Learn from the mistakes of others

here's a curly question (if a bit odd ;)

i've forgotten where i got the image i use as my default icon.
yeah, it dumb, but its been a while. and i've had a system crash in the meantime.

i'm looking to get the original again. its large. its astronomical. it probably came from a nasa image collection. at least a year or more ago.

can anyone help? (i'm working my way through nasa's archive, but they're very generous ...)