Resumen:

Centaurs are a dynamical class of small icy bodies of the solar system, short-time residents (less than 10\^7 yr) in the region between Jupiter’s and Neptune’s orbits. They are scattered from the trans-Neptunian belt (TNB) and a fraction of them become Jupiter family comets (JFCs) during even shorter lifetimes (10\^5 yr). Centaurs are an intermediate population, halfway between the distant, cold, and relatively stable bodies in the and the rapidly sublimating comets of the hot inner regions. Remarkably, some Centaurs (about 10 \%) show comet-like activity even when they are beyond the orbit of Jupiter, which suggests mass loss driven by a process, which is different from the sublimation of water ice. In their chaotic orbital evolution, some of them spend part of their life as Jupiter family comets. The study of their surface properties is important to understand the link between trans-neptunian objects (TNOs), Centaurs and comets, and how their surface composition evolve whit the time they spend at distances from the Sun were volatiles like CO and CO2 can sublimate. Near-infrared spectral observations of 10 Centaurs were obtained with the James Webb Space Telescope (JWST) Near-Infrared Spectrograph (NIRSpec) as part of the Guaranteed Time Observers (GTO) program and the 2418 DiSCo-TNOs (Discovering the composition of the trans-Neptunian objects) program (PI: Pinilla-Alonso). JWST’s exquisite sensitivity in the 1-5 micron region allow to obtain high SNR Low-resolution spectra in the 0.6-5 microns region, which provide unique surface compositional information. Ices (H2O, CO2, etc), complex organic and silicates can be identified. We show that two compositional groups as in the TNO population,on dominated by water and silicates and other dominated by carbon species coexist in the Centaur population but with less volatiles than TNOs and a larger fraction of silicate particles (dust) deposited on their surfaces during their active phases.

Resumen:

During its orbit around comet 67P/Churyumov-Gerasimenko (67P), the Rosetta mission obtained a plethora of invaluable data. In particular, dust particles with sizes up to ~0.1 mm were individually sampled and analyzed by dust collectors, while larger particles were remotely observed by the OSIRIS imaging system. Unfortunately, the remote sensing method provided only the particles' position and velocity projected onto the image plane, lacking data regarding the distance to the camera and line-of-sight velocity. To address this issue we propose a novel approach based on statistically comparing bright tracks observed in OSIRIS images with synthetic images. We implemented a semi-automatic method to detect bright tracks in multiple sets of OSIRIS images. Next, we generated synthetic images by modelling the trajectories of dust aggregates in the cometary coma, influenced by gas drag, gravity from the 3D shape model of the nucleus, solar radiation pressure, and solar tides. Lastly, the trajectories were combined with the camera's position and pointing, in order to generate synthetic images of the aggregates as OSIRIS would have observed them. This novel methodology allowed us to extract essential physical parameters of the aggregates, including size and density, while also uncovering information about their ejection, such as the source region and initial velocity, which are related to the mechanisms causing the ejections themselves. Using the particle parameterns, this approach also allows to estimate the mass flux of large particles into the tail and trail of the comet.

Resumen:

Gaia DR3 presents the reflectance spectra of some 60000 asteroids in the solar system. We analysed these spectra in an attempt to detect the feature in the spectra around 650 nm, the OH band, which is indicative of primitive aqueous alteration, namely that in the parent body (or parent planetesimal) of the asteroid where the OH feature is seen, liquid water was present at some point. In combination with the data on asteroid orbits provided by Gaia, an analysis of this feature can provide insights into where hydration (i.e. water) was present in the primitive solar system. We present the results of applying a machine learning method to classify asteroid spectra as showing or not showing the hydration feature. The resulting set of asteroids where the OH band may be present are analyzed in terms of their orbital properties. The search for such asteroids is subsequently extended to the Zwicky Transient Faciliity photometric database with the aim to uncover more candidate astreroids with OH bands.