Scientists are tracking a massive dark patch slowly spreading across the surface of Mars, specifically within a huge basin called Utopia Planitia.

While this may sound like the expository info dump from the opening seconds of a trailer for a movie about the alien invasion, it likely has a logical, non-scary explanation. The problem is, researchers don’t yet know what that explanation is. So, for now, it’s best not to let your imagination run too far ahead of the evidence.

First photographed by Viking 2 in 1976, the feature has been expanding for decades. New images from the ESA’s Mars Express orbiter, released in 2024, show that parts of the formation have shifted south by roughly 200 miles, which is unusually fast for changes on a planet that is usually considered to be an active and covered in rust, a classic hallmark of inactivity.

You can rest easy knowing that researchers are pretty sure this isn’t some creeping alien organism that will take over the planet before leaping to our own or something. They know that it’s a layer of dark material rich in volcanic minerals like olivine and pyroxene, remnants of ancient volcanic eruptions from back when Mars was actually active.

They know what it is, they just don’t know why it’s spreading.

One involves the powerful winds of Mars physically redistributing volcanic ash across its surface. The other also involves winds; this time, they are stripping lighter-colored surface dust away to reveal darker volcanic material underneath. Either way, from here on Earth, it makes Mars look like it’s somehow changing and evolving when it should be dead.

It’s nothing to be alarmed about, as the problem sounds a lot creepier than it actually is. The reality is that Mars, while basically a rusted husk of what recent discoveries seem to indicate was once a thriving planet that may have had tropical storms, is not as static as it seems. Even a “dead” planet can still shamble zombie-like every once in a while.