On Wednesday, May 30, 2018, NASA’s Mars Reconnaissance Orbiter (MRO) detected the start of a Martian dust storm. Ballooning quickly, the storm blanketed a quarter of the planet by June 12. By June 19, the storm was officially a “planet-encircling dust event”—less precisely called a "global" dust storm, though these storms never truly cover the entire globe of Mars.
Because the dust blocks out the sunlight Opportunity’s solar panels need to charge its batteries, scientists had to suspend science activities. As of July 18, no response has been received from Opportunity since June 10. Meanwhile, the nuclear-powered Curiosity rover is largely immune to the darkened skies, allowing it to continue collecting data.
Scientists observing the event say that, as of July 23, 2018, more dust is falling out than is being raised into the planet's thin air. That means the event has reached its decay phase. Once the dust settles, it will likely form a fine film only a few tens of microns thick—about the width of a human hair. This means Opportunity’s solar panels may be covered by a fine film of dust. That could delay a recovery of the rover as it gathers energy to recharge its batters. Opportunity will wake up again once it gets enough sunlight to charge its batteries, at which point it will automatically try to phone home—which scientists are cautiously optimistic will happen.