Summary
This review reports Curiosity’s scientific results and operational status during mission years 9–12 on Mars, covering August 2020–August 2024.
Major scientific findings
- Organic molecules: SAM’s first thermochemolysis experiment detected more than 20 aromatic and cyclic organic compounds—including benzene, toluene, naphthalene derivatives, sulfur-bearing organics, and ester/carboxylic-acid-related compounds—in clay-rich rocks of Glen Torridon. These findings strengthen the evidence that ancient lake and lake-margin sediments preserved organic matter for billions of years.
- Clay-to-sulfate transition: Curiosity directly investigated the orbital clay-sulfate transition on Mount Sharp. The transition corresponds to a broad environmental change from predominantly lacustrine and river/shoreline settings to increasingly arid, aeolian environments. The shift toward aridity was not uniform: wet-dry cycles, fluctuating groundwater, and intermittent surface water continued.
- Mg sulfate-bearing unit: CheMin identified magnesium sulfate minerals, including the first detection on Mars of starkeyite—a polyhydrated Mg sulfate—and also detected kieserite, a monohydrated Mg sulfate. These minerals likely formed through brine concentration and later dehydration. The unit is dominated by wind-deposited sediments, although some intervals preserve evidence of shallow water and lakes.
- Ancient ice-free lake: Wave ripples in the Amapari Marker Band indicate that an ice-free lake existed during the early Hesperian period, despite the generally arid conditions recorded by surrounding strata.
- Carbonates and climate: Many sulfate-unit samples are enriched in siderite, an iron carbonate, at levels consistent with chemical sedimentation. This may represent a substantial portion of Mars’ previously “missing” carbonate and suggests atmospheric CO₂ sequestration into minerals.
- Gediz Vallis: The canyon and associated alluvial deposits record numerous later fluvial and debris-flow events, occurring after Mount Sharp’s older strata had been deposited, lithified, and eroded. Bright clasts in the canyon were identified as native elemental sulfur, the first such detection on Mars.
- Atmosphere and radiation: Curiosity continued long-term monitoring of dust, winds, clouds, atmospheric composition, and radiation. It observed high-altitude noctilucent and iridescent clouds and completed radiation measurements spanning an entire solar cycle, including the mission’s largest measured dose rate during a May 2024 solar particle event.
Mission performance
During years 9–12, Curiosity:
- Traveled 9.1 km and climbed approximately 450 m.
- Reached a total traverse distance of 32.4 km and elevation gain of about 850 m.
- Drilled and analyzed 15 samples, bringing the mission total to 48.
- Conducted 1,083 ChemCam target analyses and 605 APXS analyses.
Rover and instrument status
All ten scientific instruments continued to return valuable data, although with important limitations:
- ChemCam: Laser operations were restricted after degradation of its high-voltage subsystem.
- Left Mastcam: A filter wheel failure eliminated narrow-band multispectral imaging through that camera.
- DAN: Its active neutron generator failed, but passive neutron measurements remain available.
- SAM: One gas-chromatograph column became obstructed; another column is being used instead.
- CheMin: Remaining sample-cell capacity is limited because several cells are clogged, though procedural changes have extended their usability.
- The rover also continues to cope with wheel wear, degraded computer redundancy, aging brakes, and declining MMRTG power.
Future plans
The mission planned to investigate:
- A regional “boxwork” ridge network thought to record ancient groundwater flow.
- Higher portions of the Mg sulfate-bearing unit.
- A major unconformity and overlying yardang-forming unit, potentially recording a significant climatic or depositional hiatus.
Overall, the review concludes that Curiosity remains scientifically productive and capable of addressing major questions about Mars’ ancient habitability, climate evolution, water history, organic preservation, and subsurface fluid activity despite substantial aging and resource constraints.
