We study the 2018 Martian global dust storm (GDS 2018) over the Southern Polar Region using images obtained by the Visual Monitoring Camera (VMC) on board Mars Express (MEx) during June and July ...2018. Dust penetrated into the polar cap region but never covered the cap completely, and its spatial distribution was nonhomogeneous and rapidly changing. However, we detected long but narrow aerosol curved arcs with a length of ~2,000–3,000 km traversing part of the cap and crossing the terminator into the nightside. Tracking discrete dust clouds allowed measurements of their motions that were toward the terminator with velocities up to 100 m/s. The images of the dust projected into the Martian limb show maximum altitudes of ~70 km but with large spatial and temporal variations. We discuss these results in the context of the predictions of a numerical model for dust storm scenario.
Plain Language Summary
Dust storms of different scales (local, regional, etc.) are common on Mars. Some Martian years a regional storm activates secondary storms and dust encircles the planet, in a dust event usually called a global dust storm. The last global dust storm took place in 2018, and we are not currently able to predict when a new one will occur. Global dust storms affect the global dynamics of the Martian atmosphere, and the dynamics of the polar regions is a good proxy to the global situation. In this paper, we take advantage of the polar orbit of Mars Express to study the Southern Polar Region during 2018 global dust storm using the Visual Monitoring Camera onboard the spacecraft. We show how the dust penetrated into the polar cap, the apparition of aerosol arcs curved around the pole, and the presence of winds blowing up to 100 m/s, not following the usual patterns expected with no global dust storm.
Key Points
The 2018 global dust storm propagated unevenly over the South Polar Region, not covering it fully, and forming elongated narrow dust arcs
Overall, dust moved toward the terminator, reaching velocities up to 100 m/s in the morningside
During June–July 2018, the top altitude of dust showed both spatial and temporal variability, ranging from 10–70 km
Abstract
The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading ...technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
We report a previously unnoticed annually repeating phenomenon consisting of the daily formation of an extremely elongated cloud extending as far as 1,800 km westward from Arsia Mons. It takes place ...in the solar longitude (Ls) range of ∼220°–320°, around the Southern solstice. We study this Arsia Mons Elongated Cloud (AMEC) using images from different orbiters, including ESA Mars Express, NASA MAVEN, Viking 2, MRO, and ISRO Mars Orbiter Mission (MOM). We study the AMEC in detail in Martian year (MY) 34 in terms of local time and Ls and find that it exhibits a very rapid daily cycle: the cloud growth starts before sunrise on the western slope of the volcano, followed by a westward expansion that lasts 2.5 h with a velocity of around 170 m/s in the mesosphere (∼45 km over the areoid). The cloud formation then ceases, detaches from its formation point, and continues moving westward until it evaporates before the afternoon, when most sun‐synchronous orbiters make observations. Moreover, we comparatively study observations from different years (i.e., MYs 29–34) in search of interannual variations and find that in MY33 the cloud exhibits lower activity, while in MY34 the beginning of its formation was delayed compared with other years, most likely due to the Global Dust Storm. This phenomenon takes place in a season known for the general lack of clouds on Mars. In this paper we focus on observations, and a theoretical interpretation will be the subject of a separate paper.
Plain Language Summary
In September and October 2018, the Visual Monitoring Camera onboard Mars Express observed a spectacular water ice cloud extending as far as 1,800 km westward from the Arsia Mons Volcano on Mars. This curious extremely elongated cloud caught the attention of the public (http://www.esa.int/Science_Exploration/Space_Science/Mars_Express/Mars_Express_keeps_an_eye_on_curious_cloud). We study this Arsia Mons Elongated Cloud (AMEC) with the aid of several instruments orbiting Mars. We find that the AMEC repeated regularly each morning for a number of months, and that it is an annually repeating phenomenon that takes place every Martian year around the Southern Hemisphere during spring and summer. The AMEC follows a rapid daily cycle: it starts to expand from Arsia Mons at dawn at an altitude of about ∼45 km, and for ∼2.5 h it expands westward as fast as 170 m/s (around 600 km/h). The cloud then detaches from Arsia Mons and evaporates before noon. In previous Martian years, few observations of this phenomenon are available because most cameras orbiting Mars are placed in orbits where they can only observe during the afternoon, whereas this cloud takes place in the early morning, when the observational coverage is much lower.
Key Points
We report a new phenomenon consisting of an extremely elongated water ice cloud (up to 1,800 km) extending westward from the Arsia Mons volcano
The cloud reaches the mesosphere (45 km), and expands at a velocity of around 170 m/s in Martian Year 34.
This cloud repeatedly forms in the early mornings, and repeats in a daily cycle between Ls 220° and 320° every Martian year
Perseverance’s Mastcam-Z instrument provides high-resolution stereo and multispectral images with a unique combination of spatial resolution, spatial coverage, and wavelength coverage along the ...rover’s traverse in Jezero crater, Mars. Images reveal rocks consistent with an igneous (including volcanic and/or volcaniclastic) and/or impactite origin and limited aqueous alteration, including polygonally fractured rocks with weathered coatings; massive boulder-forming bedrock consisting of mafic silicates, ferric oxides, and/or iron-bearing alteration minerals; and coarsely layered outcrops dominated by olivine. Pyroxene dominates the iron-bearing mineralogy in the fine-grained regolith, while olivine dominates the coarse-grained regolith. Solar and atmospheric imaging observations show significant intra- and intersol variations in dust optical depth and water ice clouds, as well as unique examples of boundary layer vortex action from both natural (dust devil) and Ingenuity helicopter–induced dust lifting. High-resolution stereo imaging also provides geologic context for rover operations, other instrument observations, and sample selection, characterization, and confirmation.
The first samples collected by the Perseverance rover on the Mars 2020 mission were from the Maaz formation, a lava plain that covers most of the floor of Jezero crater. Laboratory analysis of these ...samples back on Earth would provide important constraints on the petrologic history, aqueous processes, and timing of key events in Jezero crater. However, interpreting these samples requires a detailed understanding of the emplacement and modification history of the Maaz formation. Here we synthesize rover and orbital remote sensing data to link outcrop‐scale interpretations to the broader history of the crater, including Mastcam‐Z mosaics and multispectral images, SuperCam chemistry and reflectance point spectra, Radar Imager for Mars' subsurface eXperiment ground penetrating radar, and orbital hyperspectral reflectance and high‐resolution images. We show that the Maaz formation is composed of a series of distinct members corresponding to basaltic to basaltic‐andesite lava flows. The members exhibit variable spectral signatures dominated by high‐Ca pyroxene, Fe‐bearing feldspar, and hematite, which can be tied directly to igneous grains and altered matrix in abrasion patches. Spectral variations correlate with morphological variations, from recessive layers that produce a regolith lag in lower Maaz, to weathered polygonally fractured paleosurfaces and crater‐retaining massive blocky hummocks in upper Maaz. The Maaz members were likely separated by one or more extended periods of time, and were subjected to variable erosion, burial, exhumation, weathering, and tectonic modification. The two unique samples from the Maaz formation are representative of this diversity, and together will provide an important geochronological framework for the history of Jezero crater.
Plain Language Summary
The Perseverance rover on the Mars 2020 mission is collecting samples from Jezero crater for potential return to Earth via Mars Sample Return, and the first samples collected by the rover were from the Maaz formation, a lava plain that covers much of the crater floor. These igneous samples can be used to date when the lavas crystallized and to better understand their subsequent interactions with water, both of which will be important for reconstructing the history of habitable environments in Jezero crater. In this study we use images and reflectance spectra from the rover and orbiters, along with ground penetrating radar from the rover, to determine the history of the Maaz formation lavas. We find evidence for significant erosion and weathering in between successive flows, suggesting that they were emplaced over a long period of time. Some of the lavas underlie the Jezero delta, and so their age will provide limits on the timing of lake activity in Jezero crater, while others retain craters, so their age will help to better understand crater density‐based age estimates for surfaces across Mars.
Key Points
The Maaz formation is a series of pyroxene‐ and plagioclase‐dominated lava flows on the Jezero crater floor with variable morphologies
Significant erosion and tectonism occurred during at least one flow hiatus, suggesting emplacement over an extended period of time
The crystallization ages of Maaz formation samples will help constrain the timing of delta activity and the global cratering chronology
We examine the observed properties of the Nili Fossae olivine-clay-carbonate
lithology from orbital data and in situ by the Mars 2020 rover at the
S\'e\'itah unit in Jezero crater, including: 1) ...composition (Liu, 2022) 2)
grain size (Tice, 2022) 3) inferred viscosity (calculated based on geochemistry
collected by SuperCam (Wiens, 2022)). Based on the low viscosity and
distribution of the unit we postulate a flood lava origin for the
olivine-clay-carbonate at S\'e\'itah. We include a new CRISM map of the clay
2.38 {\mu}m band and use in situ data to show that the clay in the olivine
cumulate in the S\'e\'itah formation is consistent with talc or serpentine from
Mars 2020 SuperCam LIBS and VISIR and MastCam-Z observations. We discuss two
intertwining aspects of the history of the lithology: 1) the emplacement and
properties of the cumulate layer within a lava lake, based on terrestrial
analogs in the Pilbara, Western Australia, and using previously published
models of flood lavas and lava lakes, and 2) the limited extent of post
emplacement alteration, including clay and carbonate alteration (Clave, 2022;
Mandon, 2022).
We report a previously unnoticed annually repeating phenomenon consisting of the daily formation of an extremely elongated cloud extending as far as 1800 km westward from Arsia Mons. It takes place ...in the Solar Longitude (Ls) range of ~220-320, around the Southern solstice. We study this Arsia Mons Elongated Cloud (AMEC) using images from different orbiters, including ESA Mars Express, NASA MAVEN, Viking 2, MRO, and ISRO Mars Orbiter Mission (MOM). We study the AMEC in detail in Martian Year (MY) 34 in terms of Local Time and Ls and find that it exhibits a very rapid daily cycle: the cloud growth starts before sunrise on the western slope of the volcano, followed by a westward expansion that lasts 2.5 hours with a velocity of around 170 m/s in the mesosphere (~45 km over the areoid). The cloud formation then ceases, it detaches from its formation point, and continues moving westward until it evaporates before the afternoon, when most sun-synchronous orbiters observe. Moreover we comparatively study observations from different years (i.e. MYs 29-34) in search of interannual variations and find that in MY33 the cloud exhibits lower activity, whilst in MY34 the beginning of its formation was delayed compared to other years, most likely due to the Global Dust Storm. This phenomenon takes place in a season known for the general lack of clouds on Mars. In this paper we focus on observations, and a theoretical interpretation will be the subject of a separate paper.
We examine the observed properties of the Nili Fossae olivine-clay-carbonate lithology from orbital data and in situ by the Mars 2020 rover at the Séítah unit in Jezero crater, including: 1) ...composition (Liu, 2022) 2) grain size (Tice, 2022) 3) inferred viscosity (calculated based on geochemistry collected by SuperCam (Wiens, 2022)). Based on the low viscosity and distribution of the unit we postulate a flood lava origin for the olivine-clay-carbonate at Séítah. We include a new CRISM map of the clay 2.38 {\mu}m band and use in situ data to show that the clay in the olivine cumulate in the Séítah formation is consistent with talc or serpentine from Mars 2020 SuperCam LIBS and VISIR and MastCam-Z observations. We discuss two intertwining aspects of the history of the lithology: 1) the emplacement and properties of the cumulate layer within a lava lake, based on terrestrial analogs in the Pilbara, Western Australia, and using previously published models of flood lavas and lava lakes, and 2) the limited extent of post emplacement alteration, including clay and carbonate alteration (Clave, 2022; Mandon, 2022).
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