This series of images shows simulated views of a darkening martian sky blotting out the Sun from NASA’s Opportunity rover’s point of view, with the right side simulating Opportunity’s current view in the global dust storm (June 2018). Credit:  NASA/JPL-Caltech/TAMU.

Science operations for NASA’s Opportunity rover have been temporarily suspended as it waits out a growing dust storm on Mars. The martian dust storm that has blotted out the Sun above Opportunity has continued to intensify. The storm, which was first detected on May 30, 2018, now blankets 35 million square kilometers (14 million square miles) of martian surface — a quarter of the planet — and is causing a dark, perpetual night to settle over the rover’s location in Mars’ Perseverance Valley.

The storm’s atmospheric opacity — the veil of dust blowing around, which can blot out sunlight — is now much worse than a 2007 storm that Opportunity weathered. The previous storm had an opacity level, or tau, somewhere above 5.5; this new storm had an estimated tau of 10.8 as of June 10, 2018.

NASA engineers attempted to contact the Opportunity rover on June 14, but did not hear back from the nearly 15-year-old rover. The team is now operating under the assumption that the charge in Opportunity’s batteries has dipped below 24 volts, and that the rover has entered low power fault mode, a condition where all subsystems, except a mission clock, are turned off. The rover’s mission clock is programmed to wake the computer so it can check power levels. If the rover’s computer determines that its batteries don’t have enough charge, it will again put itself back to sleep. Due to an extreme amount of dust over Perseverance Valley, mission engineers believe it is unlikely the rover has enough sunlight to charge back up for at least the next several days. One saving grace of dust storms is that they can actually limit the extreme temperature swings experienced on the martian surface. The same swirling dust that blocks out sunlight also absorbs heat, raising the ambient temperature surrounding Opportunity.

This isn’t Opportunity’s first time hunkering down in bad weather. In 2007, a much larger storm covered the planet that led to two weeks of minimal operations, including several days with no contact from the rover to save power. The project’s management prepared for the possibility that Opportunity couldn’t balance low levels of power with its energy-intensive survival heaters, which protect its batteries from Mars’ extreme cold. It’s not unlike running a car in the winter so that the cold doesn’t sap its battery charge.

Ultimately, the storm subsided, and Opportunity prevailed. The martian cold is believed to have resulted in the loss of Spirit, Opportunity’s twin in the Mars Exploration Rover mission, back in 2010. Despite this, both rovers have vastly exceeded expectations as they were only designed to last 90 days each. Opportunity is in its 15th year; the team has operated the rover for more than 50 times longer than originally planned.

For more information, please visit https://mars.nasa.gov/mer/home/index.html.