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Salt grains in hypervelocity impacts in the laboratory: Methods to sample plumes from the ice worlds Enceladus and Europa
Author(s) -
Fisher C. R.,
Price M. C.,
Burchell M. J.
Publication year - 2021
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.13729
Subject(s) - impact crater , enceladus , astrobiology , geology , salt (chemistry) , hypervelocity , projectile , magnesium , mineralogy , meteorite , chemistry , materials science , physics , astronomy , metallurgy , organic chemistry
The plumes naturally erupting from the icy satellite Enceladus were sampled by the Cassini spacecraft in high‐speed fly‐bys, which gave evidence of salt. This raises the question of how salt behaves under high‐speed impact, and how it can best be sampled in future missions to such plumes. We present the results of 35 impacts onto aluminum targets by a variety of salts (NaCl, NaHCO 3 , MgSO 4 , and MgSO 4 ·7H 2 O) at speeds from 0.26 to 7.3 km s −1 . Using SEM‐EDX, identifiable projectile residue was found in craters at all speeds. It was possible to distinguish NaCl and NaHCO 3 from each other, and from the magnesium sulfates, but not to separate the hydrous from anhydrous magnesium sulfates. Raman spectroscopy on the magnesium sulfates and NaHCO 3 residues failed to find a signal at low impact speeds (<0.5 km s −1 ) where there was insufficient projectile material deposited at the impact sites. At intermediate speeds (0.5 to 2–3 km s −1 ), identifiable Raman spectra were found in the impact craters, but not at higher impact speeds, indicating a loss of structure during the high speed impacts. Thus, intact capture of identifiable salt residues on solid metal surfaces requires impact speeds between 0.75 and 2 km s −1 .