NASA's Perseverance Mars Rover

In 2004, the Mars Exploration Rover Opportunity spotted so-called, “Martian Blueberries” at Meridiani Planum, and since then, the Curiosity rover has observed spherules in the rocks of Yellowknife Bay at Gale crater. Just a few months ago, Perseverance itself also spied popcorn-like textures in sedimentary rocks exposed in the Jezero crater inlet channel, Neretva Vallis. In each of these cases, the spherules were interpreted as concretions, features that formed by interaction with groundwater circulating through pore spaces in the rock. Not all spherules form this way, however. They also form on Earth by rapid cooling of molten rock droplets formed in a volcanic eruption, for instance, or by the condensation of rock vaporized by a meteorite impact.

See also this recent Mars Guy episode.