In review: Green auroras occur at about 60 miles above Earth. Red auroras are much higher, from about 200 to 300 miles up, which allows people closer to the equator to see them. An important gas remaining at that altitude is oxygen; electrons that excite the oxygen atoms there produce red light.

Camped on an island in Southeast Alaska a few mornings ago, Sasha Calvey heard a commotion outside her tent.

The caterpillar stage of the aspen leaf miner feeds on a leaf. (Photo by Ned Rozell) On one of the friendliest platforms imaginable, a...