PASADENA, Calif. - NASA said Wednesday it was investigating problems with two instruments aboard the most powerful spacecraft ever flown to Mars. The problems on the Mars Reconnaissance Orbiter arose late last year, but recently worsened to the point where engineers have stowed one of the instruments.

In November, scientists operating the probe's high-resolution camera noticed that the image pixels were of poor quality. Although the problem had minimal impact on images beamed back to earth, scientists fear the problem could grow worse.

A problem also developed in an instrument that maps the temperature, ice clouds and dust in the Martian atmosphere. Scientists discovered the instrument, called a climate sounder, had a skewed field of view. The errors became more frequent last month, and engineers decided to temporarily halt work with the instrument.

The Reconnaissance Orbiter arrived at the Red Planet last year. Its other four instruments are operating normally.

Since November, the probe has sent back data that could fill nearly 1,000 CD-ROMS, tying the record of the Mars Global Surveyor, which circled Mars between 1997 and 2006. The Global Surveyor suddenly fell silent last year and is presumed dead.

The Reconnaissance Orbiter, built by Lockheed Martin, is managed by NASA's Jet Propulsion Laboratory.