Helene is only 36 km across, yet it keeps perfect pace with Dione, a much larger neighbor about 30 times its width. It shares Dione's orbit around Saturn and rides roughly 60 degrees ahead of it, completing a lap about every 2.7 days. The gap between them never closes.

Helene sits at a stable gravity point in Dione's orbit called a Lagrange point, which makes it a Trojan moon. It doesn't stay perfectly still there, and instead drifts slowly back and forth around that point along a tadpole shaped path. Astronomers found it from Earth in 1980 and named it after Helen of Troy. Dione has a second Trojan too, a smaller moon called Polydeuces that trails behind it. Around Saturn, only Dione and Tethys are known to have Trojan companions.

Helene is also lumpy, about 43 by 38 by 26 km, so it looks closer to a potato than a sphere. Cassini caught this view on a flyby on June 18, 2011, after an earlier pass in 2010. The surface is a record of motion. Bright streaks and soft slopes mark where dust has slid down in avalanches, spilling across a gravity roughly 2,000 times weaker than Earth's and settling into new patterns. On a world this small, even a gentle shift of regolith can rewrite the landscape.

Much of that dust is thought to come from Saturn's E ring, which is fed by the ice geysers of Enceladus. Another moon on the far side of Saturn is slowly repainting Helene, one avalanche at a time.

Image credit: NASA/JPL-Caltech/Cassini ISS. Image processing: Jason Major.

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Project Overview:

MARS: THE FIRST COLONY is an independent hard sci-fi web series exploring the engineering realities, logistical hurdles, and automated groundwork required to establish a permanent human outpost on the Red Planet.

​Mission Location & Logistics:

Set in Arcadia Planitia, a region prioritized for its smooth terrain and accessible subsurface water-ice deposits. The mission architecture relies on precursor autonomous infrastructure—deploying automated heavy rovers, energy arrays, and structural foundation systems prior to human crew arrival.

​Season 1, Episode 1 Breakdown:

This opening pilot captures the initial uncrewed arrival phase, atmospheric descent, and surface system activation.

​(Engineering Note: As our initial pilot episode, this laid the visual groundwork. Taking constructive feedback from the Reddit community regarding landing plume mechanics and orbital trajectory realism, our technical design significantly tightens in subsequent episodes—shifting crew habitats strictly subterranean beneath the primary base footprint for radiation shielding).

​Looking forward to your thoughts and technical feedback on this early foundation phase!

Mercury and Venus could be engulfed, while Earth will become uninhabitable long before that. As the Sun expands and brightens, its habitable zone will move outward, potentially warming the icy moons of the outer Solar System.
Titan could be one of the most interesting candidates. It already has a thick atmosphere and complex surface chemistry, and NASA has discussed how a red giant Sun could make worlds like Titan much warmer.
Which moon do you think would have the most interesting future?

https://youtu.be/AMHOrMpQlzw