A Prototype Ice-Melting Probe for Collecting Biological Samples from Cryogenic Ice at Low Pressure

Recovery of Microbes from Subsurface Europa Analog Environments: An Efficient Mechanical-Thermal Probe for Collecting Biological Samples from the Subsurface of Icy Moons

The ultra-low temperatures (<173K) and ultra-low pressures (<0.1 Pa) that exist on the surface of icy moons present a formidable challenge for collecting biological samples. Standard drilling technology is not efficient in these conditions, where conduction of thermal energy leads to the possibility of freezing in place and shear forces impart a strenuous test on microbial viability. If microbes exist within the first few meters of the surface, an extraction process must be gentle enough to recover them intact. This report describes a substantial improvement from the study by Davis in 2017, who presented a concave conical thermal probe capable of penetrating -65°C ice in 1000 Pa pressure. The current report describes a mechanical-thermal device for penetrating ≤ -150°C ice in 10 Pa pressure, which is analogous to the physical conditions on the surface of icy moons. The mechanism has an efficiency of >68% with -65°C ice and >61% with -150°C ice, which is well above the expected 10-15% for a Philberth-type probe. In addition, the probe can harvest a sensitive bacterium (Escherichia coli) from under a layer of acidified peroxide ice (pH 1.1), which is analogous to the expected surface chemical composition of the icy moon Europa. In field tests at -20°C air and -6°C ice temperatures, multiple organisms were extracted in a viable state, and chemical analysis indicated high-resolution separation of stratified layers. Finally, attaching the thermal tip to a telescopic mechanism allowed the probe to penetrate through 1.0 m of -65°C ice, which is well below the depth of harmful radiation expected at the subsurface of Europa. The current work opens the door for a lander vehicle to penetrate the upper subsurface of Europa and analyze biologically active samples.

Thermal picks for anchoring on icy moons

Europa, Enceladus, and other icy moons are exciting science targets, but our capabilities to adequately explore these planetary bodies needs to be developed. Gripping the surface ice may aid the stability and mobility of surface landers and mobile explorers that are sent to the surface of an icy moon. This paper presents an approach to anchoring into the surface of an icy moon using a heated pick.

The proposed thermodynamic approach contrasts with the traditional mechanical approach to inserting terrestrial ice anchors. This thermodynamic approach maintains the ice structure to provide a reliable hold. The low temperatures and lack of a significant atmosphere on most of the icy moons cause surface conditions to stay below the triple point of water, the primary constituent of the surface ice for both Europa and Enceladus. Under these conditions the surface water ice will sublimate when sufficiently heated. The thermal pick concept presented in this paper is used to study the nature of the sublimation that results from forced insertion of an object into ice, which could then be used as an anchor for stability and mobility.

While the surfaces of the icy moons are composed primarily of water ice at cryogenic and vacuum conditions, the nature of a sublimation process can be more readily examined with frozen CO2, which sublimates under atmospheric conditions. This paper explores the physical phenomena and thermodynamic design considerations of a heated device that uses a sublimation based insertion into frozen CO2 under atmospheric conditions. This approach was found to allow for proper insertion of thermal picks with energetic efficiencies of up to 90%.

Thermal Heads for Melt Drilling to Subglacial Lakes: Design and Testing

Antarctic subglacial lakes are often considered suitable analogues to extraterrestrial subglacial aqueous environments. Recently, an environmentally friendly RECoverable Autonomous Sonde (RECAS) was designed at the Polar Research Center of Jilin University (JLU) to sample the water of subglacial lakes without contamination. In this regard, the development of a fast-penetration thermal head is the key issue for RECAS. Two different prototypes were designed and tested at the JLU ice-well to determine the optimal design and operation parameters of the thermal heads. Practical top and bottom thermal heads were then designed based on one of the prototypes, which can penetrate ice at an average rate of 1.88 m/h. The test results for the RECAS thermal heads show that the rate of penetration (ROP) can be 1.80-1.95 m/h in -10°C ice, and the axial load on the thermal head only affects the ROP when it is lower than a specified threshold. The decrease of the ice temperature from -10°C to -30°C leads to a decrease of 17% in the ROP. The bottom thermal head can drill into dirty ice, and a simple collector positioned above the head can collect solid particles suspended in the melted ice. The top thermal head exhibited a long lifetime and stable heating performance after being powered in water for 2 weeks. In addition, the ice temperature near the borehole was monitored to evaluate the range of heat disturbance caused by the thermal head.