Discovery: Inside the Launch Pad (above), Cloudy Launch Prospects (below)
After finding water on Mars and planning to launch a Moon base, NASA is looking to cap off a big week tonight with Discovery’s scheduled 9:35 p.m. EST launch to the International Space Station—if Mother Nature doesn’t get in the way.

The lights are on at the pad with four hours left before the space agency’s 29th nighttime shuttle launch—the first since 2002—but low-hanging clouds in Cape Canaveral, Fla. (and bad weather in European emergency landing sites), may block the launch window as cold fronts sweep the country. Looks like the final “go” for the Space Shuttle’s next chapter will come down to the wire tonight, and forecasts for tomorrow are already looking so bleak that NASA’s next shot would be Saturday. Keep your fingers crossed, and watch the launch here.

UPDATE: The Shuttle team made it to the T-minus five minutes hold but could not find enough clearing in the low cloud cover before NASA's launch window expired. Discovery's 29th nighttime launch has now been rescheduled for Saturday at 8:47 EST.

Spy Case: Radioactive Leaks Pick Up Bar Tab
On the day of ex-Russian spy Alexander Litvenenko’s funeral, a Russian contact and seven employees at the London hotel bar where Litvenenko met him have tested positive for signs of radiation.

In interviews with Popular Mechanics, experts described the radioactive poison that allegedly killed Litvenenko as dangerous only if ingested or inhaled: “If you walked through it, sat in it, got it on your clothes, you're not going to get sick.” So the bar staff can probably have a stiff one and relax. Listen to The Popular Mechanics Show podcast for more. –Matt Sullivan