Coring experiments with cryogenic water and carbon dioxide ices: toward planetary surface operations

As a prelude to the design of sampling devices able to extract materials from the icy surfaces of comets, outer-planet satellites, and the martian poles, it is necessary to understand some of the physical properties of these ices. To this end we have investigated the mechanical resistance displayed by two ices subjected to coring operations at low temperatures and under vacuum. The ices used in this study were water ice, frozen from liquid water, and carbon dioxide ice grown from its vapour. The coring tool employed had dimensions and required power levels that were comparable to a sample extraction system designed for a present-day spacecraft lander. The specific cutting strength, a parameter that measures the toughness of the material, has been measured while coring these two ices. For water ice this property rose from 25MJm-3 at an ice temperature of 250K, to 60MJm-3 at 140K. At the lower temperature of 140K, pore-free carbon dioxide ice has also been measured to have a specific cutting strength approximately half that of water ice at the same temperature. These laboratory-based measurements may be used as guides for the power levels needed to core solid water and CO2 ices at certain rates

The Huygens surface science package sound speed measurements and the methane content of Titan's atmosphere

The Huygens probe descended through Titan's atmosphere in January 2005. On board was the Surface Science Package (SSP), a set of nine sensors, which included a speed-of-sound sensor. We present a detailed description of the SSP speed of sound measurements and report constraints on the methane content in Titan's lower atmosphere based on these measurements. After extensive instrument calibration and subsequent Bayesian analysis of the data, the most likely result derived from our measurements in Titan's lower atmosphere is a methane fraction of approximately 2% at 10 km, increasing to 3.5% at lower altitudes. These estimates are based on a binary composition. Our data show that any large scale variation of methane within the lower 11 km of Titan's atmosphere is unlikely. Within experimental and theoretical uncertainties, our estimates are lower than, but compatible with earlier estimates obtained from the mass spectrometry experiment

Physical properties of Titan’s surface at the Huygens landing site from the surface science package acoustic properties sensor (API-S)

We present the results from the first sonar to be deployed outside of Earth, and the first active acoustic instrument on Titan, onboard the Huygens probe, and the implications of its data for the geomorphology and characteristics of the Huygens landing site. Signals were recorded from 90 m downwards until impact, with a maximum sensor footprint diameter at the ground of 39.2 m. Probe impact speed was measured to be 4.67 m s?1. Derivation of terrain topography in a transect beneath the probe may indicate a ridge-trough terrain with an amplitude of about 1 m and a wavelength of about 10 m, although a flat surface is also consistent with the results. Modelling of the returned signal indicates that the surface acoustic properties at the landing site must be specular in nature, which may have two possible (not incompatible) causes—the surface may consist of sorted interlocking grains, smooth on the centimetre scale, which would imply either fluvial sorting or the infill of small particles interstitial to the larger particles (similar to a terrestrial playa). Alternatively, specularity may indicate the presence of methane as an interstitial liquid or as very small pools. Due to mission constraints, tens of metres around the landing site were not well-imaged by Huygens' cameras except for the narrow azimuth observed after impact (the camera did not look straight down, and was not in imaging mode during the last few hundred metres of descent). Thus the data presented are among the few direct observations of the landing site surroundings. <br/

The Beagle 2 environmental sensors: science goals and instrument description

A suite of instruments on the Beagle 2 Mars lander was designed and built in order to investigate the environmental conditions at the landing site. The sensor suite was capable of measuring air temperature at two heights, surface level pressure, wind speed and direction, saltated particle momentum, UV flux (diffuse and direct at five wavelengths), the total accumulated radiation dose and investigating the nature of the oxidising environment. The scientific goals of the instruments are discussed within the context of current understanding of the environmental conditions on Mars, and the instruments themselves are described in detail. Beagle 2 landed on Mars in late 2003, as part of the ESA Mars Express mission. The expected lifetime of the lander on the surface was 180 sols, with a landing site in Isidis Planitia, but has not responded to attempts to contact it, and has now been declared lost. The Environmental Sensor Suite (ESS) was intended to monitor and characterise the current local meteorological parameters, investigating specific areas of scientific interest raised from previous missions, most notably dust transport and transient phenomena, and additionally to add context to the conditions that any possible martian micro-organisms would have to face. The design of the instrument suite was strongly influenced by mass limitations, with eight sensor subsystems having a total mass of approximately 100 g. Although Beagle 2 has been now declared lost, the scientific goals of an Environmental Sensors Suite still remain a valid target for any future astrobiology orientated missions