It aims to determine the interior structure, composition and thermal state of Mars, as well as constrain present-day seismicity and impact cratering rates. Such information is key to understanding the differentiation and subsequent thermal evolution of Mars, and thus the forces that shape the planet's surface geology and volatile processes. Here we report an overview of the first ten months of geophysical observations by InSight. As of 30 September 2019, 174 seismic events have been recorded by the lander's seismometer, including over 20 events of moment magnitude M w = 3-4. The detections thus far are consistent with tectonic origins, with no impact-induced seismicity yet observed, and indicate a seismically active planet. An assessment of these detections suggests that the frequency of global seismic events below approximately M w = 3 is similar to that of terrestrial intraplate seismic activity, but there are fewer larger quakes; no quakes exceeding M w = 4 have been observed. The lander's other instruments-two cameras, atmospheric pressure, temperature and wind sensors, a magnetometer and a radiometer-have yielded much more than the intended supporting data for seismometer noise characterization: magnetic field measurements indicate a local magnetic field that is ten-times stronger than orbital estimates and meteorological measurements reveal a more dynamic atmosphere than expected, hosting baroclinic and gravity waves and convective vortices. With the mission due to last for an entire Martian year or longer, these results will be built on by further measurements by the InSight lander. Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

The thermal and electrical conductivity probe (TECP), a component of the Microscopy, Electrochemistry, and Conductivity Analyzer (MECA), was included on the Phoenix Lander to conduct in situ measurements of the exchange of heat and water in the Martian polar terrain. TECP measured regolith thermal conductivity, heat capacity, temperature, electrical conductivity, and dielectric permittivity throughout the mission. A relative humidity sensor returned the first in situ humidity measurements from the Martian surface. The dry overburden above the ground ice is a good thermal insulator (average κ = 0.085 W m−1 K−1 and average Cρ = 1.05 × 106 J m−3 K−1). Surface thermal inertia (I) calculated from these values agrees well with daytime orbital determinations, but differences in the spatial and temporal scale of heat transport lead to very different measurements at night. Electrical conductivity was consistent with open circuit throughout the mission; an upper limit conductivity of 2 nS cm−1 is derived. Bulk dielectric permittivity (ɛb) shows several puzzling signals but also a systematic increase overnight in the latter half of the mission, contemporaneous with H2O adsorption. The magnitude of the increase is difficult to reconcile with expected changes in unfrozen water. Atmospheric H2O averages around 1.8 Pa during the day, corresponding to a RH < 5%. At night, much of the H2O disappears from the atmosphere, and RH increases to ∼100%. Temperature and H2O partial pressure data suggest that adsorption on mineral surfaces plays a major role in scrubbing H2O, with a possible contribution from perchlorate salts.

The Heat Flow and Physical Properties Package HP 3 for the InSight mission will attempt the first measurement of the planetary heat flow of Mars. The data will be taken at the InSight landing site in Elysium planitia (136 • E, 5 • N) and the uncertainty of the measurement aimed for shall be better than ±5 mW m −2. The package consists of a mechanical hammering device called the "Mole" for penetrating into the regolith, an instrumented tether which the Mole pulls into the ground, a fixed radiometer to determine the surface brightness temperature and an electronic box. The Mole and the tether are housed in a support structure before being deployed. The tether is equipped with 14 platinum resistance temperature sensors to measure temperature differences with a 1-σ uncertainty of 6.5 mK. Depth is determined by a tether length measurement device that monitors the amount of tether extracted from the support structure and a tiltmeter that measures the angle of the Mole axis to the local gravity vector. The Mole includes temperature sensors and heaters to measure the regolith thermal conductivity to better than 3.5% (1-σ) using the Mole as a modified line heat The InSight Mission to Mars II Edited by William B.

The diffusion coefficient of water vapor in unconsolidated porous media is measured for various soil simulants at Mars‐like pressures and subzero temperatures. An experimental chamber which simultaneously reproduces a low‐pressure, low‐temperature, and low‐humidity environment is used to monitor water flux from an ice source through a porous diffusion barrier. Experiments are performed on four types of simulants: 40–70 μm glass beads, sintered glass filter disks, 1–3 μm dust (both loose and packed), and JSC Mars–1. A theoretical framework is presented that applies to environments that are not necessarily isothermal or isobaric. For most of our samples, we find diffusion coefficients in the range of 2.8 to 5.4 cm2 s−1 at 600 Pascal and 260 K. This range becomes 1.9–4.7 cm2 s−1 when extrapolated to a Mars‐like temperature of 200 K. Our preferred value for JSC Mars–1 at 600 Pa and 200 K is 3.7 ± 0.5 cm2 s−1. The tortuosities of the glass beads is about 1.8. Packed dust displays a lower mean diffusion coefficient of 0.38 ± 0.26 cm2 s−1, which can be attributed to transition to the Knudsen regime where molecular collisions with the pore walls dominate. Values for the diffusion coefficient and the variation of the diffusion coefficient with pressure are well matched by existing models. The survival of shallow subsurface ice on Mars and the providence of diffusion barriers are considered in light of these measurements.

[1] The Phoenix and Mars Reconnaissance Orbiter (MRO) missions collaborated in an unprecedented campaign to observe the northern polar region summer atmosphere throughout the Phoenix mission (25 May to 2 November 2008; L s = 76°-150°) and slightly beyond (∼L s = 158°). Five atmospherically related campaigns were defined a priori and were executed on 37 separate Martian days (sols). Phoenix and MRO observed the atmosphere nearly simultaneously. We describe the observation strategy and history, the participating experiments, and some initial results. We find that there is general agreement between measurements from different instruments and platforms and that complementary measurements provide a consistent picture of the atmosphere. Seasonal water abundance behavior matches with historical measurements. Winds aloft, as measured by cloud motions, showed the same seasonally consistent, diurnal rotation as the winds measured at the lander, during the first part of the mission (L s = 76°-118°). A diurnal cycle recorded from L s ∼ 108.3°-109.1°, in which a dust front was approaching the Phoenix Lander, is examined in detail. Cloud heights measured on subsequent orbits showed that in areas of active lifting, dust can be lofted quite high in the atmosphere, doubling in height over 2 h. The combination of experiments also revealed that there were discrete vertical layers of water ice and dust. Water vapor column abundances compared to near-surface water vapor pressure indicate that water is not well mixed from the surface to a cloud condensation height and that the depth of the layer that exchanges diurnally with the surface is 0.5-1 km.

The martian near surface layer consists of sand-sized as well as dust-sized particles (Christensen & Moore, 1992) interspersed with larger rocks, and its detailed structure depends on the deposition process as well as subsequent surface modifications by eolian and fluvial activity. Under present martian atmospheric conditions sand-sized particles in the 100-600 μm size range can be moved by winds through saltation (Kok et al., 2012), and dust particles of typical sizes around 1.5 μm are suspended in the atmosphere and can reach the ground in the form of airfall (Lemmon et al., 2019), such that aeolian processes are generally recognized to be the prevalent surface modification process on Mars today.

A new calibration function for the humidity sensor in the Thermal and Electrical Conductivity Probe (TECP) on the Phoenix (PHX) Mars mission has been developed. Two changes are incorporated: (1) it is now cast in terms of frost point (T f ) rather than relative humidity (RH), and (2) flight data, taken when the atmosphere is independently known to be saturated, are included in the calibration data set. Daytime (6:00 h-19:00 h) frost points ranged from 194 K to 209 K; the nighttime frost point ranged from 179 K to 206 K. The response of the sensor was smooth and continuous throughout. Daytime humidity exhibited large, high-frequency variance driven by turbulence, whereas nighttime humidity varied smoothly with the temperature of the atmosphere. Nighttime saturation of the atmosphere begins at L s 101°, (Martian solar day (sol) 55), which is earlier than reported by either Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) or solid-state imager (SSI). Early mornings are the most humid part of the sol after L s 113°(sol 80), due to sublimation of surface ice that precipitates overnight. H 2 O is removed from the atmosphere into the regolith, mostly during the late afternoon, although this continues into the evening. The ground ice exposed by Phoenix operations masks the naturally occurring process in the early evening and may cause the atmosphere immediately around the lander to saturate somewhat earlier in the evening than it otherwise would have. The average H 2 O vapor density is close to the summertime value expected for equilibrium with ground ice. A discrepancy between the H 2 O column calculated from TECP data and the column measured by CRISM and SSI is likely due to comparable timescales between turbulent mixing through the planetary boundary layer and adsorptive drawdown of H 2 O. We find that RH is mostly < 5% (daytime) or > 95% (nighttime), and the transition between the two extremes is extremely rapid. TECP Humidity MeasurementsThe TECP H 2 O measurement was based on a General Electric Panametrics MiniCap 2 polymer capacitive humidity sensor. The flight sensor was one of four, each mounted in one of the four flight model TECPs that were built and calibrated. The flight instrument was selected from among them based on performance and stability over all six measurement types during calibration. The humidity sensor was mounted internally, on ZENT ET AL.PHOENIX HUMIDITY RESULTS 626 PUBLICATIONS

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 ($>30~\text{cm}$ > 30 cm depth) of $4.9\pm0.4~\text{MPa}$ 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.