Ground-based monitoring of comet 67P/Churyumov-Gerasimenko gas activity throughout the <i>Rosetta</i> mission

Simultaneously to the ESA Rosetta mission, a world-wide ground-based campaign provided measurements of the large scale activity of comet 67P/Churyumov-Gerasimenko through measurement of optically active gas species and imaging of the overall dust coma. We present more than two years of observations performed with the FORS2 low resolution spectrograph at the VLT, TRAPPIST, and ACAM at the WHT. We focus on the evolution of the CN production, as a tracer of the comet activity. We find that it is asymmetric with respect to perihelion and different from that of the dust. The CN emission is detected for the first time at 1.34 au pre-perihelion and production rates then increase steeply to peak about two weeks after perihelion at (1.00±0.10) ×1025 molecules s−1, while the post-perihelion decrease is more shallow. The evolution of the comet activity is strongly influenced by seasonal effects, with enhanced CN production when the Southern hemisphere is illuminated

A Dendrogeomorphological Study of the Local Effect of Climate Change

The climatic and environmental conditions of Patagonia changed substantially after 1850 and after the mid-1970s decade. The impact of these changes is being observed in the new configuration of rivers and their riverine vegetation. The objective of this work is to integrate dendrogeomorphological techniques to the mapping and modeling of the recent distribution of vegetation of the riverine landscape, as an indicator of the local effect of climate change.The hydrological regime and the evolution of riparian vegetation at the confluence of the Cuyin Manzano and Traful Rivers were synchronized using the data obtained from 34 samples of plots of 6x6 meters. The plots were adjusted to the pixel resolution of two SPOT 7 satellite images (flood and dryness), concentric to an area of 18x18 meters, in order to validate a supervised classification of vegetation, belonging to different fluvial geoforms. In the plots with woody vegetation two trees corresponding to one or two age classes characteristic of the stands were drilled. The results indicate that, in agreement with global and Patagonia climate change estimates, there is a slight tendency of change in the flood and drought regime, with decreases in mean annual minimum flows and a period of drought in the last six years. The most outstanding result of our study indicates that the change of the hydrological regime implies a slight reduction of the average minimum flows, without this entailing a modification of the regime of flood pulses that in some cases are very extreme. This situation has a marked incidence in the fact that the woody vegetation colonizes new substrates and emerged landforms, while it is affected by frequent and intense flood events, with a change of the compositions and distribution of the vegetation

Stochastic Coherence Over Attention Trajectory For Continuous Learning In Video Streams

Devising intelligent agents able to live in an environment and learn by observing the surroundings is a longstanding goal of Artificial Intelligence. From a bare Machine Learning perspective, challenges arise when the agent is prevented from leveraging large fully-annotated dataset, but rather the interactions with supervisory signals are sparsely distributed over space and time. This paper proposes a novel neural-network-based approach to progressively and autonomously develop pixel-wise representations in a video stream. The proposed method is based on a human-like attention mechanism that allows the agent to learn by observing what is moving in the attended locations. Spatio-temporal stochastic coherence along the attention trajectory, paired with a contrastive term, leads to an unsupervised learning criterion that naturally copes with the considered setting. Differently from most existing works, the learned representations are used in open-set class-incremental classification of each frame pixel, relying on few supervisions. Our experiments leverage 3D virtual environments and they show that the proposed agents can learn to distinguish objects just by observing the video stream. Inheriting features from state-of-the art models is not as powerful as one might expect

Planetary Spectrum Generator: an accurate online radiative transfer suite for atmospheres, comets, small bodies and exoplanets

We have developed an online radiative-transfer suite (https://psg.gsfc.nasa.gov) applicable to a broad range of planetary objects (e.g., planets, moons, comets, asteroids, TNOs, KBOs, exoplanets). The Planetary Spectrum Generator (PSG) can synthesize planetary spectra (atmospheres and surfaces) for a broad range of wavelengths (UV/Vis/near-IR/IR/far-IR/THz/sub-mm/Radio) from any observatory (e.g., JWST, ALMA, Keck, SOFIA), any orbiter (e.g., ExoMars, Juno), or any lander (e.g., MSL). This is achieved by combining several state-of-the-art radiative transfer models, spectroscopic databases and planetary databases (i.e., climatological and orbital). PSG has a 3D (three-dimensional) orbital calculator for most bodies in the solar system, and all confirmed exoplanets, while the radiative-transfer models can ingest billions of spectral signatures for hundreds of species from several spectroscopic repositories. It integrates the latest radiative-transfer and scattering methods in order to compute high resolution spectra via line-by-line calculations, and utilizes the efficient correlated-k method at moderate resolutions, while for computing cometary spectra, PSG handles non-LTE and LTE excitation processes. PSG includes a realistic noise calculator that integrates several telescope / instrument configurations (e.g., interferometry, coronagraphs) and detector technologies (e.g., CCD, heterodyne detectors, bolometers). Such an integration of advanced spectroscopic methods into an online tool can greatly serve the planetary community, ultimately enabling the retrieval of planetary parameters from remote sensing data, efficient mission planning strategies, interpretation of current and future planetary data, calibration of spectroscopic data, and development of new instrument/spacecraft concepts.Comment: Journal of Quantitative Spectroscopy and Radiative Transfer, submitte

Morus alba L. Bioindicator of Pollution by Particulate Following an Urbanization Gradient in San Juan City

En hojas de Morus alba L. se evaluó la variación del contenido de sólidos en suspensión; durante un ciclo vegetativo (primavera, verano y fines de otoño), en el área urbana y suburbana de San Juan (Argentina). El estudio se realizó en San Juan muestreándose 40 árboles al azar. Los datos obtenidos se analizaron mediante ANOVA. El área foliar media externa representó el 52,1 ± 13,4 % en urbano y el 55,2 ± 9,2 % en suburbano. No se encontraron diferencias estadísticas en las partículas depositadas en la parte externa e interna de la copa. Las partículas 2 depositadas por cm de follaje no difieren estadísticamente entre urbano y suburbano. Teniendo en cuenta el censo forestal, el área 2 foliar media y los sólidos/cm , se depositaron en total 9.9 kg en primavera y 295.7 kg en otoño de sólidos.In leaves of Morus alba was analyzed the variation in air particle deposition, during a complete vegetative cycle (spring, summer and end of autumn), in urban and suburban area of San Juan (Argentina). The study was made in San Juan sampling 40 trees randomly selected. Data obtained were statistically analyzed using the ANOVA test. The treetop mean external foliar area represents 52.1 ± 13.4 % in urban and 55.2 ± 9.2 % in suburban areas. No statistical differences were found in particles accumulated in internal and external sectors of the treetop. 2 Accumulated particles by cm of foliage did not differ statistically between urban and suburban area. Taking into account the forest 2 census, the mean foliage area, and the particulate/cm , total solids deposited were 9.9 kg (spring) and 295.7 kg (fall).Fil: Moreno, Gabriela Analia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Martinez Carretero, Eduardo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Faggi, A.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; ArgentinaFil: Castro, M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentin

First detection of CO2_2 emission in a Centaur: JWST NIRSpec observations of 39P/Oterma

Centaurs are minor solar system bodies with orbits transitioning between those of Trans-Neptunian Scattered Disk objects and Jupiter Family comets. 39P/Oterma is a frequently active Centaur that has recently held both Centaur and JFC classifications and was observed with the JWST NIRSpec instrument on 2022 July 27 UTC while it was 5.82 au from the Sun. For the first time, CO$_2$ gas emission was detected in a Centaur, with a production rate of Q$_{CO_2}$ = (5.96 $\pm$ 0.80) $\times$ 10$^{23}$ molecules s$^{-1}$. This is the lowest detection of CO$_2$ of any Centaur or comet. CO and H$_2$O were not detected down to constraining upper limits. Derived mixing ratios of Q$_{CO}$/Q$_{CO_2}$ $\leq$2.03 and Q$_{CO_2}$/Q$_{H_2O}$ $\geq$0.60 are consistent with CO$_2$ and/or CO outgassing playing large roles in driving the activity, but not water, and show a significant difference between the coma abundances of 29P/Schwassmann-Wachmann 1, another Centaur at a similar heliocentric distance, which may be explained by thermal processing of 39P's surface during its previous Jupiter-family comet orbit. To help contextualize the JWST data we also acquired visible CCD imaging data on two dates in July (Gemini North) and September (Lowell Discovery Telescope) 2022. Image analysis and photometry based on these data are consistent with a point source detection and an estimated effective nucleus radius of 39P in the range of $R_{nuc}=$2.21 to 2.49~km