Calibration of Destiny Dust Analyzer (DDA) with Polypyrrole Coated Perylene Microparticles

DESTINY+(Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science) is a future JAXA interplanetary space mission to the active asteroid 3200 Phaethon (Ozaki et al. 2022). The primary scientific payload - the Destiny Dust Analyzer (DDA; Simolka et al. 2024), an impact ionisation mass spectrometer - will assess physicochemical properties of (sub-)micron-sized dust particles emitted by Phaethon. Over the mission duration, DDA will also sample dust particles originating from different environments: lunar, interplanetary, and interstellar. DDA is a time of flight (TOF) impact ionisation mass spectrometer - a successor to Cassini’s Cosmic Dust Analyzer (CDA; Srama et al. 2004), which sampled ice and dust from the Saturnian system - and similar to Europa Clipper’s SUrface Dust Analyzer (SUDA; Kempf et al. in review) that will visit the Jovian moon Europa. These instruments utilise impact ionization; nanometere- to micron-sized dust particles strike the instrument’s target at hypervelocities, ionising chemical species embedded within particles and generating a TOF mass spectrum.

Both for calibration of DDA and the generation of a cationic mass spectral library to characterise the composition of dust in space, laboratory experiments are currently underway using DDA’s engineering model. Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous organic compounds in many different space and planetary environments – e.g. they are a major constituent of carbonaceous chondrites. For this reason, we investigate polypyrrole coated perylene PAH particles prepared in the form of microparticles and accelerate them using a Van de Graaff dust accelerator. Here, we present the first analysis of the cationic TOF mass spectra of such particles accelerated at 750 kV and recorded over an impact speeds range of 3-36 km/s. The spectra successfully exhibit mass line corresponding to the molecular ion [M]⁺ of perylene at m/z 252 for impact speeds between 3 and 7 km/s. From impact speeds of 9 to 16 km/s, the spectra exhibit a sequence of consecutive mass lines above m/z 45 with mass resolution ∆m ≈ 12-14, sufficient to characterise a homologous series of cations from PAHs. In addition, these spectra also show low mass fragment cations that most likely arise from the coating material of polypyrrole and from target contamination.

Future work will investigate these particles accelerated over higher potential differences up to 2 MV, as well as the mass spectral appearance of other PAHs. This carries relevance not only for DDA, but also for other impact ionisation mass spectrometers onboard future space missions (e.g., SUDA onboard NASA’s Europa-Clipper) that look to sample interplanetary and interstellar dust.

References

Kempf et al. (2024), SUDA: A SUrface Dust Analyser for compositional mapping of the Galilean moon Europa. Space Science Reviews, in review.

Ozaki N et al. (2022), Mission design of DESTINY +: Toward active asteroid (3200) Phaethon and multiple small bodies. Acta Astronaut. 196 , 42–56.

Srama et al. (2004), The Cassini Cosmic Dust Analyser. Space Sci. Rev., 114, 465–518.

Simolka et al. (2024) The DESTINY+ Dust Analyser — a dust telescope for analysing cosmic dust dynamics and composition. Phil. Trans. R. Soc. A 382: 20230199.