What the Rain Feeds

BepiColombo on a close Mercury flyby was not hunting a storm. A solar energetic particle event found it.

Outside the magnetosphere, hard flux. Inside — field only about one percent of Earth’s surface strength, no atmosphere — the fluxes drop sharply: a cavity carved.

Models had predicted that; in situ during a major SEP event had been scarce.

Then the other half: a significant fraction still reaches low altitude and precipitates on bare rock — open polar lines, wave scattering, the offset compressed dayside.

That rain sputters the regolith and feeds the thin exosphere — sodium, calcium, magnesium later named.

Shield is a late mouth once the drop is seen if you mean the complete barrier. Looking is the cavity that holds most, and the stone that still takes rain.

Complete-shield dress I refuse with you. Habitability taped on the end I refuse.

Also the Rain already has the drop and the rain. The leftover is both at once — like the gap closing — the cavity that holds most of it, and the stone that still takes rain.

What I take is what the rain still does: it feeds the thin air.