56 research outputs found
Replication Data for: Dating Solar System's giant planet orbital instability using enstatite meteorites
No full textThis repository includes the data and codes that were used to estimate the time interval at which the giant planet instability occurred in the Solar System. This work is under revision in Science. Specifically the repository includes: (A) The code, input, and results from the thermal evolution model that we developed in order to study the cooling rate of the EL planetesimal being either a rubble pile or a monolithic object as well as the code to reproduce Figure S1. (B) Code, input and results of long dynamical simulations that were performed to study the implantation rate of terrestrial planetesimals into the inner main belt as well as the codes to plot Figure 2, Figure 3 and Figure S2. (C) The code that we developed to convert the implantation probability to the actual number of implanted objects
Hypervelocity impacts in the Solar System: An experimental investigation on the fate of the impactor.
No full textCollisions is one of the most important processes in the Solar System that have played a significant role in its evolution for 4.5 Gy. They are responsible for the formation of asteroid families, craters and regolith production on bodies surfaces. Moreover they pose a hazard for our planet's environment, human civilisation and space assets. Impacts have shaped the asteroids and their surfaces and recently there are indications that they are also responsible for the creation of multi-lithology asteroids.
The effectiveness of this process lies, apart from the collisional speed and angle, on the physical parameters of both the target and the impactor. A plethora of laboratory experiments are devoted to study the outcome of impacts, from low speeds of a few m/s to greater speeds of several km/s. In addition space missions; such as Deep Impact (NASA) in the past and AIDA (ESA/NASA) hopefully in the near future, are aiming to perform hyper-velocity impact experiments at large scales.
Although there is advance in our understanding of crater formation, target fragmentation and ejecta speeds, however the fate of the impactor is still very poorly constrained. Experiments so far were focused using materials not directly relevant to the composition of asteroids.
We start an investigation for the impactors' fate, by using lithological projectiles that impacted three different types of targets with different material and bulk porosities. For this experimental campaign was used the Light Gas Gun (LGG) of the Impact Group at the University of Kent. The study was focused on three main topics: i) the fragmentation of the impactor, ii) the implantation of exogenous material onto the target and iii) the inspection of the final state of the projectile.\\
This Thesis is divided in six Chapters. The first two, Chapters 1 and 2, are giving a review of recent advances of small bodies studies, the importance of collisions in the Solar System, and a brief description of the laboratory impact experiments, providing the current state of research on the fate of projectiles. Some open questions lead to the explanation of the aim of this study. In Chapter 3 are described the series of experiments performed, explaining the analysis methods were developed and the way that the main topics of fragmentation, implantation and characterisation of the impactor were studied. All the results for each one of these topics, along with the difficulties during the experimental procedure are provided in Chapter 4. In Chapter 5 we discuss the results giving the implications, attempting to place the outcome in the big picture of the small bodies collisions. In the last Chapter 6 there is a summary of this work, providing also possible future ideas for the continuation of this study
Temperatures of lunar impact flashes: mass and size distribution of small impactors hitting the Moon
No full textInternational audienc
Gaia view of primitive inner-belt asteroid families. Searching for the origins of asteroids Bennu and Ryugu
No full textAims. The near-Earth asteroids Ryugu and Bennu were visited, characterised, and sampled by the Hayabusa2 and OSIRIS-REx missions, where remote sensing data and sample return analysis showed that both asteroids have primitive, hydrated, and organic-rich compositions. The dark families of the inner main belt that belong to the spectroscopic C-complex have been claimed to be the sources of both Ryugu and Bennu, and hence there have been large efforts to spectroscopically characterise them by ground-based observations.
Methods. Here we used the Gaia Data Release 3 (Gaia DR3) asteroid reflectance spectra in order to characterise the 11 known inner main belt C-complex families (Chaldaea, Chimaera, Clarissa, Erigone, Eulalia, Klio, Polana, Primordial, Sulamitis, Svea, Tamara), using space-borne visible-light spectroscopic observations. For each family we extracted the family members that have known geometric visible albedo values and Gaia DR3 data, and we created an average reflectance spectrum per family between 370 and 950 nm. These averages were then compared with the ground-based visible spectroscopic surveys of the same families, and to Bennu’s and Ryugu’s space- and ground-based spectra in the same wavelength range.
Results. Gaia DR3 reflectance spectra of the dark asteroid families of the inner main belt are in general consistent with previous findings. The only exception is the case of the Svea family: previous surveys classified its members as B-types, whereas the average reflectance spectrum from Gaia DR3 is similar to a C-type. We also showed that the Polana and the Eulalia families can be distinguished in the wavelength region 370–500 nm. Among all the primitive inner main belt families, we found that the average reflectance spectra of the Eulalia and Polana families are the most similar to those of Bennu and Ryugu, respectively. In particular, Eulalia family’s average spectrum is a good match to Bennu’s in the wavelength range 450–800 nm, while beyond 800 nm the spectrum of Bennu is bluer than that of Eulalia. Moreover, the spectrum of the Polana family has the smallest discrepancy (smallest χ2) against the spectrum of Ryugu, although this match is formally unsatisfactory (reduced χ2 ~ 1.9)
<i>Gaia</i> view of primitive inner-belt asteroid families
No full textAims. The near-Earth asteroids Ryugu and Bennu were visited, characterised, and sampled by the Hayabusa2 and OSIRIS-REx missions, where remote sensing data and sample return analysis showed that both asteroids have primitive, hydrated, and organic-rich compositions. The dark families of the inner main belt that belong to the spectroscopic C-complex have been claimed to be the sources of both Ryugu and Bennu, and hence there have been large efforts to spectroscopically characterise them by ground-based observations. Methods. Here we used the Gaia Data Release 3 (Gaia DR3) asteroid reflectance spectra in order to characterise the 11 known inner main belt C-complex families (Chaldaea, Chimaera, Clarissa, Erigone, Eulalia, Klio, Polana, Primordial, Sulamitis, Svea, Tamara), using space-borne visible-light spectroscopic observations. For each family we extracted the family members that have known geometric visible albedo values and Gaia DR3 data, and we created an average reflectance spectrum per family between 370 and 950 nm. These averages were then compared with the ground-based visible spectroscopic surveys of the same families, and to Bennu’s and Ryugu’s space- and ground-based spectra in the same wavelength range. Results. Gaia DR3 reflectance spectra of the dark asteroid families of the inner main belt are in general consistent with previous findings. The only exception is the case of the Svea family: previous surveys classified its members as B-types, whereas the average reflectance spectrum from Gaia DR3 is similar to a C-type. We also showed that the Polana and the Eulalia families can be distinguished in the wavelength region 370–500 nm. Among all the primitive inner main belt families, we found that the average reflectance spectra of the Eulalia and Polana families are the most similar to those of Bennu and Ryugu, respectively. In particular, Eulalia family’s average spectrum is a good match to Bennu’s in the wavelength range 450–800 nm, while beyond 800 nm the spectrum of Bennu is bluer than that of Eulalia. Moreover, the spectrum of the Polana family has the smallest discrepancy (smallest χ2) against the spectrum of Ryugu, although this match is formally unsatisfactory (reduced χ2 ~ 1.9).</p
<i>Gaia</i> view of primitive inner-belt asteroid families
No full textAims. The near-Earth asteroids Ryugu and Bennu were visited, characterised, and sampled by the Hayabusa2 and OSIRIS-REx missions, where remote sensing data and sample return analysis showed that both asteroids have primitive, hydrated, and organic-rich compositions. The dark families of the inner main belt that belong to the spectroscopic C-complex have been claimed to be the sources of both Ryugu and Bennu, and hence there have been large efforts to spectroscopically characterise them by ground-based observations. Methods. Here we used the Gaia Data Release 3 (Gaia DR3) asteroid reflectance spectra in order to characterise the 11 known inner main belt C-complex families (Chaldaea, Chimaera, Clarissa, Erigone, Eulalia, Klio, Polana, Primordial, Sulamitis, Svea, Tamara), using space-borne visible-light spectroscopic observations. For each family we extracted the family members that have known geometric visible albedo values and Gaia DR3 data, and we created an average reflectance spectrum per family between 370 and 950 nm. These averages were then compared with the ground-based visible spectroscopic surveys of the same families, and to Bennu’s and Ryugu’s space- and ground-based spectra in the same wavelength range. Results. Gaia DR3 reflectance spectra of the dark asteroid families of the inner main belt are in general consistent with previous findings. The only exception is the case of the Svea family: previous surveys classified its members as B-types, whereas the average reflectance spectrum from Gaia DR3 is similar to a C-type. We also showed that the Polana and the Eulalia families can be distinguished in the wavelength region 370–500 nm. Among all the primitive inner main belt families, we found that the average reflectance spectra of the Eulalia and Polana families are the most similar to those of Bennu and Ryugu, respectively. In particular, Eulalia family’s average spectrum is a good match to Bennu’s in the wavelength range 450–800 nm, while beyond 800 nm the spectrum of Bennu is bluer than that of Eulalia. Moreover, the spectrum of the Polana family has the smallest discrepancy (smallest χ2) against the spectrum of Ryugu, although this match is formally unsatisfactory (reduced χ2 ~ 1.9).</p
Discovery of the first olivine-dominated A-type asteroid family
No full textThe classical theory of differentiation states that due to the heat generated by the decay of radioactive elements, some asteroids form an iron core, an olivine-rich mantle, and a crust. The collisional breakup of these differentiated bodies is expected to lead to exposed mantle fragments, creating families of newly-formed asteroids. Among these new objects, some are expected to show an olivine-rich composition in spectroscopic observations. However, several years of spectrophotometric surveys have led to the conclusion that olivine-rich asteroids are rare in the asteroid main belt, and no significant concentration of olivine-rich bodies in any asteroid family has been detected to date. Using ESA’s Gaia DR3 reflectance spectra, we show that the family (36256) 1999 XT17 presents a prominence of objects that are likely to present an olivine-rich composition (A-type spectroscopic class). If S-complex asteroids as the second most prominent spectroscopic class in the family are real family members, then arguably the 1999 XT17 family has originated from the break-up of a partially differentiated parent body. Alternatively, if the S-complex asteroids are interlopers, then the 1999 XT17 family could have originated from the breakup of an olivine-rich body. This body could have been part of the mantle of a differentiated planetesimal, which may have broken up in a different region of the Solar System, and one of its fragments (i.e. the parent body of the 1999 XT17 family) could have been dynamically implanted in the main belt
Exogenous origin of hydration on asteroid (16) Psyche: the role of hydrated asteroid families
No full textInternational audienceAsteroid (16) Psyche, which for a long time was the largest M-type with no detection of hydration features in its spectrum, was recently discovered to have a weak 3-μm band and thus it was eventually added to the group of hydrated asteroids. Its relatively high density, in combination with the high radar albedo, led researchers to classify the asteroid as a metallic object. It is believed that it is possibly a core of a differentiated body, a remnant of ‘hit-and-run’ collisions. The detection of hydration is, in principle, inconsistent with a pure metallic origin for this body. Here, we consider the scenario in which the hydration on its surface is exogenous and was delivered by hydrated impactors. We show that impacting asteroids that belong to families whose members have the 3-μm band can deliver hydrated material to Psyche. We developed a collisional model with which we test all dark carbonaceous asteroid families, which contain hydrated members. We find that the major source of hydrated impactors is the family of Themis, with a total implanted mass on Psyche of the order of ∼1014 kg. However, the hydrated fraction could be only a few per cent of the implanted mass, as the water content in carbonaceous chondrite meteorites, the best analogue for the Themis asteroid family, is typically a few per cent of their mass
Characterisation of the main belt asteroid (223) Rosa: A proposed flyby target of ESA's JUICE mission
No full textContext. The ESA JUICE space mission, on its way to study Jupiter's environment and icy moons, will pass twice through the main asteroid belt. For this reason, the possibility to perform an asteroid flyby has been investigated. Aims. We aim to gain insight into the physical properties of the outer main belt asteroid (223) Rosa, which has been proposed as a potential JUICE flyby target. Methods. We report new visible and near-infrared spectroscopic observations at different rotation phases. Additionally, we perform a literature review of all the available physical properties, such as diameter, albedo, mass, and rotational period. Results. We find that asteroid Rosa is an X-type asteroid that shows no significant spectral variability combining the new and literature spectroscopic data. Its large size and orbital semimajor axis in the outer main belt indicate that Rosa does not belong to the Themis family, while its albedo is only marginally compatible with the family. Rosa's estimated density is in agreement with those of other low-albedo X-type asteroids. Hence, we propose that Rosa is a planetesimal that accreted in the protoplanetary disk beyond the snow line
search for early-formed andesitic asteroidal crusts
No full textContext. Andesitic meteorites are among the oldest achondrites known to date. They record volcanic events and crust formation episodes in primordial planetesimals that took place about 4.565 Myr ago. However, no analogue for these meteorites has been found in the asteroid population to date.
Aims. We searched for spectroscopic analogues of the andesitic meteorite Erg Chech 002 in the asteroid population using the Gaia DR3 spectral dataset.
Methods. In order to identify which asteroids have the most similar spectrum to Erg Chech 002, we first determined the spectral parameters of Gaia DR3 asteroids (spectral slope and Band I depth) and compared them to the spectral parameters of different samples of the meteorite. In addition, we performed a spectral curve matching between Erg Chech 002 and Gaia DR3 asteroid data, and we compared the results of both methods.
Results. We found that 51 main-belt asteroids have a visible spectrum similar to the one of Erg Chech 002, and 91 have a spectrum similar to the space-weathered spectra of the meteorite, corresponding to 0.08% and 0.15% of the whole Gaia DR3 dataset of asteroids with spectra, respectively. The asteroids that best match the laboratory samples of the meteorite are mostly located in the inner main belt, while the objects matching the space-weathered meteorite models show slightly more scattering across the belt.
Conclusions. Despite the fact that we find asteroids that potentially match Erg Chech 002, these asteroids are extremely rare. Moreover, a visible spectrum alone is not completely diagnostic of an Erg Chech 002-like composition. Near-infrared spectra will be important to confirm (or rule out) the spectral matches between Erg Chech 002 and the candidate asteroid population
- …
