Atmospheric response to a Hot SST Event in November 2006 as observed by the AIRS instrument

Using Atmospheric Infrared Sounder (AIRS) products of atmospheric temperature and geopotential height, we investigate the atmospheric response to HE0611, which was found and investigated by [Qin, H., Kawamura, H., Sakaida, F., Ando, K. A case study of the tropical Hot Event in November 2006 (HE0611) using a geostationary meteorological satellite and the TAO/TRITON mooring array. J. Geophys. Res. 113, C08045, doi: 10.1029/2007JC004640, 2008]. HE0611 was formed by connecting two very high SST areas, HE0611-East and HE0611-West. The period-mean atmosphere temperatures at levels of 925 and 850 hPa in HE0611-West are higher, by about 0.5 K, than those in WE0611-East while the atmospheric temperatures at middle to high levels (700–300 hPa) are higher in HE0611-East. The period-mean geopotential heights HE0611-East are much lower than those in HE0611-West for the levels from the surface to 400 hPa. The mean geopotential heights from 400 hPa to 200 hPa are higher in HE0611-East. In the middle and high layers over HE0611-West, the atmosphere temperatures gradually decrease from 7th to 17th, and then increase significantly. The increase in HE0611-East starts from 15th November, which is earlier than that of HE0611-West. The geopotential heights in the high layer of both the areas also show corresponding behaviors. The lagged atmospheric response in the western part is confirmed by the correlation analysis. It emerges that the atmospheric response to HE0611 is well organized and associated with deep convention in HE0611-East and subsidence in HE0611-West. These are also consistent with the HE0611 features and evolution revealed by earlier HE studies.     

Analytical expression for distant retrograde orbits around a small natural satellite

An analytical expression for distant retrograde orbits (DROs) is obtained in this study. Owing to the fact that a planar DRO is a closed orbit and can be expressed as an approximately elliptical orbit, respective geometries and periods of DROs are analytically calculated. A switching point, where various properties of planar DROs change abruptly with an increase in the orbital radius, is determined. The Mars–Deimos system is taken as a case study in this work. The proposed method can be applied to cases where the Hill’s approximation of the restricted three-body problem is valid. Numerical calculations are performed to validate the proposed method.     

Chemical evolution of RNA under hydrothermal conditions and the role of thermal copolymers of amino acids for the prebiotic degradation and formation of RNA.

The roles of thermal copolymers of amino acids (TCAA) were studied for the prebiotic degradation of RNA. A weak catalytic ability of TCAA consisted of Glu, L-Ala, L-Val, L-Glu, L-Asp, and optionally L-His was detected for the cleavage of the ribose phosphodiester bond of a tetranucleotide (5'-dCrCdGdG) in aqueous solution at 80 degees C. The rate constants of the disappearance of 5'-dCrCdGdG were determined in aqueous solutions using different pH buffer and TCAA. The degradation rates were enhanced 1.3-3.0 times in the presence of TCAA at pH 7.5 and 8.0 at 80 degrees C, while the hydrolysis of oligoguanylate (oligo(G)) was accelerated about 1.6 times at pH 8.0. A weak inhibitory activity for the cleavage of oligo(G) was detected in the presence of 0.055 M TCAA-Std. On the other hand, our recent study on the influences of TCAA for the template-directed reaction of oligo(G) on a polycytidylic acid template showed that TCAA has an acceleration activity for the degradation of the activated nucleotide monomer and an acceleration activity for the formation of G5' ppG capped oligo(G). This series of studies suggest that efficient and selective catalytic or inhibitory activities for either the degradation or formation of RNA under hydrothermal conditions could have hardly emerged from the simple thermal condensation products of amino acids. A scenario is going to be deduced on the chemical evolution of enzymatic activities and RNA molecules concerning hydrothermal earth conditions.     

Signal Interference and Improvement of Signal-to-Noise Ratios in a Half-Wave Linear Detector

Signal interference in the half-wave linear detector has been studied only for amplitude modulation. In this paper, we treat signal interference for both an amplitude-and an angle-modulation communication system. The input to the half-wave linear detector is assumed to be composed of an amplitude-modulated wave, an angle-modulated wave, and narrow-band Gaussian noise. In particular, when strongweak relations exist in the input processes, a detailed analysis for the output component is presented to clarify some useful output properties.     

Stability of amino acids and their oligomerization under high-pressure conditions: implications for prebiotic chemistry

The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400°C) and high-pressure (1.0-5.5?GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination.     

Evaluating the Wind-Induced Mechanical Noise on the InSight Seismometers

The SEIS (Seismic Experiment for Interior Structures) instrument onboard the InSight mission to Mars is the critical instrument for determining the interior structure of Mars, the current level of tectonic activity and the meteorite flux. Meeting the performance requirements of the SEIS instrument is vital to successfully achieve these mission objectives. Here we analyse in-situ wind measurements from previous Mars space missions to understand the wind environment that we are likely to encounter on Mars, and then we use an elastic ground deformation model to evaluate the mechanical noise contributions on the SEIS instrument due to the interaction between the Martian winds and the InSight lander. Lander mechanical noise maps that will be used to select the best deployment site for SEIS once the InSight lander arrives on Mars are also presented. We find the lander mechanical noise may be a detectable signal on the InSight seismometers. However, for the baseline SEIS deployment position, the noise is expected to be below the total noise requirement \(>97~\%\) of the time and is, therefore, not expected to endanger the InSight mission objectives.     

Modeling of Ground Deformation and Shallow Surface Waves Generated by Martian Dust Devils and Perspectives for Near-Surface Structure Inversion

We investigated the possible seismic signatures of dust devils on Mars, both at long and short period, based on the analysis of Earth data and on forward modeling for Mars. Seismic and meteorological data collected in the Mojave Desert, California, recorded the signals generated by dust devils. In the 10–100 s band, the quasi-static surface deformation triggered by pressure fluctuations resulted in detectable ground-tilt effects: these are in good agreement with our modeling based on Sorrells’ theory. In addition, high-frequency records also exhibit a significant excitation in correspondence to dust devil episodes. Besides wind noise, this signal includes shallow surface waves due to the atmosphere-surface coupling and is used for a preliminary inversion of the near-surface S-wave profile down to 50 m depth. In the case of Mars, we modeled the long-period signals generated by the pressure field resulting from turbulence-resolving Large-Eddy Simulations. For typical dust-devil-like vortices with pressure drops of a couple Pascals, the corresponding horizontal acceleration is of a few nm/s² for rocky subsurface models and reaches 10–20 nm/s² for weak regolith models. In both cases, this signal can be detected by the Very-Broad Band seismometers of the InSight/SEIS experiment up to a distance of a few hundred meters from the vortex, the amplitude of the signal decreasing as the inverse of the distance. Atmospheric vortices are thus expected to be detected at the InSight landing site; the analysis of their seismic and atmospheric signals could lead to additional constraints on the near-surface structure, more precisely on the ground compliance and possibly on the seismic velocities.     

Mineral-enhanced hydrothermal oligopeptide formation at the second time scale

Accumulation of biopolymers should have been an essential step for the emergence of life on primitive Earth. However, experimental simulations for submarine hydrothermal vent systems in which high-temperature water spouts through minerals within a short time scale have not been attempted. Here, we show that enhancement of hydrothermal oligopeptide elongation by naturally occurring minerals was successfully verified for the first time by using a mineral-mediated hydrothermal flow reactor system (MMHF). MMHF consists of a narrow tubular reactor packed with mineral particles, and the enhancement or inhibitory activities of 10 types of naturally occurring minerals were successfully evaluated for an elongation reaction from (Ala)(4) to (Ala)(5) and higher oligopeptides in the absence of condensation reagents. It was unexpected that calcite and dolomite facilitated the elongation from (Ala)(4) to (Ala)(5) and higher oligopeptides with 28% yield at pH 7, while tourmaline, galena, apatite, mica, sphalerite, quartz, chalcopyrite, and pyrite did not show enhancement activities. These facts suggest the importance of carbonate minerals for the accumulation of peptide in primitive Earth environments.     

Dynamic particle accumulation structure (PAS) in half-zone liquid bridge – Reconstruction of particle motion by 3-D PTV

Three-dimensional (3-D) velocity field reconstruction of oscillatory thermocapillary convections in a half-zone liquid bridge with a radius of O (1 mm) was carried out by applying 3-D particle tracking velocimetry (PTV). Simultaneous observation of the particles suspended in the bridge by two CCD cameras was carried out by placing a small cubic beam splitter above a transparent top rod. The reconstruction of the 3-D trajectories and the velocity fields of the particles in the several types of oscillatory-flow regimes were conducted successfully for sufficiently long period without losing particle tracking. With this application the present authors conducted a series of experiments focusing upon the collapse and re-formation process of the PAS by mechanically disturbing fully developed PAS.     

Atmospheric Science with InSight

In November 2018, for the first time a dedicated geophysical station, the InSight lander, will be deployed on the surface of Mars. Along with the two main geophysical packages, the Seismic Experiment for Interior Structure (SEIS) and the Heat-Flow and Physical Properties Package (HP³), the InSight lander holds a highly sensitive pressure sensor (PS) and the Temperature and Winds for InSight (TWINS) instrument, both of which (along with the InSight FluxGate (IFG) Magnetometer) form the Auxiliary Sensor Payload Suite (APSS). Associated with the RADiometer (RAD) instrument which will measure the surface brightness temperature, and the Instrument Deployment Camera (IDC) which will be used to quantify atmospheric opacity, this will make InSight capable to act as a meteorological station at the surface of Mars. While probing the internal structure of Mars is the primary scientific goal of the mission, atmospheric science remains a key science objective for InSight. InSight has the potential to provide a more continuous and higher-frequency record of pressure, air temperature and winds at the surface of Mars than previous in situ missions. In the paper, key results from multiscale meteorological modeling, from Global Climate Models to Large-Eddy Simulations, are described as a reference for future studies based on the InSight measurements during operations. We summarize the capabilities of InSight for atmospheric observations, from profiling during Entry, Descent and Landing to surface measurements (pressure, temperature, winds, angular momentum), and the plans for how InSight’s sensors will be used during operations, as well as possible synergies with orbital observations. In a dedicated section, we describe the seismic impact of atmospheric phenomena (from the point of view of both “noise” to be decorrelated from the seismic signal and “signal” to provide information on atmospheric processes). We discuss in this framework Planetary Boundary Layer turbulence, with a focus on convective vortices and dust devils, gravity waves (with idealized modeling), and large-scale circulations. Our paper also presents possible new, exploratory, studies with the InSight instrumentation: surface layer scaling and exploration of the Monin-Obukhov model, aeolian surface changes and saltation / lifing studies, and monitoring of secular pressure changes. The InSight mission will be instrumental in broadening the knowledge of the Martian atmosphere, with a unique set of measurements from the surface of Mars.