  In the absence of direct observations of Europa's particle plumes, deposits
left behind during eruptive events would provide the best evidence for recent
geological activity, and would serve as indicators of the best places to search
for ongoing activity on the icy moon. Here, we model the morphological and
spectral signatures of europan plume deposits, utilizing constraints from
recent Hubble Space Telescope observations as model inputs. We consider
deposits emplaced by plumes that are 1 km to 300 km tall, and find that in the
time between the Galileo Mission and the arrival of the Europa Clipper
spacecraft, plumes that are < 7 km tall are most likely to emplace deposits
that could be detected by spacecraft cameras. Deposits emplaced by larger
plumes could be detected by cameras operating at visible wavelengths provided
that their average particle size is sufficiently large, their porosity is high,
and/or they are salt-rich. Conversely, deposits emplaced by large plumes could
be easily detected by near-IR imagers regardless of porosity, or individual
particle size or composition. If low-albedo deposits flanking lineated features
on Europa are indeed cryoclastic mantlings, they were likely emplaced by plumes
that were less than 4 km tall, and deposition could be ongoing today.
Comparisons of the sizes and albedos of these deposits between the Galileo and
Europa Clipper missions could shed light on the size and frequency of
cryovolcanic eruptions on Europa.
