Jezero Crater

Jezero Crater is a 45-kilometer-diameter impact crater located at 18.38° N, 77.58° E in the Syrtis Major quadrangle of Mars, situated along the northwestern rim of the 1,500-kilometer Isidis Planitia giant impact basin. Named in 2007 by the International Astronomical Union after the municipality of Jezero in Bosnia and Herzegovina—a toponym derived from the Proto-Slavic word jezero meaning "lake"—the crater formed during the Middle Noachian epoch (~3.9 to 3.8 Ga) and subsequently hosted a deep, hydrologically open standing lake during the Late Noachian to Early Hesperian transition (~3.7 to 3.5 Ga).

Following a multi-year evaluation of more than 60 candidate regions across Mars, NASA selected Jezero Crater as the landing site for the Mars 2020 flagship mission. On 18 February 2021, the Perseverance rover and the Ingenuity Mars Helicopter (which subsequently completed 72 powered flights across the crater floor and river channel) touched down at Octavia E. Butler Landing with the primary astrobiology objective of characterizing ancient habitable environments, searching for in situ biosignatures, and drilling and sealing a cache of rock and regolith cores for return to Earth laboratories via the Mars Sample Return (MSR) campaign.

Open-Basin Paleolake Architecture

Unlike closed-basin crater lakes whose water levels fluctuate wildly with evaporation, Jezero Crater operated during its main lacustrine phase as an open-basin paleolake (Fassett & Head, 2005; Goudge et al., 2015). Surface runoff draining an ~15,000 km² watershed in the Nili Fossae highlands entered the crater through two inlet valleys breaching its western and northwestern rim—Neretva Vallis and Sava Vallis—filling the basin until the water level overtopped and incised the eastern crater rim to drain outward into Isidis Planitia through Pliva Vallis. At its overflow highstand near −2,260 meters elevation, Lake Jezero spanned ~35 km in diameter, reached water depths of up to 250 meters, and held roughly 300 km³ of liquid water, maintaining a stable shoreline before hydrological decline transitioned the crater into a closed basin.

Where Neretva Vallis discharged sediment into the standing waters of Lake Jezero, deceleration of the river current constructed a prominent Gilbert-type fan delta extending ~10 km across the western crater floor. High-resolution imaging by *Perseverance*'s Mastcam-Z and SuperCam instruments at the isolated delta remnant Kodiak butte confirmed classic three-tiered deltaic clinoform stratigraphy: horizontal bottomset beds of fine-grained lacustrine mudstone at the base, steeply dipping (~15°–25°) foreset beds of prograding fluvial sandstone in the middle, and horizontal topset beds containing meter-scale rounded cobbles and boulders at the top—signaling a late-stage transition to high-energy episodic flash floods capable of transporting coarse bedload.

Mineralogical Diversity and Marginal Carbonates

Orbital visible/near-infrared reflectance spectroscopy from the Mars Reconnaissance Orbiter CRISM instrument revealed that Jezero's watershed eroded some of the oldest and most mineralogically diverse crust on Mars. The delta and crater floor preserve detrital Fe/Mg-smectite phyllosilicate clays (formed by low-temperature weathering of basalt), ultramafic olivine ((Mg,Fe)₂SiO₄), low- and high-calcium pyroxenes, and hydrated amorphous silica. Most distinctively, Jezero hosts a continuous belt of marginal carbonates—dominated by magnesium carbonate (magnesite, MgCO₃) and Fe/Ca-carbonate solid solutions analogous to calcite and dolomite—lining the inner western crater rim between −2,200 and −2,400 meters elevation. Because littoral lacustrine carbonates precipitate directly in shallow, sunlit wave-washed lake margins, they represent premier taphonomic targets capable of entombing microbial mats, stromatolitic laminations, and organic macromolecules.

Igneous Crater Floor: The Séítah and Máaz Formations

During its first year of exploration on the crater floor (2021–2022), Perseverance resolved a multi-decade geological debate by demonstrating that the bedrock units underlying the delta are igneous rather than ancient lakebed muds. Using the PIXL X-ray fluorescence spectrometer and SHERLOC deep-UV Raman and luminescence spectrometer on abraded rock patches, the science team identified two distinct igneous formations: the older Séítah formation and the overlying Máaz formation.

The Séítah formation consists of coarse-grained, equigranular olivine grains (2–3 mm) poikilitically enclosed within augite pyroxene crystals—a classic wehrlite cumulate texture formed by crystal settling in a slowly cooling magma body or thick lava lake, subsequently altered by low-temperature carbonated water to form Fe/Mg-carbonate and serpentine rims along fractures. The overlying Máaz formation comprises iron-rich basaltic and trachyandesitic lava flows containing pore-filling sulfate and perchlorate salts precipitated during late-stage brine evaporation, providing ideal igneous targets for high-precision radiometric geochronology (⁴⁰Ar/³⁹Ar and U–Pb dating) to calibrate the absolute age of the Martian cratering record.

Delta Mudstones and the "Cheyava Falls" Redox Biosignature Candidate

Ascending onto the western delta front in 2022–2023 (Shenandoah formation), Perseverance investigated finely laminated mudstones and siltstones at Hogwallow Flats and Wildcat Ridge. These rocks consist of Fe/Mg-smectite clays cemented by hydrated calcium and magnesium sulfates deposited in a quiet, low-energy lake bottom, where SHERLOC detected UV fluorescence doublets consistent with one- and two-ring aromatic organic carbon spatially correlated with sulfate minerals.

In July 2024, while exploring the Bright Angel formation along the northern margin of the Neretva Vallis inlet channel, Perseverance discovered an arrowhead-shaped, reddish mudstone outcrop named Cheyava Falls (cored as the Sapphire Canyon sample). Cut by white veins of calcium sulfate (CaSO₄), the rock displays dozens of millimeter-scale, irregular off-white reaction halos termed "leopard spots." Combined PIXL elemental mapping and SHERLOC Raman spectroscopy revealed that Cheyava Falls contains indigenous organic carbon compounds alongside dark reaction rims enriched in ferrous iron phosphate (vivianite, Fe₃(PO₄)₂·8H₂O) and mixed-valence iron sulfide (greigite, Fe₃S₄). In terrestrial aquatic sediments, localized millimeter-scale reduction of ferric iron (Fe³⁺) and sulfate (SO₄²⁻) coupled to organic carbon oxidation at ambient temperatures is frequently catalyzed by subsurface dissimilatory iron- and sulfate-reducing microorganisms. Because abiotic magmatic sulfidation requires elevated temperatures (>150–200 °C) for which the unrecrystallized Bright Angel mudstone shows no thermal evidence, Cheyava Falls stands as a high-priority candidate biosignature on the Life Detection Ladder (Confidence of Life Detection [CoLD] scale Level 1–2), awaiting isotopic (δ¹³C, δ³⁴S, δ⁵⁶Fe) and nanoscale structural testing upon return to Earth.

Why did NASA build a backup sample depot at Three Forks inside Jezero Crater?

Between December 2022 and January 2023, Perseverance deposited 10 sealed titanium sample tubes—containing duplicate cores of the Séítah and Máaz igneous units, the Shenandoah delta mudstones, regolith, and an atmospheric sample—on flat ground at Three Forks on the crater floor. While the rover carries the primary collection of >20 unique cores inside its belly to deliver directly to the future Mars Sample Return Lander, the Three Forks depot provides an insurance cache that sample-recovery helicopters can retrieve if Perseverance experiences a mechanical failure before the lander arrives.

Why are the marginal carbonates in Jezero Crater so important for astrobiology?

Carbonate minerals such as magnesite (MgCO₃) and calcite (CaCO₃) precipitate rapidly in alkaline, shallow lake margins where sunlight penetrates the water column. On early Earth, littoral carbonate environments preserved the oldest known 3.48-Ga stromatolites (microbialite mounds built by sediment-trapping benthic microbial mats) in the Dresser Formation of Western Australia, while fine-grained carbonate cements shield organic molecules from radiolytic degradation.

How did the Ingenuity Mars Helicopter assist Perseverance in Jezero Crater?

Designed as a 30-day technology demonstration to test aerodynamic flight in Mars's thin atmosphere (~1% of Earth's surface air density, requiring counter-rotating coaxial carbon-fiber blades spinning at ~2,400–2,800 rpm), Ingenuity operated for nearly three years (April 2021 to January 2024), flying 72 times over 17.0 km. Its color aerial reconnaissance scouted boulder fields in Neretva Vallis, mapped impassable sand ripples in South Séítah, and identified accessible stratigraphic outcrops ahead of the rover.

1. Goudge, T. A., Mustard, J. F., Head, J. W., Fassett, C. I., & Wiseman, S. M. (2015). "Assessing the mineralogy of the watershed and fan deposits of the Jezero crater paleolake system, Mars." Journal of Geophysical Research: Planets, 120(4), 775–808. https://doi.org/10.1002/2014JE004782
2. Mangold, N., Gupta, S., Gasnault, O., Dromart, G., Tarnas, J. D., Sholes, S. F., Horgan, B., Quantin-Nataf, C., Brown, A. J., Le Mouélic, S., Yingst, R. A., Bell, J. F., Beyssac, O., Bosak, T., Calef, F., Ehlmann, B. L., Farley, K. A., Grotzinger, J. P., Hickman-Lewis, K., Holm-Alwmark, S., Kah, L. C., Martinez-Frias, J., McLennan, S. M., Maurice, S., Nuñez, J. I., Ollila, A. M., Pilleri, P., Rice, J. W., Rice, M., Simon, J. I., Shuster, D. L., Stack, K. M., Sun, V. Z., Treiman, A. H., Weiss, B. P., Wiens, R. C., Williams, A. J., Williams, N. R., & Williford, K. H. (2021). "Perseverance rover reveals an ancient delta-lake system and flood deposits at Jezero crater, Mars." Science, 374(6568), 711–717. https://doi.org/10.1126/science.abl4051
3. Farley, K. A., Stack, K. M., Shuster, D. L., Horgan, B. H. N., Hurowitz, J. A., Tarnas, J. D., Simon, J. I., Sun, V. Z., Scheller, E. L., Moore, K. R., McLennan, S. M., Vasconcelos, P. M., Wiens, R. C., Treiman, A. H., Mayhew, L. E., Beyssac, O., Kizovski, T. V., Tosca, N. J., Williford, K. H., Crumpler, L. S., Beegle, L. W., Bell, J. F., Ehlmann, B. L., Liu, Y., Maki, J. N., Schmidt, M. E., Allwood, A. C., Amundsen, H. E. F., Bhartia, R., Bosak, T., Brown, A. J., Clark, B. C., Cousin, A., Forni, O., Gabriel, T. S. J., Goreva, Y., Gupta, S., Hamran, S.-E., Herd, C. D. K., Kah, L. C., Kelemen, P. B.,litz, K. B., Mangold, N., Maurice, S., McCubbin, F. M., Núñez, J. I., Ollila, A. M., Pilleri, P., Quantin-Nataf, C., Rice, M. S., Russell, P., Sharma, S., Siljeström, S., Steele, A., Sullivan, R., Udry, A., Wade, L. A., Weiss, B. P., Williams, A. J., Wogsland, B. V., & Zorzano, M.-P. (2022). "Aqueously altered igneous rocks sampled on the floor of Jezero crater, Mars." Science, 377(6614), eabo2196. https://doi.org/10.1126/science.abo2196
4. Bosak, T.,Stack, K. M., Simon, J. I., & the Mars 2020 Science Team (2024). "Habitability and organic preservation in the western delta of Jezero crater, Mars." AGU Advances, 5(4), e2024AV001241. https://doi.org/10.1029/2024AV001241