Data from the National Aeronautics and Space Administration (NASA) Curiosity rover indicates that individual crystals within the iron oxide hematite can serve as a mineralogical marker for changes in Mars's ancient climate. The shape and structure of these crystallites reflect the conditions under which they formed. These conditions include temperature and the presence of water.
Scientists analyzed twenty samples collected by Curiosity at various elevations within Gale Crater. The crater's layers provide a historical record of Mars's environment. Deeper layers represent earlier periods. The team used the rover's Chemistry and Mineralogy (CheMin) instrument for analysis.
Researchers found that hematite crystallite sizes varied with elevation. Hematite crystallites from higher elevations were smaller, less than ten nanometers. Those from lower elevations were larger, up to sixty-five nanometers. The mineral goethite was present in samples from higher elevations but absent in lower ones. Goethite typically forms alongside hematite.
These findings suggest that warm groundwater persisted in the deepest layers of Gale Crater for up to 4.7 million years. During much of this time, these aquifers could have been habitable. Warmer conditions, with neutral or slightly alkaline water pH, can transform goethite into hematite. Such conditions also promote the growth of hematite crystallites through Ostwald ripening. This process involves smaller crystallites dissolving and contributing to the growth of larger ones.
The smaller crystallites at higher elevations indicate colder conditions or shorter periods of water presence. Larger crystallites in lower layers point to long-standing warm water. This study used direct Martian sample data, not theoretical models. CheMin's X-ray diffraction patterns allowed for detailed analysis of hematite crystal size and dimensions. This information cannot be obtained from satellite imagery alone.
Ashwin Vasavada, Curiosity's project scientist, noted CheMin's ability to make precise measurements. It identifies hematite and determines the size and shape of its crystallites. It also detects related minerals, which were crucial for this study's conclusions.
Related stories
Rising Temperatures Impair Animal Cognition and Behavior
New research indicates that rising temperatures impair animal cognition and alter behavior, posing significant threats to species survival and ecosystem stability.
Complex Organic Molecules Discovered in Protostar Shock Waves
Astronomers have found complex organic molecules, including methanol, in the shockwaves of a protostar, shedding light on the origins of life's building blocks.
Parasitic Deer Keds Reduce Vision After Finding Host
Parasitic deer keds reduce their visual sensitivity by half after finding a host, shedding their wings and conserving energy for parasitic life functions.