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2025 Vol. 122 No. 2 e2404255121
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RESEARCH ARTICLE
|
Significance
The NASA Perseverance Rover
has collected numerous sealed
sample tubes containing rock,
regolith, and atmosphere that
represent the different rock types
encountered within Jezero Crater,
Mars. Analysis of these samples
in laboratories on Earth would
enable fundamental questions to
be addressed, including how
Mars formed, its geologic
evolution, and whether Mars ever
hosted life.
Author affiliations:
a
Department of Earth and
Atmospheric Sciences, University of Alberta, Edmonton,
AB T6G 2E3, Canada;
b
Department of Earth, Atmospheric,
and Planetary Sciences, Massachusetts Institute of
Technology, Cambridge, MA 02139;
c
Department
of Geoscience, University of Nevada, Las Vegas, NV
89154;
d
School of Natural Sciences, Birkbeck, University
of London, London WC1E 7HX, United Kingdom;
e
Dipartimento di Scienze Biologiche, Geologiche e
Ambientali, Università di Bologna, Bologna 40126,
Italy;
f
Department of Geological Sciences, University of
Colorado, Boulder, CO 80309;
g
Department of Earth and
Planetary Science, University of California, Berkeley, CA
94720;
h
Research Institutes of Sweden, Stockholm 11
486, Sweden;
i
Center for Isotope Cosmochemistry and
Geochronology, Astromaterials Research and Exploration
Science, NASA Johnson Space Center, Houston, TX 77058;
j
School of Earth and Space Exploration, Arizona State
University, Tempe, AZ 85287;
k
Centro de Astrobiología,
Consejo Superior de Investigaciones Cientificas
-
Instituto
Nacional de Técnica Aeroespacial, Madrid 28850,
Spain;
l
Jet Propulsion Laboratory, California Institute
of Technology, Pasadena, CA 91109; and
m
Division of
Geological and Planetary Sciences, California Institute of
Technology, Pasadena, CA 91125
Author contributions: C.D.K.H., T.B., E.M.H., K.H.
-
L.,
L.E.M., D.L.S., S.S., J.I.S., B.P.W., M.W., M.
-
P.Z., J.N.M.,
K.A.F., and K.M.S. wrote the paper.
The authors declare no competing interest.
This article is a PNAS Direct Submission.
Copyright © 2025 the Author(s). Published by PNAS.
This open access article is distributed under
Creative
Commons Attribution
-
NonCommercial
-
NoDerivatives
License 4.0 (CC BY
-
NC
-
ND)
.
1
To whom correspondence may be addressed. Email:
herd@ualberta.ca.
Published January 6, 2025.
EARTH, ATMOSPHERIC, AND PLANETARY SCIENCES
Sampling Mars: Geologic context and preliminary
characterization of samples collected by the NASA Mars
2020 Perseverance Rover Mission
Christopher D. K. Herd
a,1
, Tanja Bosak
b
, Elisabeth M. Hausrath
c
, Keyron Hickman
-
Lewis
d
,e
, Lisa E. Mayhew
f
, David L. Shuster
g
, Sandra Siljeström
h
,
Justin I. Simon
i
, Benjamin P. Weiss
b
, Meenakshi Wadhwa
j
, Maria
-
Paz Zorzano
k
, Justin N. Maki
l
, Kenneth A. Farley
l
,m
, and Kathryn M. Stack
l
Edited by Mark Thiemens, University of California San Diego, La Jolla, CA; received April 4, 2024; accepted September 25, 2024
The NASA Mars 2020 Perseverance Rover Mission has collected samples of rock,
regolith, and atmosphere within the Noachian
-
aged Jezero Crater, once the site of a
delta
-
lake system with a high potential for habitability and biosignature preservation.
Between sols 109 and 1,088 of the mission, 27 sample tubes have been sealed, includ
-
ing witness tubes. Each sealed sample tube has been collected along with detailed docu
-
mentation provided by the Perseverance instrument payload, preserving geological and
environmental context. Samples representative of the stratigraphy within each of four
campaigns have been collected: samples from the Crater Floor Campaign represent a
suite of potentially petrogenetically related igneous rocks displaying variable degrees
of aqueous alteration; samples from the Fan Front record fluvial to deltaic sediments
formed by the transport and deposition of materials from the Jezero watershed; reg-
olith samples from the Fan Front preserve material possibly representative of global
dust as well as diverse, locally derived clasts; Upper Fan samples record the latest stages
of aqueous activity within Jezero; and samples from the Margin Campaign preserve
lacustrine, littoral, or possibly igneous processes that may have occurred early in the
history of the crater. Along with anticipated samples from the older rocks within the
rim of Jezero Crater, Perseverance promises to deliver a suite of samples preserving
a diversity of formation environments and ages. Upon return to Earth and analysis
in terrestrial laboratories, these samples would address longstanding questions per-
taining to the geologic evolution of Mars, its habitability, and the potential for life
outside the Earth.
Mars | Jezero Crater | sample return | geology
A primary goal of the NASA Mars 2020 Perseverance rover mission is to select, acquire, and
document a scientifically return
-
worthy collection of martian samples for return to Earth
by future missions (1). To achieve this task, the rover is equipped with an integrated suite
of science instruments that operate together as part of a mobile sampling platform. Data
from remote sensing instruments mounted on a pan/tilt mast and proximity instruments
mounted on a robotic arm provide detailed contextual information for each sample
(
Materials and Methods
).
Mars Sample Return (MSR) has been a high priority of the scientific community for
decades (McSween, ( 2 ); McCubbin, ( 3 )). Detailed analyses in Earth
-
based laboratories
of carefully documented martian samples collected from regions with known geologic
contexts will be essential for addressing the highest
-
priority science questions relating to
Mars ( 4 ). These questions include those about the geologic history of Mars, particularly
the role of water, the evolution of volatiles and climate on Mars, the timeline of planetary
scale processes, and the potential biological history of Mars ( 5 ).
Perseverance is currently exploring the Noachian
-
aged Jezero Crater, once the site of a
delta
-
lake system with a high potential for habitability and biosignature preservation. The
rover carried 38 identical sample tubes designed for rock core or regolith samples and five
witness tube assemblies (“witness blanks”) for characterizing contamination from the rover.
At the time of writing, 24 of 38 sample tubes have been sealed, as have 3 of the witness tubes
( Table
1 ). Of these, nine sample tubes (seven containing rock cores, one containing regolith,
and one filled with Mars atmosphere) and 1 witness tube have been deposited at the Three
Forks depot in Jezero Crater, while the rest are being carried onboard Perseverance. The
orientations of all rock core samples have been estimated relative to martian geographic
coordinates to enable their records of geological and geophysical processes to be oriented at
the time they formed and/or were altered (Weiss et al. ( 6 )).
OPEN ACCESS
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Once a sampling target has been identified, each sample is docu-
mented by a standardized set of required activities and observations.
These activities are called the Standardized Observation Protocol, or
STOP list. The STOP list includes imagery at multiple scales and
resolutions, together with chemical and mineralogical analyses (“prox
-
imity science”) of the outcrop surface (e.g., ref. 7 ). An
~
1 cm deep
and 5 cm diameter abrasion target is acquired within a few tens of
centimeters of the sample target, within the same lithology or sedi-
mentary layer, in order to provide a fresh rock surface for proximity
science. In this “sample proxy” abraded patch, high
-
resolution images
and detailed maps of elemental composition, mineralogy, and poten
-
tial organic matter are obtained. After coring, an image is taken of
the sample in the tube, the amount of sample is estimated, and the
tube is hermetically sealed ( 8 ). Unique serial numbers are readily
visible on the tube and seal exteriors to ensure unambiguous identi-
fication even decades after acquisition.
Sample documentation comprises a Sample Dossier and an Initial
Report; these are uploaded to the NASA Planetary Data System
Table 1. List of samples collected by the Perseverance Rover
#
Sample designation
*
Location of collection
Type (Fm
)
Notes
Current location
1
M2020
-
109
-
1
WB
-
1
Witness Blank
P r e
-
launch exposure
Perseverance
Crater Floor Campaign
2
M2020
-
164
-
2
Roubion
Séítah "Thumb"
Atmosphere
§
Polygonal low
-
lying outcrop within
Máaz formation
Three Forks
3
M2020
-
190
-
3
Montdenier
Rochette target, Artuby Ridge
Igneous (Máaz fm.)
Float associated with ridge
Three Forks
4
M2020
-
196
-
4
Montagnac
Same as Montdenier
Perseverance
5
M2020
-
262
-
5
Salette
Brac outcrop within Séítah
South
Igneous (Séítah fm.)
Outcrop. Low
-
lying, layered
Perseverance
6
M2020
-
271
-
6
Coulettes
Same as Salette
Three Forks
7
M2020
-
298
-
7
Robine
Issole outcrop within Séítah
South
Igneous (Séítah fm.)
Outcrop. Ridge, layered, resistant
Perseverance
8
M2020
-
337
-
8
Malay
Same as Robine
Three Forks
9
M2020
-
371
-
9
Hahonih
Sid target
Igneous (Máaz fm.)
Float associated with massive, blocky
rocks
Perseverance
1 0
M2020
-
377
-
10
Atsah
Same as Hahonih
Three Forks
Fan Front Campaign
1 1
M2020
-
490
-
11
Swift Run
Skinner Ridge outcrop,
Hawksbill Gap
Sedimentary (Shenandoah
fm.)
Outcrop. Horizontally
-
layered,
medium
-
grained, resistant
Perseverance
1 2
M2020
-
495
-
12
Skyland
Same as Swift Run
Three Forks
1 3
M2020
-
499
-
18
WB2
Witness Blank
Perseverance
1 4
M2020
-
509
-
14
Hazeltop
Wildcat Ridge outcrop,
Hawksbill Gap
Sedimentary (Shenandoah
fm.)
Outcrop. Horizontally
-
layered,
fine
-
grained, recessive
Perseverance
1 5
M2020
-
516
-
15
Bearwallow
Same as Hazeltop
Three Forks
1 6
M2020
-
575
-
16
Shuyak
Amalik outcrop, Cape Nukshak
Sedimentary (Shenandoah
fm.)
Outcrop. Horizontally
-
layered,
fine
-
grained, recessive
Perseverance
1 7
M2020
-
579
-
17
Mageik
Same as Shuyak
Three Forks
1 8
M2020
-
584
-
18
WB3
Witness Blank
Three Forks
1 9
M2020
-
623
-
19
Kukaklek
Hidden Harbor outcrop, Cape
Nukshak
Sedimentary (Shenandoah
fm.)
Outcrop. Horizontally
-
layered,
fine
-
grained, recessive
Perseverance
2 0
M2020
-
634
-
20
Atmo Mountain
Observation Mountain, Cape
Nukshak
Regolith
Megaripple
Perseverance
2 1
M2020
-
639
-
21
Crosswind Lake
Same as Atmo Mountain
Three Forks
Upper Fan Campaign
2 2
M2020
-
749
-
22
Melyn
Berea outcrop
Sedimentary (Tenby fm.)
Outcrop. Alternating dm
-
scale resistant
sandstone and recessive coarser
-
grained layers
Perseverance
2 3
M2020
-
822
-
23
Otis Peak
Onahu outcrop
Sedimentary (Otis Peak
fm.)
Outcrop. Cross
-
stratified conglomerate,
resistant
Perseverance
2 4
M2020
-
882
-
24
Pilot Mountain
Dream Lake outcrop
Sedimentary (Otis Peak
fm.)
Outcrop. Low
-
lying, medium
-
grained,
recessive
Perseverance
Margin Campaign (ongoing)
2 5
M2020
-
923
-
25
Pelican Point
Hans Amundsen M.W. within
Mandu Wall
Sedimentary (TBD fm.)
Outcrop. Minimally
-
layered, low
-
lying,
medium
-
to coarse
-
granular,
recessive
Perseverance
2 6
M2020
-
949
-
26
Lefroy Bay
Turquoise Bay within Mandu
Wall
Sedimentary (TBD fm.)
Outcrop. Minimally
-
layered, low
-
lying,
medium
-
to coarse
-
granular,
recessive
Perseverance
2 7
M2020
-
1088
-
27
Comet Geyser
Bunsen Peak
Sedimentary
Probable outcrop. Resistant, massive
Perseverance
Notes: Images of rock and regolith cores are shown in Fig. 5.
*
Date and order of collection is encoded in the sample designation, e.g., M2020
-
164
-
2 was collected on sol 164 of the mission, and was the second sample collected
Fm = formation, where applicable
Denotes whether the sample is currently onboard the
Perseverance
rover, or at the Three Forks sample depot. Total numbers in each location: 10 tubes at Three Forks, 17 tubes onboard
Perseverance
.
§
No sample retained in the coring tube; contains
~
4.9
μ
mol of martian atmosphere, collected at L
S
= 81.87 and an ambient temperature of 221 K (4, 7).
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(PDS) on a regular (6
-
mo) cadence. The Sample Dossier contains all
observations from the STOP list, along with relevant rover data (e.g.,
temperatures, rover location, rover arm position and actions, etc.) at
the time of sampling. The Sample Dossier primarily consists of point
-
ers to the relevant instrument
-
specific and engineering data products,
which are also available on the PDS. Thus, the dossier acts as a
“one
-
stop shop” for sample
-
specific results. The Initial Report consists
of a description of each sample in a standardized narrative format that
is written by Returned Sample Science Participating Scientists and
the Science Team within three weeks of sample acquisition. Initial
Reports capture the rationale for sampling and describe the interpre-
tations available at the time of sampling and the completion of the
STOP list. The Initial Report can be thought of as a set of field notes
associated with each sample; in this way, they are perhaps the most
accessible types of sample documentation for the community.
However, like field notes, the Initial Reports do not include extensive
assessment or interpretation of the collected samples; these are
reported elsewhere, primarily within the peer
-
reviewed literature.
In parallel with these observations, the MEDA weather station has
been used to study the local, present
-
day environment and to estimate
the amount of gas in the headspace of each sealed sample and witness
tube—an estimated total of 44.3
μ
moles of martian atmospheric gas
[a preliminary MSR study estimated that the atmospheric sample
needed to implement volatile studies should be at least 19
μ
moles
( 9 )]. Results from MEDA suggest that the present
-
day environmental
conditions at Jezero allow for a diurnal atmospheric
-
surface water
exchange of 0.5 to 10 g water per m
2
( 10 ). This water can hydrate
the sulfates, chlorides, and perchlorates and the occasional formation
of frost at Jezero crater. However, the environmental conditions at
the surface of Jezero Crater, and within the sealed samples, are incom
-
patible with the cell replication limits currently known on Earth ( 10 ).
At the time of writing, Perseverance has completed three cam-
paigns—the Crater Floor, Fan Front, and Upper Fan—and is in
the midst of the Margin Unit campaign ( Fig.
1 ). The purpose of
this contribution is to provide an overview of the samples collected
to date during each campaign, including their mineralogy and
petrology from rover
-
based investigations, and their potential
returned sample science, if and when the samples are returned to
Earth and analyzed in laboratories. Sources of information for this
review include the peer
-
reviewed literature, as well as Initial
Reports for the most recently collected samples.
Crater Floor Campaign Samples
Geological Context.
The first rock samples collected by the Mars
2020 mission represent units exposed on the Jezero Crater floor,
from the potentially oldest Séítah formation outcrops to the
younger rocks of the heavily cratered Máaz formation (Fig. 2).
The Máaz formation had previously been mapped as the Crater
floor fractured rough unit (Cf
-
fr), and the Séítah formation as the
Crater floor fractured unit (Cf
-
f
-
1) by Stack et al. (11). Proximal
and remote analyses carried out during the campaign suggest that
all crater floor outcrops investigated are igneous in origin and
dominantly ultramafic to mafic in composition (12–14). Surface
investigations further reveal landscape
-
to
-
microscopic textural,
mineralogical, and geochemical evidence that these crater floor
units were likely emplaced as lava flows; furthermore, these rocks
exhibit variable amounts of aqueous alteration and the formation
of secondary carbonate and sulfate phases, among others (12–20).
The Máaz formation is a widespread extrusive unit that exhibits
a smooth morphology lower in the stratigraphy, and a rougher,
more massive, rubbly, and cratered morphology upsection
(19, 21). The sample cores
Montdenier
and
Montagnac
are
representative of the lower Máaz members, which are more mafic
and pyroxene
-
dominated. In contrast, the upper Máaz members—
represented by the
Hahonih
and
Atsah
sample cores—are more
silicic and plagioclase
-
dominated. Taken as a whole, the Máaz
formation provides important stratigraphic and geochronological
constraints for the other major geological units in Jezero crater (19,
22), including the underlying Séítah formation and the overlying
strata of the Jezero delta.
On the crater floor, the Máaz formation overlies the Séítah
formation, which, morphologically, comprises an irregular eroded
region of the crater floor consisting of NE
-
SW
-
trending ridges
surrounded by megaripples, loose rocks, and boulders; it is largely
devoid of craters. Outcrop exposures of the Séítah formation are
composed of coarse
-
grained, thickly bedded, and tabular layers
interpreted to represent layering of an olivine
-
dominated cumulate
likely originating within a thick lava flow, laccolith, or lava lake
on the crater floor ( 13 ). The sample cores
Robine
and
Malay
were
collected near the boundary with the Máaz formation, toward the
southernmost exposure of Séítah, while sample cores
Salette
and
Coulettes
were collected further into the unit. The eight core sam-
ples collected from the Jezero crater floor represent four
“double
-
sampled” outcrop exposures—two of Máaz and two of
Séítah—that are all interpreted to be stratigraphically below (i.e.,
older than) the western fan sediments ( 23 ).
All crater floor samples contain major igneous rock
-
forming min
-
erals such as pyroxene, olivine, and feldspar, accessory minerals
including oxides and phosphates, and evidence for various degrees
of aqueous activity in the form of water
-
soluble salt, carbonate,
sulfate, iron oxide, and iron silicate minerals ( 7 , 12 , 24 ). The natural
surfaces of the Máaz formation exhibit fine
-
grained textures with
occasional millimeter
-
sized grains. Abraded surfaces show holocrys
-
talline, equigranular to porphyritic igneous textures. Some Máaz
formation flow layers and surfaces contain millimeter
-
to
centimeter
-
sized irregular to circular voids or pits (e.g., ref. 16 ). The
primary mineralogy is dominated by Fe
-
rich pyroxene and plagi-
oclase and the Máaz formation contains some of the lowest Mg
contents reported for martian magmatic rocks ( 16 ). On abraded
surfaces, secondary minerals appear to line the edges of the voids or
pits, and in some cases completely fill voids or replace grains (e.g.,
the
Guillaumes
abrasion patch; 4). Secondary minerals include
hydrated Mg
-
sulfate
-
anhydrite
-
perchlorate grain mixtures, pervasive
reddish
-
brown staining, and rare carbonate ( 15 , 20 , 24 ). The Séítah
formation exposures are mainly composed of coarse
-
grained olivine
( 12 , 13 , 25 ). On natural surfaces these 2 to 3 mm diameter dark
gray to green olivine grains appear densely packed ( 14 , 18 ). On
abraded surfaces, a granular texture of both olivine and pyroxene
grains can be seen. PIXL X
-
ray fluorescence maps of the abraded
patches reveal that the olivine has a uniform composition (
~
Fo
55
)
making up
~
60 to 70 vol% of the rock, evidence of large interstitial
augite grains (exhibiting a poikilitic texture), and fine
-
grained
Al
-
rich crystalline mesostasis with Na
-
and K
-
rich feldspars,
Fe
-
Cr
-
Ti oxides, and Ca
-
phosphates ( 13 ). Compositional and tex-
tural evidence exists for some dissolution of olivine, but much less
than typically observed in terrestrial olivine
-
rich lithologies ( 25 ).
Likewise, the areas of mesostasis show few signs of secondary salts
( 13 ). The secondary mineralogy in the Séítah formation is similar
to that observed in the Máaz formation rocks and includes hydrated
Mg
-
sulfates, anhydrite, and possible perchlorates, although car-
bonate appears to be more abundant ( 15 , 20 , 24 , 25 ).
Potential Returned Sample Science.
Following sample return,
the compositions and ages of the variably altered igneous rocks
collected from the Jezero crater floor would be expected to reveal
the geophysical and geochemical characteristics of the planet's
interior at the time of emplacement, enabling comparison with
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other igneous rock compositions from other parts of Mars and
from meteorites, helping to characterize martian magmatism, and
placing timing constraints on geologic processes, both in Jezero
Crater and more widely on Mars (5, 7). Geochronological analyses
would provide critical constraints on the timing of events in Jezero
crater, including the emplacement of the crater floor as well as
potentially the onset of lake activity (7). The complex history of
the crater floor (26) provides a challenge for achieving the goal of
constraining the absolute chronology of Mars (5); however, only
with sample analysis in terrestrial laboratories can the absolute
and relative ages of events recorded within them be reconciled
with the Máaz formation’s erosional, burial, and exhumation
history. Further to this point, petrographic observations and
geochemical analyses, coupled with geochronology of secondary
minerals, would reveal the timing and characteristics of aqueous
activity while constraining the chemical and physical conditions
of the environments in which these minerals precipitated.
Understanding the nature, chemistry, and mechanisms of water–
rock interactions at the microscale may help to establish whether
habitable microniches, for example, potential endolithic habitats,
were ever present in the crater floor sequences. High
-
sensitivity
and high
-
resolution terrestrial laboratory analyses would also be
crucial to determine the nature and composition of any organic
compounds preserved in association with these phases (15, 27).
Evidence for near
-
surface secondary alteration processes, requiring
(sub)micron
-
scale measurements, will thus be key to constraining
the style and duration of aqueous activity in Jezero Crater, past
habitability, and cycling of organic elements in Jezero Crater.
Fan Front Campaign Rock Samples
Geological Context.
Sedimentary rocks in the western sedimentary
fan in Jezero crater were major targets for exploration and sampling
by Perseverance because of their potential to record past fluvial
and lacustrine environments, habitable conditions, and potential
biosignatures (1, 28); this was one of the main factors in the selection
of the Jezero crater landing site (29, 30). The oldest such rocks are
found at the base of the eroded fan front, which exposes a sequence
of sedimentary rocks totaling
~
65 m in thickness. The mission team
explored this area for more than one Earth year during the Fan
Front Campaign, during which seven rock samples were collected
(Table 1). Primary lithologies or features of interest during this
campaign included indicators of past habitable environments and
climate conditions, such as fluvial, lacustrine, and deltaic deposits
and minerals precipitated in solution; rocks that can assist in
constraining the timing and duration of aqueous activity; and rocks
that can provide optimal conditions for biosignature preservation
and may therefore be instrumental in the search for potential traces
of life (28). The initial sampling plan for the fan front included two
cores of fine
-
grained and clay
-
rich bedrock and two coarser
-
grained
sedimentary rocks, one from a stratigraphically high site and one
from a stratigraphically low site. Fine
-
grained sedimentary rocks
are generally associated with an increased likelihood of preserving
organic materials and other potential biosignatures and would thus
have a higher astrobiological potential, whereas the coarser
-
grained
samples would enable constraining the timing of the aqueous
activity in the fan. Oriented bedrock samples were collected from
Máaz
Séítah
Delta truncated
curvilinear
Delta block
y
Margin fractured
Crater rim
block
y
Crater Floor
Fan Fron
t
Upper Fan
Margin
Fig. 1.
Map showing mission progress at the time of writing, superimposed on a geologic map of Jezero crater, after ref. 11. Rover traverse and waypoints
shown with white line and dots, respectively; sampling locations shown with red crosses. Labeled black boxes show approximate extent of each campaign.
Names of major units or formations encountered—or expected to be encountered—are labeled in white italics. Approximate location of images shown in Fig. 2
are denoted with a red star.
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throughout the stratigraphy with the objective of reconstructing
aspects of the paleodepositional ecosystem and planetary evolution
throughout this period of sedimentary deposition. The set of samples
collected at the fan front comprises the first and oldest aqueously
deposited sedimentary rocks that can be returned to Earth for future
analyses, filling a total of nine tubes with four duplicate samples
and one singleton; four of the duplicate samples were placed in the
Three Forks Cache in early 2023 (Table 1).
Remote (Mastcam
-
Z, SuperCam) and proximity (PIXL,
SHERLOC, WATSON) payload science instruments provided
structural, textural, and chemical evidence for both the aqueous
deposition and aqueous alteration of the rocks in the Fan Front,
and enabled these rocks to be placed in a stratigraphic sequence of
fluvial to lacustrine and overlying deltaic deposits ( 31 ). The cores
Shuyak
and
Mageik
were collected from flat, laminated, fine
-
grained
sandstones interpreted as fluvial ( 31 ) ( Fig.
3 ). These grainstones
contain detrital igneous minerals such as olivine and pyroxene and
layers that appear to concentrate heavy detrital minerals such as
chromite, ilmenite, and zircon or baddeleyite ( 32 ). The rocks are
hydrated, containing serpentine
-
like minerals ( 31 , 33 ) and aque-
ously precipitated sulfates and carbonates ( 28 , 31 , 34 , 35 ).
The light
-
toned mudstones/siltstones and sandstones along the
fan front are interpreted either as lacustrine deposits ( 31 ), or as
subaerial deposits of transported sulfate mineral grains ( 35 ). The
matrix of the siltstone/mudstone
Hogwallow Flats
outcrop (from
which the
Hazeltop
and
Bearwallow
samples were collected) is
composed of fine
-
grained magnesium and ferrous iron clays and
very soluble, aqueously precipitated and hydrated magnesium and
ferrous iron sulfates ( 28 , 31 , 34 , 35 ). Spectroscopy is consistent
with ferric iron sulfates, indicating some oxidation ( 33 , 36 ). The
Kukaklek
sample from a similarly light
-
toned outcrop ( Fig.
3 ) in
the western part of the explored area ( Fig.
3 ) is somewhat
coarser
-
grained and characterized as a sandstone ( 36 ). The numer
-
ous, cm
-
scale bright veins on this outcrop and some large grains
in its abraded patch
Uganik Island
contain anhydrite ( 35 , 36 ),
suggesting more pervasive postdepositional fluid flow through this
sediment. SHERLOC did not detect any Raman bands indicative
of carbonaceous materials at any light
-
toned sulfate
-
rich outcrops,
but it did measure strong doublet UV luminescence signals in the
abraded patches. This luminescence was particularly strong in
light
-
toned veins and grains, where SHERLOC Raman spectros-
copy and PIXL X
-
ray fluorescence spectroscopy detected anhy-
drite. The strong UV
-
luminescence signal was initially attributed
to one
-
or two
-
ring aromatic organic compounds ( 27 ), but the
combined observations can be instead best interpreted as the inor
-
ganic doublet luminescence of Ce
-
bearing sulfate minerals ( 37 ).
The cross
-
stratified sandstones and pebble conglomerates that
overlie the light
-
toned sulfate
-
rich deposits are interpreted as del-
taic strata that formed by the transport of materials from the Jezero
watershed forming multiple lobes of the sediment fan ( 31 ).
Represented by the sandstone cores
Skyland
and
Swift Run
, these
strata are the youngest components of the fan front stratigraphy
( 31 ). The rocks represented by
Skyland
and
Swift Run
contain
detrital sand
-
sized grains of igneous and aqueously altered igneous
minerals, i.e., materials transported from the Jezero watershed that
may not be accessed by the rover in the future. A strong hydration
signal and the detection of iron
-
magnesium carbonates around
lithic clasts and in some composite grains ( 28 , 33 – 35 ) suggest the
precipitation of authigenic minerals from carbonate
-
bearing aque
-
ous solutions. These rocks exhibit UV luminescence signals
Fig. 2.
Images showing the local contexts of Crater Floor samples: (
A
) 2 to 3 m tall cliff exposures of widespread Máaz formation that locally define the NW
-
SE
trending Artuby Ridge. Kodiak mesa sediments that lie stratigraphically above can be seen in the distance. Boundary with southern edge of Séítah formation
lies to the
Right
side of image. (
B
) Layering in lower Máaz formation outcrops near southern and eastern side of Séítah. Bouldery, crater
-
retaining, upper Máaz
formation outcrops can be seen in the distance. (
C
) Tabular
~
10 cm thick beds of Séítah formation (
Left
) grade into more massive, but still locally layered Séítah
formation outcrops (
Right
).
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primarily in areas that contained phosphate, as would be expected
from Ce
-
containing phosphate minerals ( 37 ).
Potential Returned Sample Science.
Upon the completion of
the MSR Campaign, the suite of sedimentary rocks collected
by Perseverance at the Jezero fan front could provide an entirely
new window into martian habitability and the potential of the
planet to initiate and sustain life more than 3.5 billion years ago
(31). Due to their hydration and the presence of clay minerals
and precipitated minerals such as Mg/Fe sulfates and the later
anhydrite, the finest
-
grained rocks from the fan front have the
highest value for astrobiology. These lacustrine mudstones/
siltstones are conducive to the preservation of organic matter and
biosignatures (e.g., refs. 36 and 38), particularly if they were not
subject to extensive flow or percolation of oxidizing fluids during
diagenesis (e.g., refs. 28, 38, and 39).
The Perseverance rover payload did not detect any conclusive
signals of organic matter in the sampled sedimentary rocks ( 37 ).
However, the rather low sensitivity of the SHERLOC instrument
to carbonaceous material
-
relative to the instrumentation on Earth
or on the Curiosity rover (e.g., refs. 37 , 40 , and 41 )
-
emphasizes
the need to search for organic materials in the returned samples of
these rocks. These analyses can be coupled with petrographic, geo-
chemical, and isotopic analyses of all returned sedimentary rock to
search for textural and geochemical signals of life
-
related processes
before and during the earliest stages of fan deposition ( 28 , 36 ).
The lithic clasts and precipitated minerals in coarser
-
grained
samples from the bottom and the top of the fan front stratigraphy
can constrain both the timing and the duration of habitable con-
ditions and past climate in Jezero crater, and more broadly, on
Mars ( 28 , 31 ). Moreover, geochronological analyses of carbonate
cements in these rocks can be used to determine when the deltaic
Fig. 3.
Stratigraphic columns for the Shenandoah formation at (
A
) Cape Nukshak, (
B
) Hawksbill Gap West, and (
C
) Hawksbill Gap East. See ref. 31 for locations
and other details. The
Inset
(
D
) shows the Mastcam
-
Z workspace image of the
Skinner Ridge
outcrop after sampling the
Swift Run
core. The tailings pile after
sampling, as well as the 5 cm wide
Thornton Gap
abrasion patch, are visible. The inset (
E
) shows the tailings after sampling the
Hazeltop
core, and the 5 cm wide
Berry Hollow
abrasion patch.
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PNAS
2025 Vol. 122 No. 2 e2404255121
https://doi.org/10.1073/pnas.2404255121
7 of 12
sediments became lithified (e.g., ref. 42 ), whereas isotopic analyses
of mineral
-
bound water and carbonate and sulfate minerals across
the sample suite can reconstruct the parallel histories of martian
volatiles and paleoenvironment.
Fan Front Campaign Regolith Samples
Geological Context.
The Perseverance rover has collected two
samples from the inactive megaripple
Observation Mountain
:
Atmo
Mountain,
which remains on the rover, and
Crosswind Lake,
which
has been deposited in the Three Forks sample depot (Table 1). A
megaripple was selected as a sampling location because megaripples
have poor particle sorting (43, 44). A sample of a megaripple
will therefore allow collection both of coarser, likely more locally
derived materials, as well as fine
-
grained material that may come
from more distant locations. The specific megaripple
Observation
Mountain
was selected because it showed morphological features
and grain size that indicate relative immobility (45), as well as
a soil crust, widely observed at Jezero crater (46), that indicates
the likely presence of substantial collected airfall dust. Because
the Perseverance rover is able to sample to a depth of
~
4 to 6 cm
beneath the regolith surface, but the stratigraphy of the sample is
not preserved, a scuff was generated to allow the analysis of the
subsurface material (Fig. 4).
In situ analyses of the megaripple sediment indicate the pres-
ence of both mm
-
size lithic fragments and fine
-
grained material.
The lithic fragments likely originate from at least two different
source regions, and some of the lithic fragments lack a coherent
diffraction pattern measured by PIXL, consistent with poorly
ordered secondary phases ( 45 ). WATSON images and MEDA
thermal inertia measurements of the fine
-
grained material col-
lected from a depth of
~
4 to 6 cm indicate grain sizes of
~
125
μ
m
and
~
150
μ
m, respectively, denoting that its characteristics are
similar to those of previously proposed global soils ( 45 ).
Potential Returned Sample Science.
Analyses of the fine
-
grained
material collected in the regolith sample would help to address the
formation processes of the martian soil; a major unknown in Mars
science. Formation of relatively uniform martian regolith in widely
spaced locations on Mars that has been previously documented
(e.g., refs. 47–50) may indicate either relatively uniform parent
material across multiple widely spaced locations on Mars, or a
truly globally mixed material; grain
-
by
-
grain examination of
the regolith sample would help to address potential formation
mechanisms. In addition, the presence of airfall dust in the sample
would enable measurements of the composition, shape, and size
distribution of dust grains to help better understand the radiative
and microphysical effects of dust on past and present martian
climate. Samples of dust would also allow an assessment of the risk
to human health and equipment on future human missions (5).
Also, although sampling disrupts the soil crust, the components of
the soil crust likely have been collected within the volume of the
sample tube, allowing the future assessment and characterization
of these components.
As a sample containing a potentially high diversity of larger
lithic fragments that themselves likely contain altered secondary
phases ( 45 ), analysis of these fragments could preserve past poten-
tially habitable, and possibly inhabited environments. As such,
possible biosignatures could be present in these heavily altered
materials. Three different patterns of fluorescence were detected
by the SHERLOC instrument, patterns that are consistent with
inorganic emissions from REEs or silica defects, with organic ori-
gins unable to be excluded ( 37 , 45 ). Analysis of these materials in
Earth’s laboratories promises to better identify past potential
biosignatures.
An additional aspect of the regolith sample is its potential for
in
-
situ resource utilization (ISRU) technologies, to support the
future sustained exploration of Mars; regolith has the potential to
be used with additive manufacturing as a building material ( 51 );
as raw material to extract iron ore, silicates, and alumina; and as
a substrate for biomining methods ( 52 ).
Upper Fan Campaign Samples
Geological Context.
The Jezero upper fan, from which the cores
Melyn
,
Otis Peak
, and
Pilot Mountain
were acquired (Table 1),
records the latest stages of aqueous activity in the crater and contains
some of the coarsest
-
grained materials observed thus far. The upper
fan is composed largely of two units identified from orbital data:
the Delta truncated curvilinear (D
-
tcl) and Delta blocky (D
-
bl)
units (11). Delta truncated strata are visible in orbital images as
sets of 100 m arcing layers of alternating bright and dark layers.
Rover images of the D
-
tcl Tenby formation, where
Melyn
was
acquired, show that these layers correspond to resistant sandstones
and recessive coarser grained rocks. Proximity science observations
of the
Solva
abrasion patch paired with the
Melyn
sample indicate
that the detrital grains are largely of mafic igneous origin, being
composed of olivine, feldspar, possibly pyroxene, and minor Fe
-
,
Cr
-
, and Ti
-
oxides and phosphate. The presence of hydrated sulfates,
carbonate, and possibly also phyllosilicates and silica indicate that
the materials experienced aqueous alteration (53).
These rocks clearly overly the fan front lithologies, although the
contact is obscured. Delta blocky rocks, which sit unconformably
over the older
Tenby
formation, consist of steep
-
sided lobes covered
with boulders and poorly lithified materials. As observed in the
Otis Peak
formation, from which the
Otis Peak
and
Pilot Mountain
cores were acquired, these rocks are poorly lithified, granule and
pebble conglomerates and sandstones covered by angular cobbles
and boulders. Proximity science observations of the
Ouzel Falls
and
Gabletop Mountain
abrasion patches, which are paired with
Otis
Peak
and
Pilot Mountain
, respectively, show that the clasts at this
location are dominantly monomineralic and polymineralic and
Fig. 4.
Navcam image of the immobile megaripple
Observation Mountain
which contains the regolith sampling locations of
Atmo_Mountain
(
Left
) and
Crosswind_Lake
(
Right
). The rover performed a scuff to expose the subsurface
material that likely makes up the majority of the sample, and analyses were
performed of both the undisturbed surface, the wall of the wheel scuff, the
wheel track, and the tailings pile from the scuff (see ref. 45 for details). For
scale, the rover wheel is 33.6 cm wide.
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composed of altered olivine, carbonate, and polymineralic grains
of feldspar and Cr spinels. These are cemented by silica, sulfate,
and carbonate, again indicating aqueous alteration ( 54 , 55 ).
Potential Returned Sample Science.
The Upper Fan samples
are of great value for returned sample science for at least two
major reasons. First, they are collectively the youngest and
stratigraphically highest samples acquired by the rover on the
fan and could ultimately be the youngest samples acquired by
the rover during the full mission. As such, geochronological
analyses could put an upper bound on the timing of fluvial
activity in the crater and, when combined with ages from
crater floor and fan front samples, constrain the duration of
fluvial activity. Furthermore, given current age constraints on
the fan (31), these samples are from lithologies thought to be
Hesperian in age. Given that there are no known Hesperian
martian meteorites (Udry et al. (56)), the Upper Fan samples
will fill a critical gap in the rock record available for laboratory
analyses from this crucial juncture of major climate change in
martian history.
Second, the Upper Fan samples contain the coarsest detrital grains
yet sampled by the rover. Some of these clastic materials are almost
certainly derived from the Nili Planum region outside Jezero that
serves as the watershed for Jezero lake. As such, these detrital mate-
rials offer two unique opportunities for returned sample science
investigations. They provide samples from distal regions up to 200
km from the western crater rim that will likely never be sampled
in situ by the rover; these also include some of the oldest known
rocks from Mars (e.g., ref. 57 ) and so will provide invaluable records
of early planetary processes, e.g., magmatism, aqueous activity, cli-
mate, and the evolution of the martian dynamo. Many of the rocks
are also thought to be from deeper parts of the crust and possibly
even the mantle. Therefore, these samples may provide records of
planetary differentiation and sample a subsurface potentially habit-
able environment distinct from the surface waters of Jezero lake.
Laboratory investigations of these samples will enable the study of
a source
-
to
-
sink sedimentary system on Mars that will inform how
aqueous processes and habitability evolved through time, both
within the catchment and the fan. Crystallization ages of detrital
igneous silicate clasts will provide upper bounds on the timing of
fan deposition and therefore the timing of lake Jezero. Furthermore,
the potential exists for, the coarse grains in these samples to enable
a conglomerate test that can constrain the ages of paleomagnetic
records in the samples. Records that predate deposition will tend to
be expressed heterogeneously between different clasts, whereas
records acquired secondarily after deposition will tend to be
expressed homogenously across clasts and within the matrix.
Margin Campaign Samples
Geological Context.
The Margin unit—situated at the interior of, and
adjacent to, the western crater rim—is primarily of interest for the
strong carbonate signal recognized in orbital reflectance spectroscopy
data (11, 58), in addition to the potential presence of hydrated silica
(59). Stratigraphically, the unit lies beneath the previously explored
curvilinear and blocky units of the fan top and is therefore older
than those units (60). The position of the Margin unit relative to
other fan deposits and the crater floor units is unknown (11); it is
possible this is one of the oldest units explored so far. Based on its
position near the crater rim and the strong carbonate detections,
the Margin unit has been proposed to be a shoreline deposit with
possible lacustrine carbonates (58). Alternative hypotheses include
pyroclastic, extrusive igneous, fluviolacustrine, and aeolian deposits,
or a combination of several mechanisms (60–64).
The planning of the Margin campaign took place during the
summer of 2023, and continues at the time of writing. Between
3 and 5 samples are baselined to be collected, and three have been
so far successfully obtained ( Table
1 ): the
Pelican Point
core at the
Hans Amundsen Memorial Workspace in the Mandu Wall region,
the
Lefroy Bay
core at Lake Newell in the Turquoise Bay region,
and the
Comet Geyser
core at the
Bunsen Peak
outcrop. Data from
the
Castle Geyser
sample abrasion patch associated with the
Comet
Geyser
sample have yet to be processed and interpreted at the time
of writing.
Pelican Point
and
Lefroy Bay
were collected from the
eastern part of the Margin ( Fig.
1 ), corresponding to near the
regolith
-
covered contact to Lobe H of the western fan as mapped
by ( 65 ). The location of the
Lefroy Bay
sample (
Lake Newell
) is
slightly higher in elevation and located in a more carbonate
-
rich
area as indicated by orbital data ( 58 ). The outcrops at both loca-
tions exhibit a similar appearance: low
-
lying, granular, fractured,
and minimally layered slabs of in
-
place bedrock. Plane
-
parallel
laminations were observed near the sampling outcrops, some at
low dipping angles ( 63 ); in contrast, more resistant, massive rocks
are present looking west into the Margin unit.
Proximity observations of the abrasions
Amherst Point
and
Bills
Bay
(corresponding to
Pelican Point
and
Lefroy Bay
, respectively)
indicate clastic rocks of likely sedimentary origin, classified as mod
-
erately to poorly sorted medium
-
to coarse
-
grained sandstones.
Both abrasions contain similar mineral assemblages, as indicated
by PIXL, SCAM, and SHERLOC data, primarily containing oli-
vine, pyroxene, and altered silicates such as serpentine, Mg–Fe
carbonates, and a high
-
silica phase, likely as a pore
-
filling cement
( 66 – 68 ). The bulk composition is consistent with that of an altered
basalt and is in family with the fan top samples; minor phases
include Mg
-
sulfates, oxides, feldspar, and chlorides ( 67 ). In
Amherst
Point
the carbonate mostly appears as coatings while in
Bills Bay
carbonate is also present as clasts; carbonate is also more abundant
in
Bills Bay.
SHERLOC data indicate that some of the silica in
Bills
Bay
is hydrated silica. SHERLOC data also indicate that some of
the carbonates in
Amherst Point
are hydrated; this represents the
first time during the mission that such carbonates have been
detected. The hydrated carbonates appear in bright patches together
with hydrated sulfates. The very low fluorescence signal and absence
of Raman signals indicate that any organic materials present are in
the sample in low abundance (<0.1 wt%) ( 37 ).
Potential Returned Sample Science.
Margin samples are of
high interest for constraining the timing of lake Jezero through
geochronology of clasts and cements in the cores. The cements
may also constrain aqueous geochemistry (pH, Eh, salinity,
etc.) and potential fluid sources. Together with the fan samples,
these materials would be used to understand sources to sinks in
sedimentary systems on Mars as some clastic material is likely
detrital material sourced from outside Jezero crater. Chemical
characterization of alteration phases would provide insights
into sediment diagenesis. As expected from orbital data, rocks
in the Margin are rich in carbonate; carbonate chemistry would
constrain the climate of Mars at the time of deposition and/or
diagenesis, may allow inferences about the aqueous chemistry and
paleoenvironmental conditions of lake Jezero to be made, and
would contribute to reconstructing past martian climate.
If the interpretation of the Margin as a possible shoreline/
lacustrine deposit is correct, the presence of minerals formed by
water would indicate that the Margin unit was once a habitable
environment. Lakeshore environments are known to be habitable
in similar settings on Earth and are commonly colonized by
microbial communities, for example, microbial mat ecosystems.
Lacustrine shoreline environments on Earth are frequently
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