PS: Helene has two faces

[bystander]

Helene has two faces
Planetary Society - 2010 March 11

Helene is two-faced; it has two very different hemispheres. The Saturn-facing hemisphere is peppered with small impacts, little craters one to a few kilometers across (Helene is a little more than 30 kilometers in diameter). But the anti-Saturn hemisphere doesn't have that peppering of craters; there are a few, much larger craters closer to 10 kilometers across.

Why does Helene have this dichotomy? I haven't the slightest idea. The ring system is Saturnward of Helene, so maybe that peppering of impacts has something to do with the rings; I don't know. But with the benefit of this helpful montage, I can observe that that dichotomy exists, and ask for an explanation!

Cassini's views of Helene through March 2010
Ian Regan composed this montage of Cassini's highest resolution views of Dione's co-orbital moon Helene
to attempt to make sense of the positions of its features. The small moon appears very different seen
from different angles and under different lighting conditions. (NASA / JPL / SSI / Ian Regan)

[neufer]

<<Painters often depict Helen on the ramparts of Troy, her face expressionless, blank, inscrutable.
In Gustave Moreau's painting, Helen will finally become faceless; a blank eidonon in the middle of Troy's ruins.>>


Both Frederick Leighton (left), and Gustave Moreau (right)
depict an expressionless Helen; a blank or anguished face.

[neufer]

Helene has two faces
Planetary Society - 2010 March 11

Helene is two-faced; it has two very different hemispheres. The Saturn-facing hemisphere is peppered with small impacts, little craters one to a few kilometers across (Helene is a little more than 30 kilometers in diameter). But the anti-Saturn hemisphere doesn't have that peppering of craters; there are a few, much larger craters closer to 10 kilometers across. Why does Helene have this dichotomy? I haven't the slightest idea. The ring system is Saturnward of Helene, so maybe that peppering of impacts has something to do with the rings; I don't know. But with the benefit of this helpful montage, I can observe that that dichotomy exists, and ask for an explanation!

At 6.26 Saturn radii, Helene is rather in the middle of the E Ring (at 3 – 8 Saturn radii) generated by the plumes of Enceladus (at 3.95 Saturn radii).

Hypothesis:

• 1) E Ring particles are swept up by Dione and deposited on the leading face of Helene.
  
  2) Once enough E Ring particles have been deposited Helene becomes unstable
  and Helene's leading face now becomes the Saturn-facing hemisphere.

GEORGE: So, [Gwen is] attractive one day - not attractive the next?

JERRY: Have you come across this?

GEORGE: Yes, I am familiar with this syndrome -- she's a two-face.

JERRY: (Relating) Like the Batman villain?

GEORGE: (Annoyed) If that helps you..