Abstract The seismometer deployed on the surface of Mars as part of the InSight mission ( In terior Exploration using S eismic I nvestigations, G eodesy and H eat T ransport) has recorded several hundreds of marsquakes in the first 478 sols after landing. The majority of these are classified as high‐frequency (HF) events in the frequency range from approximately 1 to 10 Hz on Mars' surface. All the HF events excite a resonance around 2.4 Hz and show two distinct but broad arrivals of seismic energy that are separated by up to 450 s. Based on the frequency content and vertical‐to‐horizontal energy ratio, the HF event family has been subdivided into three event types, two of which we show to be identical and only appear separated due to the signal‐to‐noise ratio. We show here that the envelope shape of the HF events is explained by guided Pg and Sg phases in the Martian crust using simple layered models with scattering. Furthermore, the relative travel times between these two arrivals can be related to the epicentral distance, which shows distinct clustering. The rate at which HF events are observed varies by an order of magnitude over the course of one year and cannot be explained by changes of the background noise only. The HF content and the absence of additional seismic phases constrain crustal attenuation and layering, and the coda shape constrains the diffusivity in the uppermost shallow layers of Mars.
Seismic observations of impacts on Mars indicate a higher impact flux than previously measured. Using six confirmed seismic impact detections near the NASA InSight lander and two distant large impacts, we calculate appropriate scalings to compare these rates with lunar-based chronology models. We also update the impact rate from orbital observations using the most recent catalog of new craters on Mars. The snapshot of the current impact rate at Mars recorded seismically is higher than that found using orbital detections alone. The measured rates differ between a factor of 2 and 10, depending on the diameter, although the sample size of seismically detected impacts is small. The close timing of the two largest new impacts found on Mars in the past few decades indicates either a heightened impact rate or a low-probability temporal coincidence, perhaps representing recent fragmentation of a parent body. We conclude that seismic methods of detecting current impacts offer a more complete dataset than orbital imaging.
Clues to a planet's geologic history are contained in its interior structure, particularly its core. We detected reflections of seismic waves from the core-mantle boundary of Mars using InSight seismic data and inverted these together with geodetic data to constrain the radius of the liquid metal core to 1830 ± 40 kilometers. The large core implies a martian mantle mineralogically similar to the terrestrial upper mantle and transition zone but differing from Earth by not having a bridgmanite-dominated lower mantle. We inferred a mean core density of 5.7 to 6.3 grams per cubic centimeter, which requires a substantial complement of light elements dissolved in the iron-nickel core. The seismic core shadow as seen from InSight's location covers half the surface of Mars, including the majority of potentially active regions-e.g., Tharsis-possibly limiting the number of detectable marsquakes.
The S1222a marsquake detected by InSight on May 4, 2022 somewhat resembled previous impact-generated events• We performed an image search in the estimated source region, using data from multiple Mars orbiter missions• No new impact crater has been discovered in this area, pointing to a tectonic origin for the quake.
Abstract We report confirmed impact sources for two seismic events on Mars detected by the NASA InSight mission. These events have been positively associated with fresh impact craters identified from orbital images, which match predicted locations and sizes to within a factor of 3, and have formation time constraints consistent with the seismic event dates. They are both of the very high frequency family of seismic events and are present with chirps (dispersed infrasound/acoustic waves). This brings the total number of confirmed Martian impact-related seismic events to eight thus far. All seismic events with chirp signals have now been confirmed as having been caused by impact cratering events. This includes all seismic activity within 100 km of the lander and two out of the four events with source locations between 100 and 300 km distance.
Abstract Geologic and climatic processes on modern‐day Mars are heavily influenced by aeolian surface activity, yet the relationship between atmospheric conditions and sediment mobilization is not well understood. The Interior Exploration using Seismic Investigations, Geodesy, and Heat Transport (InSight) spacecraft is uniquely able to address this issue, due to its joint imaging and continuous high‐frequency meteorological capabilities, which allow for direct comparison between surface activity and atmospheric conditions. Since landing in the volcanic plains of Elysium Planitia, InSight's camera's have recorded intermittent, small‐scale surface changes, including removal of fine material on the lander footpad, linear tracks and localized surface darkening caused by minor dust removal, and surface creep of granules, as presented in Part 1 (Charalambous et al., 2021, this issue). Surface activity is found to correlate well with the timing of abrupt pressure drops (Δ P ∼ 1–9 Pa) and transient wind gusts ( v ∼ 14–31 m/s) associated with convective vortex passage. Here we identify the major erosive forces acting on surface particles during these events, including the vertical pressure gradient force at the vortex core and the drag force generated by quickly‐rotating tangential winds. Orbital and ground‐truth data suggest that aeolian activity at InSight's landing site is sporadic under modern climatic conditions. Ongoing aeolian surface modifcation is driven primarily by turbulent vortices that sporadically lift dust and redistribute coarser sediment (i.e., sand and granules) but do not aid in the development of organized aeolian bedforms. Surface erosion is localized within the path these vortices take across the surface which is controlled by seasonally‐reversing background circulation patterns.
<p>On the 1222nd sol of the InSight mission (or May the Fourth of 2022), a seismic event was detected that turned out to be the largest marsquake recorded so far. At a moment magnitude of 4.7, event S1222a released as much seismic moment as all seismic events previously catalogued by InSight together, and greatly surpasses the second largest event, S0976a.</p><p>The frequency of occurrence of earthquakes follows a power law with an exponent (the <em>b</em> value) close to 1 over a wide range of magnitudes. The class of Low Frequency marsquakes, to which S1222a belongs, shows a similar behaviour. At low magnitudes, the slope of the cumulative distribution suggests that the InSight marsquake catalog for Low Frequency events is representative for events with moment magnitude exceeding 3 (Figure 1). Up to and including the occurrence of event S0976a one could however guess that events larger than magnitude approx. 3.6 might be less frequent than predicted by this power law. Event S1222a mends this apparent decrease, and the <em>b</em> value derived from all events is 1 within the formal uncertainty. Hence the resulting distribution follows a power law for events exceeding magnitude 3.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.0abf7cf6a48268660682561/sdaolpUECMynit/2202CSPE&app=m&a=0&c=df52b409c3c1a3cef4ec386a90d38821&ct=x&pn=gnp.elif&d=1" alt=""></p><p><strong>Figure 1 Size frequency distribution of Low Frequency and Broadband events. Red: status before occurrence of S1222a, blue: afterwards. The dashed lines represent the Maximum Likelihood solutions for fitting a Power Law distribution, with b-values as indicated in the legend.</strong></p><p>Since S0976a occurred at an epicentral distance of about 140&#176; (Horleston et al., 2022) at night time(02:26 LMST), but was recorded with amplitudes high enough to be visible during typical day time noise, we can infer that the catalog is complete for events the size of S0976a or larger. Since the slope of the distribution appears to be stable over the entire magnitude range from 3 up to that of S1222a, we conclude that the catalogue of Low Frequency events is not only representative, but complete for events larger than 3.</p><p>The magnitude of S1222a is slightly to the right of the value predicted by the power law, but, compared to other deviations, not excessively so. Also, the distribution does not show an indication of increasing slope any more. With about 30 events of magnitude 3 during the 3.3 years of InSight observations so far, this suggests that events larger than S1222a can be expected with respective recurrence rates: A magnitude 5 event appears likely about once in 11 years, i.e. on a decadal scale.</p><p>We use the approach of Knapmeyer et al. (2018) to estimate the seismic moment rate of Mars, and also the corner magnitude above which the size-frequency distribution becomes much steeper and events larger than the corner magnitude extremely unlikely (our analysis uses the Tapered Gutenberg-Richter distribution with an exponential roll-off above the corner frequency). The simple idea of Knapmeyer et al. (2018) was that, since a few large events release most of the seismic moment, the moment of the largest event ever observed, scaled with the duration covered by the catalog and a factor depending on <em>b</em> value and corner moment, provides a good estimation of the moment rate. Including not only the one largest, but the <em>n</em> largest events (with n between 1 and 10 or so) provides an even better estimation. In the 2018 study we have shown that the approach yields a surprisingly good estimation of the Earth's moment rate after a few months of registration, rather than after the many decades necessary to witness a magnitude 9 event.</p><p>We employ here an estimation based on the 5 largest events in the catalog. Knapmeyer et al. (2018) have shown that this low number may already provide a reasonable rate estimate. At the same time we attempt to avoid using events too small to be globally detectable. Future analyses will show if the use of 5 events is actually the best choice. The inclusion of event S1222a shifts the estimated moment rate slightly upwards, as well as the estimated corner moment. Figure 2 shows that both parameters are slightly below those of the WeakMany model of Knapmeyer et al., (2006). Compared to the catalog from before its occurrence, the parameter modifications due to S1222a are hardly significant (and not shown here). At least as important is the reduction of the uncertainty region in the moment-rate / corner-moment parameter space. We cannot yet exclude that the moment rate of Mars is as low as that of the Moon, but if it were, it would be rather unlikely to observe the event sequence that InSight observed.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.1c2bd657a48268570682561/sdaolpUECMynit/2202CSPE&app=m&a=0&c=e8e5c17853dfb5df63781bebe30b5dd1&ct=x&pn=gnp.elif&d=1" alt=""></p><p><strong>Figure 2 Estimation of Moment Rate and Corner Moment. For each Pixel, 10000 synthetic catalogs were evaluated to compare their parameters with the five largest events from the InSight catalog (KS<sub>5</sub> estimation). Colour indicates the probability that the five largest events drawn from a tapered Gutenberg Richter distribution in 3.3 years reproduce the KS5 estimation obtained from the observed events, to within an 80 %&#160; interdecile around the median. The vertical line indicates the moment rate for the Moon (observed, from Shallow Moonquakes), markers indicate the WeakMany and Medium models of Knapmeyer et al. (2006). The moment rate of the Earth corresponds to an equivalent magnitude of about 8.5 (Knapmeyer et al., 2018). Horizontal lines indicate the magnitude of the largest event and its uncertainty. The maximum of the distribution is marked by a small white circle.</strong></p><p>&#160;</p><p><strong>References</strong></p><p>Horleston, A. C., et al. (2022). The Far Side of Mars: Two Distant Marsquakes Detected by InSight, <em>The Seismic Record</em>. 2(2), 88&#8211;99, doi: 10.1785/0320220007</p><p>Knapmeyer, M., Oberst, J., Hauber, E., W&#228;hlisch, M., Deuchler, C., Wagner, R. (2006). Working models for spatial distribution and level of Mars' seismicity. <em>Journal of Geophysical Research</em>, vol. 111, E11006, doi:10.1029/2006JE002708</p><p>Knapmeyer, M., et al. (2018). Estimation of the Seismic Moment Rate from an Incomplete Seismicity Catalog, in the Context of the InSight Mission to Mars, <em>Bull. Seis. Soc. Am.</em>, vol. 109, No. 3, 1125-1147, doi: 10.1785/0120180258</p><p>Taylor et al., (2013). Estimates of seismic activity on the Cerberus Fossae region of Mars, <em>Journal of Geophysical Research</em>, vol. 118, 2570-2581, doi:10.1002/2013JE004469</p>
This repository contains derived data presented and described in the article “Super high frequency events: a new class of events recorded by the InSight seismometers on Mars” by Nikolaj L. Dahmen, John F. Clinton, Savas Ceylan, Martin van Driel, Domenico Giardini, Amir Khan, Simon C. Stähler, Maren Böse, Constantinos Charalambous, Anna Horleston, Taichi Kawamura, Guenolé Orhand-Mainsant, John-Robert Scholz, Fabian Euchner, William T. Pike, Renee C. Weber, Philippe Lognonné and William B. Banerdt, submitted to JGR Planets (2020). Information on the provided data is given in the README file
