Scientists had hoped NASA's Mars rover Curiosity would be back at work, following a computer glitch that suspended science operations two weeks ago.
But another problem surfaced Sunday night that will keep rover operations on hold until later in the week, lead scientist John Grotzinger said at the Lunar and Planetary Science Conference in Houston.
PHOTOS: Curiosity Drills Hole Into Mars Rock
"This is not something that is rare or even uncommon," Grotzinger told reporters.
The second shutdown comes on the heels of a key discovery that the rover's Gale Crater landing site had all the ingredients for microbial life to exist in Mars' past.
Scientists are eager for additional chemical analysis of a sample drilled out from a mudstone in Yellowknife Bay, where the rover is presently located. Eventually, the rover is expected to explore a mound of sediment rising from the center of Gale Crater.
On Monday, scientists unveiled results from Curiosity's infrared camera and other instruments that provide additional evidence for past water in the Yellowknife Bay area.
PHOTOS: Mars Through Curiosity's Powerful MAHLI Camera
The rover is seven months into a planned two-year mission to look for places that had the chemical and geological conditions to support and preserve ingredients necessary for microbial life.
Photo: The red planet is not always red, as indicated by the blueish-gray color found inside a rock, which was broken apart after the rover drove over it. The rock is about 5 inches wide at the end closest to Curiosity's camera. Credit: NASA/JPL-Caltech