Dust-Proof Seal Allows Sample Characterisation on Small Missions

Heating samples to extract volatiles is a standard way to characterise solid samples. By heating a sample and recording the temperature profile results it can explain a lot about the nature of those volatiles and allow them to be collected and analysed further. This technique is, in principle, a standard process in terrestrial laboratories and the same principle is applied in-situ for planetary analysis where solid samples are delivered to an oven, which is sealed and heated to produce signatures of the volatiles. Several planetary mission instruments, such as those on Viking, Beagle II, Rosetta and Curiosity all use this technique but have shown that developing an oven with a strong sealing mechanism, which is both lightweight and robust, is challenging. This is especially true in environment 

such as the lunar surface, where the pervasive nature of the dust has the potential to interfere with the tight seal. Large, expensive hardware such as that on the Curiosity rover can have extensive dust mitigation in place to prevent this, but this is not a feasible solution for smaller more mass restricted hardware such as that on Rosetta.
An activity with TDE and the Open University, UK has developed, tested and validated a reliable and re-usable sealing and heating mechanism, which ensured sufficiently low leak rates and heating performance up to 1000oC of the sample in a dusty environment.
The oven can provide reliable and reusable heating and sealing using pyrolysis, as the activity identified a mechanism that could seal under a relatively low compressive force (~400N) and 

maintain integrity, even in the presence of dust, while at the same time allowing a sample to be heated to 1000°C.
The activity, through a combination of existing oven designs and investigation into the performance of different seal gasket materials and geometry, was able to determine that seals compressed between two symmetrical 90° knife edges were able to close even in the presence of up to 9 per cent dust coverage. The testing also demonstrated that using polytetrafluoroethylene (PTFE) less than 2 mm thick, was capable of resealing at least five times before it failed.
This technology, if further developed, can be used in all future missions where sealing force or dust mitigation measures (or both) are limited.

4000128701 c lose d in 2021. All documentation is available on Nebula.