The launch of the most sophisticated spacecraft designed to land on Mars so far has been postponed by two years, because of setbacks in testing the flight systems that will take it to the Red Planet.

Instead of blasting off in October next year, Nasa's Mars Science Laboratory rover has been rescheduled for a launch in autumn 2011, the American space agency announced today.

The two-year delay will be required because Mars missions must always leave Earth during one of the narrow launch windows when the relative positions of the two planets are most favourable. Though the extra testing will not take as long as two years, the next available launch window is in late 2011.

Charles Elachi, director of Nasa's Jet Propulsion Laboratory in Pasadena, California, which leads the Mars programme, said: “Despite exhaustive work in multiple shifts by a dedicated team, the progress in recent weeks has not come fast enough on solving technical challenges and pulling hardware together. The right and smart course now for a successful mission is to launch in 2011.”

The postponement is a disappointment for Nasa and for astronomers and planetary scientists around the world, who have been eagerly anticipating the insights that the Mars Science Laboratory (MSL) rover will offer into the nature of the Red Planet.

The advanced robotic vehicle will carry a scientific payload ten times heavier than that deployed aboard the Spirit and Opportunity rovers which landed on Mars in 2003, and which have since returned reams of data about the planet's geology, history and capacity for bearing life.

The MSL rover will also be able to cover longer distances than the previous generation of rovers. It will be capable of identifying signs of biological processes at work, though it is unlikely to directly detect past or present life.

The spacecraft will be guided to the planet's surface using a precision entry, descent and landing system, and it is the flight element of its technology that has caused the delay.

A three-month assessment of engineering progress has concluded that too much still needs to be done to allow a launch in 2009.

Doug McCuistion, director of Nasa's Mars Exploration Programme, said: “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.

“Up to this point, efforts have focused on launching next year, both to begin the exciting science and because the delay will increase taxpayers' investment in the mission. However, we've reached the point where we cannot condense the schedule further without compromising vital testing.”

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