There are Dark Forces at Work in the Universe

Just when you thought Dark Energy couldn't get any stranger, new measurements of the history of the expansion of the universe show an era well after the big bang and inflation but long, long ago when the rate of expansion was different than today. We are running out of dark names for the unknown. Closer to home the astroquarks discuss evidence for rain and water on Mars at a surprisingly recent (well, still a long time ago) epoch. All that plus space news and nerd trivia can be found on this episode of Walkabout the Galaxy.