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The InSight Mission began acquiring the first seismic data on Mars in early 2019 and has detected hundreds of events. The largest events recorded to date originate at Cerberus Fossae, a young volcanic region characterized by high volume, low viscosity lava flows. A handful of Low Frequency (LF) quakes that share key attributes of Long Period quakes recorded on Earth's volcanoes are also traced to Cerberus Fossae. This study explores whether a traditional volcanic source model that simulates the generation of tremor as pressurized fluid makes its way through a channel at depth, can explain these atypical LF events. We consider a wide range of physical parameters including fluid viscosity, the ratio of driving pressure to lithostatic pressure, aspect ratio of the channel, and the equilibrium channel opening. We find that the model can produce the observed seismic signature, with a combination of low‐viscosity magma and high volume flux of ∼104 − 105 m3/s that are within an order‐of‐magnitude agreement with Cerberus Fossae lava flow properties deduced from analysis of lava flow dimensions. It is impossible, however, at this stage to conclude whether or not this is a likely explanation for Mars, as the model results in fluxes that are extreme for Earth yet are just within bounds of what has been inferred for Cerberus Fossae. We therefore conclude that we cannot rule out active magma flow as the mechanism responsible for the atypical LF events that likely originate from Cerberus Fossae. Plain Language Summary: A number of Marsquakes are located at a region of Mars that hosted geologically recent volcanic eruptions. A subset of these events resemble seismic events recorded at volcanoes on Earth. We set out to study whether these events can be explained by fluid flow at depth, using a model of fluid flow through a channel. We find that low viscosities and high flow rates that are within an order‐of‐magnitude agreement with flow properties deduced from modeling of Cerberus Fossae lava flows are required to match the observed events in question. It is impossible at this stage of the InSight mission, however, to conclude whether or not this is a likely explanation for Mars. Key Points: Low Frequency (LF) events that share attributes of volcanic quakes are traced to a young volcanic region on MarsLF events are modeled as deep volcanic quakes caused by pressure‐driven flow across a channel at Cerberus FossaeLF attributes are matched by fluids less viscous and of higher fluxes than terrestrial flood basalts [ABSTRACT FROM AUTHOR]

Abstract: The thermal and volatile evolution of Mars has not been studied from the perspective of consistency with the preservation of the Martian global dichotomy and with estimates of the elastic thickness over time. We use three thermal evolution models for Mars: (1) stagnant lid, (2) early plate tectonics followed by stagnant lid, and (3) mantle overturn, to calculate the amount of relaxation of the dichotomy boundary and elastic thickness values for Noachian- and Hesperian-aged terrains. To explore a wide range of parameters, we evaluate two different initial mantle temperatures, and wet and dry rheologies. Our model results show that the relative water content of the crust has an effect roughly equal to 500K variations of initial mantle temperature. For all three thermal models, a lower crust viscosity of 1020–1021 Pas during the first 0.1Ga after formation of dichotomy would allow for the preservation of the long-wavelength topography of Mars and fitting of the elastic thickness. This viscosity range implies either wet, cold (∼1500K) lower crust, or dry, hot (∼2000K) lower crust in Noachian. Additional constraints are necessary to distinguish between the individual thermal models. For the stagnant lid model, neither the cold, wet crust nor the hot, dry crust agree with timing and amount of the crustal production [Hauck II., S.A., Phillips, R.J., 2002. Thermal and crustal evolution of Mars. J. Geophys. Res. 107, 5052]. Moreover, drying of the crust is required for this model in order to match the admittance elastic thickness at the Hesperian/Amazonian boundary implying remelting of the crust. The hot, dry crust in the early plate tectonics model limits a plate tectonic epoch to only 100–200Myr and implies dry mantle, which is in disagreement with water found in meteorites. The cold, wet crustal rheology implies the formation of crust during the plate tectonics regime because of the low crustal production during the stagnant lid regime. For mantle overturn, the temperature required for wet crust does not fit the original mantle profile while the dry crust does; however, in order to explain the initially hot thermal profile the crust must have been emplaced very fast. Generally, dry crustal rheology does not fit low elastic values in the Hesperian and implies either that rheology may differ between the southern and northern hemispheres: wet in northern hemisphere and dry in southern hemisphere, or that local weakening occurred. Wet crustal rheology fits well all elastic data except S. Hellas rim, which may be anomalous. Mantle rheology is unconstrained by our modeling and can be either dry or wet. [Copyright &y& Elsevier]

Abstract: We examine gravity, topography, and magnetic field data along the well-preserved Martian dichotomy boundary between 105° and 180°E to better understand the origin and modification of the dichotomy boundary. Admittance modeling indicates bottom-loading for the Amenthes region (105–135°E) with crustal and elastic thickness estimates of 15–40km, and 15–35km and top-loading for the Aeolis region (145–180°E) with crustal and elastic thickness estimates of 10–20km and 10–15km, respectively. There is a general trend from bottom-loading in the west, to top-loading in the east. The bottom-loading signature near Amenthes may reflect its proximity to the Isidis basin or a broad valley southeast of Isidis. Surface volcanic deposits may produce the top-loading seen at Aeolis. Additional processes such as erosion and faulting have clearly affected the dichotomy and may contribute to the loading signature. Low elastic thickness estimates are consistent with loading in the Noachian, when heat flow was high. Significant Bouguer and isostatic gravity anomalies in these areas indicate substantial variations in the crustal density structure. Crater age dating indicates that major surface modification occurred early in the Noachian, and the small elastic thickness estimates also suggest that subsurface modification occurred in the Noachian. Magnetic and gravity anomalies show comparable spatial scales (several hundred kilometers). The similarity in scale and the constant ratio of the amplitudes of the isostatic and Bouguer gravity to the magnetic anomalies along the dichotomy suggest a common origin for the anomalies. Igneous intrusion and/or local thinning or thickening of the crust, possibly with a contribution from hydrothermal alteration, are the most likely mechanisms to create the observed anomalies. [Copyright &y& Elsevier]

The Shallow Radar (SHARAD) on the Mars Reconnaissance Orbiter has imaged the internal stratigraphy of the north polar layered deposits of Mars. Radar reflections within the deposits reveal a Laterally continuous deposition of layers, which typically consist of four packets of finely spaced reflectors separated by homogeneous interpacket regions of nearly pure ice. The packet/interpacket structure can be explained by approximately million-year periodicities in Mars' obliquity or orbital eccentricity. The observed ~100-meter maximum deflection of the underlying substrate in response to the ice load implies that the present-day thickness of an equilibrium elastic lithosphere is greater than 300 kilometers. Alternatively, the response to the load may be in a transient state controlled by mantle viscosity. Both scenarios probably require that Mars has a subchondritic abundance of heat-producing elements. [ABSTRACT FROM AUTHOR]

Shallow Radar soundings from the Mars Reconnaissance Orbiter reveal a buried deposit of carbon dioxide (CO2) ice within the south polar layered deposits of Mars with a volume of 9500 to 12,500 cubic kilometers, about 30 times that previously estimated for the south pole residual cap. The deposit occurs within a stratigraphic unit that is uniquely marked by collapse features and other evidence of interior CO2 volatile release. If released into the atmosphere at times of high obliquity, the CO2 reservoir would increase the atmospheric mass by up to 80%, leading to more frequent and intense dust storms and to more regions where liquid water could persist without boiling. [ABSTRACT FROM AUTHOR]

Abstract: With 2years of tracking data collection from the MRO spacecraft, there is noticeable improvement in the high frequency portion of the spherical harmonic Mars gravity field. The new JPL Mars gravity fields, MRO110B and MRO110B2, show resolution near degree 90. Additional years of MGS and Mars Odyssey tracking data result in improvement for the seasonal gravity changes which compares well to global circulation models and Odyssey neutron data and Mars rotation and precession (). Once atmospheric dust is accounted for in the spacecraft solar pressure model, solutions for Mars solar tide are consistent between data sets and show slightly larger values (k 2 =0.164±0.009, after correction for atmospheric tide) compared to previous results, further constraining core models. An additional 4years of Mars range data improves the Mars ephemeris, determines 21 asteroid masses and bounds solar mass loss (dGMSun /dt <1.6×10−13 GMSun year−1). [ABSTRACT FROM AUTHOR]

The InSight lander successfully delivered geophysical instrument package on the Martian surface on November 26th, 2018, including a broadband and a short-period seismometer (Seismic Experiment for Interior Structure, SEIS). The seismic instrument package is specifically designed to record marsquakes and meteoritic impacts in Martian conditions. Routine operations are split into two services: the Mars Structure Service (MSS) and the Marsquake Service (MQS), which are responsible for defining structure models and seismicity catalogs, respectively. The first "deliverable" of the MSS will be a model based on the events detected during the first 3 months of seismic monitoring of the mission, for which only a few quakes might be expected based on current estimates of Mars seismic activity. To test our approach of determining the interior model of Mars and to prepare the InSight science team for data return, we made use of a "blind test" time series for which the Marsquake parameters (location, depth, origin time, and moment tensor) and interior model were unknown to the group at large.In preparation for the mission, the goal was to develop mature algorithms to handle the data as efficiency as possible. Synthetic seismic waveforms were computed in a 1D mantle model with a 3D crust on top using AxiSEM and Salvus. The time series were created by adding seismic noise that relies on pre-landing estimates of noise generated by the sensors, electronic system, environment, and nearby lander. To characterize what we could learn about Mars interior structure with only one station and with the first seismic event, we performed inversions of a synthetic data following a blind test process, where the interior model was unknown to all team members carrying out data analysis and inversion. We detail and compare the results of this "blind test" using different methods including inversion of surface wave dispersion data, body waves travel times, and the waveforms themselves. We have used mainly Bayesian techniques to obtain robust probability density functions of interior structure parameters. The effects on the retrieved model distributions of fixing mars quake location and origin time are investigated, as is the effect of using fixed Vs flexible parameterizations. To allow for tighter constraints, we also test the use of priors based on thermodynamically-constrained models together with seismic observations, as well as seismic confirmation/rejection of models purely based on thermodynamical modelling. These techniques considered here form a large part of the planned modeling of the MSS that will be ultimately employed with the first recording of a seismic event by InSight. [ABSTRACT FROM AUTHOR]

The Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight)mission successfully landed on Mars on 26 November, 2018 at 4.50∘N, 135.62∘E in ElysiumPlanitia. The Insight FluxGate magnetometer (IFG) is part of the Auxiliary Payload SensorSuite (APSS) of instruments that will monitor environmental conditions at the lander, for theprimary purpose of accounting for sources of wind, temperature, pressure and magnetic fieldnoise in the seismic data. The IFG is the first magnetometer to be deployed on thesurface of Mars, and thus affords unique opportunities for magnetic field-basedstudies of the martian interior, the ionosphere, and the extent to which conditions inthe solar wind affect the martian surface environment. In this, and a companionpaper (Russell et et al., 2019), we report on initial results from the IFG instrument.Here, we focus on approaches for estimating the local crustal magnetic field at theInSight lander, yielding the first surface-based estimates of Mars&#x2019; crustal magneticfield. We use two approaches to estimate the local crustal field: (1) In theory, IFG data canprovide a direct estimate of the crustal field via the DC field. However, such estimates requireaccurate characterization of the DC spacecraft field, with instruments in their deck and/ordeployed configurations. Characterization of spacecraft fields prior to landing provideestimates for the magnitude of the spacecraft field of ∼700 nT. (2) Vibrations ofthe InSight lander in response to the daily winds have been recorded by the ShortPeriod sensors of the seismic experiment SEIS. These high frequency tilts resultin accelerations and magnetic field perturbations that may be detectable on theshort-period seismometer, SP, and the IFG respectively. Calculations based on Viking dataprior to InSight ground operations, suggested that wind speeds of at least 10 m/sexpected at the InSight landing site, would produce lander tilts of ∼ 10−4 degrees.These in turn could produce magnetic field perturbations on the IFG resolvable with∼20 hrs of data. Measurement of the horizontal signals on SP and the horizontalperturbations to the magnetic field in the resonance frequency band of the landerallow a least squares solution for the vertical component, BZ, of the ambient crustalmagnetic field. Accordingly, over 40 hours of simultaneous IFG and SP data havebeen collected while the SP is on deck and we will report on results from thesedata. [ABSTRACT FROM AUTHOR]