Determining the source(s) of hydrogen, carbon, and nitrogen accreted by Earth is important for understanding the origins of water and life and for constraining dynamical processes that operated ...during planet formation. Chondritic meteorites are asteroidal fragments that retain records of the first few million years of solar system history. The deuterium/hydrogen (D/H) values of water in carbonaceous chondrites are distinct from those in comets and Saturn's moon Enceladus, implying that they formed in a different region of the solar system, contrary to predictions of recent dynamical models. The D/H values of water in carbonaceous chondrites also argue against an influx of water ice from the outer solar system, which has been invoked to explain the nonsolar oxygen isotopic composition of the inner solar system. The bulk hydrogen and nitrogen isotopic compositions of CI chondrites suggest that they were the principal source of Earth's volatiles.
Martian meteorites are the only direct samples from Mars, thus far. Currently, there are a total of 262 individual samples originating from at least 11 ejection events. Geochemical analyses, through ...techniques that are also used on terrestrial rocks, provide fundamental insights into the bulk composition, differentiation and evolution, mantle heterogeneity, and role of secondary processes, such as aqueous alteration and shock, on Mars. Martian meteorites display a wide range in mineralogy and chemistry, but are predominantly basaltic in composition. Over the past 6 years, the number of martian meteorites recovered has almost doubled allowing for studies that evaluate these meteorites as suites of igneous rocks. However, the martian meteorites represent a biased sampling of the surface of Mars with unknown ejection locations. The geology of Mars cannot be unraveled solely by analyzing these meteorites. Rocks analyzed by rovers on the surface of Mars are of distinct composition to the meteorites, highlighting the importance of Mars missions, especially sample return. The Mars 2020 Perseverance rover will collect and cache—for eventual return to Earth—over 30 diverse surface samples from Jezero crater. These returned samples will allow for Earth‐based state‐of‐the‐art analyses on diverse martian rocks with known field context. The complementary study of returned samples and meteorites will help to constrain the evolution of the martian interior and surface. Here, we review recent findings and advances in the study of martian meteorites and examine how returned samples would complement and enhance our knowledge of Mars.
Plain Language Summary
Scientists learn about the formation and evolution of planets, such as Mars, by studying rock samples. Obtaining rock samples from Mars makes it possible to study them in state‐of‐the‐art laboratories on Earth with high degrees of precision and accuracy. Currently, samples from Mars are obtained as meteorites that have been ejected from the planet. We can study these rocks to learn about volcanic processes and their chemistry and timing in the context of martian geology. This review paper summarizes the information we have learned about Mars's geology by analyzing martian meteorites. Most of the data collected provide evidence that the interior of Mars is compositionally varied with high diversity in chemical makeup throughout time. However, most meteorites are relatively young with few older rocks (older than 2.4 billion years old) analyzed to date. The Mars 2020 mission plans on collecting older samples directly from Mars's surface, in the Jezero crater, for eventual return to Earth, as early as 2031. The study of both meteorites and returned samples is essential to gain a full understanding of the interior composition, evolution, and geological characteristics of different locations on the Red Planet.
Key Points
Martian meteorites are currently the only samples that we possess from the Red Planet
Martian meteorites reveal the compositional diversity of the interior of Mars
Returned samples from Mars would allow us to better constrain the compositions of the martian interior and its evolution through time
Tissint (Morocco) is the fifth martian meteorite collected after it was witnessed falling to Earth. Our integrated mineralogical, petrological, and geochemical study shows that it is a depleted ...picritic shergottite similar to EETA79001A. Highly magnesian olivine and abundant glass containing martian atmosphere are present in Tissint. Refractory trace element, sulfur, and fluorine data for the matrix and glass veins in the meteorite indicate the presence of a martian surface component. Thus, the influence of in situ martian weathering can be unambiguously distinguished from terrestrial contamination in this meteorite. Martian weathering features in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmic-ray exposure age of 0.7 ± 0.3 million years, consistent with those of many other shergottites, notably EETA79001, suggesting that they were ejected from Mars during the same event.
A Reduced Organic Carbon Component in Martian Basalts Steele, A.; McCubbin, F. M.; Fries, M. ...
Science (American Association for the Advancement of Science),
07/2012, Letnik:
337, Številka:
6091
Journal Article
Recenzirano
The source and nature of carbon on Mars have been a subject of intense speculation. We report the results of confocal Raman imaging spectroscopy on 11 martian meteorites, spanning about 4.2 billion ...years of martian history. Ten of the meteorites contain abiotic macromolecular carbon (MMC) phases detected in association with small oxide grains included within high-temperature minerals. Polycyclic aromatic hydrocarbons were detected along with MMC phases in Dar al Gani 476. The association of organic carbon within magmatic minerals indicates that martian magmas favored precipitation of reduced carbon species during crystallization. The ubiquitous distribution of abiotic organic carbon in martian igneous rocks is important for understanding the martian carbon cycle and has implications for future missions to detect possible past martian life.
Here, we present the results of a multitechnique study of the bulk properties of insoluble organic material (IOM) from the Tagish Lake meteorite, including four lithologies that have undergone ...different degrees of aqueous alteration. The IOM C contents of all four lithologies are very uniform and comprise about half the bulk C and N contents of the lithologies. However, the bulk IOM elemental and isotopic compositions vary significantly. In particular, there is a correlated decrease in bulk IOM H/C ratios and δD values with increasing degree of alteration—the IOM in the least altered lithology is intermediate between CM and CR IOM, while that in the more altered lithologies resembles the very aromatic IOM in mildly metamorphosed CV and CO chondrites, and heated CMs. Nuclear magnetic resonance (NMR) spectroscopy, C X‐ray absorption near‐edge (XANES), and Fourier transform infrared (FTIR) spectroscopy confirm and quantitate this transformation from CR‐like, relatively aliphatic IOM functional group chemistry to a highly aromatic one. The transformation is almost certainly thermally driven, and probably occurred under hydrothermal conditions. The lack of a paramagnetic shift in 13C NMR spectra and 1s‐σ* exciton in the C‐XANES spectra, both typically seen in metamorphosed chondrites, shows that the temperatures were lower and/or the timescales were shorter than experienced by even the least metamorphosed type 3 chondrites. Two endmember models were considered to quantitatively account for the changes in IOM functional group chemistry, but the one in which the transformations involved quantitative conversion of aliphatic material to aromatic material was the more successful. It seems likely that similar processes were involved in producing the diversity of IOM compositions and functional group chemistries among CR, CM, and CI chondrites. If correct, CRs experienced the lowest temperatures, while CM and CI chondrites experienced similar more elevated temperatures. This ordering is inconsistent with alteration temperatures based on mineralogy and O isotopes.
Mars 2020 Mission Overview Farley, Kenneth A.; Williford, Kenneth H.; Stack, Kathryn M. ...
Space science reviews,
12/2020, Letnik:
216, Številka:
8
Journal Article
Recenzirano
The Mars 2020 mission will seek the signs of ancient life on Mars and will identify, prepare, document, and cache a set of samples for possible return to Earth by a follow-on mission. Mars 2020 and ...its
Perseverance
rover thus link and further two long-held goals in planetary science: a deep search for evidence of life in a habitable extraterrestrial environment, and the return of martian samples to Earth for analysis in terrestrial laboratories.
The Mars 2020 spacecraft is based on the design of the highly successful Mars Science Laboratory and its
Curiosity
rover, but outfitted with a sophisticated suite of new science instruments. Ground-penetrating radar will illuminate geologic structures in the shallow subsurface, while a multi-faceted weather station will document martian environmental conditions. Several instruments can be used individually or in tandem to map the color, texture, chemistry, and mineralogy of rocks and regolith at the meter scale and at the submillimeter scale. The science instruments will be used to interpret the geology of the landing site, to identify habitable paleoenvironments, to seek ancient textural, elemental, mineralogical and organic biosignatures, and to locate and characterize the most promising samples for Earth return. Once selected, ∼35 samples of rock and regolith weighing about 15 grams each will be drilled directly into ultraclean and sterile sample tubes.
Perseverance
will also collect blank sample tubes to monitor the evolving rover contamination environment.
In addition to its scientific instruments,
Perseverance
hosts technology demonstrations designed to facilitate future Mars exploration. These include a device to generate oxygen gas by electrolytic decomposition of atmospheric carbon dioxide, and a small helicopter to assess performance of a rotorcraft in the thin martian atmosphere.
Mars 2020 entry, descent, and landing (EDL) will use the same approach that successfully delivered
Curiosity
to the martian surface, but with several new features that enable the spacecraft to land at previously inaccessible landing sites. A suite of cameras and a microphone will for the first time capture the sights and sounds of EDL.
Mars 2020’s landing site was chosen to maximize scientific return of the mission for astrobiology and sample return. Several billion years ago Jezero crater held a 40 km diameter, few hundred-meter-deep lake, with both an inflow and an outflow channel. A prominent delta, fine-grained lacustrine sediments, and carbonate-bearing rocks offer attractive targets for habitability and for biosignature preservation potential. In addition, a possible volcanic unit in the crater and impact megabreccia in the crater rim, along with fluvially-deposited clasts derived from the large and lithologically diverse headwaters terrain, contribute substantially to the science value of the sample cache for investigations of the history of Mars and the Solar System. Even greater diversity, including very ancient aqueously altered rocks, is accessible in a notional rover traverse that ascends out of Jezero crater and explores the surrounding Nili Planum.
Mars 2020 is conceived as the first element of a multi-mission Mars Sample Return campaign. After Mars 2020 has cached the samples, a follow-on mission consisting of a fetch rover and a rocket could retrieve and package them, and then launch the package into orbit. A third mission could capture the orbiting package and return it to Earth. To facilitate the sample handoff,
Perseverance
could deposit its collection of filled sample tubes in one or more locations, called depots, on the planet’s surface. Alternatively, if
Perseverance
remains functional, it could carry some or all the samples directly to the retrieval spacecraft.
The Mars 2020 mission and its
Perseverance
rover launched from the Eastern Range at Cape Canaveral Air Force Station, Florida, on July 30, 2020. Landing at Jezero Crater will occur on Feb 18, 2021 at about 12:30 PM Pacific Time.
This study examined nine pristine samples representing seven lithologies of the ungrouped C2 carbonaceous chondrite Tagish Lake from the University of Alberta Meteorite Collection using scanning ...electron microscope and electron probe microanalyzer analyses to characterize the sulfide mineralogy, textures, and compositions present. Four distinct sulfide morphologies were identified including pyrrhotite containing exsolved pentlandite, unexsolved pyrrhotite, and unexsolved pentlandite, and a unique “bull’s‐eye” sulfide morphology. The at% Fe/Ni of the pyrrhotite grains within these samples decreases with increasing degree of alteration and roughly places them in the alteration order of TL11v chip1 < TL4 < TL11v chip2 < TL5b ≤ TL10a < TL 11h < TL1 < TL11i. The at% Fe/Ni of low Ni (<1 wt% Ni) pyrrhotite indicates that the overall degree of alteration of Tagish Lake lies between that of CM1/2 and CI chondrites. Comparison of the composition of the sulfides to established Fe‐Ni‐S phase diagrams at different temperatures indicates two separate generations of sulfide formation. They are (1) high‐temperature formation of exsolved pyrrhotite–pentlandite and much of the unexsolved pentlandite at ~500–600 °C, likely by cooling of a monosulfide solid solution melt during chondrule formation; and (2) low‐temperature formation of unexsolved pyrrhotite, some unexsolved pentlandite, pyrrhotite containing flame‐like pentlandite bodies, and bull’s‐eye sulfides at ~25–100 °C, likely formed during aqueous alteration events on the Tagish Lake parent body.
Compound-specific carbon isotope analysis (delta(exp 13)C) of meteoritic organic compounds can be used to elucidate the abiotic chemical reactions involved in their synthesis. The soluble organic ...content of the Murchison carbonaceous chondrite has been extensively investigated over the years, with a focus on the origins of amino acids and the potential role of Strecker-cyanohydrin synthesis in the early solar system. Previous delta(exp 13)C investigations have targeted alpha-amino acid and alpha-hydroxy acid Strecker products and reactant HCN; however, delta(exp 13)C values for meteoritic aldehydes and ketones (Strecker precursors) have not yet been reported. As such, the distribution of aldehydes and ketones in the cosmos and their role in prebiotic reactions have not been fully investigated. Here, we have applied an optimized O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA) derivatization procedure to the extraction, identification, and delta(exp 13)C analysis of carbonyl compounds in the Murchison meteorite. A suite of aldehydes and ketones, dominated by acetaldehyde, propionaldehyde, and acetone, were detected in the sample. delta(exp 13)C values, ranging from -10.0(0/00) to +66.4(0/00), were more (exp 13)C-depleted than would be expected for aldehydes and ketones derived from the interstellar medium, based on interstellar (exp 12)C/(exp 13)C ratios. These relatively (exp 13)C-depleted values suggest that chemical processes taking place in asteroid parent bodies (e.g., oxidation of the IOM) may provide a secondary source of aldehydes and ketones in the solar system. Comparisons between delta(exp 13)C compositions of meteoritic aldehydes and ketones and other organic compound classes were used to evaluate potential structural relationships and associated reactions, including Strecker synthesis and alteration-driven chemical pathways.
The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater’s sedimentary delta, finding that ...the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide–rich water under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core samples of these rocks have been stored aboard Perseverance for potential return to Earth.
Igneous rocks in Jezero crater
The Perseverance rover landed in Jezero crater on Mars in February 2021. Farley
et al
. describe the geologic units investigated by the rover as it began to traverse the crater floor, based on images and spectroscopy. The authors found that the rocks are of igneous origin, later modified by reactions with liquid water. They also describe the collection of drilled samples for potential return to Earth by another spacecraft. Liu
et al
. present compositional data for these igneous rocks based on x-ray fluorescence measurements. They found similarities with some Martian meteorites and conclude that the igneous rocks formed from crystals that sank in a thick sheet of magma. Together, these studies constrain the history of Jezero crater and provide geological context for analysis of the drill samples. —KTS
Jezero crater on Mars contains igneous rocks that were modified by liquid water, samples of which were collected by the Perseverance rover.
INTRODUCTION
The Perseverance rover landed in Jezero crater on Mars on 18 February 2021 with three scientific objectives: to explore the geologic setting of the crater, to identify ancient habitable environments and assess the possibility of past martian life, and to collect samples for potential transport to Earth for analysis in laboratories. In the 290 martian days (sols) after landing, Perseverance explored rocks of the Jezero crater floor.
RATIONALE
Jezero, a 45-km-diameter crater, was selected for investigation by Perseverance because orbital observations had shown that it previously contained an open-system lake, prior to ~3.5 billion years ago. Major climate change then left Mars in its current cold and dry state. On Earth, broadly similar environments of similar age to Jezero contain evidence of microbial life. Jezero crater contains a well-preserved delta, identified as a target for astrobiological investigation by the rover. Perseverance landed ~2 km away from the delta, on rocks of the crater floor. Previously proposed origins for these rocks have ranged from lake (or river) sediments to lava flows. Olivine-rich rocks identified on the crater floor, as well as in the area surrounding Jezero, have previously been attributed to a widely distributed impact melt or volcanic deposit, variably altered to carbonate. We used Perseverance to investigate the origin of the crater floor rocks and to acquire samples of them.
RESULTS
The Jezero crater floor consists of two geologic units: the informally named Máaz formation covers much of the crater floor and surrounds the other unit, which is informally named the Séítah formation. Máaz rocks display a range of morphologies: structureless boulders, flagstone-like outcrops, and ridges that are several meters high. The ridges expose prominent layers, ranging in thickness from a few centimeters to a few tens of centimeters. Rocks of Séítah are often tabular and strongly layered, with layer thicknesses ranging from centimeters to meters. Máaz and Séítah rocks display no outcrop or grain-scale evidence for transport by wind or water.
Perseverance observations show that the Máaz rocks consist of 0.5- to 1-mm interlocking crystals of pyroxene and plagioclase. Combined with bulk chemical composition measurements, this suggests Máaz is an igneous unit that cooled slowly. In contrast, most Séítah rocks are very rich in magnesium and are dominated by densely packed 2- to 3-mm-diameter crystals of olivine, surrounded by pyroxene. These properties indicate settling and accumulation of olivine near the base of a thick magma body, such as an intrusion, lava lake, or thick lava flow. Ground-penetrating radar indicates that Séítah rocks dip beneath the Máaz formation. We hypothesize that Máaz could be the magmatic complement to the Séítah olivine-rich rocks or, alternatively, Máaz could be a series of basaltic lavas that flowed over and around the older Séítah formation.
The olivines in the Séítah formation are rimmed with magnesium-iron carbonate, likely produced by interaction with CO
2
-rich water. Máaz formation rocks contain an aqueously deposited iron oxide or iron silicate alteration product. Both units commonly contain patches of bright-white salts, including sodium perchlorate and various sulfate minerals. Although both rock units have been altered by water, preservation of the original igneous minerals and the absence of aluminous clay minerals indicate that the alteration occurred under low water/rock ratio and that there was little loss of soluble species to the surroundings. It remains unclear when these aqueous processes occurred and whether they relate to the lake that once filled Jezero.
The exposure of the olivine-rich Séítah rocks at the surface, the absence of lake or river sediment in the exploration area, and several nearby erosional remnant hills of delta sediment indicate that substantial crater floor erosion occurred after formation of these igneous units.
Samples of both of these geologic units were collected as drill cores. The drill cores were stored in ultraclean sample tubes, for potential transport to Earth by future missions in the early 2030s.
CONCLUSION
The floor of Jezero crater explored by Perseverance consists of two distinct igneous units that have both experienced reactions with liquid water. Multiple rock cores were collected from these units for potential transport to Earth and analysis in terrestrial laboratories.
Sample collection by Perseverance on Mars.
This image mosaic was acquired by the WATSON camera on the rover’s robot arm. Rock cores were drilled from the two holes (arrow) in an igneous rock of the Máaz formation. The 6-cm-long, 1.3-cm-diameter cores were sealed into individual sample tubes and are now stored inside the rover.
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