Measuring cosmological distances by coalescing binaries

Gravitational waves detected from well-localized inspiraling binaries would allow us to determine, directly and independently, binary luminosity and redshift. In this case, such systems could behave as "standard candles" providing an excellent probe of cosmic distances up to z <0.1 and complementing other indicators of cosmological distance ladder.Comment: 4 pages, 2 figures and 2 tables. To appear in the Proceeding of the Spanish Relativity Meeting 2011 (Madrid, Spain, 29th August - 2nd September 2011

Thermal convection regimes in asteroid (1) Ceres

By using a finite difference 2D method, we study the possible thermal convection regimes in asteroid (1) Ceres and its effects on the crust. We numerically solve the system of equations made of the Navier-Stokes and heat transfer. Different physical conditions as well as initial compositions are explored

(1) Ceres: Study of Thermal Convection in the Mantle and its Mechanical Effects

Ceres is the largest body of the Main Belt, which is characterized by a huge abundance of water ice in its interior. This feature is suggested by its relatively low bulk density (2162 kg m-3, Russell et al. 2016, Park et al. 2016) and by several geological and geochemical evidences (specific minerals or salts produced by acqueous alteration, icy patches on the surface, lobate morphologies interpretable as surface flows (De Sanctis et al. 2016, Carrozzo et al. 2018, Raponi et al. 2018, Zolotov 2017 and Schmidt et al., 2017).Ceres is partially differentiated as suggested by its normalized moment of inertia, 0.37 (Park et al. 2016). A typical internal structure proposed for Ceres is: a rocky core (300-350 km), an icy (or muddy) mantle (100-150 km) and a rocky crust some kilometers in depth (eg. Mc Cord & Sotin 2005, Neveu & Desch, 2015). The temperature gradient across the mantle, estimated through numerical modelling (e.g. McCord & Sotin 2005, Neveu & Desch 2015) would be large enough to initiate a thermal convection in the mantle. Since the mantle is not uniquely defined from a composition point of view, in this work we explore how the composition and, in particular the "degree" of muddiness of the mantle, can influence the characteristic of thermal convection. We also estimate the thickness of the top conductive boundary layer and the mechanical stress, which can cause its deformation. - De Sanctis, M., et al. (2015) doi:10.1038/nature16172.- Russell, C., et al. (2016), doi:10.1126/science.aaf4219.- Park, R., et al. (2016),Lunar and Planetary Science Conference, vol. 47, p. 1781.- Schmidt, B. E., et al. (2017), doi:doi:10.1038/ngeo2936- Zolotov, M. Y. (2017), doi:https://doi.org/10.1016 j.icarus.2017.06.018.- Carrozzo, F., et al. (2018), Nature, formation and distribution of carbonates on ceres, Science Advances.- Raponi, A., et al. (2018), Variations in the amount of water ice on ceres' surface suggest a seasonal water cycle, Science Advances.- McCord, T., and C. Sotin (2005), doi:10.1029/2004JE002244.- Neveu, M., and S. Desch (2015), Geochemistry, thermal evolution, and cryovolcanism on Ceres with a muddy ice mantle, Geophys. Res. Lett

A study regarding the stability of the primordial crust of asteroid Ceres

Ceres is a particular object of the solar system, since it is a "transition body" between the icy satellites of the outer solar system and the rocky bodies of the inner part. Probably it is differentiated [1,2], i.e. it has a core made of "rock" (silicates) with a weak presence of metals, a large icy mantle and a rocky crust. In particular, it has been proposed the existence on the surface of the ammoniated phyllosilicates, compatible with an outer solar system origin [3]. Also water in clay minerals, brucite, and iron-rich serpentine have been proposed to exist on the surface [4]. Ice directly on the surface regolith seems to be very unstable: numerical simulations of [5] indicate that it can last for very few orbits. A crust made of a mixture of ice and rock is potentially unstable. In the solar system, for example, Callisto has such a crust but its surface temperature is below the critical temperature for the Rayleigh-Taylor instability [6]: this seems not to be the case of Ceres. In this work, we verify the stability of the primordial crust, by assuming a certain initial composition (ice and rock) and thickness. We assume a post-differentiation Ceres, made of three layers (rocky core, icy mantle and crust). The key role is played by the viscosity of the layers, which influenced the survival or not of the primordial crust. We applied the method of the parametrized thermal convection widely diffused in literature. [1] McCord, T.B. and Sotin, C., 2005, JGR 110 [2] Castillo-Rogez, J.C., and McCord, T.B., 2010, Icarus 205, 443-459 [3] De Sanctis, M.C. et al., 2015, doi:10.1038/nature16172 [4] Rivkin, A.S., et al., 2014, Space Sci Rev, 95-116, 163, doi 10.1007/s11214-010-9677-4 [5] Formisano, M., et al., 2016, MRAS 455, 1892-1904 [6] Shoji, D. and Kurita, K., 2014, doi:10.1002/2014JE004695

PROSPECTing the Moon: Numerical Simulations of Temperature and Sublimation Rate on a Regolith Cylindric Sample

We performed numerical simulations for the mission PROSPECT in order to predict ice sublimation rates of a cylndrical regolith sample of the lunar south pole

Ceres water regime: surface temperature, water sublimation and transient exo(atmo)sphere

Recent observations of water emission around Ceres suggest the presence of an ice layer on or beneath the surface of this asteroid. Several mechanisms have been suggested to explain these plumes, among which cometary-like sublimation seems to be plausible, since there is a correlation between the magnitude of the emission and the change in the heliocentric distance along the orbit. In this work, we applied a comet sublimation model to study the plausible scenarios that match with Herschel observations of the water flux (1026 molecules s-1). Each scenario is characterized by a well-defined set of physical and orbital parameters. Moreover, a study of the dynamic evolution of the H2O plume has been performed, showing that an optically thin transient atmospheric envelope, with a typical timescale of some tens of days, can be maintained by the H2O surface emission. Our simulations could be useful theoretical support for the Dawn NASA mission by giving a better understanding of the physical conditions for water sublimation and ice stability

A core dynamo in Vesta?

A recent study of Fu et al. analysed the remaining magnetization in the eucrite meteorite Allan Hills A81001, which mostly likely has been produced during the cooling phase of the life of the asteroid Vesta, arguing that an ancient dynamo in the advective liquid metallic core could be set in. Using petrographic and paleomagnetic arguments, Fu et al. estimated a surface magnetic field of at least 2 μT. In this work, we verify the possibility that an early core dynamo took place in Vesta by analysing four different possible fully differentiated configurations of Vesta, characterized by different chondritic compositions, with the constraints on core size and density provided by Ermakov et al. We only incorporate the thermal convection, by neglecting the effects of the compositional convection, so our results in terms of magnetic Reynolds number and duration of the dynamo can be interpreted as a lower bound. The presence of a magnetic field would make Vesta a peculiar object of the Solar system, a `small-Earth', since it has also a differentiated structure like Earth and the magnetic field has preserved Vesta from the space weathering