Taxonomy of Centaurs and Trans-Neptunian Objects

The original publication is available at http://iopscience.iop.org/1538-3881/.International audienceTrans-Neptunian objects (TNOs) and Centaurs display thewidest color diversity in comparison to other small solar system bodies. The investigation of their properties can help in understanding the evolution of these objects. In this paper we propose a classification scheme based on multivariate statistical analysis of a homogeneous, high-quality set of B - V, V - R, V - I , and V - J color indices. Analyzing a sample of 51 objects and using a high confidence level, four groups have been identified and named: BB, BR, IR, and RR. The group BB contains objects with neutral color and RR those with very red color, while the others have intermediate behavior. We extend the analysis to 84 other objects for which three colors are available, obtaining a preliminary classification. A tentative interpretation of these groups in terms of surface characteristics is given

E-type asteroid (2867) Steins: flyby target for Rosetta

Reproduced with permission. Copyright ESO. Article published by EDP Sciences and available at http://www.aanda.org.International audienceAims. The mineralogy of the asteroid (2867) Steins was investigated in the framework of a ground-based science campaign dedicated to the future encounter with Rosetta spacecraft. Methods. Near-infrared (NIR) spectra of the asteroid in the 0.8−2.5 μm spectral range have been obtained with SpeX/IRTF in remoteobserving mode from Meudon, France, and Cambridge, MA, in December 2006 and in January and March 2007. A spectrum with a combined wavelength coverage from 0.4 to 2.5 μm was constructed using previously obtained visible data. To constrain the possible composition of the surface, we constructed a simple mixing model using a linear (areal) mix of three components obtained from the RELAB database. A space-weathering model was applied to the aubrite ALH-78113 spectrum. Results. The four new NIR spectra reveal no major absorption features. The best-fit model for the constructed visible-plus-NIR spectrum is represented by a mixture of 57% enstatite, 42% oldhamite, and 1% orthopyroxene. These results place Steins in a subdivision of the E-type class with objects like Angelina, Eger, and Nereus. This group is not sampled by the current collection of aubrite meteorites. Interestingly, the reddened aubrite spectrum also provides a good match to the Steins VNIR spectrum

Near-IR spectroscopy of asteroids 21 Lutetia, 89 Julia, 140 Siwa, 2181 Fogelin, and 5480 (1989YK8), potential targets for the Rosetta mission; remote observations campaign on IRTF

In the frame of the international campaign to observe potential target asteroids for the Rosetta mission, remote observations have been carried out between Observatoire de Paris, in Meudon-France, and the NASA Infrared Telescope Facility on Mauna Kea. The SpeX instrument was used in the 0.8-2.5 microns spectral region, for two observing runs in March and June 2003. This paper presents near-IR spectra of the asteroids 21 Lutetia, 89 Julia, 140 Siwa, 2181 Fogelin, and 5480 (1989YK8). Near-IR spectra of the asteroids 21 Lutetia and 140 Siwa are flat and featureless. The spectrum of 89 Julia reveals absorption bands around 1 and 2 microns, which may indicate the presence of olivine and olivine-pyroxene mixtures and confirm the S-type designation. The small main-belt asteroids 2181 Fogelin and 5480 (1989YK8) are investigated spectroscopically for the first time. Near-IR spectra of these asteroids also show an absorption feature around 1 micron, which could be and indicator of igneous/metamorphic surface of the objects; new observations in visible as well as thermal albedo data are necessary to draw a reliable conclusion on the surface mineralogy of both asteroids.Comment: Sent: October 2003, Accepted: December, 200

Asteroid target selection for the new Rosetta mission baseline: 21 Lutetia and 2867 Steins

Reproduced with permission. Copyright ESO. Article published by EDP Sciences and available at http://www.aanda.org.International audienceThe new Rosetta mission baseline to the comet 67P/Churyumov-Gerasimenko includes two asteroid fly-bys. To help in target selection we studied all the candidates of all the possible scenarios. Observations have been carried out at ESO-NTT (La Silla, Chile), TNG (Canaries), and NASA-IRTF (Hawaii) telescopes, in order to determine the taxonomy of all the candidates. The asteroid targets were chosen after the spacecraft interplanetary orbit insertion manoeuvre, when the available total amount of ΔV was known. On the basis of our analysis and the available of ΔV, we recommended to the ESA ScienceWorking Group the asteroids 21 Lutetia and 2867 Steins as targets for the Rosetta mission. The nature of Lutetia is still controversial. Lutetia's spectral properties may be consistent with a composition similar to carbonaceous chondrite meteorites. The spectral properties of Steins suggest a more extensive thermal history. Steins may have a composition similar to relatively rare enstatite chondrite/achondrite meteorites

MarcoPolo-R: Near Earth Asteroid Sample Return Mission candidate as ESA-M3 class mission

MarcoPolo-R is a sample return mission to a primitive Near-Earth Asteroid (NEA) selected in February 2011 for the Assessment Study Phase at ESA in the framework of ESAfs Cosmic Vision 2 program. MarcoPolo-R is a European-led mission with a proposed NASA contribution. MarcoPolo-R takes advantage of three industrial studies completed as part of the previous Marco Polo mission (see ESA/SRE (2009)3). The aim of the new Assessment Study is to reduce the cost of the mission while maintaining its high science level, on the basis of advanced studies and technologies, as well as optimization of the mission. MarcoPolo-R will rendezvous with a unique kind of target, a primitive binary NEA, scientifically characterize it at multiple scales, and return a unique pristine sample to Earth unaltered by the atmospheric entry process or terrestrial weathering. The baseline target of MarcoPolo-R is the primitive binary NEA (175706) 1996 FG3, which offers a very efficient operational and technical mission profile. A binary target also provides enhanced science return: the choice of this target will allow new investigations to be performed more easily compared to a single object, and also enables investigations of the fascinating geology and geophysics of asteroids that are impossible to obtain from a single object. Precise measurements of the mutual orbit and rotation state of both components can be used to probe higher-level harmonics of the gravitational potential, and therefore the internal structure. A unique opportunity is offered to study the dynamical evolution driven by the YORP/Yarkovsky thermal effects. Possible migration of regolith on the primary from poles to equator allows the increasing maturity of asteroidal regolith with time to be expressed as a latitude-dependent trend, with the most-weathered material at the equator matching what is seen in the secondary. MarcoPolo-R will allow us to study the most primitive materials available to investigate early solar system formation processes. Moreover, MarcoPolo-R will provide a sample from a known target with known geological context. Direct investigation of both the regolith and fresh interior fragments is also impossible by any means other than sample return. The main goal of the MarcoPolo-R mission is to return unaltered NEA material for detailed analysis in ground-based laboratories. The limited sampling provided by meteorites does not offer the most primitive material available in near-Earth space. More primitive material, having experienced less alteration on the asteroid, will be more friable and would not survive atmospheric entry in any discernible amount. Only in the laboratory can instruments with the necessary precision and sensitivity be applied to individual components of the complex mixture of materials that forms an asteroid regolith, to determine their precise chemical and isotopic composition. Such measurements are vital for revealing the evidence of stellar, interstellar medium, pre-solar nebula and parent body processes that are retained in primitive asteroidal material, unaltered by atmospheric entry or terrestrial contamination. It is no surprise therefore that sample return missions are considered a priority by a number of the leading space agencies

ESO-VLT large program on Centaurs and TNOs

International audienceThe ESO Large Program on the study of Trans-Neptunian Objects (TNOs) and Centaurs has been carried out during the last two years (April 2001-March 2003) at the Paranal (Very Large Telescope VLT) and La Silla (New Technology Telescope NTT) observatories of the European Southern Observatory (ESO) in Chile. The aim of the Large Program was to investigate the physical properties of this population composed of cold and primitive objects. Results has been obtained for multi-wavelength imaging BVRI and JHK filters of ~70 and ~30 objects respectively as well as for low-dispersion visible and near-IR spectroscopy of ~12 objects. The photometric results and analyses of the relative correlations between colours photometric gradients and dynamical properties of the objects will be presented and discussed. The spectroscopic results have been interpreted with models computed using geographical mixture of organics minerals and ices in order to constrain the surface composition. The spectra show a wide range of slopes some are featureless with almost constant gradients over the visible-NIR range while others show absorption signatures of ices. The limit and the utility of the ground-based observations will be discussed together with the necessity of a space exploration

ESO-VLT large program on Centaurs and TNOs

International audienceThe ESO Large Program on the study of Trans-Neptunian Objects (TNOs) and Centaurs has been carried out during the last two years (April 2001-March 2003) at the Paranal (Very Large Telescope VLT) and La Silla (New Technology Telescope NTT) observatories of the European Southern Observatory (ESO) in Chile. The aim of the Large Program was to investigate the physical properties of this population composed of cold and primitive objects. Results has been obtained for multi-wavelength imaging BVRI and JHK filters of ~70 and ~30 objects respectively as well as for low-dispersion visible and near-IR spectroscopy of ~12 objects. The photometric results and analyses of the relative correlations between colours photometric gradients and dynamical properties of the objects will be presented and discussed. The spectroscopic results have been interpreted with models computed using geographical mixture of organics minerals and ices in order to constrain the surface composition. The spectra show a wide range of slopes some are featureless with almost constant gradients over the visible-NIR range while others show absorption signatures of ices. The limit and the utility of the ground-based observations will be discussed together with the necessity of a space exploration

Spectrophotometry of Trans-Neptunian Objects

International audienceThe Trans-Neptunian Objects (TNOs) are very difficult to observe due to their faintness. Spectra can be obtained for only few objects. For this reason, broad band photometry is the only available technique to study their physical properties from a statistical point of view. To improve the knowledge about the physical nature of the Kuiper Belt, we have obtained several observing runs at different four-meter class telescopes (NTT - Chile; CFHT - Hawaii). The data presented here were obtained at NTT (ESO - Chile) during three observing runs from 1997 to 2000. We used the SUSI and SUSI 2 CCD cameras with the Bessel B, V, R, and I filters

Spectrophotometry of Trans-Neptunian Objects

International audienceThe Trans-Neptunian Objects (TNOs) are very difficult to observe due to their faintness. Spectra can be obtained for only few objects. For this reason, broad band photometry is the only available technique to study their physical properties from a statistical point of view. To improve the knowledge about the physical nature of the Kuiper Belt, we have obtained several observing runs at different four-meter class telescopes (NTT - Chile; CFHT - Hawaii). The data presented here were obtained at NTT (ESO - Chile) during three observing runs from 1997 to 2000. We used the SUSI and SUSI 2 CCD cameras with the Bessel B, V, R, and I filters