Publications


Potential vorticity structure of Titan’s polar vortices from Cassini CIRS observations

Icarus Elsevier BV (2020) 114030

J Sharkey, NA Teanby, M Sylvestre, DM Mitchell, WJM Seviour, CA Nixon, PGJ Irwin


Jupiter in the Ultraviolet: Acetylene and Ethane Abundances in the Stratosphere of Jupiter from Cassini Observations between 0.15 and 0.19 mu m

ASTRONOMICAL JOURNAL American Astronomical Society 159 (2020) ARTN 291

H Melin, L Fletcher, P Irwin, S Edgington

© 2020. The American Astronomical Society. All rights reserved. At wavelengths between 0.15 and 0.19 μm, the far-ultraviolet spectrum of Jupiter is dominated by the scattered solar spectrum, attenuated by molecular absorptions primarily by acetylene and ethane, and to a lesser extent ammonia and phosphine. We describe the development of our radiative transfer code that enables the retrieval of abundances of these molecular species from ultraviolet reflectance spectra. As a proof-of-concept we present an analysis of Cassini Ultraviolet Imaging Spectrograph (UVIS) observations of the disk of Jupiter during the 2000/2001 flyby. The ultraviolet-retrieved acetylene abundances in the upper stratosphere are lower than those predicted by models based solely on infrared thermal emission from the mid-stratosphere observed by the Composite Infrared Spectrometer (CIRS), requiring an adjustment to the vertical profiles above 1 mbar. We produce a vertical acetylene abundance profile that is compatible with both CIRS and UVIS, with reduced abundances at pressures <1 mbar: the 0.1 mbar abundances are 1.21 ± 0.07 ppm for acetylene and 20.8 ± 5.1 ppm for ethane. Finally, we perform a sensitivity study for the JUICE ultraviolet spectrograph, which has extended wavelength coverage out to 0.21 μm, enabling the retrieval of ammonia and phosphine abundances, in addition to acetylene and ethane.


Thermal versus mechanical topography: an experimental investigation in a rotating baroclinic annulus

Geophysical and Astrophysical Fluid Dynamics Taylor and Francis (2020)

SD Marshall, P Read

We present a series of experimental investigations in which a differentially-heated annulus was used to investigate the effects of topography on rotating, stratified flows. In particular, we investigate blocking effects via azimuthally varying differential-heating and compare them to previous experiments utilising partial mechanical barriers. The thermal topography used consisted of a flat patch of heating elements covering a small azimuthal extent of the base, forming an equivalent of a partial barrier, to study the difference between blocked and unblocked flow. These azimuthally-varying heating experiments produced results with many similarities to our previous experiments with a mechanical barrier, despite the lack of a physical obstacle or formation of bottom-trapped waves. In particular, a unique flow structure was found when the drifting flow and the topography interacted in the form of an “interference” regime at low Taylor number, but forming an erratic “irregular” regime at higher Taylor number. This suggests that blocking may be induced by either or both of a thermal or mechanical inhomogeneity. Evidence of coherent/persistent resonant wave triads was noted in both kinds of experiment, though the component wavenumbers of the wave-triads and their impact on the flow was found to depend on the topography in question.


Advanced Net Flux Radiometer for the Ice Giants

Space Science Reviews Springer Verlag 216 (2020)

S Aslam, RK Achterberg, SB Calcutt, V Cottini, NJ Gorius, T Hewagama, PG Irwin, CA Nixon, G Quilligan, M Roos-Serote, AA Simon, D Tran, G Villanueva

The design of an advanced Net Flux Radiometer (NFR), for inclusion as a payload on a future Ice Giants probe mission, is given. The Ice Giants NFR (IG-NFR) will measure the upward and downward radiation flux (hence net radiation flux), in seven spectral bands, spanning the range from solar to far infra-red wavelengths, each with a 5∘ Field-Of-View (FOV) and in five sequential view angles ( ±80∘ , ±45∘ , and 0∘ ) as a function of altitude. IG-NFR measurements within either Uranus or Neptune’s atmospheres, using dedicated spectral filter bands will help derive radiative heating and cooling profiles, and will significantly contribute to our understanding of the planet’s atmospheric heat balance and structure, tropospheric 3-D flow, and compositions and opacities of the cloud layers. The IG-NFR uses an array of non-imaging Winston cones integrated to a matched thermopile detector Focal Plane Assembly (FPA), with individual bandpass filters, housed in a diamond windowed vacuum micro-vessel. The FPA thermopile detector signals are read out in parallel mode, amplified and processed by a multi-channel digitizer application specific integrated circuit (MCD ASIC) under field programmable gate array (FPGA) control. The vacuum micro-vessel rotates providing chopping between FOV’s of upward and downward radiation fluxes. This unique design allows for small net flux measurements in the presence of large ambient fluxes and rapidly changing ambient temperatures during the probe descent to ≥10 bar pressure.


Ice giant circulation patterns: Implications for atmospheric probes

Space Science Reviews Springer 216 (2020) 21

L Fletcher, DP Imke, G Orton, M Hofstadter, P Irwin, M Roman, D Toledo Carrasco

Atmospheric circulation patterns derived from multi-spectral remote sensing can serve as a guide for choosing a suitable entry location for a future in situ probe mission to the Ice Giants. Since the Voyager-2 flybys in the 1980s, three decades of observations from ground- and space-based observatories have generated a picture of Ice Giant circulation that is complex, perplexing, and altogether unlike that seen on the Gas Giants. This review seeks to reconcile the various competing circulation patterns from an observational perspective, accounting for spatially-resolved measurements of: zonal albedo contrasts and banded appearances; cloud-tracked zonal winds; temperature and para-H2 measurements above the condensate clouds; and equator-to-pole contrasts in condensable volatiles (methane, ammonia, and hydrogen sulphide) in the deeper troposphere. These observations identify three distinct latitude domains: an equatorial domain of deep upwelling and upper-tropospheric subsidence, potentially bounded by peaks in the retrograde zonal jet and analogous to Jovian cyclonic belts; a mid-latitude transitional domain of upper-tropospheric upwelling, vigorous cloud activity, analogous to Jovian anticyclonic zones; and a polar domain of strong subsidence, volatile depletion, and small-scale (and potentially seasonally-variable) convective activity. Taken together, the multi-wavelength observations suggest a tiered structure of stacked circulation cells (at least two in the troposphere and one in the stratosphere), potentially separated in the vertical by (i) strong molecular weight gradients associated with cloud condensation, and by (ii) transitions from a thermally-direct circulation regime at depth to a wave- and radiative-driven circulation regime at high altitude. The inferred circulation can be tested in the coming decade by 3D numerical simulations of the atmosphere, and by observations from future world-class facilities. The carrier spacecraft for any probe entry mission must ultimately carry a suite of remote-sensing instruments capable of fully constraining the atmospheric motions at the probe descent location.


Uranus in Northern Mid-spring: Persistent Atmospheric Temperatures and Circulations Inferred from Thermal Imaging (vol 159, 45, 2020)

ASTRONOMICAL JOURNAL American Astronomical Society 160 (2020) ARTN 56

MT Roman, LN Fletcher, GS Orton, N Rowe-Gurney, PGJ Irwin


Ice, fire, or fizzle: The climate footprint of Earth's supercontinental cycles

Geochemistry, Geophysics, Geosystems American Geophysical Union 21 (2020) e2019GC008464

M Jellinek, A Lenardic, R Pierrehumbert

Supercontinent assembly and breakup can influence the rate and global extent to which insulated and relatively warm subcontinental mantle is mixed globally, potentially introducing lateral oceanic‐continental mantle temperature variations that regulate volcanic and weathering controls on Earth's long‐term carbon cycle for a few hundred million years. We propose that the relatively warm and unchanging climate of the Nuna supercontinental epoch (1.8–1.3 Ga) is characteristic of thorough mantle thermal mixing. By contrast, the extreme cooling‐warming climate variability of the Neoproterozoic Rodinia episode (1–0.63 Ga) and the more modest but similar climate change during the Mesozoic Pangea cycle (0.3–0.05 Ga) are characteristic features of the effects of subcontinental mantle thermal isolation with differing longevity. A tectonically modulated carbon cycle model coupled to a one‐dimensional energy balance climate model predicts the qualitative form of Mesozoic climate evolution expressed in tropical sea‐surface temperature and ice sheet proxy data. Applied to the Neoproterozoic, this supercontinental control can drive Earth into, as well as out of, a continuous or intermittently panglacial climate, consistent with aspects of proxy data for the Cryogenian‐Ediacaran period. The timing and magnitude of this cooling‐warming climate variability depends, however, on the detailed character of mantle thermal mixing, which is incompletely constrained. We show also that the predominant modes of chemical weathering and a tectonically paced abiotic methane production at mid‐ocean ridges can modulate the intensity of this climate change. For the Nuna epoch, the model predicts a relatively warm and ice‐free climate related to mantle dynamics potentially consistent with the intense anorogenic magmatism of this period.


Studying the Composition and Mineralogy of the Hermean Surface with the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) for the BepiColombo Mission: An Update

Space Science Reviews 216 (2020)

H Hiesinger, J Helbert, G Alemanno, KE Bauch, M D’Amore, A Maturilli, A Morlok, MP Reitze, C Stangarone, AN Stojic, I Varatharajan, I Weber, G Arnold, M Banaszkiewicz, K Bauch, J Benkhoff, A Bischoff, M Blecka, N Bowles, S Calcutt, L Colangeli, S Erard, S Fonti, BT Greenhagen, O Groussain, J Helbert, H Hiesinger, H Hirsch, J Jahn, R Killen, J Knollenberg, E Kührt, E Lorenz, I Mann, U Mall, A Maturilli, A Morlok, L Moroz, G Peter, M Rataj, M Robinson, W Skrbek, T Spohn, A Sprague, D Stöffler, A Stojic, F Taylor, I Varatharajan, H Venus, J Warrell, I Walter, I Weber, A Witzke, C Wöhler

© 2020, The Author(s). Launched onboard the BepiColombo Mercury Planetary Orbiter (MPO) in October 2018, the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) is on its way to planet Mercury. MERTIS consists of a push-broom IR-spectrometer (TIS) and a radiometer (TIR), which operate in the wavelength regions of 7-14 μm and 7-40 μm, respectively. This wavelength region is characterized by several diagnostic spectral signatures: the Christiansen feature (CF), Reststrahlen bands (RB), and the Transparency feature (TF), which will allow us to identify and map rock-forming silicates, sulfides as well as other minerals. Thus, the instrument is particularly well-suited to study the mineralogy and composition of the hermean surface at a spatial resolution of about 500 m globally and better than 500 m for approximately 5-10% of the surface. The instrument is fully functional onboard the BepiColombo spacecraft and exceeds all requirements (e.g., mass, power, performance). To prepare for the science phase at Mercury, the team developed an innovative operations plan to maximize the scientific output while at the same time saving spacecraft resources (e.g., data downlink). The upcoming fly-bys will be excellent opportunities to further test and adapt our software and operational procedures. In summary, the team is undertaking action at multiple levels, including performing a comprehensive suite of spectroscopic measurements in our laboratories on relevant analog materials, performing extensive spectral modeling, examining space weathering effects, and modeling the thermal behavior of the hermean surface.


Constraints on the shallow elastic and anelastic structure of Mars from InSight seismic data

Nature Geoscience Springer Nature 13 (2020) 213-220

P Lognonné, WB Banerdt, WT Pike, T Nissen-Meyer, S Calcutt, T Warren

Mars’s seismic activity and noise have been monitored since January 2019 by the seismometer of the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) lander. At night, Mars is extremely quiet; seismic noise is about 500 times lower than Earth’s microseismic noise at periods between 4 s and 30 s. The recorded seismic noise increases during the day due to ground deformations induced by convective atmospheric vortices and ground-transferred wind-generated lander noise. Here we constrain properties of the crust beneath InSight, using signals from atmospheric vortices and from the hammering of InSight’s Heat Flow and Physical Properties (HP3) instrument, as well as the three largest Marsquakes detected as of September 2019. From receiver function analysis, we infer that the uppermost 8–11 km of the crust is highly altered and/or fractured. We measure the crustal diffusivity and intrinsic attenuation using multiscattering analysis and find that seismic attenuation is about three times larger than on the Moon, which suggests that the crust contains small amounts of volatiles.


First detection of ozone in the mid-infrared at Mars: implications for methane detection

Astronomy & Astrophysics EDP Sciences (2020)

K Olsen, F Lefèvre, F Montmessin, A Trokhimovskiy, L Baggio, A Fedorova​, J Alday​, A Lomakin​, D Belyaev, A Patrakeev, A Shakun​, O Korablev


Understanding and mitigating biases when studying inhomogeneous emission spectra with JWST

Monthly Notices of the Royal Astronomical Society Royal Astronomical Society (2020)

J Taylor, V Parmentier, P Irwin, S Aigrain, G Lee, J Krissansen-Totton

Exoplanet emission spectra are often modelled assuming that the hemisphere observed is well represented by a horizontally homogenised atmosphere. However this approximation will likely fail for planets with a large temperature contrast in the James Webb Space Telescope (JWST) era, potentially leading to erroneous interpretations of spectra. We first develop an analytic formulation to quantify the signal-to-noise ratio and wavelength coverage necessary to disentangle temperature inhomogeneities from a hemispherically averaged spectrum. We find that for a given signal-to-noise ratio, observations at shorter wavelengths are better at detecting the presence of inhomogeneities. We then determine why the presence of an inhomogeneous thermal structure can lead to spurious molecular detections when assuming a fully homogenised planet in the retrieval process. Finally, we quantify more precisely the potential biases by modelling a suite of hot Jupiter spectra, varying the spatial contributions of a hot and a cold region, as would be observed by the different instruments of JWST/NIRSpec. We then retrieve the abundances and temperature profiles from the synthetic observations. We find that in most cases, assuming a homogeneous thermal structure when retrieving the atmospheric chemistry leads to biased results, and spurious molecular detection. Explicitly modelling the data using two profiles avoids these biases, and is statistically supported provided the wavelength coverage is wide enough, and crucially also spanning shorter wavelengths. For the high contrast used here, a single profile with a dilution factor performs as well as the two-profile case, with only one additional parameter compared to the 1-D approach.


First observation of the magnetic dipole CO2 main isotopologue absorption band at 3.3 µm in the atmosphere of Mars by the ExoMars Trace Gas Orbiter ACS instrument

Astronomy & Astrophysics EDP Sciences (2020)

A Trokhimovskiy, V Perevalov, O Korablev, A Fedorova, K Olsen, J Bertaux, A Patrakeev, A Shakun, F Montmessin, F Lefèvre


Color and aerosol changes in Jupiter after a North Temperate Belt disturbance

Icarus Elsevier BV 352 (2020) 114031

S Pérez-Hoyos, A Sánchez-Lavega, J Sanz-Requena, N Barrado-Izagirre, O Carrión-González, A Anguiano-Arteaga, P Irwin, A Braude


Thermodynamic and energetic limits on continental silicate weathering strongly impact the climate and habitability of wet, rocky worlds

Astrophysical Journal American Astronomical Society 896 (2020) 115

R Graham, R Pierrehumbert

The “liquid water habitable zone” (HZ) concept is predicated on the ability of the silicate weathering feedback to stabilize climate across a wide range of instellations. However, representations of silicate weathering used in current estimates of the effective outer edge of the HZ do not account for the thermodynamic limit on concentration of weathering products in runoff set by clay precipitation, nor for the energetic limit on precipitation set by planetary instellation. We find that when the thermodynamic limit is included in an idealized coupled climate/weathering model, steady-state planetary climate loses sensitivity to silicate dissolution kinetics, becoming sensitive to temperature primarily through the effect of temperature on runoff and to pCO2 through an effect on solute concentration mediated by pH. This increases sensitivity to land fraction, CO2 outgassing, and geological factors such as soil age and lithology, all of which are found to have a profound effect on the position of the effective outer edge of the HZ. The interplay between runoff sensitivity and the energetic limit on precipitation leads to novel warm states in the outer reaches of the HZ, owing to the decoupling of temperature and precipitation. We discuss strategies for detecting the signature of silicate weathering feedback through exoplanet observations in light of insights derived from the revised picture of weathering.


Colour and tropospheric cloud structure of Jupiter from MUSE/VLT: retrieving a universal chromophore

Icarus Elsevier 338 (2020) 113589

AS Braude, P Irwin, GS Orton, LN Fletcher

Recent work by Sromovsky et al. (2017, Icarus 291, 232-244) suggested that all red colour in Jupiter’s atmosphere could be explained by a single colour-carrying compound, a so-called ‘universal chromophore’. We tested this hypothesis on ground-based spectroscopic observations in the visible and near-infrared (480- 930 nm) from the VLT/MUSE instrument between 2014 and 2018, retrieving a chromophore absorption spectrum directly from the North Equatorial Belt, and applying it to model spatial variations in colour, tropospheric cloud and haze structure on Jupiter. We found that we could model both the belts and the Great Red Spot of Jupiter using the same chromophore compound, but that this chromophore must exhibit a steeper blue-absorption gradient than the proposed chromophore of Carlson et al. (2016, Icarus 274, 106–115). We retrieved this chromophore to be located no deeper than 0.2±0.1 bars in the Great Red Spot and 0.7±0.1 bars elsewhere on Jupiter. However, we also identified some spectral variability between 510 nm and 540 nm that could not be accounted for by a universal chromophore. In addition, we retrieved a thick, global cloud layer at 1.4 ± 0.3 bars that was relatively spatially invariant in altitude across Jupiter. We found that this cloud layer was best characterised by a real refractive index close to that of ammonia ice in the belts and the Great Red Spot, and poorly characterised by a real refractive index of 1.6 or greater. This may be the result of ammonia cloud at higher altitude obscuring a deeper cloud layer of unknown composition.


Spatial structure in Neptune’s 7.90-m stratospheric CH emission, as measured by VLT-VISIR

Icarus Elsevier 345 (2020) 113748

J Sinclair, G Orton, L Fletcher, M Roman, I de Pater, T Encrenaz, H Hammel, R Giles, T Velusamy, J Moses, P Irwin, T Momary, N Rowe-Gurney, F Tabataba-Vakili

We present a comparison of VLT-VISIR images and Keck-NIRC2 images of Neptune, which highlight the coupling between its troposphere and stratosphere. VLT-VISIR images were obtained on September 16th 2008 (UT) at 7.90 μm and 12.27 μm, which are primarily sensitive to 1-mbar CH4 and C2H6 emission, respectively. NIRC2 images in the H band were obtained on October 5th, 6th and 9th 2008 (UT) and sense clouds and haze in the upper troposphere and lower stratosphere (from approximately 600 to 20 mbar). At 7.90 μm, we observe enhancements of CH4 emission in latitude bands centered at approximately 25∘S and 48∘S (planetocentric). Within these zonal bands, tentative detections (<2σ) of discrete hotspots of CH4 emission are also evident at 24∘S, 181∘W and 42∘S, 170∘W. The longitudinal-mean enhancements in the CH4 emission are also latitudinally-coincident with bands of bright (presumably CH4 ice) clouds in the upper troposphere and lower stratosphere evidenced in the H-band images. This suggests the Neptunian troposphere and stratosphere are coupled in these specific regions. This could be in the form of (1) ‘overshoot’ of strong, upwelling plumes and advection of CH4 ice into the lower stratosphere, which subsequently sublimates into CH4 gas and/or (2) generation of waves by plumes impinging from the tropopause below, which impart their energy and heat the lower stratosphere. We favor the former process since there is no evidence of similar smaller-scale morphology in the C2H6 emission, which probes a similar atmospheric level. However, we cannot exclude temperature variations as the source of the morphology observed in CH4 emission. Future, near-infrared imaging of Neptune performed near-simultaneously with future mid-infrared spectral observations of Neptune by the James Webb Space Telescope would allow the coupling of Neptune's troposphere and stratosphere to be confirmed and studied in greater detail.


Constraints on Neptune’s haze structure and formation from VLT observations in the H-band

Icarus Elsevier (2020)

D Toledo Carrasco, P Irwin, P Rannou, L Fletcher, N Teanby, M Wong, G Orton

A 1-dimensional microphysics model has been used to constrain the structure and formation of haze in Neptune's atmosphere. These simulations were coupled to a radiative-transfer and retrieval code (NEMESIS) to model spectral observations of Neptune in the H-band performed by the SINFONI Integral Field Unit Spectrometer on the Very Large Telescope (VLT) in 2013. It was found that observations in the H-band and with emission angles ≤60° are largely unaffected by the imaginary refractive index of haze particles, allowing a notable reduction of the free parameters required to fit the observations. Our analysis shows a total haze production rate of (2.61 ± 0.18) × 10−14 kg m−2 s−1, about 10 times larger than that found in Uranus's atmosphere, and a particle electric charge of q = 8.6 ± 1.1 electrons per μm radius at latitudes between 5 and 15° S. This haze production rate in Neptune results in haze optical depths about 10 times greater than those in Uranus. The effective radius reff was found to be 0.22 ± 0.01 and 0.26 ± 0.02 μm at the 0.1 and 1-bar levels, respectively, with haze number densities of 8.48+1.78−1.31 and 9.31+2.52−1.91 particles per cm3. The fit at weak methane-absorbing wavelengths reveals also the presence of a tropospheric cloud with a total optical depth >10 at 1.46 μm. The tropospheric cloud base altitude was found near the 2.5-bar level, although this estimation may be only representative of the top of a thicker and deeper cloud. Our analysis leads to haze opacities about 3.5 times larger than that derived from Voyager-2 observations (Moses et al., 1995). This larger opacity indicates a haze production rate 2 times larger at least. To study this difference haze opacity or production rate, we performed a timescale analysis with our microphysical model to estimate the time required for haze particles to grow and settle out. Although this analysis shows haze timescales (∼15 years) shorter than the time lapsed between Voyager-2 observations and 2013, the solar illumination at the top of the atmosphere has not varied significantly during this period (at the studied latitudes) to explain the increase in haze production. This difference in haze production rate derived for these two periods may arise from: a) the fact that in our analysis we employed spectral observations in the infrared (H-band), while Moses et al. (1995) used photometric images taken at 5 different filters in the visible. While high-phase-angle Voyager observations are more sensitive to small haze particles and at altitudes above the 0.1-bar level, the haze constraints derived from VLT spectra in H-band are limited to pressures greater than 0.1 bar. As a result of the different phase angles of the two set of observations, differences in the estimation of M0 may arise from the use of Mie phase functions as well. b) our 1-dimensional model does not account for latitudinal redistributions of the haze by dynamics. A possible meridional transport of haze with wind velocities greater than ∼0.03 m s−1 would result in dynamics timescales shorter than 15 years and thus might explain the observed variations in the haze production rate during this period. Compared with our estimations, photochemical models point to even larger production rates on Neptune (by a factor of 2.4). Assuming that the photochemical simulations are correct, we found that this discrepancy can be explained if haze particles evaporate before reaching the tropospheric-cloud levels. This scenario would decrease the cumulative haze opacity above the 1-bar level, and thus a larger haze production rate would be required to fit our observations. However, to validate this haze vertical structure future microphysical simulations that include the evaporation rates of haze particles are required.


The turbulent dynamics of Jupiter's and Saturn's weather layers: order out of chaos?

GEOSCIENCE LETTERS 7 (2020) ARTN 10

PL Read, RMB Young, D Kennedy


Baroclinic and barotropic instabilities in planetary atmospheres: energetics, equilibration and adjustment

NONLINEAR PROCESSES IN GEOPHYSICS 27 (2020) 147-173

P Read, D Kennedy, N Lewis, H Scolan, F Tabataba-Vakili, Y Wang, S Wright, R Young


Initial results from the InSight mission on Mars

Nature Geoscience Springer Nature (2020)

SE Smrekar, D Giardini, M Golombek, CL Johnson, P Lognonné, A Spiga, T Spohn, C Perrin, SC Stähler, C Beghein, E Bozdag, P Chi, U Christensen, GS Collins, I Daubar, M Drilleau, M Fillingim, W Folkner, RF Garcia, J Garvin, M Grott, JCE Irving, G Kargl, T Kawamura, S Kedar

NASA’s InSight (Interior exploration using Seismic Investigations, Geodesy and Heat Transport) mission landed in Elysium Planitia on Mars on 26 November 2018. 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 Mw = 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 Mw = 3 is similar to that of terrestrial intraplate seismic activity, but there are fewer larger quakes; no quakes exceeding Mw = 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.

Pages