Mission engineers are doubtful that the rover has enough sunlight to charge back up for at least the next several days.
Spirit and an identical rover, Opportunity, scheduled to land on the opposite side of the Red Planet January 24, are part of the $820 million Mars Exploration Rover project.
Dust storms are a frequent feature on Mars, occurring in all seasons. "Regardless of what happens, this little rover has been a great investment to help us explore the Red Planet".
In 2007, another strong Martian storm had blasted the Opportunity and forced it to silence for four days.
Maxwell, who left NASA in 2013 for Google, notes in the spirit of anthropomorphizing common to those involved with rovers, "She did more than anyone expected from her or ever could have expected from her, and if we can all say that at the end of our lives, then we'll be as lucky as she is".
Today it is in the so-called "Valley of Insistence", where the dust from the storm is so dense that there is darkness throughout the day of the Martian. But the pace at which the storm grew is unprecedented. Occasionally, they can balloon into regional storms in a matter of days, and sometimes even expand until they envelop the planet.
The Curiosity rover is now entrenched in the Gale Crater area where dust activity is starting to pick up. That would trigger a "clock fault", when the rover loses track of time entirely.
"Each observation of these large storms brings us closer to being able to model these events-and maybe, someday, being able to forecast them", Rich Zurek, chief scientist for the Mars Program Office at JPL in California, said.
The massive dust storm, first detected on May 30, now blankets a quarter of the planet - some 14 million square miles (35 million sq km) of Martian surface. "Each offers a unique look at how dust storms form and behave - knowledge that will be essential for future robotic and human missions".
Scientists aren't sure what causes huge, planet-scale dust storms like the one now raging.
"We think we can ride this out for a while", Callas said. (Curiosity, which landed in 2012, is nuclear-powered and mostly unaffected by the dust.) The storm is being monitored by a fleet of orbiting spacecraft, particularly the Mars Reconnaissance Orbiter.
"Dust on Mars gets lofted tens of kilometers into the air and in such quantities - like now - that it significantly changes the sunlight reaching the ground and the heat deposited in the air from the sunlight". As long as the rover stays warm enough, it can endure. It's been a remarkably resilient rover.