[Greg Bryant]

NASA's Dawn spacecraft, which will travel to the Main Asteroid Belt and orbit around Vesta and Ceres, has had its launch postponed (having already endured a few delays) to September. The launch had been scheduled for this weekend but was then delayed to Monday.

Because of the upcoming August launch of the Phoenix mission to Mars, NASA felt the squeeze on available launch windows.

If September's launch gets pushed beyond late October, Dawn will not be able to travel to both Vesta and Ceres, and so Ceres will be dropped.