u/Crazed_Monkeypox

While replaying Echoes of the Eye, I noticed that one of the solar system slide reels (shown on the second slide) seems to depict Ash Twin with rivers and surface water, while Ember Twin doesn’t appear to have any visible water. At first, this confused me because the base game strongly suggests Ember Twin once had abundant water, with evidence including a massive dry lakebed and fossils of marine plants and animals.

My theory is that the Hourglass Twins originally exchanged both water and sand

The reel may simply capture a moment when most of the water happened to be on Ash Twin, just as we see all of the sand begin each loop on Ash Twin before naturally transferring to Ember Twin.

Inspired from this comment: https://www.reddit.com/r/outerwilds/s/BpdGNBRFbs