Global characteristics of the small‐scale gravity wave (GW) field in the Martian atmosphere obtained from a high‐resolution general circulation model (GCM) are presented for the first time. The ...simulated GW‐induced temperature variances are in a good agreement with available radio occultation data in the lower atmosphere between 10 and 30 km. The model reveals a latitudinal asymmetry with stronger wave generation in the winter hemisphere and two distinctive sources of GWs: mountainous regions and the meandering winter polar jet. Orographic GWs are filtered, while propagating upward, and the mesosphere is primarily dominated by harmonics with faster horizontal phase velocities. Wave fluxes are directed mainly against the local wind. GW dissipation in the upper mesosphere generates body forces of tens of m s−1 per Martian solar day (sol−1), which tend to close the simulated jets. The results represent a realistic surrogate for missing observations, which can be used for constraining GW parameterizations and validating GCM simulations.
Key Points
First global distributions of small‐scale gravity waves on Mars from a new high‐resolution GCM
Simulated wave activity in the lower atmosphere is in a good agreement with available observations
First direct modeling validation of the predicted dynamical effects of GWs in the mesosphere of Mars
Former extent of glacier-like forms on Mars Brough, Stephen; Hubbard, Bryn; Hubbard, Alun
Icarus (New York, N.Y. 1962),
August 2016, 2016-08-00, 20160801, Letnik:
274
Journal Article
Recenzirano
Odprti dostop
•436 glacier-like forms (GLFs) show evidence of recession in Mars’ mid-latitudes.•Hemispheric distribution of recession indicates widespread climatic change.•Ice flow modelling is used to reconstruct ...the former extent of a case study GLF.•The reconstructed GLF lost an area of 6.85 km2 and ice volume of 0.31 km3.•Approximation suggests 135 km3 of ice removed from mid-latitude GLFs.
Mars’ mid-latitude glacier-like forms (GLFs) have undergone substantial mass loss and recession since a hypothesised last martian glacial maximum (LMGM) stand. To date, there is a lack of knowledge of the nature and timing of the LMGM, the subsequent mass loss and whether this mass loss has been spatially variable. Here, we present the results of a population-scale inventory of recessional GLFs, derived from analysis of 1293 GLFs33In their inventory Souness et al. (2012) identified 1309 GLFs. We refine the number of GLFs to 1293, due to the identification of duplicate entries. identified within Context Camera (CTX) imagery, to assess the distribution and controls on GLF recession. A total of 436 GLFs were identified showing strong evidence of recession: 197 in the northern hemisphere and 239 in the southern hemisphere. Relative to their parent populations, recessional GLFs are over-represented in the low latitude belts between 25 and 40° and in areas of high relief, suggesting that these zones exert some control over GLF sensitivity and response to forcing. This analysis is complemented by the reconstruction of the maximum extent and morphology of a specific GLF for which High Resolution Imaging Science Experiment (HiRISE) derived digital elevation data are available. Using Nye's (Nye, J.F. 1951 Proc. Roy. Soc. Lond, Ser. a—Mat. Phys. Sci., 207, 554–572) perfect plastic approximation of ice flow applied to multiple flow-lines under an optimum yield strength of 22kPa, we calculate that the reconstructed GLF has lost an area of 6.86 km2 with a corresponding volume loss of 0.31 km3 since the LMGM. Assuming the loss reconstructed at this GLF occurred at all mid-latitude GLFs yields a total planetary ice loss from Mars’ GLFs of 135 km3, similar to the current ice volume in the European Alps on Earth.
The MEGANE instrument onboard the MMX mission will acquire gamma-ray and neutron spectroscopy data of Phobos to determine the elemental composition of the martian moon and provide key constraints on ...its origin. To produce accurate compositional results, the irregular shape of Phobos and its proximity to Mars must be taken into account during the analysis of MEGANE data. The MEGANE team is adapting the Small Body Mapping Tool (SBMT) to handle gamma-ray and neutron spectroscopy investigations, building on the demonstrated record of success of the SBMT being applied to scientific investigations on other spacecraft missions of irregularly shaped bodies. This is the first application of the SBMT to a gamma-ray and neutron spectroscopy dataset, and the native, three-dimensional foundation of the SBMT is well suited to MEGANE’s needs. In addition, the SBMT will enable comparisons between the MEGANE datasets and other datasets of the martian moons, including data from previous spacecraft missions and MMX’s multi-instrument suite.
The seismometer Seismic Experiment for Interior Structure (SEIS) onboard the InSight lander was used to continuously record the seismicity on Mars from February 2019 to December 2022. To maximize the ...information that can be extracted from the seismic data, it is critical to identify and to suppress undesired features (e.g., environmental noise, scattered waves, seismic imprint of lander vibrations) and non‐seismic noise (e.g., instrument related artifacts). We present an advanced polarization filtering workflow in the time‐frequency domain to suppress undesired features and to enhance the signal‐to‐noise ratio of the SEIS recordings. We estimate time‐frequency‐dependent polarization attributes such as the ellipticity, directionality of the particle motion, and the degree of polarization to identify and filter out undesired data parts. After filtering in the time‐frequency domain, the seismic data are transformed back to the time domain, yielding broadband waveform data that can be used for further seismological analysis. We illustrate the benefits of our filtering approach with three use cases. Firstly, we show how polarization filtered data can help to constrain the source mechanism of the sol 1,222 event, the largest marsquake detected so far. Using the proposed polarization filtering techniques, we are able to enhance the S‐wave arrival by suppressing interfering randomly polarized scattered waves to successfully infer on the moment tensor of this event. Secondly, we show that polarization filters can be used to suppress instrument‐related glitches and, thirdly, to remove the seismic imprint left by the vibrating lander (mechanical resonances of the lander).
Plain Language Summary
The NASA InSight mission brought a seismometer to the surface of Mars that continuously monitored ground vibrations at the landing site. The goal was to record vibrations caused by marsquakes. Since seismic waves from marsquakes travel through the planet, such recordings contain information that allows scientists to image the interior structure of Mars. The signals from most of the quakes recorded by InSight are faint due to their low magnitudes and the large epicentral distance. Additionally, the recordings are contaminated by noise from local winds and the harsh temperature conditions on Mars lead to sudden stress relaxations inside the seismometer that are visible as distinct pulses (so‐called glitches) in the data stream. To accurately image the interior structure of the planet, it is of crucial importance to distinguish and separate such local, distorting signals from signals that originate from deeper parts of the planet. To do so, we make use of a method called polarization filtering, which is based on the analysis of the motion of the seismometer in three‐dimensional space as a function of time and frequency. We show that this motion is distinct for environmental noise, glitches, and marsquake signals and exploit it to clean the data from local disturbances.
Key Points
InSight's Seismic Experiment for Interior Structure (SEIS) data are contaminated by various types of seismic and non‐seismic noise components
Time‐frequency domain polarization filtering allows one to automatically identify and suppress undesired noise components
Polarization‐filtered waveform data enable a more stable moment tensor inversion and facilitate the interpretation of SEIS data
Since the internally-generated magnetic field of Mars is weak, strong coupling is expected between the solar wind, planetary magnetosphere, and planetary ionosphere. However, few previous ...observational studies of this coupling incorporated data that extended from the solar wind to deep into the ionosphere. Here we use solar wind, magnetosphere, and ionosphere data obtained by the Mars Express spacecraft during March/April 2010 to investigate this coupling. We focus on three case studies, each centered on a pair of ionospheric electron density profiles measured by radio occultations, where the two profiles in each pair were obtained from the same location at an interval of only a few days. We find that high dynamic pressures in the solar wind are associated with compression of the magnetosphere, heating of the magnetosheath, reduction in the vertical extent of the ionosphere, and abrupt changes in electron density at the top of the ionosphere. The first three of these associations are analogous to the behavior of the plasma environment of Venus, but the final one is not. These results reinforce the notion that changes in solar forcing influence the behaviors of all of the tightly coupled regions within the Martian plasma environment.
•Coordinated solar wind, magnetosphere, and ionosphere observations.•Variations in solar wind dynamic pressure.•Regions within the martian plasma environment are tightly coupled.
The final stage of terrestrial planet formation consists of the clean-up of residual planetesimals after the giant impact phase. Dynamically, a residual planetesimal population is needed to damp the ...high eccentricities and inclinations of the terrestrial planets to circular and coplanar orbits after the giant impact stage. Geochemically, highly siderophile element (HSE) abundance patterns inferred for the terrestrial planets and the Moon suggest that a total of about 0.01 M sub(+ in circle) of chondritic material was delivered as "late veneer" by planetesimals to the terrestrial planets after the end of giant impacts. Here, we combine these two independent lines of evidence for a leftover population of planetesimals and show that: (1) a residual population of small planetesimals containing 0.01 M sub(+ in circle) is able to damp the high eccentricities and inclinations of the terrestrial planets after giant impacts to their observed values. (2) At the same time, this planetesimal population can account for the observed relative amounts of late veneer added to the Earth, Moon, and Mars provided that the majority of the accreted late veneer was delivered by small planetesimals with radii <, ~10 m. These small planetesimal sizes are required to ensure efficient damping of the planetesimal's velocity dispersion by mutual collisions, which in turn ensures sufficiently low relative velocities between the terrestrial planets and the planetesimals such that the planets' accretion cross sections are significantly enhanced by gravitational focusing above their geometric values. Specifically, we find that, in the limit that the relative velocity between the terrestrial planets and the planetesimals is significantly less than the terrestrial planets' escape velocities, gravitational focusing yields a mass accretion ratio of Earth/Mars ~(rho sub(+ in circle)/rho sub(mars))(R sub(+ in circle)/R sub(mars)) super(4) ~ 17, which agrees well with the mass accretion ratio inferred from HSEs of 12-23. For the Earth-Moon system, we find a mass accretion ratio of ~200, which, as we show, is consistent with estimates of 150-700 derived from HSE abundances that include the lunar crust as well as the mantle component. We conclude that small residual planetesimals containing about ~1% of the mass of the Earth could provide the dynamical friction needed to relax the terrestrial planet's eccentricities and inclinations after giant impacts, and also may have been the dominant source for the late veneer added to Earth, Moon, and Mars.
Carbon dioxide (CO2) ice clouds have been routinely observed in the
middle atmosphere of Mars. However, there are still uncertainties concerning
physical mechanisms that control their altitude, ...geographical, and seasonal
distributions. Using the Max Planck Institute Martian General Circulation
Model (MPI-MGCM), incorporating a state-of-the-art whole atmosphere
subgrid-scale gravity wave parameterization (Yiğit et al., 2008), we
demonstrate that internal gravity waves generated by lower atmospheric
weather processes have a wide-reaching impact on the Martian climate.
Globally, GWs cool the upper atmosphere of Mars by ∼10 % and
facilitate high-altitude CO2 ice cloud formation. CO2 ice
cloud seasonal variations in the mesosphere and the mesopause region
appreciably coincide with the spatio-temporal variations of GW effects,
providing insight into the observed distribution of clouds. Our results
suggest that GW propagation and dissipation constitute a necessary physical
mechanism for CO2 ice cloud formation in the Martian upper atmosphere
during all seasons.
The Miniature Thermal Emission Spectrometer (Mini-TES) on Opportunity investigated the mineral abundances and compositions of outcrops, rocks, and soils at Meridiani Planum. Coarse crystalline ...hematite and olivine-rich basaltic sands were observed as predicted from orbital TES spectroscopy. Outcrops of aqueous origin are composed of 15 to 35% by volume magnesium and calcium sulfates a high-silica component modeled as a combination of glass, feldspar, and sheet silicates (~20 to 30%), and hematite; only minor jarosite is identified in Mini-TES spectra. Mini-TES spectra show only a hematite signature in the millimeter-sized spherules. Basaltic materials have more plagioclase than pyroxene, contain olivine, and are similar in inferred mineral composition to basalt mapped from orbit. Bounce rock is dominated by clinopyroxene and is close in inferred mineral composition to the basaltic martian meteorites. Bright wind streak material matches global dust. Waterlain rocks covered by unaltered basaltic sands suggest a change from an aqueous environment to one dominated by physical weathering.
The Space Race in the second half of the 20th century was primarily concerned with getting there and back. Gradually, technology and international collaboration opened new horizons, but human ...activity was mostly restricted around Earth’s orbit, while robotic missions were sent to solar system planets and moons. Now, nations and companies claim extraterrestrial resources and plans are in place to send humans and build bases on the Moon and Mars. Exploration and discovery are likely to be followed by exploitation and settlement. History suggests that the next step is the development of space industry. The new industrial revolution will take place in space. Chemical engineers have been educated for more than a century on designing processes adapted to the Earth’s conditions, involving a range of raw materials, atmospheric pressure, ambient temperature, solar radiation, and 1-g. In space, the raw materials differ, and the unique pressure, temperature and solar radiation conditions require new approaches and methods. In the era of space exploration, a new educational concept for chemical engineers is necessary to prepare them for playing key roles in space. To this end, we introduce Astrochemical Engineering as an advanced postgraduate course and we propose a 2-year 120 ECTS MEng curriculum with a brief description of the modules and learning outcomes. The first year includes topics such as low-gravity process engineering, cryogenics, and recycling systems. The second year includes the utilization of planetary resources and materials for space resources. The course culminates in an individual design project and comprises two specializations: Process Engineering and Space Science. The course will equip engineers and scientists with the necessary knowledge for the development of advanced processes and industrial ecologies based on closed self-sustained systems. These can be applied on Earth to help reinvent sustainability and mitigate the numerous challenges humanity faces.
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