What is this jet of material spraying out from Stage 2 during the SPACE-XSpaceX PAZ mission?

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asked Feb 23, 2018 at 10:00

What is this jet of material spraying out from Stage 2 during the SPACE-X PAZ mission?

This spray seemed to be there throughout the entirety of the Stage 2 burn but was especially visible once Stage 2 cutoff had happened.

As that nozzle uses radiant cooling, it can't be cooling fluid, so what could it be?

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