NASA announced this news today, but the title is not quite right. It's evidence of flowing water on Mars. It's briny so it doesn't evaporate. Briny makes me think of the presence of microbes, so I think the next big Martian news may make us all reach for David Bowie:
That's Mike Garson on the keys. :-)
Presence of water below the surface and frozen at the caps has been known for quite some time.
This is the Google doodle for today.