mars dust storm

After it forced poor Opportunity to go into emergency shutdown last week, the great Mars dust storm seemed like it couldn’t get any worse. But the universe is cruel and boundless: Now, NASA reports, the storm, which used to be about the size of North America, has grown to an even more mind-boggling size. As of Wednesday, it’s officially a “planet-encircling” event.

We know this thanks to the selfie-snapping Curiosity rover, which has fared better than its sibling Opportunity in the storm because of its nuclear-powered batteries. Opportunity’s energy source, sadly, is solar-powered, which is not very useful on a planet where immense clouds of dust blot out the sun to create what NASA dramatically called a “dark perpetual night.” From its perch in Gale Crater, Curiosity has been sending home photos of the thickening dust.

The photo below shows what the Duluth drill site (the name refers to the two-inch hole dug up by Curiosity) looked like on May 21 and June 17. It reveals an insane decrease in visibility due to the amount of dust in the air. To think this isn’t even the worst of it: Gale Crater is on the other side of the planet relative to the dark-enshrouded Perseverance Valley, where Opportunity has been forced to hunker down in its attempt to weather the storm.

mars dust storm gale crater
On the left is the amount of dust in the Gale Crater on May 21; on the right is the same spot on June 17.

The dust has more than doubled over the weekend, leading to record-high measurements of tau, or opacity level. In the last set of data it sent home, Opportunity had measured a tau of 11; now, Curiosity has measured its highest tau ever. The animation below, revealing a glimpse into Curiosity’s increasingly dangerous surroundings over the course of several weeks, shows just how hazy a tau of 8.0 can look.

dust storm mars gale crater
A series of photos taken by Curiosity over several weeks shows the thickening haze due to the now-global dust storm.

Despite the worsening storm, Curiosity is expected to make it through unscathed. The latest update on Opportunity isn’t as encouraging: NASA still hasn’t received any signal from it, even though it is making attempts to communicate. A recent analysis of Opportunity’s hardware, however, suggests its electronics and batteries will be able to withstand the cold, and NASA says it doesn’t expect to hear back until the storm clears, anyway.

Opportunity dealt with a giant dust storm in 2007, but the ongoing, planet-encircling one is officially the biggest one it’s ever had to deal with. And according to NASA, there’s no telling how long it’s going to last.