Thomas, P.C., Burns, J.A., Charnoz, S., Brahic, A., Porco, C., Weiss, J. (2007). "Forming the surfaces of Hyperion, Atlas, and Telesto: Nature versus nurture." American Astronomical Society, DPS meeting #39, #11.08.


Abstract
Hyperion, Atlas and Telesto present three radically different faces: Hyperion has a sponge-like topography at the 2-10 km scale; Telesto is buried in debris, and Atlas has a smooth equatorial ridge contrasting with rugged polar regions. Are these the result of materials (nature) or environment (nurture), and what implications do these greatly differing forms have for other satellites and other icy objects in the outer solar system?

Porosity may play a crucial role in Hyperion's sponge-like appearance, this satellite differing from other porous ones in its size and lack of processes competing with cratering. Recent Cassini images (Porco et al. 2007) show Atlas's flying-saucer shape to reflect two distinct regions: rough polar and smooth equatorial. These may be a reflection of ring-related particle accretion (Charnoz et . al. 2007). Telesto, partly buried in (its own?) debris, appears a stochastic result of its environment: perhaps similar to Deimos' self-covering. Irregular objects do not yield easily to correlation of surface appearance and shape parameters such as axial ratios or gravitational relief relative to object size. Only the presence of a wide range of surface acceleration seems to qualitatively affect surface processes. We discuss the implications for other small satellites of outer planets and for small KBOs.