Spheres in the Sand – NASA Science
Written by Andrew Shumway, postdoctoral researcher at Washington University
It is not common for a rover to spot almost perfect spheres in the ground under its wheels. More than two decades ago, the Rover opportunity discovered hematite spherules (nicknamed “Blueberries”) near its landing site in Meridiani Plan. More recently, the Rover Perseverance has also encountered spherules rooted in the foundation and dispersed in a loose way throughout the region called “Witch Hazel”. In a previous blog article, we described perseverance surveys on a sph that was abrasion patch of “Hare Bay”, where the team then collected a nucleus. With the “Bell Island” sample added to the Rover collection, the scientific team then decided to take a closer look at the bulk spherules in the region, which seem to have been eroded from the nearby foundation.
On the soil 1555, while the United States celebrated on July 4 with hot dogs and fireworks, perseverance worked hard to study the regolithe rich in spherules with the target “Rowsell Hill” using proximity instruments on its robotic arm. The context imaging and the Sherloc context imagery and the Watson camera have both captured high resolution images of the target (illustrated above), while Pixl has measured the elementary composition of the surrounding spherules and grains.
Despite their superficial similarity with the “blueberries” of the opportunity, the spherules of “Rowsell Hill” have a very different composition and origin. In Meridiani Planum, the spherules were made up of mineral hematite and were interpreted as formed in saturated sediments of groundwater in the distant past of Mars. In comparison, the spherules of “Rowsell Hill” have a basaltic composition and are probably formed during a meteoroid impact or a volcanic eruption. When a meteoroid crashes in the surface of Mars, it can melt the rock and send melted molten droplets into the air. These droplets can then cool quickly, solidifying in spherules that rain on the surroundings. Alternatively, the spherules can have been formed from melted lava during a volcanic eruption.
With these new data in hand, the Science Perseverance team continues to seek answers on the origin of these spherules. If they were formed during an ancient impact, they can be able to tell us about the composition of the meteoroid and the importance of impact crat in the history of early March. If they rather formed during a volcanic eruption, they could preserve clues on volcanism passed in the region around Jezero Crater. Anyway, these spherules are a rest of an energetic and dynamic period of the history of Mars!
