Using the HP3 mole on InSight to probe the thermal and mechanical properties of the Martian regolith

The NASA InSight Lander on Mars includes the Heat Flow and Physical Properties Package HP3 (see Spohn et al. (2018) for a description of the package) 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, it reached a depth of 40 cm, bringing the mole body 1-2 cm below the surface. A discussion of the lessons learned from the penetration failure and suggestions for an improved mole have been given by Spohn et al. (2022). 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. (compare Figure 1)Figure 1. The HP3 mole before complete burial and the properties of the hole that the mole had punched in the duricrustDuring the campaign the mole penetrated further aided by friction applied using the scoop at the end of the robotic Instrument Deployment Arm and direct support by the latter. The mole reversed its downward motion twice during attempts to provide friction through pressure on the regolith instead of directly with the scoop to the hull. The penetration record of the mole and its thermal sensors were used to measure thermal and mechanical soil parameters such as the penetration resistance of the duricrust. These parameter values are summarized in Table 1 below. The combined data suggest a model of the regolith that has an about 20 cm thick duricrust underneath a 1 cm thick sand layer and above another 10 cm of sand. Underneath the latter, a layer more resistant to penetration and possibly consisting of debris from a small impact crater was found. The thermal conductivity increases from 14 mW/m K in the 1 cm sand layer to 34 mW/m K in the duricrust and the sand layer underneath the duricrust to 64 mW/m K in the gravel layer below. Applying cone penetration theory, the resistance of the duricrust was used to estimate a cohesion of the latter of 4 - 25 kPa depending on the friction angle of the crust. Pushing the scoop with its blade into the surface and chopping of a piece of crust provided another estimate of the cohesion of 5.8 kPa.The hammerings of the mole were recorded by the seismometer SEIS and the signals could be used to derive a P-wave velocity and an S-wave as listed (see also Brinkman et al., 2022) representative of the topmost tens of cm of the regolith. Together with a density provided by a thermal conductivity and diffusivity measurement using the mole thermal sensors of about 1211 (Grott et al., 2021), the elastic moduli could be calculated from the seismic velocities.Table 1. Model of the InSight landing site regolith After burial, the mole was used to measure the thermal conductivity of the regolith as a function of the solar longitude (the seasons on Mars). The variations of the thermal conductivity are consequences of the variations in atmosphere pressure with the seasons and the contribution of atmosphere gas in the porous regolith contributing to the thermal conductivity. Figure 2 Thermal conductivity in the regolith top 40 cm as measured by sensors on the HP3 mole as a function of the solar longitude (seasons on Mars). Brinkmann et al. (2022), submitted to J. Geophys. Res. PlanetsGrott et al. (2021), Planet and Space Sci, DOI: 10.1029/2019EA000670Spohn et al. (2018), Space Sci Rev, DOI:10.1007/s11214-018-0531-4 Spohn et al. (2022), Advances in Space Research, DOI: 10.1016/j.asr.2022.02.00

First Report of Soybean Vein Necrosis Disease Caused by Soybean vein necrosis-associated virus in Wisconsin and Iowa

Several viral diseases of soybean (Glycine max) have been identified in the north-central U.S. soybean production area, which includes Wisconsin and Iowa (2). Previously, Soybean vein necrosis disease (SVND) caused by Soybean vein necrosis-associated virus was reported in Arkansas, Tennessee, and other southern states (4). In September 2012, soybean plants with symptoms similar to those reported for SVND (4) were observed in fields across Wisconsin and Iowa. Symptoms included leaf-vein and leaf chlorosis, followed by necrosis of the leaf veins and eventually necrosis of the entire leaf. Six samples with symptoms indicative of SVNaV were collected from research plots located at the West Madison Agricultural Research Station located in Madison, WI. An additional three samples were collected from three locations in central Iowa. Total RNA extracted from each sample using the Trizol Plus RNA purification kit (Invitrogen, Carlsbad, CA) was used to generate complementary DNA (cDNA) using the iScript cDNA synthesis kit (Bio-Rad Laboratories, Hercules, CA) following the manufacturers\u27 suggested protocols. The resulting cDNA was used as template in a PCR with SVNaV-specific primers, SVNaV-f1 and SVNaV-r1 (3). PCRs of two of the six Wisconsin samples and two Iowa samples were positive. Amplification products were not detected in the other five samples. The amplification products from the four strongly positive samples were purified using the Wizard SV Gel and PCR Purification Kit (Promega, Madison, WI) following the manufacturer\u27s suggested protocol and were subjected to automated sequencing (University of Wisconsin Biotechnology Center or Iowa State University, DNA Sequencing Facilities). BLASTn (1) alignments of the 915-bp consensus sequence revealed 98% and \u3e99% identity of the Wisconsin and Iowa samples, respectively, with the ‘S’ segment of the SVNaV ‘TN’ isolate (GenBank Accession No. GU722319.1). Samples from the same leaf tissue used above, were subjected to serological tests for SVNaV using antigen coated-indirect ELISA (3). Asymptomatic soybeans grown in the greenhouse were used as a source of leaves for negative controls. These tests confirmed the presence of SVNaV in eight symptomatic soybean leaflets collected in Wisconsin and Iowa. The asymptomatic control and one Iowa sample, which was also PCR-negative, were also negative by serological testing. Six additional samples from soybean fields in as many Wisconsin counties (Fond Du Lac, Grant, Green, Juneau, Richland, Rock) tested positive for SVNaV using specific primers that amplify the ‘L’ segment (4). The sequenced amplification products (297-bp) showed 99 to 100% homology to the L segment of the TN isolate (GU722317.1). To our knowledge, this is the first report of SVNaV associated with soybean and the first report of SVND in Wisconsin and Iowa. Considering that little is known about SVNaV, it is assumed that it is like other Tospoviruses and can cause significant yield loss (4). Soybean is a major cash crop for Wisconsin and Iowa, and infection by SVNaV could result in potential yield loss in years where epidemics begin early and at a high initial inoculum level

Level structures of 96,97,98Ru at high angular momentum

The high-spin level structures of 96,97,98Ru (Z544) have been investigated using the 65Cu(36S, pxn)96,97,98Ru (x54,3,2) reactions. About 130 new transitions have been observed and unambiguously placed in the decay schemes of these nuclei. The level schemes have been extended up to spin J'22– 34\, and excitation energies Ex'20224 MeV. Spherical shell model calculations have been performed and theoretical level energies compared with experimental values. Calculations using 88Sr as the core give a reasonable agreement for the observed energy levels up to J16\), possibly manifesting vibrational behavior

Level structure of 94,95,96Tc at high spins and shell-model calculations

High-spin states in the 94,95,96Tc (N = 51, 52, and 53) nuclei have been investigated using the 65Cu+H36S reaction at a beam energy of 142 MeV. More than 60 new transitions have been identified and placed in their level schemes, which now extend up to spin J ≈ 22ℏ and excitation energies Ex ≈ 12 MeV. Spherical shell-model calculations have been performed using different model spaces. A restricted model space, using 88Sr as the core and the π(p 1/2,g9/2) ν(d5/2,s1/2) valence orbitals, reproduces the experimental excitation energies up to J ≈ 14ℏ. The higher-angular-momentum states are dominated by the excitation of a g9/2 neutron across the N = 50 magic core, as indicated by large-basis shell model calculations

Nuclear structure of 94,95Mo at high spins

The high-spin level structures of 94,95Mo (N552,53) have been investigated via the 65Cu(36S, a p2n)94Mo and 65Cu(36S, a pn)95Mo reactions at 142 MeV. The level schemes have been extended up to spin J'19\ and excitation energies Ex'12 MeV. Spherical shell-model calculations have been performed and compared with the experimental energy levels. The level structure of 94Mo exhibits a single-particle nature and the higher-angular-momentum states are dominated by the excitation of a g9/2 neutron across the N550 shell gap. The level sequences observed in 95Mo have been interpreted on the basis of the spherical shell model and weak coupling of a d5/2 or a g7/2 neutron to the 94Mo core

High-spin states in 97,98Rh

High-spin states in 97,98Rh (Z545) were populated via the 65Cu( 36S,xn)97,98Rh (x54,3) fusion-evaporation reactions. More than 40 additional transitions have been identified and placed in the decay schemes of these nuclei. The level scheme of 97Rh has been extended up to tentative spins of Jp 539/21,37/22, and the placement of some of the previously known transitions has been revised. The level structure of 97Rh indicates a single-particle nature and the observed levels are reproduced well by spherical shell-model calculations. The level scheme of 98Rh has been extended up to spins J;20\ and up to an excitation energy of ;10 MeV. The low-spin structure of 98Rh (J<10\), appears to indicate also a singleparticle structure, as supported by the stretched coupling scheme @ 97Rh(J8)^n (d5/2)598Rh (J)#

Alignment additivity in the two-quasiparticle superdeformed bands of 192Tl

Four superdeformed bands have been confirmed in 192Tl. Two of these bands have script T sign(2) dynamic moments of inertia which are nearly constant with rotational frequency ℏω. The other two bands show the characteristic rise of script T sign(2) with increasing ℏω seen in most superdeformed bands of the A = 190 region of superdeformation. From comparisons with the odd-A neighbors, it was found that the alignments of these bands relative to a 192Hg core can be accounted for from the additive contributions of the assigned quasiproton and quasineutron orbitals

Prolate collectivity in Tl187

High-spin states of Tl187 populated in the Gd156(35Cl,4n) reaction have been investigated with -ray coincidence techniques. Two decoupled bands feeding the oblate 9/2- isomeric state have been established. These bands are built on h9/2 and i13/2 configurations associated with prolate shapes. The first observation of a low-K h9/2 structure in an odd-A Tl nucleus is used to draw conclusions on the role of this proton orbital in stabilizing the prolate minimum seen in light Hg isotopes

Limits to the sensitivity of a low noise compact atomic gravimeter

A detailed analysis of the most relevant sources of phase noise in an atomic interferometer is carried out, both theoretically and experimentally. Even a short interrogation time of 100 ms allows our cold atom gravimeter to reach an excellent short term sensitivity to acceleration of $1.4\times 10^{-8}$g at 1s. This result relies on the combination of a low phase noise laser system, efficient detection scheme and good shielding from vibrations. In particular, we describe a simple and robust technique of vibration compensation, which is based on correcting the interferometer signal by using the AC acceleration signal measured by a low noise seismometer.Comment: 30 pages, 14 figure