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Register a new userUnderstanding and Mitigating Plume Effects During Powered Descents on the Moon and Mars
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This 2020 Decadal Survey White Paper reviews what is known about lunar and martian lander Plume Surface Interactions (PSI) during powered descent. This includes an overview of the phenomenology and a description of the induced hardware and environmental impacts. Then it provides an overview of mitigation techniques and a summary of the outstanding questions and strategic knowledge gaps. It finishes with five recommendations: to include dedicated descent imagers on every surface mission so that PSI can be directly recorded and reviewed by ground teams; as far as possible, to make all data related to PSI effects publicly accessible; to develop methods and instruments for making key measurements of PSI; to assess and record key flight data; and to invest funding into studies of long-term infrastructure architectures and mitigation techniques.
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We present initial analysis and conclusions from plasma observations made during the reported Mars plume event of March - April 2012. During this period, multiple independent amateur observers detected a localized, high-altitude plume over the Martian dawn terminator [Sanchez-Lavega et al., Nature, 2015, doi:10.1038/nature14162], the cause of which remains to be explained. The estimated brightness of the plume exceeds that expected for auroral emissions, and its projected altitude greatly exceeds that at which clouds are expected to form. We report on in-situ measurements of ionospheric plasma density and solar wind parameters throughout this interval made by Mars Express, obtained over the same surface region, but at the opposing terminator. Measurements in the ionosphere at the corresponding location frequently show a disturbed structure, though this is not atypical for such regions with intense crustal magnetic fields. We tentatively conclude that the formation and/or transport of this plume to the altitudes where it was observed could be due in part to the result of a large interplanetary coronal mass ejection (ICME) encountering the Martian system. Interestingly, we note that the only similar plume detection in May 1997 may also have been associated with a large ICME impact at Mars.
In order for off-Earth top surface structures built from regolith to protect astronauts from radiation, they need to be several meters thick. Technical University Delft (TUD) proposes to excavate into the ground to create subsurface habitats. By excavating not only natural protection from radiation can be achieved but also thermal insulation because the temperature is more stable underground. At the same time through excavation valuable resources can be mined for through in situ resource utilization (ISRU). The idea is that a swarm of autonomous mobile robots excavate the ground in a sloped downwards spiral movement. The excavated regolith will be mixed with cement, which can be reproduced on Mars through ISRU, in order to create concrete. The concrete is 3D printed/sprayed on the excavated tunnel to reinforce it. As soon as the tunnels are reinforced, the material in-between the tunnels can be removed in order to create a larger cavity that can be used for inhabitation. Proposed approach relies on Design-to-Robotic-Production (D2RP) technology developed at TUD1 for on-Earth applications. The rhizomatic 3D printed structure is a structurally optimized porous shell structure with increased insulation properties. In order to regulate the indoor pressurised environment an inflatable structure is placed in the 3D printed cavity. This inflatable structure is made of materials, which can also be at some point reproduced on Mars through ISRU. Depending on location the habitat and the production system are powered by a system combining solar and kite power. The ultimate goal is to develop an autarkic D2RP system for building subsurface autarkic habitats on Mars from locally obtained materials.
Lockdown periods in response to COVID-19 have provided a unique opportunity to study the impacts of economic activity on environmental pollution (e.g. NO$_2$, aerosols, noise, light). The effects on NO$_2$ and aerosols have been very noticeable and readily demonstrated, but that on light pollution has proven challenging to determine. The main reason for this difficulty is that the primary source of nighttime satellite imagery of the earth is the SNPP-VIIRS/DNB instrument, which acquires data late at night after most human nocturnal activity has already occurred and much associated lighting has been turned off. Here, to analyze the effect of lockdown on urban light emissions, we use ground and satellite data for Granada, Spain, during the COVID-19 induced confinement of the citys population from March 14 until May 31, 2020. We find a clear decrease in light pollution due both to a decrease in light emissions from the city and to a decrease in anthropogenic aerosol content in the atmosphere which resulted in less light being scattered. A clear correlation between the abundance of PM10 particles and sky brightness is observed, such that the more polluted the atmosphere the brighter the urban night sky. An empirical expression is determined that relates PM10 particle abundance and sky brightness at three different wavelength bands.
The Los Alamos National Laboratory designed and built Mars Odyssey Neutron Spectrometer (MONS) has been in excellent health operating from February 2002 to the present. MONS measures the neutron leakage albedo from galactic cosmic ray bombardment of Mars. These signals can indicate the presence of near-surface water deposits on Mars, and can also be used to study properties of the seasonal polar CO$_2$ ice caps. This work outlines a new analysis of the MONS data that results in new and extended time-series maps of MONS thermal and epithermal neutron data. The new data are compared to previous publications on the MONS instrument. We then present preliminary results studying the inter-annual variability in the polar regions of Mars based on 8 Mars-Years of MONS data from the new dataset.
The Mars Express (MEX) mission has been successfully operated around Mars since 2004. Among many results, MEX has provided some of the most accurate astrometric data of the two Mars moons, Phobos and Deimos. In this work we present new ephemerides of Mars moons benefitting from all previously published astrometric data to the most recent MEX SRC data. All in all, observations from 1877 until 2018 and including spacecraft measurements from Mariner 9 to MEX were included. Assuming a homogeneous interior, we fitted Phobos forced libration amplitude simultaneously with the Martian tidal k2/Q ratio and the initial state of the moons. Our solution of the physical libration 1.09 +/- 0.01 degrees deviates notably from the homogeneous solution. But considering the very low error bar, this may essentially suggest the necessity to consider higher order harmonics, with an improved rotation model, in the future. While most data could be successfully fitted, we found a disagreement between the Mars Reconnaissance Orbiter and the Mars Express astrometric data at the kilometer level probably associated with a biased phase correction. The present solution precision is expected at the level of a few hundreds of meters for Phobos and several hundreds of meters for Deimos for the coming years. The real accuracy of our new ephemerides will have to be confirmed by confrontation with independent observational means.
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