Origin and flatness of ponds on asteroid 433 Eros

Abstract

Abstract-NEAR-Shoemaker Multi-Spectral Imager data reveal several hundred "ponds" on 433 Eros: smooth deposits that sharply embay the bounding depressions in which they lie, and whose spectra appear blue relative to that of the surrounding terrain. We investigate the topography of these ponds on Eros using a new shape model derived from stereophotoclinometric analysis, and validated against altimetry from the NEAR Laser Rangefinder, to constrain the mode of pond formation from three existing models. We update the locations of 55 pond candidates identified in images registered to the new shape model. We classify the flatness of these features according to the behavior of the first and second derivatives of the topography. We find that less than half of pond candidates have clearly flat floors. Based on the pond topography, we favor an external origin for the ponds' deposits. We suggest that fine dust may be transported into bounding depressions by electrostatic levitation, but may adhere to slopes, and that seismic shaking may not be sufficient to bring the deposits to an equipotential surface. Disaggregation of a central boulder should result in an obvious break in slope, such a variation is only observed in roughly half the pond candidates.

Redistribution of Particles Across the Nucleus of Comet 67p/Churyumov-Gerasimenko

“…The features on 67P are up to 160 m diameter (see Fig. 23) and therefore similar in size to those seen on Eros (Roberts et al 2014;their Table 1). The SPC shape model was used to estimate a maximum depth of 35 m from the depression rim to the floor.…”

“…The flattening is produced by seismic shaking of ponds in response to impact. Roberts et al (2014) have criticized this by showing that the pond material follows the underlying topography, which is inconsistent with the material originating by erosion of central boulders. Electrostatic levitation of dust and transport has been proposed and investigated by several authors.…”

“…Morphologically, they follow the description of those seen on 433 Eros (Robinson et al 2001), being flat-floored and sharply embaying the bounding depression in which they sit (Dombard et al 2010), although Roberts et al (2014) stated that fewer than half the pond candidates on 433 Eros have clearly flat floors. The features on 67P are up to 160 m diameter (see Fig.…”

Size Sorting on the Rubble-Pile Asteroid Itokawa

“…Mechanisms such as electrostatic levitation and micrometeorite abrasion have been proposed for the origin of these ponds. Whatever their origin, all existing models appeal to a secondary mechanism such as seismic shaking to impose flatness 44 .…”

Formation of the “ponds” on asteroid (433) Eros by fluidization

“…a crater inclined to the local gravitational potential will have an off-set pond. However, recent work suggests this may not be as straightforward as previously suggested (Roberts et al, 2014a). The morphology of the ponds is fairly uniform, but spectroscopically the surface of the ponds is slightly blue relative to the surrounding plains, suggesting a finer grain size or younger regolith (less space "weathered") material (e.g., Heldmann et al, 2010).…”