Future of Venus Research and Exploration

Despite the tremendous progress that has been made since the publication of the Venus II book in 1997, many fundamental questions remain concerning Venus’ history, evolution and current geologic and atmospheric processes. The international science community has taken several approaches to prioritizing these questions, either through formal processes like the Planetary Decadal Survey in the United States and the Cosmic Vision in Europe, or informally through science definition teams utilized by Japan, Russia, and India. These questions are left to future investigators to address through a broad range of research approaches that include Earth-based observations, laboratory and modeling studies that are based on existing data, and new space flight missions. Many of the highest priority questions for Venus can be answered with new measurements acquired by orbiting or in situ missions that use current technologies, and several plausible implementation concepts have been studied and proposed for flight. However, observations needed to address some science questions pose substantial technological challenges, for example, long term survival on the surface of Venus and missions that require surface or controlled aerial mobility. Missions enabled by investments in these technologies will open the door to completely new ways of exploring Venus to provide unique insights into Venus’s past and the processes at work today.     

On the Detectability and Use of Normal Modes for Determining Interior Structure of Mars

The InSight mission to Mars is well underway and will be the first mission to acquire seismic data from a planet other than Earth. In order to maximise the science return of the InSight data, a multifaceted approach will be needed that seeks to investigate the seismic data from a series of different frequency windows, including body waves, surface waves, and normal modes. Here, we present a methodology based on globally-averaged models that employs the long-period information encoded in the seismic data by looking for fundamental-mode spheroidal oscillations. From a preliminary analysis of the expected signal-to-noise ratio, we find that normal modes should be detectable during nighttime in the frequency range 5–15 mHz. For improved picking of (fundamental) normal modes, we show first that those are equally spaced between 5–15 mHz and then show how this spectral spacing, obtained through autocorrelation of the Fourier-transformed time series can be further employed to select normal mode peaks more consistently. Based on this set of normal-mode spectral frequencies, we proceed to show how this data set can be inverted for globally-averaged models of interior structure (to a depth of \(\sim 250~\mbox{km}\)), while simultaneously using the resultant synthetically-approximated normal mode peaks to verify the initial peak selection. This procedure can be applied iteratively to produce a “cleaned-up” set of spectral peaks that are ultimately inverted for a “final” interior-structure model. To investigate the effect of three-dimensional (3D) structure on normal mode spectra, we constructed a 3D model of Mars that includes variations in surface and Moho topography and lateral variations in mantle structure and employed this model to compute full 3D waveforms. The resultant time series are converted to spectra and the inter-station variation hereof is compared to the variation in spectra computed using different 1D models. The comparison shows that 3D effects are less significant than the variation incurred by the difference in radial models, which suggests that our 1D approach represents an adequate approximation of the global average structure of Mars.     

Enrichment of the Hot Intracluster Medium: Observations

Four decades ago, the firm detection of an Fe-K emission feature in the X-ray spectrum of the Perseus cluster revealed the presence of iron in its hot intracluster medium (ICM). With more advanced missions successfully launched over the last 20 years, this discovery has been extended to many other metals and to the hot atmospheres of many other galaxy clusters, groups, and giant elliptical galaxies, as evidence that the elemental bricks of life—synthesized by stars and supernovae—are also found at the largest scales of the Universe. Because the ICM, emitting in X-rays, is in collisional ionisation equilibrium, its elemental abundances can in principle be accurately measured. These abundance measurements, in turn, are valuable to constrain the physics and environmental conditions of the Type Ia and core-collapse supernovae that exploded and enriched the ICM over the entire cluster volume. On the other hand, the spatial distribution of metals across the ICM constitutes a remarkable signature of the chemical history and evolution of clusters, groups, and ellipticals. Here, we summarise the most significant achievements in measuring elemental abundances in the ICM, from the very first attempts up to the era of XMM-Newton, Chandra, and Suzaku and the unprecedented results obtained by Hitomi. We also discuss the current systematic limitations of these measurements and how the future missions XRISM and Athena will further improve our current knowledge of the ICM enrichment.     

JIRAM, the image spectrometer in the near infrared on board the Juno mission to Jupiter

The Jovian InfraRed Auroral Mapper (JIRAM) has been accepted by NASA for inclusion in the New Frontiers mission "Juno," which will launch in August 2011. JIRAM will explore the dynamics and the chemistry of Jupiter's auroral regions by high-contrast imaging and spectroscopy. It will also analyze jovian hot spots to determine their vertical structure and infer possible mechanisms for their formation. JIRAM will sound the jovian meteorological layer to map moist convection and determine water abundance and other constituents at depths that correspond to several bars pressure. JIRAM is equipped with a single telescope that accommodates both an infrared camera and a spectrometer to facilitate a large observational flexibility in obtaining simultaneous images in the L and M bands with the spectral radiance over the central zone of the images. Moreover, JIRAM will be able to perform spectral imaging of the planet in the 2.0-5.0 microm interval of wavelengths with a spectral resolution better than 10 nm. Instrument design, modes, and observation strategy will be optimized for operations onboard a spinning satellite in polar orbit around Jupiter. The JIRAM heritage comes from Italian-made, visual-infrared imaging spectrometers dedicated to planetary exploration, such as VIMS-V on Cassini, VIRTIS on Rosetta and Venus Express, and VIR-MS on the Dawn mission.     

Transforming Dust to Planets

We review recent progress in understanding how nebular dust and gas are converted into the planets of the present-day solar system, focusing particularly on the “Grand Tack” and pebble accretion scenarios. The Grand Tack can explain the observed division of the solar system into two different isotopic “flavours”, which are found in both differentiated and undifferentiated meteorites. The isotopic chronology inferred for the development of these two “flavours” is consistent with expectations of gas-giant growth and nebular gas loss timescales. The Grand Tack naturally makes a small Mars and a depleted, dynamically-excited and compositionally mixed asteroid belt (as observed); it builds both Mars and the Earth rapidly, which is consistent with the isotopically-inferred growth timescale of the former, but not the latter. Pebble accretion can explain the rapid required growth of Jupiter and Saturn, and the number of Kuiper Belt binaries, but requires specific assumptions to explain the relatively protracted growth timescale of Earth. Pure pebble accretion cannot explain the mixing observed in the asteroid belt, the fast proto-Earth spin rate, or the tilt of Uranus. No current observation requires pebble accretion to have operated in the inner solar system, but the thermal and compositional consequences of pebble accretion have yet to be explored in detail.     

Neutrinos from Supernovae

Neutrinos are fundamental particles in the collapse of massive stars. Because of their weakly interacting nature, neutrinos can travel undisturbed through the stellar core and be direct probes of the still uncertain and fascinating supernova mechanism. Intriguing recent developments on the role of neutrinos during the stellar collapse are reviewed, as well as our current understanding of the flavor conversions in the stellar envelope. The detection perspectives of the next burst and of the diffuse supernova background will be also outlined. High-energy neutrinos in the GeV-PeV range can follow the MeV neutrino emission. Various scenarios concerning the production of high-energy neutrinos are discussed.     

Recent Advancements and Motivations of Simulated Pluto Experiments

This review of Pluto laboratory research presents some of the recent advancements and motivations in our understanding enabled by experimental simulations, the need for experiments to facilitate models, and predictions for future laboratory work. The spacecraft New Horizons at Pluto has given a large amount of scientific data already rising to preliminary results, spanning from the geology to the atmosphere. Different ice mixtures have now been detected, with the main components being nitrogen, methane, and carbon monoxide. Varying geology and atmospheric hazes, however, gives us several questions that need to be addressed to further our understanding. Our review summarizes the complexity of Pluto, the motivations and importance of laboratory simulations critical to understanding the low temperature and pressure environments of icy bodies such as Pluto, and the variability of instrumentation, challenges for research, and how simulations and modeling are complimentary.     

Research on High-Precision Measurement Systems of Modern Aircraft

High-precision measurement systems of modern aircraft are studied in this paper. A measurement system with correction in the structure of inertial navigation system is introduced for highprecision aircraft. In the correction algorithms, a linear error model of the navigation system is usually used. With the aim of increasing the accuracy of the navigation system, we propose a nonlinear correction algorithm based on the state dependent coefficient representation of the nonlinear model.