Robotic missions will serve as trailblazers, the advanced guard to the unknown.

CNN: Bush: 'It is time for America to take the next steps' in space

The slick stretched about 100 miles across the north-central Gulf on Wednesday afternoon and had advanced to within 16 miles of the mouth of the Mississippi River, the U.S. Coast Guard said.

CNN: Oil spill from rig explosion at 5,000 barrels a day