Sub-Micrometer Particles Remote Detection in Enceladus’ Plume Based on Cassini’s UV Spectrograph Data

eng Article in English DOI: 10.14313/PAR_251/107

send Jan Kotlarz *, Katarzyna Kubiak *, Natalia Zalewska ** * Research Network Łukasiewicz – Institute of Aviation, Al. Krakowska 110/114, 02-256 Warsaw, Poland ** Space Research Center, Polish Academy of Sciences, Bartycka 18A, 00-716 Warsaw, Poland

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Abstract

Enceladus is the Saturnian satellite is known to have water vapor erupting from its south pole region called „Tiger Stripes”. Data collected by Cassini Ultraviolet Imaging Spectrograph during Enceladus transiting Saturn allow us to estimate water plume absorption from 1115.35–1912.50 Å and compare it to the Mie solutions of Maxwell equations for particles with a diameter in the range from 10 nm up to 2 µm. The best fit performed using Gradient Descent method indicates a presence of sub-micrometer particles of diameters: 120–180 nm and 240–320 nm consistent with Thermofilum sp., Thermoproteus sp., and Pyrobaculum sp. cell sizes present in hydrothermal vents on Earth.

Keywords

astrobiology, Enceladus, Mie scattering, remote sensing, space mission

Detekcja cząstek submikrometrowych w pióropuszu Enceladusa na podstawie danych ze spektrografu UV sondy Cassini

Streszczenie

Enceladus, księżyc Saturna, jest charakterystyczny ze względu na erupcje pary wodnej z regionu jego bieguna południowego, tzw. „Tiger Stripes”. Dane zebrane przez instrument sondy Cassini: Ultraviolet Imaging Spectrograph podczas tranzytu Enceladusa przed tarczą Saturna pozwalają oszacować absorpcję światła przez pióropusze wodne w zakresie 1115,35–1912,50 Å i porównać ją z rozwiązaniami Mie równań Maxwella dla cząsteczek o średnicach w zakresie od 10 nm do 2 µm. Najlepsze dopasowanie wykonane metodą Gradient Descent wskazuje na obecność cząstek sub-mikrometrowych o średnicach: 120–180 nm i 240–320 nm zgodnych z rozmiarami komórek Thermofilum sp., Thermoproteus sp. i Pyrobaculum sp. obecnych w kominach hydrotermalnych na Ziemi.

Słowa kluczowe

astrobiologia, Enceladus, misja kosmiczna, rozpraszanie Mie, teledetekcja

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