  Estimates of the total particulate mass of the plumes of Enceladus are
important to constrain theories of particle formation and transport at the
surface and interior of the satellite. We revisit the calculations of Ingersoll
& Ewald (2011), who estimated the particulate mass of the Enceladus plumes from
strongly forward scattered light in Cassini ISS images. We model the plume as a
combination of spherical particles and irregular aggregates resulting from the
coagulation of spherical monomers, the latter of which allows for plumes of
lower particulate mass. Though a continuum of solutions are permitted by the
model, the best fits to the ISS data consist either of low mass plumes composed
entirely of small aggregates or high mass plumes composed of mostly spheres.
The high particulate mass plumes have total particulate masses of (166 $\pm$
42) $\times$ 10$^3$ kg, consistent with the results of Ingersoll & Ewald
(2011). The low particulate mass plumes have masses of (25 $\pm$ 4) $\times$
10$^3$ kg, leading to a solid to vapor mass ratio of 0.07 $\pm$ 0.01 for the
plume. If indeed the plumes are made of such aggregates, then a vapor-based
origin for the plume particles cannot be ruled out. Finally, we show that the
residence time of the monomers inside the plume vents is sufficiently long for
Brownian coagulation to form the aggregates before they are ejected to space.
