MEVTV Workshop on Tectonic Features on Mars

The state of knowledge of tectonic features on Mars was determined and kinematic and mechanical models were assessed for their origin. Three sessions were held: wrinkle ridges and compressional structure; strike-slip faults; and extensional structures. Each session began with an overview of the features under discussion. In the case of wrinkle ridges and extensional structures, the overview was followed by keynote addresses by specialists working on similar structures on the Earth. The first session of the workshop focused on the controversy over the relative importance of folding, faulting, and intrusive volcanism in the origin of wrinkle ridges. The session ended with discussions of the origin of compressional flank structures associated with Martian volcanoes and the relationship between the volcanic complexes and the inferred regional stress field. The second day of the workshop began with the presentation and discussion of evidence for strike-slip faults on Mars at various scales. In the last session, the discussion of extensional structures ranged from the origin of grabens, tension cracks, and pit-crater chains to the origin of Valles Marineris canyons. Shear and tensile modes of brittle failure in the formation of extensional features and the role of these failure modes in the formation of pit-crater chains and the canyons of Valles Marineris were debated. The relationship of extensional features to other surface processes, such as carbonate dissolution (karst) were also discussed

Pathfinder landing sites at candidate SNC impact ejection sites

If Mars Pathfinder were able to land at a site on Mars from which the SNC meteorites were ejected by impact, the Pathfinder mission would essentially represent a very inexpensive sample return mission. Geologic units that contain four potential impact craters from which SNC meteorites could have been ejected from Mars are accessible to the Mars Pathfinder lander. Determining that SNC meteorites came from a particular spot on Mars raises the intriguing possibility of using Pathfinder as a sample return mission and providing a radiometric age for the considerably uncertain martian crater-age timescale. Pathfinder instruments are capable of determining if the rock type at the landing site is similar to that of one or more of the SNC meteorites, which would strengthen the hypothesis that the SNC meteorites did, in fact, come from Mars. Unfortunately, instrument observations from Pathfinder are probably not capable of determining if the geologic unit sampled by the lander is definitively the unit from which a SNC meteorite came from as opposed to Mars in general or perhaps a particular region on Mars. This abstract evaluates the possibility of landing at potential SNC ejection sites and the ability of Pathfinder to identify the landing site as the place from which an SNC meteorite came

The science process for selecting the landing site for the 2020 Mars rover

The process of identifying the landing site for NASA's Mars 2020 rover began in 2013 by defining threshold mission science criteria related to seeking signs of ancient habitable conditions, searching for biosignatures of past microbial life, assembling a returnable cache of samples for possible future return to Earth, and collecting data for planning eventual human missions to the surface of Mars. Mission engineering constraints on elevation and latitude were used to identify candidate landing sites that addressed the scientific objectives of the mission. However, for the first time these constraints did not have a major influence on the viability of candidate sites and, with the new entry, descent, and landing capabilities included in the baseline mission, the vast majority of sites were evaluated and down-selected on the basis of science merit. More than 30 candidate sites with likely acceptable surface and atmospheric conditions were considered at a series of open workshops in the years leading up to the launch. During that period, iteration between engineering constraints and the evolving relative science potential of candidate sites led to the identification of three final candidate sites: Jezero crater (18.4386°N, 77.5031°E), northeast (NE) Syrtis (17.8899°N,77.1599°E) and Columbia Hills (14.5478°S, 175.6255°E). The final landing site will be selected by NASA's Associate Administrator for the Science Mission Directorate. This paper serves as a record of landing site selection activities related primarily to science, an inventory of the number and variety of sites proposed, and a summary of the science potential of the highest-ranking sites

The science process for selecting the landing site for the 2020 Mars rover

The process of identifying the landing site for NASA's Mars 2020 rover began in 2013 by defining threshold mission science criteria related to seeking signs of ancient habitable conditions, searching for biosignatures of past microbial life, assembling a returnable cache of samples for possible future return to Earth, and collecting data for planning eventual human missions to the surface of Mars. Mission engineering constraints on elevation and latitude were used to identify candidate landing sites that addressed the scientific objectives of the mission. However, for the first time these constraints did not have a major influence on the viability of candidate sites and, with the new entry, descent, and landing capabilities included in the baseline mission, the vast majority of sites were evaluated and down-selected on the basis of science merit. More than 30 candidate sites with likely acceptable surface and atmospheric conditions were considered at a series of open workshops in the years leading up to the launch. During that period, iteration between engineering constraints and the evolving relative science potential of candidate sites led to the identification of three final candidate sites: Jezero crater (18.4386°N, 77.5031°E), northeast (NE) Syrtis (17.8899°N,77.1599°E) and Columbia Hills (14.5478°S, 175.6255°E). The final landing site will be selected by NASA's Associate Administrator for the Science Mission Directorate. This paper serves as a record of landing site selection activities related primarily to science, an inventory of the number and variety of sites proposed, and a summary of the science potential of the highest-ranking sites

Influence of Body Waves, Instrumentation Resonances, and Prior Assumptions on Rayleigh Wave Ellipticity Inversion for Shallow Structure at the InSight Landing Site

Based on an updated model of the regolith’s elastic properties, we simulate the ambient vibrations background wavefield recorded by InSight’s Seismic Experiment for Interior Structure (SEIS) on Mars to characterise the influence of the regolith and invert SEIS data for shallow subsurface structure. By approximately scaling the synthetics based on seismic signals of a terrestrial dust devil, we find that the high-frequency atmospheric background wavefield should be above the self-noise of SEIS’s SP sensors, even if the signals are not produced within 100–200 m of the station. We compare horizontal-to-vertical spectral ratios and Rayleigh wave ellipticity curves for a surface-wave based simulation on the one hand with synthetics explicitly considering body waves on the other hand and do not find any striking differences. Inverting the data, we find that the results are insensitive to assumptions on density. By contrast, assumptions on the velocity range in the upper-most layer have a strong influence on the results also at larger depth. Wrong assumptions can lead to results far from the true model in this case. Additional information on the general shape of the curve, i.e. single or dual peak, could help to mitigate this effect, even if it cannot directly be included into the inversion. We find that the ellipticity curves can provide stronger constraints on the minimum thickness and velocity of the second layer of the model than on the maximum values. We also consider the effect of instrumentation resonances caused by the lander flexible modes, solar panels, and the SEIS levelling system. Both the levelling system resonances and the lander flexible modes occur at significantly higher frequencies than the expected structural response, i.e. above 35 Hz and 20 Hz, respectively. While the lander and solar panel resonances might be too weak in amplitude to be recorded by SEIS, the levelling system resonances will show up clearly in horizontal spectra, the H/V and ellipticity curves. They are not removed by trying to extract only Rayleigh-wave dominated parts of the data. However, they can be distinguished from any subsurface response by their exceptionally low damping ratios of 1% or less as determined by random decrement analysis. The same applies to lander-generated signals observed in actual data from a Moon analogue experiment, so we expect this analysis will be useful in identifying instrumentation resonances in SEIS data

Properties and distribution of paired candidate stony meteorites at Meridiani Planum, Mars

The Mars Exploration Rover Opportunity investigated four rocks, informally dubbed Barberton, Santa Catarina, Santorini, and Kasos, that are possible stony meteorites. Their chemical and mineralogical composition is similar to the howardite, eucrite, and diogenite group but with additional metal, similar to mesosiderite silicate clasts. Because of their virtually identical composition and because they appear to represent a relatively rare group of meteorites, they are probably paired. The four rocks were investigated serendipitously several kilometers apart, suggesting that Opportunity is driving across a larger population of similar rock fragments, maybe a meteorite strewn field. Small amounts of ferric Fe are a result of weathering. We did not observe evidence for fusion crusts. Four iron meteorites were found across the same area. Although mesosiderites are stony irons, a genetic link to these irons is unlikely. The stony meteorites probably fell later than the irons. The current atmosphere is sufficiently dense to land such meteorites at shallow entry angles, and it would disperse fragments over several kilometers upon atmospheric breakup. Alternatively, dispersion by spallation from an impacting meteoroid may have occurred. Santa Catarina and a large accumulation of similar rocks were found at the rim of Victoria crater. It is possible that they are associated with the impactor that created Victoria crater, but our limited knowledge about their distribution cannot exclude mere coincidence

Continued Use of Exogenic Materials found on Mars as Planetary Research Tools

Exogenic materials (meteorites, micrometeorites and chemical tracers) are encountered both serendipitously and as campaign targets during Mars rover terrain traverse and reconnaissance. We advocate the continued study of these materials in-situ when encountered and permitted by extended and new Mars surface missions in the 2023–2032 decade.Whitepaper submitted to the Planetary Science and Astrobiology Decadal Survey 2023-2032. Additional co-authors: Sara Motaghian, Brandi L. Carrier, William H. Farrand, Marc D. Fries, Peter Grindrod, Andrew Langedam, Jérémie Lasue

The Marsquake Service: Securing Daily Analysis of SEIS Data and Building the Martian Seismicity Catalogue for InSight

Abstract The InSight mission expects to operate a geophysical observatory on Mars for at least two Earth years from late 2018. InSight includes a seismometer package, SEIS. The Marsquake Service (MQS) is created to provide a first manual review of the seismic data returned from Mars. The MQS will detect, locate, quantify and classify seismic events, whether tectonic or impact in origin. A suite of new and adapted methodologies have been developed to allow location and quantification of seismic events at the global scale using a single station, and a software framework has been developed that supports these methods. This paper describes the expected signals that will be recorded by SEIS, the methods used for their identification and interpretation, and reviews the planned MQS operational procedures. For each seismic event, the MQS will locate events using all available body and surface phases, using the best estimates of the Martian structure, which will become more accurate as more Martian marsquakes are identified and located. The MQS will curate the Mars seismicity catalogue, with all events being relocated to use revised suites of structure models as they are introduced