[throwawayaway12]

I think it is still an open (and hotly debated) question on if planets need magnetospheres to retain an atmosphere.

[ethbro]

* also, retain an atmosphere "over long enough timescales"

From the MAVEN research papers I've read, we're talking ~5,000 metric tons / yr of atmosphere being stripped.

Which is a lot, but not an insurmountable lot.

[toomuchtodo]

A magnetosphere is required to shield from charges particles and other harmful radiation.