Coordinating orbital hyperspectral imaging with Perseverance's ground observations, researchers confirmed widespread deposits of clays and carbonates, both markers of ancient water. The rover also discovered unusual millimeter-sized nodules of iron phosphate and iron sulfide in mudstone near Neretva Vallis. Their association with organic-rich zones suggests organics may have driven unusual redox reactions.
Analyses showed the mudstone consisted mainly of smectite clays, ferric oxides and hydroxides, and calcium sulfates, while reduced minerals appeared more abundant where oxidation was lower. "My group observed redox reactions in lab experiments where ferrihydrite containing oxidized iron was heated with organic compounds, including amino acids, to produce the mineral magnetite containing reduced iron," said Bishop.
Such reactions, which transfer electrons between minerals, are important because they generate energy that microbes on Earth often exploit. Perseverance's SHERLOC instrument detected organics in Jezero Crater, indicating they may have interacted with minerals in ways similar to prebiotic chemistry on Earth.
Some of the green-toned nodules were likely vivianite, a phosphate mineral that changes form when oxidized. At other sites such as Onahu, Perseverance found oxidized remnants of vivianite, while sediment studies revealed alternating iron-rich layers, reflecting shifting environmental conditions that may have influenced habitability.
Laboratory comparisons were essential for interpreting rover and orbital data. Bishop's team continues testing phyllosilicates, sulfates, carbonates, and phosphates under Martian-like conditions to improve mineral identification. Parente and colleagues advanced orbital imaging by cleaning CRISM hyperspectral data of distortions from Mars' atmosphere and sensors, revealing subtle mineral signatures. AI mapping techniques then created the clearest mineral distribution maps yet of Jezero Crater, showing overlooked outcrops and confirming widespread carbonates, clays, and pyroxenes.
On Earth, microbes alter mineral chemistry in lakes and swamps, producing sulfides and vivianite under anoxic conditions. While no direct evidence of Martian life exists, similar abiotic reactions could explain reduced minerals in Jezero's oxidized mudstones. Bishop noted that sulfur isotope testing on returned samples could distinguish whether such minerals formed biologically or chemically.
The samples Perseverance cached at Bright Angel and Masonic Temple may eventually resolve these questions. Once studied on Earth, they could provide detailed insights into ancient Martian chemistry, helping determine whether Mars once hosted the building blocks of life.
Research Report:Mystery Martian minerals hint at the planet's complex geochemical past
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