Opportunity, the longest-running Mars rover, is currently in a bad spot. It's smack in the middle of an intensifying dust storm, where fine particles of dust as thin as talcum powder billow so thickly that they block out the Sun.
NASA researchers put it in a power-saving mode last week, suspending science operations to prioritize Opportunity's survival. The rover was supposed to check in periodically until the storm passed, sleeping during the stretches of silence.
It missed its scheduled call home on Tuesday, leaving its minders on the ground worried about its welfare—and with no way to check and see if it's OK.
"At this point we’re in a waiting mode. We’re listening every day for possible signals from the rover and are prepared to respond to that," John Callas, Opportunity project manager at NASA's Jet Propulsion Laboratory, said at a press conference on Wednesday.

For us, and the people at NASA who work most closely with the rover, there is nothing to do but wait. Callas described the mood as similar to watching over a loved one in a coma.

“This team has a very strong bond with the rover, and we have a tight emotional connection with it,” Callas said. “By no means are we out of the woods here. This storm is threatening, and we don’t know how long it will last and what the environment will be like when it clears. We’re all concerned.”

“Hey Opportunity, it's Earth again. Call home when you get a chance, we're worried about you.”