The space agency has funded another extension of their mission, for an additional six months, if they last.
The latest funding came as NASA regained reliable contact with the rovers Spirit and Opportunity after a 12-day period in which Mars passed nearly behind the sun, the Jet Propulsion Laboratory said.
The rovers, which have found evidence of past water activity on the Red Planet, landed on opposite sides of Mars in January and completed their primary, three-month missions on the surface in April.
"Although Spirit and Opportunity are well past warranty, they are showing few signs of wearing out," project manager Jim Erickson said in a statement. "We really don't know how long they will keep working, whether days or months. We will do our best to continue getting the maximum possible benefit from these great national resources."
The rovers did no driving during the period in which the sun was between Earth and Mars. Commands for activities resumed for Opportunity on Monday and for Spirit on Tuesday.
Erickson said it was a relief to get through the past two weeks not only because communications were disrupted, but also because it was the part of the Martian year in which the solar-powered rovers received the least sunlight.