Ion weathering of the surface of the Martian moon Phobos as inferred from MAVEN ion observations

2020 ◽  
Author(s):  
Quentin Nenon ◽  
Andrew Poppe
Keyword(s):  
Solar Wind ◽  
Molecular Oxygen ◽  
Alpha Particles ◽  
Space Weathering ◽  
The Moon ◽  
Atmospheric Escape ◽  
Flux Measurements ◽  
The One ◽  
Energy Dependent ◽  
Sputtering Yields

<p>Phobos is the closest of the two moons of Mars and its surface is not only exposed to ions coming from the solar wind (mainly protons H+ and alpha particles He<sup>++</sup>), but is also bombarded by ions coming from Mars itself (mainly atomic and molecular oxygen ions O<sup>+</sup> and O<sub>2</sub><sup>+</sup>). Space weathering at Phobos would be intimately linked to the planetary atmospheric escape if Martian ions significantly alter the properties of the moon’s surface.<br />In this presentation, the long-term averaged ion environment seen by the surface of Phobos (omnidirectional and directional fluxes, and composition) is constructed from 4 years of ion measurements gathered in-situ by the NASA MAVEN mission. The MAVEN spacecraft repeatedly crossed the orbit of Phobos from January 2015 to February 2019 and was uniquely suited to unprecedently observe ions there with its three ion instruments: SWIA, STATIC, and SEP. These three experiments together constrain the entire range of ion kinetic energies that impact Phobos, from cold ions of a few eV to solar energetic ions of several MeV. In addition, the STATIC instrument (1 eV to 30 keV) is able to discriminate the mass of the observed ions by measuring their time-of-flight. This capability is important to understand the weathering of the surface of Phobos, as for instance the effect on the surface of a precipitating heavy molecular oxygen ion is significantly different from the one of a proton.<br />The relative importance of Martian and solar wind ions is in turn assessed from the observed ion omnidirectional fluxes for two space weathering effects: (1) surface sputtering, which is computed by using ion specie and energy-dependent sputtering yields available in the literature and (2) the production of vacancies inside the regolith grains, which is estimated with the SRIM software. (1) We find that Martian ions dominate solar wind ions in sputtering the surface of Phobos when the moon crosses the Martian magnetotail. We also reveal that molecular oxygen O<sub>2</sub><sup>+</sup> ions sputter as much as or more from the surface of Phobos than atomic O<sup>+</sup> ions. (2) Martian heavy ions significantly contribute to the production of vacancies in the uppermost nanometer of Phobos regolith grains. Finally, MAVEN directional flux measurements are used to study the anisotropy of the bombarding ion fluxes at Phobos, which we find implies an asymmetric weathering of the surface: the near side (always facing Mars) is primarily weathered by Martian ions, whereas the far side is primarily altered by solar wind ions. </p>

Implantation of ions escaping the atmosphere of Mars within the regolith of Phobos, and Phobos’ surface ion weathering

2020 ◽  
Author(s):  
Quentin Nénon ◽  
Andrew R Poppe ◽  
Ali Rahmati ◽  
James P McFadden
Keyword(s):  
Solar Wind ◽  
Atomic Oxygen ◽  
The Moon ◽  
Ion Composition ◽  
Atmospheric Escape ◽  
The Past ◽  
Lunar Samples ◽  
Singly Charged

<p>Mars has lost and is losing its atmosphere into space. Strong evidences of this come from the observation of planetary singly charged heavy ions (atomic oxygen, molecular oxygen, carbon dioxide ions) by Mars Express and MAVEN. Phobos, the closest moon of Mars, orbits only 6,000 kilometers above the red planet’s surface and is therefore a unique vantage point of the planetary atmospheric escape, with the escaping ions being implanted within the regolith of Phobos and altering the properties of the moon’s surface.</p> <p>In this presentation, we aggregate all ion observations gathered in-situ close to the orbit of Phobos by three ion instruments onboard MAVEN, from 2015 to 2019, to constrain the long-term averaged ion environment seen by the Martian moon at all longitudes along its orbit. In particular, the SupraThermal and Thermal Ion Composition (STATIC) instrument onboard MAVEN distinguishes between solar wind and planetary ions. The newly constrained long-term ion environment seen by Phobos is combined with numerical simulations of ion transport and effects in matter.</p> <p>This way, we find that planetary ions are implanted on the near side of Phobos (pointing towards Mars) inside the uppermost tens of nanometers of regolith grains. The composition of near-side grains that may be sampled by future Phobos sample return missions is therefore not only contaminated by planetary ions, as seen in lunar samples with the terrestrial atmosphere, but may show a unique record of the past atmosphere of Mars.</p> <p>The long-term fluxes of planetary ions precipitating onto Phobos are so intense that these ions weather the moon’s surface as much as or more than solar wind ions. In particular, Martian ions accelerate the long-term sputtering and amorphization of the near side regolith by a factor of 2. Another implication is that ion weathering is highly asymmetric between the near side and far side of Phobos.</p>

Combining Experiments and Modelling to Understand the Role of Potential Sputtering by Solar Wind Ions

2020 ◽  
Author(s):  
Paul Stefan Szabo ◽  
Herbert Biber ◽  
Noah Jäggi ◽  
Matthias Brenner ◽  
David Weichselbaum ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar System ◽  
Surface Composition ◽  
Space Weathering ◽  
Mineral Surfaces ◽  
Multiply Charged ◽  
History Of ◽  
System 2 ◽  
Sputtering Yields ◽  
Weathering Effects

<p>In the absence of a protecting atmosphere, the surfaces of rocky bodies in the solar system are affected by significant space weathering due to the exposure to the solar wind [1]. Fundamental knowledge of space weathering effects, such as optical changes of surfaces as well as the formation of an exosphere is essential for gaining insights into the history of planetary bodies in the solar system [2]. Primarily the exospheres of Mercury and Moon are presently of great interest and the interpretation of their formation processes relies on the understanding of all space weathering effects on mineral surfaces.</p><p>Sputtering of refractory elements by solar wind ions is one of the most important release processes. We investigate solar wind sputtering by measuring and modelling the sputtering of pyroxene samples as analogues for the surfaces of Mercury and Moon [3, 4]. These measurements with thin film samples on Quartz Crystal Microbalance (QCM) substrates allow recording of sputtering yields in-situ and in real time [5]. For the simulation of kinetic sputtering from the ion-induced collision cascade we use the software SDTrimSP with adapted input parameters that consistently reproduce measured kinetic sputtering yields [4, 6].</p><p>This study focuses on investigating the potential sputtering of insulating samples by multiply charged ions [7]. Changes of these sputtering yields with fluence are compared to calculations with a model based on inputs from SDTrimSP simulations. This leads to a very good agreement with steady-state sputtering yields under the assumption that only O atoms are sputtered by the potential energy of the ions. The observed decreasing sputtering yields can be explained by a partial O depletion on the surface [4]. Based on these findings expected surface composition changes and sputtering yields under realistic solar wind conditions can be calculated. Our results are in line with previous investigations (see e.g. [8, 9]), creating a consistent view on solar wind sputtering effects from experiments to established modelling efforts.</p><p> </p><p><strong>References:</strong></p><p>[1]          B. Hapke, J. Geophys. Res.: Planets, <strong>106</strong>, 10039 (2001).</p><p>[2]          P. Wurz, et al., Icarus, <strong>191</strong>, 486 (2007).</p><p>[3]          P.S. Szabo, et al., Icarus, <strong>314</strong>, 98 (2018).</p><p>[4]          P.S. Szabo, et al., submitted to Astrophys. J. (2020).</p><p>[5]          G. Hayderer, et al., Rev. Sci. Instrum., <strong>70</strong>, 3696 (1999).</p><p>[6]          A. Mutzke, et al., “SDTrimSP Version 6.00“, IPP Report, (2019).</p><p>[7]          F. Aumayr, H. Winter, Philos. Trans. R. Soc. A, <strong>362</strong>, 77 (2004).</p><p>[8]          H. Hijazi, et al., J. Geophys. Res.: Planets, <strong>122</strong>, 1597 (2017).</p><p>[9]          S.T. Alnussirat, et al., Nucl. Instrum. Methods Phys. Res. B, <strong>420</strong>, 33 (2018).</p>

scholarly journals Moon Mapping Project Results on Solar Wind Ion Flux and Composition

Universe ◽  
2021 ◽  
Vol 7 (5) ◽  
pp. 157
Author(s):  
Francesco Nozzoli ◽  
Pietro Richelli
Keyword(s):  
Solar Wind ◽  
Solar Activity ◽  
Ministry Of Education ◽  
The Moon ◽  
Remotely Sensed Data ◽  
The Earth ◽  
Space Agency ◽  
Time Variations ◽  
Italian Space Agency ◽  
The One

The “Moon Mapping” project is a collaboration between the Italian and Chinese Governments allowing cooperation and exchange between students from both countries. The main aim of the project is to analyze remotely-sensed data collected by the Chinese space missions Chang’E-1/2 over the Moon surface. The Italian Space Agency is responsible for the Italian side and the Center of Space Exploration, while the China Ministry of Education is responsible for the Chinese side. In this article, we summarize the results of the “Moon Mappining” project topic #1: “map of the solar wind ion” using the data collected by Chang’E-1 satellite. Chang’E-1 is a lunar orbiter, its revolution period lasts 2 h, and its orbit is polar. The satellite is equipped with two Solar Wind Ion Detectors (SWIDs) that are two perpendicular electrostatic spectrometers mapping the sky with a field of view of 15° × 6.7° × 24 ch. The spectrometers can measure solar wind flux in the range 40 eV/q–17 keV/q with an energy resolution of 8% and time resolution of ∼3 s. The data collected by the two Solar Wind Ion Detectors are analyzed to characterize the solar wind flux and composition on the Moon surface and to study the time variations due to the solar activity. The data measured by Chang’E-1 compared with the one measured in the same period by the electrostatic spectrometers onboard the ACE satellite, or with another solar activity indicator as the sunspot number, enrich the multi-messenger/multi-particle view of the Sun, gathering valuable information about the space weather outside the Earth magnetosphere.

scholarly journals Space Weathering Asymmetrically Alters Lunar Crater Walls

Eos ◽  
2018 ◽  
Vol 99 ◽  
Author(s):  
Sarah Stanley
Keyword(s):  
Solar Wind ◽  
Optical Properties ◽  
Space Weathering ◽  
Lunar Crater ◽  
The Moon ◽  
Main Driver

Directional differences in craters’ optical properties suggest that the solar wind, not tiny meteorites, is the main driver of space weathering on the Moon.

Mineral powder samples for solar wind ion sputtering experiments relevant for Moon and Mercury

2020 ◽  
Author(s):  
Noah Jäggi ◽  
André Galli ◽  
Peter Wurz ◽  
Herbert Biber ◽  
Paul S. Szabo ◽  
...  
Keyword(s):  
Thin Films ◽  
Solar Wind ◽  
The Moon ◽  
Before And After ◽  
First Results ◽  
Powder Samples ◽  
Mineral Powder ◽  
Singly Charged ◽  
Mir Spectra ◽  
Sputtering Yields

<p>The surfaces of Mercury and Moon are thought to be similar in terms of being rocky, regolith covered planetary bodies, dominated by pyroxene and plagioclase (Taylor et al. 1991, McCoy et al. 2018). Contrary to the Moon, Mercury possesses a global dipole magnetic field, resulting in a highly dynamic magnetosphere that varies surface exposure to solar wind ions and energetic electrons (Winslow et al. 2017, Gershman et al. 2015). The energy of these particles is thereby transferred and material is sputtered from the surface (Sigmund 2012), providing the main contributions to the exospheres of the Moon and Mercury. Parametrizing the underlying sputtering processes is of great interest for successfully linking exosphere observations with surface compositions (e.g. Wurz et al. 2010, Merkel et al. 2018).</p><p>The understanding of sputtering from the kinetic energy transfer is sufficient to predict sputter yields of singly charged impinging ions on conducting surfaces (e.g., Stadlmayr et al. 2018). Hijazi et al. (2017) and Szabo et al. (2018) have also made advancements on potential sputtering, investigating the interaction of multiply charged ions with glassy thin films. We expand on their studies and use mineral powder pellets as analogues for sputtering experiments relevant to the surfaces of the Moon and Mercury. The powder pellets include plagioclase, pyroxene, and wollastonite. The latter is a pyroxene-like Ca-rich mineral with Fe contents below detection limits, which allows investigating the effect on reflectivity during sputtering of Fe-free minerals. With these analogues, we strive to supply infrared spectra with a focus on the robust mid infrared (MIR) range for Mercury and sputter yields for both the Moon and Mercury. </p><p>First results of irradiated mineral pellets include MIR spectra of the minerals before and after irradiation as well as sputtering yields and visual alteration effects. So far, no relevant changes in the MIR spectra were observed nor any visual alteration of wollastonite. The first irradiation with 4 keV <sup>4</sup>He<sup>+</sup> reached a fluence of about 29 E+20 ions per m<sup>2</sup> at an angle of 30°. Presumably, the lack of visual alteration is due to the absence of Fe in wollastonite. Further results are expected to bring clarity in the reaction of pellets to irradiation and if their sputtering characteristics differ from those of glassy thin films.</p><p>Gershman, D. J., et al. (2015). J. Geophys. Res.-Space, 120(10).</p><p>Hiesinger, H., & Helbert, J. (2010). Planet. Space Sci., 58(1–2).</p><p>Hijazi, H., et al. (2017). J. Geophys. Res.-Planet, 122(7).</p><p>McCoy, T. J., et al. (2018). Mercury: The View after MESSENGER.</p><p>Sigmund, P. (2012). Thin Solid Films, 520(19).</p><p>Stadlmayr, R., et al. (2018). Nucl. Instrum. Meth. B, 430.</p><p>Szabo, P. S., et al. (2018). Icarus, 314.</p><p>Taylor, G. J., et al. (1991). Lunar sourcebook-A user’s guide to the moon.</p><p>Winslow, R. M., et al. (2017). J. Geophys. Res.-Space, 122(5).</p><p> </p>

scholarly journals Is There Water Ice in the Lunar Polar Craters?

2020 ◽  
Author(s):  
Tianxi Sun
Keyword(s):  
Solar Wind ◽  
Solid State ◽  
Hydroxyl Radicals ◽  
Low Temperatures ◽  
Hydroxyl Groups ◽  
The Moon ◽  
Water Ice ◽  
Spectral Identity ◽  
The One

This literature review found that it is doubtful that there is water ice in the polar craters on the Moon. In the course of this review, the following findings were found: (1) The absorption strength of hydroxyl radicals and hydroxyl groups are all 2.9μm, so it is easy to confuse hydroxyl radicals and hydroxyl groups when interpreting M3 spectra data. I do not doubt the ability of LCROSS to detect OH from water, but only suspect that LCROSS is unable to distinguish between hydroxyl radicals from water ice and hydroxyl groups from Moon's methanol due to ignore their spectral identity; (2) The water brought by comets and asteroids and the one caused by solar wind has been exhausted by reacts with the widespread methanol on the Moon in the presence of Pt/α-MoC or Pt/C catalysts. These reacts form large amount of hydrogen, thus clarifying a question NASA raised that "Scientists have long speculated about the source of vast quantities of hydrogen that have been observed at the lunar poles"; (3) The vast quantities of hydrogen in lunar polar craters at extremely low temperatures might be in liquid or solid state now, easy to confuse with water ice. It seems that all our previous misconceptions about water ice in the lunar polar craters might be due to the neglect of the widespread chemical role of lunar methanol. It is necessary to conduct in-depth research in this field in the future.

scholarly journals Space weathering on the Moon: Farside-nearside solar wind precipitation asymmetry

2019 ◽  
Vol 166 ◽  
pp. 9-22 ◽  
Author(s):  
E. Kallio ◽  
S. Dyadechkin ◽  
P. Wurz ◽  
M. Khodachenko
Keyword(s):  
Solar Wind ◽  
Space Weathering ◽  
The Moon

Quantum Tunneling

2017 ◽  
Author(s):  
Frank S. Levin
Keyword(s):  
Quantum Tunneling ◽  
Alpha Particles ◽  
Attractive Potential ◽  
Scanning Tunneling ◽  
Finite Width ◽  
Potential Well ◽  
Surface Molecules ◽  
Repulsive Coulomb ◽  
The Subject ◽  
The One

Quantum tunneling, wherein a quanject has a non-zero probability of tunneling into and then exiting a barrier of finite width and height, is the subject of Chapter 13. The description for the one-dimensional case is extended to the barrier being inverted, which forms an attractive potential well. The first application of this analysis is to the emission of alpha particles from the decay of radioactive nuclei, where the alpha-nucleus attraction is modeled by a potential well and the barrier is the repulsive Coulomb potential. Excellent results are obtained. Ditto for the similar analysis of proton burning in stars and yet a different analysis that explains tunneling through a Josephson junction, the connector between two superconductors. The final application is to the scanning tunneling microscope, a device that allows the microscopic surfaces of solids to be mapped via electrons from the surface molecules tunneling into the tip of the STM probe.

scholarly journals Coordinated analysis of space weathering characteristics in lunar samples to understand water distribution on the Moon

2021 ◽  
Vol 27 (S1) ◽  
pp. 2260-2262
Author(s):  
Alexander Kling ◽  
Michelle Thompson ◽  
Jennika Greer ◽  
Philipp Heck
Keyword(s):  
Water Distribution ◽  
Space Weathering ◽  
The Moon ◽  
Lunar Samples

Foreshock ULF fluctuations near the Moon: THEMIS observations

2021 ◽  
Author(s):  
Anna Salohub ◽  
Jana Šafránková ◽  
Zdeněk Němeček
Keyword(s):  
Solar Wind ◽  
Rest Frame ◽  
Low Frequency ◽  
Solar Wind Plasma ◽  
Turbulent Plasma ◽  
Bow Shock ◽  
Ulf Waves ◽  
The Moon ◽  
Shock Surface ◽  
The Earth

<p>The foreshock is a region filled with a turbulent plasma located upstream the Earth’s bow shock where interplanetary magnetic field (IMF) lines are connected to the bow shock surface. In this region, ultra-low frequency (ULF) waves are generated due to the interaction of the solar wind plasma with particles reflected from the bow shock back into the solar wind. It is assumed that excited waves grow and they are convected through the solar wind/foreshock, thus the inner spacecraft (close to the bow shock) would observe larger wave amplitudes than the outer (far from the bow shock) spacecraft. The paper presents a statistical analysis of excited ULF fluctuations observed simultaneously by two closely separated THEMIS spacecraft orbiting the Moon under a nearly radial IMF. We found that ULF fluctuations (in the plasma rest frame) can be characterized as a mixture of transverse and compressional modes with different properties at both locations. We discuss the growth and/or damping of ULF waves during their propagation.</p>

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