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The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP3 to measure the surface heat flow of the planet. The package uses temperature sensors that would have been brought to the target depth of 3–5 m by a small penetrator, nicknamed the mole. The mole requiring friction on its hull to balance remaining recoil from its hammer mechanism did not penetrate to the targeted depth. Instead, by precessing about a point midway along its hull, it carved a 7 cm deep and 5–6 cm wide pit and reached a depth of initially 31 cm. The root cause of the failure – as was determined through an extensive, almost two years long campaign – was a lack of friction in an unexpectedly thick cohesive duricrust. During the campaign – described in detail in this paper – the mole penetrated further aided by friction applied using the scoop at the end of the robotic Instrument Deployment Arm and by direct support by the latter. The mole tip finally reached a depth of about 37 cm, bringing the mole back-end 1–2 cm below the surface. It reversed its downward motion twice during attempts to provide friction through pressure on the regolith instead of directly with the scoop to the mole hull. The penetration record of the mole was used to infer mechanical soil parameters such as the penetration resistance of the duricrust of 0.3–0.7 MPa and a penetration resistance of a deeper layer (> 30 cm depth) of 4.9±0.4 MPa. Using the mole’s thermal sensors, thermal conductivity and diffusivity were measured. Applying cone penetration theory, the resistance of the duricrust was used to estimate a cohesion of the latter of 2–15 kPa depending on the internal friction angle of the duricrust. Pushing the scoop with its blade into the surface and chopping off a piece of duricrust provided another estimate of the cohesion of 5.8 kPa. The hammerings of the mole were recorded by the seismometer SEIS and the signals were used to derive P-wave and S-wave velocities representative of the topmost tens of cm of the regolith. Together with the density provided by a thermal conductivity and diffusivity measurement using the mole’s thermal sensors, the elastic moduli were calculated from the seismic velocities. Using empirical correlations from terrestrial soil studies between the shear modulus and cohesion, the previous cohesion estimates were found to be consistent with the elastic moduli. The combined data were used to derive a model of the regolith that has an about 20 cm thick duricrust underneath a 1 cm thick unconsolidated layer of sand mixed with dust and above another 10 cm of unconsolidated sand. Underneath the latter, a layer more resistant to penetration and possibly containing debris from a small impact crater is inferred. The thermal conductivity increases from 14 mW/m K to 34 mW/m K through the 1 cm sand/dust layer, keeps the latter value in the duricrust and the sand layer underneath and then increases to 64 mW/m K in the sand/gravel layer below., Space Science Reviews, 218 (8), ISSN:1572-9672, ISSN:0038-6308

The sedimentary infill of glacially overdeepened valleys (i.e., structures eroded below the fluvial base level) is an excellent but yet underexplored archive with regard to the age, extent, and nature of past glaciations. The ICDP project DOVE (Drilling Overdeepened Alpine Valleys) Phase 1 investigates a series of drill cores from glacially overdeepened troughs at several locations along the northern front of the Alps. All sites will be investigated with regard to several aspects of environmental dynamics during the Quaternary, with focus on the glaciation, vegetation, and landscape history. Geophysical methods (e.g., seismic surveys), for example, will explore the geometry of overdeepened structures to better understand the process of overdeepening. Sedimentological analyses combined with downhole logging, analysis of biological remains, and state-of-the-art geochronological methods, will enable us to reconstruct the erosion and sedimentation history of the overdeepened troughs. This approach is expected to yield significant novel data quantifying the extent and timing of Middle and Late Pleistocene glaciations of the Alps. In a first phase, two sites were drilled in late 2021 into filled overdeepenings below the paleolobe of the Rhine Glacier, and both recovered a trough filling composed of multiphase glacial sequences. Fully cored Hole 5068_1_C reached a depth of 165m and recovered 10m molasse bedrock at the base. This hole will be used together with two flush holes (5068_1_A, 5068_1_B) for further geophysical cross-well experiments. Site 5068_2 reached a depth of 255m and bottomed out near the soft rock-bedrock contact. These two sites are complemented by three legacy drill sites that previously recovered filled overdeepenings below the more eastern Alpine Isar-Loisach, Salzach, and Traun paleoglacier lobes (5068_3, 5068_4, 5068_5). All analysis and interpretations of this DOVE Phase 1 will eventually lay the ground for an upcoming Phase 2 that will complete the pan-Alpine approach. This follow-up phase will investigate overdeepenings formerly occupied by paleoglacier lobes from the western and southern Alpine margins through drilling sites in France, Italy, and Slovenia. Available geological information and infrastructure make the Alps an ideal area to study overdeepened structures; however, the expected results of this study will not be restricted to the Alps. Such features are also known from other formerly glaciated mountain ranges, which are less studied than the Alps and more problematic with regards to drilling logistics. The results of this study will serve as textbook concepts to understand a full range of geological processes relevant to formerly glaciated areas all over our planet., Scientific drilling, 31, ISSN:1816-8957, ISSN:1816-3459

Shallow 3-D reflection seismic surveys using S-waves have rarely been carried out, even though S-waves can provide higher resolution subsurface images than P-waves. We conducted a 3-D near-surface multicomponent source and receiver survey in Quaternary sediments. We employed a small electrodynamic seismic source with a horizontal shaking unit operated in two orientations. Three-component geophones in an orthogonal layout covering an area of 117×99 m2 were used for recording. Changes in weather and ground conditions, including freezing and thawing during acquisition, directly influenced the data quality and resulted in discernible relative time shifts in the data. Our seismic processing flow included a four-component rotation of the data from the Cartesian acquisition geometry into the ‘natural’ coordinate frame to orient sources and receivers in radial or transverse orientation to separate different S-wave polarizations. The rotation increased the signal strength and helped, for example, to improve the quality of the images of the basin base. The irregular offset distribution in the common midpoint gathers impedes filtering to suppress surface waves in the f–k domain. We, therefore, applied a common-reflection surface processing flow. After regularization, we could better remove the energy of the surface waves. Both stacked 3-D S-wave volumes of vertical and horizontal polarizations provide images of the Quaternary overdeepened Tannwald Basin that was partly known from previous P- and S-wave 2-D surveys. Compared to a P-wave profile adjacent to the volume, however, the S-wave volumes provide higher resolution images of the basin base and internal structure. The basin base is well mapped in three dimensions and shows undulations that were not obvious from the P-wave data. Comparing the S-wave volumes of different polarizations, we find only minor differences in the stacks and interpretations., Near Surface Geophysics, 20 (4), ISSN:1569-4445, ISSN:1873-0604

We analyzed the seismological data collected by the InSight mission, which landed on Mars in November 2018, in order to reveal the first tens of meters of the subsurface structure underneath the landing site. Here, we performed horizontal-to-vertical analysis (H/V) for different wind-dependent noise periods and for martian seismic events data (marsquakes). The final H/V curve presents a characteristic trough at 2.4 Hz and a strong peak at 8 Hz. We inverted this H/V curve for the 1D shear-wave velocity structure at the InSight landing site. Based on our inversion results, we propose a strong site effect at the InSight site to be due to the presence of a shallow high-velocity layer (SHVL) over low-velocity units. The SHVL is likely placed below a layer of coarse blocky ejecta and can be associated with Early Amazonian basaltic lava flows. The units below the SHVL have lower velocities, possibly related to a Late Hesperian or Early Amazonian epoch with a different magmatic regime and/or a greater impact rate and more extensive weathering. An extremely weak buried low-velocity layer (bLVL) between these lava flows explains the data around the 2.4 Hz trough, whereas a more competent bLVL would not generate this latter feature. These subsurface models are in good agreement with results from hammering experiments and compliance measurements at the InSight landing site. Finally, this site effect is revealed only by seismic events data and it explains the larger horizontal than vertical ground motion recorded for some marsquakes.

The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP3 to measure the surface heat flow of the planet. The package uses temperature sensors that would have been brought to the target depth of 3--5 m by a small penetrator, nicknamed the mole. The mole requiring friction on its hull to balance remaining recoil from its hammer mechanism did not penetrate to the targeted depth. Instead, by precessing about a point midway along its hull, it carved a 7 cm deep and 5-6 cm wide pit and reached a depth of initially 31 cm. The root cause of the failure - as was determined through an extensive, almost two years long campaign - was a lack of friction in an unexpectedly thick cohesive duricrust. During the campaign -- described in detail in this paper -- the mole penetrated further aided by friction applied using the scoop at the end of the robotic Instrument Deployment Arm and by direct support by the latter. The mole finally reached a depth of 40 cm, bringing the mole body 1--2 cm below the surface. The penetration record of the mole and its thermal sensors were used to measure thermal and mechanical soil parameters such as the thermal conductivity and the penetration resistance of the duricrust and its cohesion. The hammerings of the mole were recorded by the seismometer SEIS and the signals could be used to derive a P-wave velocity and a S-wave velocity and elastic moduli representative of the topmost tens of cm of the regolith. The combined data were used to derive a model of the regolith that has an about 20 cm thick duricrust underneath a 1 cm thick unconsolidated layer of sand mixed with dust and above another 10 cm of unconsolidated sand. Underneath the latter, a layer more resistant to penetration and possibly consisting of debris from a small impact crater is inferred., arXiv

On the 26th of November 2018, NASA’s InSight lander successfully touched down on the Martian ground in Elysium Planitia. The lander transported among other instruments a single three-component broadband seismometer to measure seismic events and subsequently determine the seismic activity level and eventually the internal structure of Mars. In this study we focus on characterizing the source mechanisms of the highest-quality marsquakes detected so far: The events with highest SNR occurred on sols 173 (S0173a, May 23rd 2019) and 235 (S0235b, July 27th 2019) with Mw > 3.5, showing clearly polarized P and S waves. The InSight MarsQuake Service has estimated their distances to be around 27 degrees, nearby the Cerberus Fossae Graben system. Two more events, S0183a and S0325b have less clear body wave phases and locations, but are also interpreted to be related to it.We have developed a grid-search based method to fit synthetic waveforms to the observed first arriving P and S wave trains. The four source parameters we invert for in this study are the three unique orientation angles of the source mechanism, strike (φ), dip (δ) and rake (λ), and the depth of the event. Synthetic seismograms are generated by computing Green’s functions based on the epicentral distance determined by the InSight MarsQuake Service (MQS) and radially symmetric velocity models. These Green’s function are then convolved with a source time function including an estimated global body wave attenuation to obtain realistic seismograms. The two high-quality event recordings originating from the Cerberus Fossae (CF) fault system were analyzed. Multiple velocity models, frequency bands and window lengths around the arriving phases were used to explore the non-uniqueness in the inverse problem of the inherently ambiguous single-station data. We found that using plausible structural models based on geophysical modeling, the first 10-15 seconds of the waveforms can be fit, constraining the source mechanism and depth, but that the estimation of the uncertainty remains challenging.

A 6 degrees-of-freedom (6DoF) sensor, measuring three components of translational acceleration and three components of rotation rate, provides the full history of motion it is exposed to. In Earth sciences 6DoF sensors have shown great potential in exploring the interior of our planet and its seismic sources. In space sciences, apart from navigation, 6DoF sensors are, up to now, only rarely used to answer scientific questions. As a first step of establishing 6DoF motion sensing deeper into space sciences, this article describes novel scientific approaches based on 6DoF motion sensing with substantial potential for constraining the interior structure of planetary objects and asteroids. Therefore we estimate 6DoF-signal levels that originate from lander–surface interactions during landing and touchdown, from a body’s rotational dynamics as well as from seismic ground motions. We discuss these signals for an exemplary set of target bodies including Dimorphos, Phobos, Europa, the Earth’s Moon and Mars and compare those to self-noise levels of state-of-the-art sensors., Earth, Planets and Space, 72 (1), ISSN:1343-8832, ISSN:1880-5981

EGUsphere

Geophysical Research Abstracts, 21, ISSN:1029-7006, ISSN:1607-7962

Geophysical Research Abstracts, 21, ISSN:1029-7006, ISSN:1607-7962

Geophysical Research Abstracts, 21, ISSN:1029-7006, ISSN:1607-7962

Geophysical Research Abstracts, 21, ISSN:1029-7006, ISSN:1607-7962

EPSC Abstracts, 132

Geophysical Research Abstracts, 21, ISSN:1029-7006, ISSN:1607-7962

Geophysical Research Abstracts, 20, ISSN:1029-7006, ISSN:1607-7962

Geophysical Research Abstracts, 20, ISSN:1029-7006, ISSN:1607-7962