In the 21st century, planetary scientists have become increasingly aware that subsurface oceans consisting of liquid water exist within objects throughout the solar system. Because water is a universal requirement for life on Earth, these bodies—mostly moons—are enticing targets in the search for extraterrestrial life.

A primary way of deducing the existence of an unseen ocean is through an induced magnetic field. These fields originate from a unique application of Faraday's law of induction, which states that a time-varying magnetic field creates an electric current when applied to a circuit. Water that is salty enough to remain liquid in cold space environments is very conductive; at the same time, a moon's orbit through a planet's rotating magnetic field exposes the moon to a field strength that varies with time.

It looks like the Perseverance rover has an unwanted passenger, a rock stuck inside one of its wheels. The image of the stone was selected by public input as the "Image of the Week" for Week 54 (Feb. 20–26, 2022) of the Perseverance mission. Perseverance captured this image on February 25, 2022.

The rover's Front Left Hazard Avoidance Camera A captured the image. When the rover is driving, it makes periodic stops to let the Hazard Cameras survey the immediate surroundings. The Hazard Cameras help evaluate the hazards in front of and behind the rover, like large boulders, deep trenches, or dunes. The cameras create 3D views of the surroundings that help the rover make its own decisions without consulting with the rover team on Earth on every move.

The rock's been there for a few days, based on images from March 2. It's difficult to tell from the picture for sure, but it doesn't appear to be wedged in. Will it fall out during normal operations?

The rock doesn't appear to be causing any damage or hindering the rover's operations.