The space agency has announced that NASA's Mars Science Laboratory will launch two years later than previously planned.

Initially, the space agency has scheduled for 2009 the launch of its next-generation rover which will study the early environmental history of Mars.

The rover is intended to carry an instrument payload 10 times heavier than the twin rovers Spirit and Opportunity, which landed on Mars in 2004.

Mars Science Laboratory is intended to be the first planetary mission to use precision landing techniques, steering itself toward the Martian surface similar to the way the space shuttle controls its entry through Earth's upper atmosphere.

In this way, the spacecraft would fly to a desired location above the surface of Mars before deploying its parachute for the final landing. As currently envisioned, in the final minutes before touchdown, the spacecraft would activate its parachute and retro rockets before lowering the rover package to the surface on a tether (similar to the way a skycrane helicopter moves a large object).

This landing method would enable the rover to land in an area 20 to 40 kilometers (12 to 24 miles) long, about the size of a small crater or wide canyon and three to five times smaller than previous landing zones on Mars.

Mars Science Laboratory would have six wheels and cameras mounted on a mast. Unlike the twin rovers, it would carry a laser for vaporizing a thin layer from the surface of a rock and analyzing the elemental composition of the underlying materials. It would then be able to collect and crush rock and soil samples and distribute them to on-board test chambers for chemical analysis.

Its design includes a suite of scientific instruments for identifying organic compounds such as proteins, amino acids, and other acids and bases that attach themselves to carbon backbones and are essential to life as we know it. It could also identify features such as atmospheric gases that may be associated with biological activity.

Using these tools, Mars Science Laboratory would examine Martian rocks and soils in greater detail than ever before to determine the geologic processes that formed them; study the Martian atmosphere; and determine the distribution and circulation of water and carbon dioxide, whether frozen, liquid, or gaseous.

However, is seems like the that the scientists were unable to overcome the problems developed in the design and operation of 31 actuators - combination motors and gearboxes that control the mechanical parts of the craft, including the steering mechanism, the robotic arm and the drill that will bore into Martian rocks.

And because 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.

"Costs and schedules are taken very seriously on any science mission," said Ed Weiler, associate administrator for NASA's Science Mission Directorate at NASA Headquarters. "However, when it's all said and done, the passing grade is mission success."

But the setback to 2011 will add $400 million to the spacecraft's cost, raising its total price to as much as $2.3 billion.

In October NASA said that the mission’s budget has already grown from $1.6 billion to $1.9 billion.