As soldiers took over for riot police, tanks rolled through the streets of Cairo and Alexandria tonight. Tens of thousands of protesters were demanding the removal of Egypt's President Hosni Mubarak. Also, 25 years after the Challenger disaster, what's the future of NASA?
Banner image: Egyptian demonstrators shout slogans next to burning police vehicles in Cairo on January 28, 2011. Photo: Mohammed Abed/AFP/Getty Images