The magnetic fields originate as coronal fields that are convected into space by the supersonic, infinitely conducting, solar wind. On average, the sun’s rotation causes the field to wind up and form an Archimedes Spiral. However, the field direction changes almost continuously on a variety of scales and the irregular nature of these changes is often interpreted as eviclence that the solar wind flow is turbulent. To a surprising extent, the large-scale field near the ecliptic (solar equator), where observations have been made (between 0.3 and 35 AU), appears to be dominated by dipole-like fields from the sun’s polar corona. The (open) field lines, however, are attached to the sun at only one end, the other end being carried off into the outer heliosphere by the solar wind. The oppositely-directed fields in the northern and southern hemispheres are separated by a thin, wavy current sheet that encloses the sun and extends throughout the heliosphere. A complication to this otherwise straight-forward description is the presence of solar wind structure associated with high speed streams that corotate with the Sun. Another cause of structure is the (frequent) presence of Coronal Mass Ejections whose origins, magnetic topology, internal dynamics and interaction with the pre-existing solar wind are still being actively studied. Recent interest has also been directed to understanding the topology of the field between the shock that is thought to terminate the supersonic solar wind flow and the heliopause. The three-dimensional field properties at high latitudes and in the vicinity of the polar heliosphere ha~’e attracted recent interest as a result of the Ulysses mission, A brief description of the recent results obtained when this spacecraft reached the Sun’s south pole are included.

The Jet Propulsion Laboratory

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. Description 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 CO2-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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Aqueously altered igneous rocks sampled on the floor of Jezero crater, Mars

The Perseverance rover landed in Jezero crater, Mars in February 2021. We used the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) instrument to perform deep ultraviolet Raman and fluorescence spectroscopy of three rocks within the crater. We identify evidence for two distinct ancient aqueous environments at different times. Reactions with liquid water formed carbonates in an olivine-rich igneous rock. A sulfate-perchlorate mixture is present in the rocks, probably formed by later modifications of the rocks by brine. Fluorescence signatures consistent with aromatic organic compounds occur throughout these rocks, preserved in minerals related to both aqueous environments. Description

http://spiral.imperial.ac.uk/bitstream/10044/1/102749/2/SchellerRazzellHollis_maintextandsupp_final_october2022.pdf

Aqueous alteration processes in Jezero crater, Mars−implications for organic geochemistry

Abstract The Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC) is a robotic arm-mounted instrument onboard NASA’s Perseverance rover. SHERLOC combines imaging via two cameras with both Raman and fluorescence spectroscopy to investigate geological materials at the rover’s Jezero crater field site. SHERLOC requires in situ calibration to monitor the health and performance of the instrument. These calibration data are critically important to ensure the veracity of data interpretation, especially considering the extreme martian environmental conditions where the instrument operates. The SHERLOC Calibration Target (SCT) is located at the front of the rover and is exposed to the same atmospheric conditions as the instrument. The SCT includes 10 individual targets designed to meet all instrument calibration requirements. An additional calibration target is mounted inside the instrument’s dust cover. The targets include polymers, rock, synthetic material, and optical pattern targets. Their primary function is calibration of parameters within the SHERLOC instrument so that the data can be interpreted correctly. The SCT was also designed to take advantage of opportunities for supplemental science investigations and includes targets intended for public engagement. The exposure of materials to martian atmospheric conditions allows for opportunistic science on extravehicular suit (i.e., “spacesuit”) materials. These samples will be used in an extended study to produce direct measurements of the expected service lifetimes of these materials on the martian surface, thus helping NASA facilitate human exploration of the planet. Other targets include a martian meteorite and the first geocache target to reside on another planet, both of which increase the outreach and potential of the mission to foster interest in, and enthusiasm for, planetary exploration. During the first 200 sols (martian days) of operation on Mars, the SCT has been analyzed three times and has proven to be vital in the calibration of the instrument and in assisting the SHERLOC team with interpretation of in situ data. 

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The SHERLOC Calibration Target on the Mars 2020 Perseverance Rover: Design, Operations, Outreach, and Future Human Exploration Functions

The NASA Mars 2020 Perseverance rover is currently exploring Jezero crater, a Noachian–Hesperian locality that once hosted a delta–lake system with high habitability and biosignature preservation potential. Perseverance conducts detailed appraisals of rock targets using a synergistic payload capable of geological characterization from kilometer to micron scales. The highest-resolution textural and chemical information will be provided by correlated WATSON (imaging), SHERLOC (deep-UV Raman and fluorescence spectroscopy), and PIXL (X-ray lithochemistry) analyses, enabling the distributions of organic and mineral phases within rock targets to be comprehensively established. Herein, we analyze Paleoarchean microbial mats from the ∼3.42 Ga Buck Reef Chert (Barberton greenstone belt, South Africa)—considered astrobiological analogues for a putative ancient martian biosphere—following a WATSON–SHERLOC–PIXL protocol identical to that conducted by Perseverance on Mars during all sampling activities. Correlating deep-UV Raman and fluorescence spectroscopic mapping with X-ray elemental mapping, we show that the Perseverance payload has the capability to detect thermally and texturally mature organic materials of biogenic origin and can highlight organic–mineral interrelationships and elemental colocation at fine spatial scales. We also show that the Perseverance protocol obtains very similar results to high-performance laboratory imaging, Raman spectroscopy, and μXRF instruments. This is encouraging for the prospect of detecting microscale organic-bearing textural biosignatures on Mars using the correlative micro-analytical approach enabled by WATSON, SHERLOC, and PIXL; indeed, laminated, organic-bearing samples such as those studied herein are considered plausible analogues of biosignatures from a potential Noachian–Hesperian biosphere. Were similar materials discovered at Jezero crater, they would offer opportunities to reconstruct aspects of the early martian carbon cycle and search for potential fossilized traces of life in ancient paleoenvironments. Such samples should be prioritized for caching and eventual return to Earth.

In Situ Identification of Paleoarchean Biosignatures Using Colocated Perseverance Rover Analyses: Perspectives for In Situ Mars Science and Sample Return

A deep-ultraviolet Raman and Fluorescence spectral library of 62 minerals for the SHERLOC instrument onboard Mars 2020

The SHERLOC instrument (Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals) is an ultraviolet (UV) Raman and fluorescence spectrometer that will be deployed on the Mars 2020 rover mission. The instrument includes a context microscopic imager with resolution of $10\ \mu\mathrm{m}$ , and the scanning laser has a spot size of $100\ \mu\mathrm{m}$ , which allows SHERLOC to generate spatially and spectrally resolved data cubes without contact with the Martian surface (typically ∼5 cm of standoff from an abraded surface); it is designed to detect and characterize organics and astrobiologically relevant minerals in the search for past life. The instrument is led by Jet Propulsion Laboratory (JPL) with electronics, software, and electronic ground support equipment provided by Los Alamos National Laboratory (LANL), among others. The instrument is composed of two main physical components: the SHERLOC body assembly (SBA) and the turret assembly (STA). The SBA resides in the main body of the rover and operates in a relatively benign environment, while the STA is mounted on the rover arm turret and experiences extreme temperature fluctuations. The SBA conditions power from the rover, interfaces with the rover for command and data handling, and provides the control for the scanner and spectrometer. The SBA incorporates a LEON3 processor that runs all of the spectroscopy flight software. The STA houses the laser, laser power supply, imagers, scanning mirror, optics, and charge coupled device detector. The STA and SBA communicate via Spacewire over 12m of flex circuit routed down the rover robotic arm. The instrument is designed to autonomously scan a sample scene of approximately 7 × 7 mm, process the resulting data, and then subsequently interrogate regions of interest with much higher spatial and spectral resolution. This paper will describe the instrument spectroscopy electronics design and operation. It will cover the sampling and acquisition of data from the CCD, the detector noise performance, as well as storage and transmission of data to the vehicle.

The Processing Electronics and Detector of the Mars 2020 SHERLOC Instrument

We report deep ultraviolet (DUV) Raman and Fluorescence spectra obtained on a SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals) analog instrument for 51 pure organic compounds, including 5 carboxylic acids, 10 polycyclic aromatic hydrocarbons, 24 amino acids, 6 nucleobases, and 6 different grades of macromolecular carbon from humic acid to graphite. Organic mixtures were not investigated. We discuss how the DUV fluorescence and Raman spectra exhibited by different organic compounds allow for detection, classification, and identification of organics by SHERLOC. We find that 1- and 2-ring aromatic compounds produce detectable fluorescence within SHERLOC's spectral range (250–355 nm), but fluorescence spectra are not unique enough to enable easy identification of particular compounds. However, both aromatic and aliphatic compounds can be identified by their Raman spectra, with the number of Raman peaks and their positions being highly specific to chemical structure, within SHERLOC's reported spectral uncertainty of ±5 cm−1. For compounds that are not in the Library, classification is possible by comparing the general number and position of dominant Raman peaks with trends for different kinds of organic compounds.

A Deep Ultraviolet Raman and Fluorescence Spectral Library of 51 Organic Compounds for the SHERLOC Instrument Onboard Mars 2020

A broadband, high efficiency polarized beam splitter (PBS) metagrating based on integrated resonant units (IRUs) to enable simultaneous polarization analysis, spectral dispersion, and spatial imaging in the near infrared (NIR) is developed. A PBS metagrating with a diameter of 60 mm is the key technology component of the high‐resolution multiple‐species atmospheric profiler in the NIR (HiMAP‐NIR), which is a spaceborne instrument concept crafted to be a core payload of NASA's new generation Earth System Observatory. HiMAP‐NIR will enable the aerosol profiling in Earth's planetary boundary layer (from surface to2 km altitude) by simultaneously measuring four spatial‐spectral‐polarimetric images from 680 to 780 nm. Through detailed optimization of hybridized resonant modes in IRUs, the PBS metagrating shows a diffraction efficiency of 70% (or better) for all four linear‐polarized incident light, and polarization contrasts between orthogonal states are 0.996 (or better) from 680 to 780 nm. It meets the stringent performance required by the HiMAP‐NIR exploiting a new paradigm for the broad applications of metasurfaces.

An Ultra‐Broadband High Efficiency Polarization Beam Splitter for High Spectral Resolution Polarimetric Imaging in the Near Infrared (Adv. Sci. 27/2022)

Austin Nordman

Papers

A deep-ultraviolet Raman and Fluorescence spectral library of 62 minerals for the SHERLOC instrument onboard Mars 2020

The Processing Electronics and Detector of the Mars 2020 SHERLOC Instrument

A Deep Ultraviolet Raman and Fluorescence Spectral Library of 51 Organic Compounds for the SHERLOC Instrument Onboard Mars 2020

An Ultra‐Broadband High Efficiency Polarization Beam Splitter for High Spectral Resolution Polarimetric Imaging in the Near Infrared (Adv. Sci. 27/2022)