REDUCING WORKING TIME IN AN EFFICIENCY WAGE ECONOMY WITH A DUAL LABOUR MARKET

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Seismic constraints from a Mars impact experiment using InSight and Perseverance

NASA’s InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission has operated a sophisticated suite of seismology and geophysics instruments on the surface of Mars since its arrival in 2018. On 18 February 2021, we attempted to detect the seismic and acoustic waves produced by the entry, descent and landing of the Perseverance rover using the sensors onboard the InSight lander. Similar observations have been made on Earth using data from both crewed1,2 and uncrewed3,4 spacecraft, and on the Moon during the Apollo era5, but never before on Mars or another planet. This was the only seismic event to occur on Mars since InSight began operations that had an a priori known and independently constrained timing and location. It therefore had the potential to be used as a calibration for other marsquakes recorded by InSight. Here we report that no signal from Perseverance’s entry, descent and landing is identifiable in the InSight data. Nonetheless, measurements made during the landing window enable us to place constraints on the distance–amplitude relationships used to predict the amplitude of seismic waves produced by planetary impacts and place in situ constraints on Martian impact seismic efficiency (the fraction of the impactor kinetic energy converted into seismic energy)

Seismic Constraints on the Thickness and Structure of the Martian Crust from InSight

NASA¿s InSight mission [1] has for the first time placed a very broad-band seismometer on the surface of Mars. The Seismic Experiment for Interior Structure (SEIS) [2] has been collecting continuous data since early February 2019. The main focus of InSight is to enhance our understanding of the internal structure and dynamics of Mars, which includes the goal to better constrain the crustal thickness of the planet [3]. Knowing the present-day crustal thickness of Mars has important implications for its thermal evolution [4] as well as for the partitioning of silicates and heat-producing elements between the different layers of Mars. Current estimates for the crustal thickness of Mars are based on modeling the relationship between topography and gravity [5,6], but these studies rely on different assumptions, e.g. on the density of the crust and upper mantle, or the bulk silicate composition of the planet and the crust. The resulting values for the average crustal thickness differ by more than 100%, from 30 km to more than 100 km [7]. New independent constraints from InSight will be based on seismically determining the crustal thickness at the landing site. This single firm measurement of crustal thickness at one point on the planet will allow to constrain both the average crustal thickness of Mars as well as thickness variations across the planet when combined with constraints from gravity and topography [8]. Here we describe the determination of the crustal structure and thickness at the InSight landing site based on seismic receiver functions for three marsquakes compared with autocorrelations of InSight data [9].We acknowledge NASA, CNES, partner agencies and institutions (UKSA, SSO,DLR, JPL, IPGP-CNRS, ETHZ, IC, MPS-MPG) and the operators of JPL, SISMOC, MSDS, IRIS-DMC and PDS for providing SEED SEIS data. InSight data is archived in the PDS, and a full list of archives in the Geosciences, Atmospheres, and Imaging nodes is at https://pds-geosciences.wustl.edu/missions/insight/. This work was partially carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. ©2021, California Institute of Technology. Government sponsorship acknowledge

Effect of intraperitoneally administered recombinant murine granulocyte-macrophage colony-stimulating factor (rmGM-CSF) on the cytotoxic potential of murine peritoneal cells

We studied the effect of recombinant murine granulocyte–macrophage colony-stimulating factor(rmGM-CSF) on the cytotoxic potential of murine peritoneal cells. Mice received rmGM-CSF intraperitoneally using different dosages and injection schemes. At different time points after the last injection, mice were sacrificed, peritoneal cells isolated and their tumour cytotoxicity was determined by a cytotoxicity assay using syngeneic [methyl-3H]thymidine-labelled colon carcinoma cells. Also, the cytotoxic response to a subsequent in vitro stimulation with lipopolysaccharide was determined. Upon daily injection of 6000–54 000 U rmGM-CSF over a 6-day period, the number of peritoneal cells increased over ten fold with the highest rmGM-CSF dose. Increases in cell numbers was mainly due to increases in macrophage numbers. Upon injection of three doses of 3000 U rmGM-CSF per day for 3 consecutive days, the number of macrophages remained elevated for minimally 6 days. Although the peritoneal cells from rmGM-CSF-treated mice were not activated to a tumoricidal state, they could be activated to high levels of cytotoxicity with an additional in vitro stimulation of lipopolysaccharide. Resident cells isolated from control mice could be activated only to low levels of tumour cytotoxicity with lipopolysaccharide. Tumour cytotoxicity strongly correlated with nitric oxide secretion. When inhibiting nitric oxide synthase, tumour cell lysis decreased. Thus, the expanded peritoneal cell population induced by multiple injections of rmGM-CSF has a strong tumour cytotoxic potential and might provide a favourable condition for immunotherapeutic treatment of peritoneal neoplasms. © 1999 Cancer Research Campaig

Surface waves and crustal structure on Mars

We detected surface waves from two meteorite impacts on Mars. By measuring group velocity dispersion along the impact-lander path, we obtained a direct constraint on crustal structure away from the InSight lander. The crust north of the equatorial dichotomy had a shear wave velocity of approximately 3.2 kilometers per second in the 5- to 30-kilometer depth range, with little depth variation. This implies a higher crustal density than inferred beneath the lander, suggesting either compositional differences or reduced porosity in the volcanic areas traversed by the surface waves. The lower velocities and the crustal layering observed beneath the landing site down to a 10-kilometer depth are not a global feature. Structural variations revealed by surface waves hold implications for models of the formation and thickness of the martian crust.D.K., S.C., D.G., J.C., C.D., A. K., S.C.S., N.D., and G.Z. were supported by the ETH+ funding scheme (ETH+02 19-1: “Planet Mars”). Marsquake Service operations at ETH Zürich were supported by ETH Research grant ETH-06 17-02. N.C.S. and V.L. were supported by NASA PSP grant no. 80NSSC18K1628. Q.H. and E.B. are funded by NASA grant 80NSSC18K1680. C.B. and J.L. were supported by NASA InSight PSP grant no. 80NSSC18K1679. S.D.K. was supported by NASA InSight PSP grant no. 80NSSC18K1623. P.L., E.B., M.D., H.S., E.S., M.W., Z.X., T.W., M.P., R.F.G. were supported by CNES and the Agence Nationale de la Recherche (ANR-19-CE31-0008-08 MAGIS) for SEIS operation and SEIS Science analysis. A.H., C.C. and W.T.P. were supported by the UKSA under grant nos. ST/R002096/1, ST/ W002523/1 and ST/V00638X/1. Numerical computations of McMC Approach 2 were performed on the S-CAPAD/DANTE platform (IPGP, France) and using the HPC resources of IDRIS under the allocation A0110413017 made by GENCI. A.H. was supported by the UKSA under grant nos. ST/R002096/1 and ST/W002523/1. F.N. was supported by InSight PSP 80NSSC18K1627. I.J.D. was supported by NASA InSight PSP grant no. 80NSSC20K0971. L.V.P. was funded by NASANNN12AA01C with subcontract JPL-1515835. The research was carried out in part by W.B.B., M.G. and M.P.P. at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004)Peer reviewe

Seismic detection of the martian core

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.This is InSight contribution 200. We acknowledge NASA, CNES, and partner agencies and institutions (UKSA, SSO, ESA-PRODEX, DLR, JPL, IPGP-CNRS, ETHZ, IC, and MPS-MPG) for the development of SEIS. Numerical simulations were supported by a grant from the Swiss National Supercomputing Centre (CSCS) under project ID s922 as well as HPC resources of CINES under the allocation A0090407341, made by GENCI. We thank B. Dintrans, director of CINES, for his efficient handling of our request for computational time. Figures were created using matplotlib (83), seismic data processing was done in ObsPy (84), and numerical evaluation was done in NumPy and SciPy (85, 86). Funding: S.C.S., A.K., D.G., J.C., A.C.D., G.Z., and N.D. acknowledge support from ETHZ through the ETH+ funding scheme (ETH+2 19-1: “Planet MARS”). S.C.S. acknowledges funding from ETH research grant ETH-10 17-3. W.B.B., A.G.M., M.P.P., and S.E.S. were supported by the NASA InSight mission and funds from the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). D.A. has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreement 724690). The French teams acknowledge support from CNES as well as Agence Nationale de la Recherche (ANR-14-CE36-0012-02 and ANR-19-CE31-0008-08). A.R. was financially supported by the Belgian PRODEX program managed by the European Space Agency in collaboration with the Belgian Federal Science Policy Office. M.S. wishes to thank SANIMS (RTI2018-095594-B-I00). M.v.D. received support from the ERC under the European Union’s Horizon 2020 program (grant no. 714069). D.S. and C.S. acknowledge funding from ETH research grant ETH-06 17-02. J.C.E.I. acknowledges support from NASA grant 80NSSC18K1633. N.S., D.K., Q.H., R.M., V.L., and A.G.M. acknowledge NASA grant 80NSSC18K1628 for support. V.L. acknowledges support from the Packard Foundation. W.T.P. and C.C. received funding from the UK Space Agency, grant ST/S001239/1. A.H. was funded by the UK Space Agency (grant ST/R002096/1). A.-C.P. acknowledges the financial support and endorsement from the DLR Management Board Young Research Group Leader Program and the Executive Board Member for Space Research and Technology. Author contributions: S.C.S., D.G., S.C., R.F.G., Q.H., D.K., V.L., M.S., N.S., D.S., É.S., C.S., and G.Z. analyzed the seismic data and made ScS arrival time picks. S.C.S., P.L., D.G., Z.X., C.C., and W.T.P. performed the statistical analysis of the observed signals. S.C.S., Q.H., N.S., R.M., and A.G.M. identified the arrivals as ScS waves based on interior models from A.K., H.S., and A.R. A.K., M.D., A.C.D., and H.S. performed the inversions. S.C.S., A.K., P.L., D.G., D.A., J.C.E.I., M.K., C.P., A.-C.P., A.R., T.G., and S.E.S. participated and contributed to the interpretation of the results. Review of the continuous data and detection of marsquakes was done by S.C.S., S.C., G.Z., C.C., N.D., J.C., M.v.D., T.K., M.P., and A.H. with operational support by É.B., C.P., and P.M.D. S.C.S. and A.K. wrote the central part of the paper with contributions from H.S., N.S., D.A., J.C.E.I., A.G.M., A.-C.P., A.R., J.C., and M.v.D. J.C.E.I., R.M., M.K., and V.L. reviewed the contributions to the supplementary materials. The InSight mission is managed by W.B.B., M.P.P., and S.E.S. The SEIS instrument development was led by P.L., D.G., W.T.P., and W.B.B. Supplementary section 1 was written by M.S., D.S., and É.S. with contributions from S.C.S., C.S., and Z.X. Supplementary section 2 was written by D.K. and V.L. with contributions from J.C.E.I. and N.S. Supplementary section 3 was written by M.S. and É.S. Supplementary section 4 was written by R.F.G. with contributions from M.D. Supplementary section 5 was written by Q.H. with contributions from N.S. Supplementary section 6 was written by S.C.S. with contributions from the authors of the other supplements. Supplementary section 7 was written by Z.X. and C.C. with contributions from P.L. and W.T.P. Supplementary section 8 was written by A.K., M.D., A.C.D., and H.S. Supplementary section 9 was written by M.D. Supplementary section 10 was written by A.C.D., A.K., and M.D. Supplementary section 11 was written by D.A. and A.R. with contributions from A.K. Competing interests: The authors declare that they have no competing interests. Data and materials availability: We thank the operators of JPL, SISMOC, MSDS, IRIS-DMC, and PDS for providing SEED SEIS data (87). Three hundred interior models derived in this study are available from MSDS (88)

The interior of Mars as seen by InSight (Invited)

InSight is the first planetary mission dedicated to exploring the whole interior of a planet using geophysical methods, specifically seismology and geodesy. To this end, we observed seismic waves of distant marsquakes and inverted for interior models using differential travel times of phases reflected at the surface (PP, SS...) or the core mantle-boundary (ScS), as well as those converted at crustal interfaces. Compared to previous orbital observations1-3, the seismic data added decisive new insights with consequences for the formation of Mars: The global average crustal thickness of 24-75 km is at the low end of pre-mission estimates5. Together with the the thick lithosphere of 450-600 km5, this requires an enrichment of heat-producing elements in the crust by a factor of 13-20, compared to the primitive mantle. The iron-rich liquid core is 1790-1870 km in radius6, which rules out the existence of an insulating bridgmanite-dominated lower mantle on Mars. The large, and therefore low-density core needs a high amount of light elements. Given the geochemical boundary conditions, Sulfur alone cannot explain the estimated density of ~6 g/cm3 and volatile elements, such as oxygen, carbon or hydrogen are needed in significant amounts. This observation is difficult to reconcile with classical models of late formation from the same material as Earth. We also give an overview of open questions after three years of InSight operation on the surface of Mars, such as the potential existence of an inner core or compositional layers above the CM