WASHINGTON, Dec. 4  -- The U. S. space agency says it is postponing the launch of its Mars Science Laboratory until 2011.

National Aeronautics and Space Administration officials said the original October 2009 launch is no longer feasible because of "testing and hardware challenges" that must be addressed to ensure mission success.

NASA said the relative positions of Earth and Mars are favorable for flights to Mars only a few weeks every two years. The next launch opportunity after 2009 is in 2011.

"We will not lessen our standards for testing the mission's complex flight systems, so we are choosing the more responsible option of changing the launch date," said Doug McCuistion, director of the space agency's Mars Exploration Program.

NASA said the Mars Science Laboratory, intended to study the early environmental history of the planet, will be one of the most technologically challenging interplanetary missions ever designed, equipped with unprecedented research tools.

It will use new technologies to adjust its flight while descending through the Martian atmosphere and will place its rover onto the planet's surface by lowering it on a tether from a hovering descent stage, NASA said.

The total science payload will be 10 times the mass of instruments that are on NASA's Spirit and Opportunity Mars rovers. (UPI)