10 research outputs found
Thermal evolution and activity of Comet 9P/Tempel 1 and simulation of a deep impact
We use a quasi 3-D thermal evolution model for a spherical comet nucleus,
which takes into account the diurnal and latitudinal variation of the solar
flux, but neglects lateral heat conduction. We model the thermal evolution and
activity of Comet 9P/Tempel 1, in anticipation of the Deep Impact mission
encounter with the comet. We also investigate the possible outcome of a
projectile impact, assuming that all the energy is absorbed as thermal energy.
An interesting result of this investigation, is that the estimated amount of
dust ejected due to the impact is equivalent to 2--2.6 days of activity, during
"quiet" conditions, at perihelion.
We show that production rates of volatiles that are released in the interior
of the nucleus depend strongly on the porous structure, in particular on the
surface to volume ratio of the pores. We develop a more accurate model for
calculating this parameter, based on a distribution of pore sizes, rather than
a single, average pore size.Comment: 25 pages, 8 figures, accepted for publication in PASP (in press). For
fig.xx (composite image, sec.4) and a better resolution of fig.6 see,
http://geophysics.tau.ac.il/personal/gal%5Fsarid
The ESA Hera Mission: Detailed Characterization of the DART Impact Outcome and of the Binary Asteroid (65803) Didymos
Hera is a planetary defense mission under development in the Space Safety and Security Program of the European Space Agency for launch in 2024 October. It will rendezvous in late 2026 December with the binary asteroid (65803) Didymos and in particular its moon, Dimorphos, which will be impacted by NASA’s DART spacecraft on 2022 September 26 as the first asteroid deflection test. The main goals of Hera are the detailed characterization of the physical properties of Didymos and Dimorphos and of the crater made by the DART mission, as well as measurement of the momentum transfer efficiency resulting from DART’s impact. The data from the Hera spacecraft and its two CubeSats will also provide significant insights into asteroid science and the evolutionary history of our solar system. Hera will perform the first rendezvous with a binary asteroid and provide new measurements, such as radar sounding of an asteroid interior, which will allow models in planetary science to be tested. Hera will thus provide a crucial element in the global effort to avert future asteroid impacts at the same time as providing world-leading science
After DART: Using the First Full-scale Test of a Kinetic Impactor to Inform a Future Planetary Defense Mission
NASA’s Double Asteroid Redirection Test (DART) is the first full-scale test of an asteroid deflection technology. Results from the hypervelocity kinetic impact and Earth-based observations, coupled with LICIACube and the later Hera mission, will result in measurement of the momentum transfer efficiency accurate to ∼10% and characterization of the Didymos binary system. But DART is a single experiment; how could these results be used in a future planetary defense necessity involving a different asteroid? We examine what aspects of Dimorphos’s response to kinetic impact will be constrained by DART results; how these constraints will help refine knowledge of the physical properties of asteroidal materials and predictive power of impact simulations; what information about a potential Earth impactor could be acquired before a deflection effort; and how design of a deflection mission should be informed by this understanding. We generalize the momentum enhancement factor β, showing that a particular direction-specific β will be directly determined by the DART results, and that a related direction-specific β is a figure of merit for a kinetic impact mission. The DART β determination constrains the ejecta momentum vector, which, with hydrodynamic simulations, constrains the physical properties of Dimorphos’s near-surface. In a hypothetical planetary defense exigency, extrapolating these constraints to a newly discovered asteroid will require Earth-based observations and benefit from in situ reconnaissance. We show representative predictions for momentum transfer based on different levels of reconnaissance and discuss strategic targeting to optimize the deflection and reduce the risk of a counterproductive deflection in the wrong direction
Hydrocode simulations of few Lutetia craters
The flyby of the Main Belt asteroid Lutetia by the Rosetta spacecraft allows the camera OSIRIS to obtain very
good images of about half body at the maximum resolution of 60 m per pixel. Moreover, the data obtained by the
Rosetta instruments include the asteroid density of about (3.4 ± 0.3) g/cm3.
Many impact craters have been observed on the surface of Lutetia. The largest among them is called Massilia
and has a diameter of about 55 km. Relative to the size of Lutetia (the longest axis is approximately 126 km) the
crater represents one of the dominating features on the surface. Whether the impact that formed the crater
affected the entire asteroid can only be estimated from numerical analysis of hydrocode modeling of the impact
processes. The results of a suite of iSALE simulations are compared with the crater profile derived from the
Digital Terrain Model of the observed surface. The final hydrocode simulations allowed to determine the
impactor size having a diameter of 7.5 km which suggests a primordial origin of Lutetia due to the low
probability for such an impact event.
A second interesting impact structure has been identified nearby Massilia within the North Pole Crater Cluster.
This crater, having a diameter of 24 km and lying over the other craters of the North Pole Crater Cluster, seems
to be the youngest largest structure of Lutetia.- The numerical simulations of this feature constrain the impactor
to be of 3.8 km in diameter, assuming the same material properties for target and impactor as in the model of the
formation of Massilia
The science return of the ESA Hera Misson: The European component of the AIDA collaboration that will combine Hera and NASA DART missions data
Hera is a planetary defence mission with mission goals dedicated to that field. However, the data it collects will provide significant insights into asteroidal science and the evolutionary history of our Solar System. The uniqueness of the Hera target in the history of Solar System exploration - a small binary asteroid - will allow several current models and paradigms in planetary science to be tested. Hera will thus provide world-leading science at the same time as providing a crucial element in the global effort to avert future asteroid impacts