NASA’s Opportunity rover spent 14 years exploring Mars’ Meridiani Planum region for a reason: The district could hold vital clues about the Red Planet’s initial geography and climate.
Scientists are particularly interested in the Burns Formation, a layer of sandstone embedded with “blueberries” of hematite, due to its characteristics of liquid water and sulfur-rich composition that are similar to those found on Mars. A new study, which was published in the Journal of Geophysical Research, found that the Grasberg formation, a thin rock layer, is on top of the Burns formation. In Planets, Brian Hynek and Thomas McCollom propose a novel origin story for the two of them.
The thought depends on the new finding that the Consumes and Grasberg rocks are synthetically comparable; then again, the previous are enhanced in magnesium and sulfate.
In the past, there were two main hypotheses for the chemical composition of the Burns formation. One set of models suggested that the first sands were a mixture of ancient silicates and iron, magnesium, and calcium sulfate salts that formed when groundwater evaporated from the shores of ancient lakes. A second set of models suggested that volcanic or atmospheric sulfuric acid changed the basaltic ash that formed the sandstones.
The third possibility suggested by the new study’s authors is that the two formations may have originated from the same or very similar material. They suggested that the Burns/Grasberg precursor fell as dust or ash from nearby volcanic eruptions onto Meridiani Planum.
These substances became solid, weathered to the size of sand grains, and were carried to their current location by the wind. When settled, the sand rose and experienced occasional progressions of groundwater, which advanced the upper layers in magnesium and sulfate. The sandstones Opportunity observed were also consolidated by water flow.
The review’s writers built a mass equilibrium model reproducing this situation, and utilizing information gathered by Opportunity’s Alpha Molecule X-beam Spectrometer, they verified that the new speculation matches Opportunity’s perceptions better than other recently proposed systems do.
The findings could change how scientists think about the environment on early Mars and how they think sulfate-rich deposits elsewhere on the planet came to be.
More information: Thomas M. McCollom and Brian Hynek, Proposed Origin of the Burns Formation (Meridiani Planum, Mars) by Erosion, Reworking, and Diagenetic Alteration of a Grasberg‐Like Precursor, Journal of Geophysical Research: Planets (2023). DOI: 10.1029/2022JE007374