problem, i.e. we will infer the liquid composition strictly from our measurements of density, refractive index, permittivity, thermal conductivity and speed of sound. Other a priori information can later be used to improve (or reject) the model obtained from these measurements.
Heat flow is an important constraint on planetary formation and evolution. It has been suggested that Martian obliquity cycles might cause periodic collapses in atmospheric pressure, leading to ...corresponding decreases in regolith thermal conductivity (which is controlled by gas in the pore spaces). Geothermal heat would then build up in the subsurface, potentially affecting present-day heat flow - and thus the measurements made by a heat-flow probe such as the InSight HP\(^{3}\) instrument. To gauge the order of magnitude of this effect, we model the diffusion of a putative heat pulse caused by thermal conductivity changes with a simple numerical scheme and compare it to the heat-flow perturbations caused by other effects. We find that an atmospheric collapse to 300 Pa in the last 40 kyr would lead to a present-day heat flow that is up to \(2-8\%\) larger than the average geothermal background. Considering the InSight mission with expected \(5-15\%\) error bars on the HP\(^{3}\) measurement, this perturbation would only be significant in the best-case scenario of full instrument deployment, completed measurement campaign, and a well-modelled surface configuration. The prospects for detecting long-term climate perturbations via spacecraft heat-flow experiments remain challenging.
With Huygens’ descent into Titan’s atmosphere drawing nearer, the composition and state of Titan’s surface remained largely unknown. The idea of a global ocean on Titan has become less popular over ...the last decade, though the possibility of lakes and seas has remained, and recently Campbell, D.B., Black, G.J., Carter, L.M., Ostro, S.J. Radar evidence for liquid surfaces on Titan. Science 302, 431–434, 2003 reported radar evidence for liquid surfaces.
Ground truth for the existence of an ocean, sea or lake on Titan or, more precisely, a liquid surface at the specific impact point of the Huygens probe, came from the sensors of the Huygens Surface Science Package (SSP). The state of the surface material can be derived on impact using the onboard accelerometers. In the case of an impact into a liquid the SSP sensors would have been able to measure not only density but also acoustic properties, permittivity, refractive index and thermal properties. In this work, we describe possible ways of constraining the composition of a liquid surface on Titan by combining various measurements made by SSP.
The thermal sensors on the penetrator of the MUPUS experiment package selected for the ESA Rosetta mission will enable us to determine the near-surface energy balance of the nucleus of comet ...P/Wirtanen by measuring the subsurface temperature profile and the thermal conductivity of the near-surface layers. Model calculations suggest that the penetrator itself will perturb the ambient temperature field such that the temperature profile will be smoothed if the thermal diffusivity of the nucleus is significantly smaller than that of the penetrator tube. It is possible, however, to calculate the undisturbed temperature profile from the data using a method based on a solution of the transient inverse heat conduction problem. Our model calculations show that a satisfactory estimate of the undisturbed temperature field can be obtained in comparatively little computing time by calculating the temperature distribution in the model volume from temperature histories at discrete points representing the penetrator temperature sensors.
European Space Agencies fifth cornerstone mission
BepiColombo includes a ‘Surface Element’ to land a scientific payload on the surface of Mercury. The current strawman payload includes a heat flow ...and physical properties package (HP
3), focussing on key thermal and mechanical properties of the near-surface material (down to a depth of 2–
5
m)
and the measurement of heat flow from Mercury's interior, an important constraining parameter for models of the planet's interior and evolution. We present here an overview of the HP
3 experiment package and its possible accommodation in a self-inserting ‘mole’ device. A mole is considered to be the most appropriate deployment method for HP
3, at least in the currently-assumed case of an airbag-assisted soft landing architecture for the Mercury Surface Element.
We use the surface temperature response to Phobos transits as observed by a radiometer on board of the InSight lander to constrain the thermal properties of the uppermost layer of regolith. Modeled ...transit lightcurves validated by solar panel current measurements are used to modify the boundary conditions of a 1D heat conduction model. We test several model parameter sets, varying the thickness and thermal conductivity of the top layer to explore the range of parameters that match the observed temperature response within its uncertainty both during the eclipse as well as the full diurnal cycle. The measurements indicate a thermal inertia of 103+48-24 Jm-2K-1s-1/2 in the uppermost layer of 0.2 to 4 mm, significantly smaller than the thermal inertia of 200 Jm-2K-1s-1/2 derived from the diurnal temperature curve. This could be explained by larger particles, higher density, or a very small amount of cementation in the lower layers.
Asteroid (162173) Ryugu is the target object of Hayabusa2, an asteroid exploration and sample return mission led by Japan Aerospace Exploration Agency (JAXA). Ground-based observations indicate that ...Ryugu is a C-type near-Earth asteroid with a diameter of less than 1 km, but the knowledge of its detailed properties is still very limited. This paper summarizes our best understanding of the physical and dynamical properties of Ryugu based on remote sensing and theoretical modeling. This information is used to construct a design reference model of the asteroid that is used for formulation of mission operations plans in advance of asteroid arrival. Particular attention is given to the surface properties of Ryugu that are relevant to sample acquisition. This reference model helps readers to appropriately interpret the data that will be directly obtained by Hayabusa2 and promotes scientific studies not only for Ryugu itself and other small bodies but also for the Solar System evolution that small bodies shed light on.
We have designed and built a compact breadboard prototype instrument called WatSen: a combined ATR mid-IR spectrometer, fixed-focus microscope, and humidity sensor. The instrument package is enclosed ...in a rugged cylindrical casing only 26mm in diameter. The functionality, reliability and performance of the instrument was tested in an environment chamber set up to resemble martian surface conditions. The effective wavelength range of the spectrometer is 6.2 - 10.3 micron with a resolution delta-wavelength/wavelength = 0.015. This allows detection of silicates and carbonates, including an indication of the presence of water (ice). Spectra of clusters of grains < 1mm across were acquired that are comparable with spectra of the same material obtained using a commercial system. The microscope focuses through the diamond ATR crystal. Colour images of the grains being spectroscopically analysed are obtainable with a resolution of ~ 20 micron.
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