9 research outputs found
Near-infrared spatially resolved spectroscopy of (136108) Haumea's multiple system
The transneptunian region of the solar system is populated by a wide variety
of icy bodies showing great diversity. The dwarf planet (136108) Haumea is
among the largest TNOs and displays a highly elongated shape and hosts two
moons, covered with crystalline water ice like Hamuea. Haumea is also the
largest member of the sole TNO family known to date. A catastrophic collision
is likely responsible for its unique characteristics. We report here on the
analysis of a new set of observations of Haumea obtained with SINFONI at the
ESO VLT. Combined with previous data, and using light-curve measurements in the
optical and far infrared, we carry out a rotationally resolved spectroscopic
study of the surface of Haumea. We describe the physical characteristics of the
crystalline water ice present on the surface of Haumea for both regions, in and
out of the Dark Red Spot (DRS), and analyze the differences obtained for each
individual spectrum. The presence of crystalline water ice is confirmed over
more than half of the surface of Haumea. Our measurements of the average
spectral slope confirm the redder characteristic of the spot region. Detailed
analysis of the crystalline water-ice absorption bands do not show significant
differences between the DRS and the remaining part of the surface. We also
present the results of applying Hapke modeling to our data set. The best
spectral fit is obtained with a mixture of crystalline water ice (grain sizes
smaller than 60 micron) with a few percent of amorphous carbon. Improvements to
the fit are obtained by adding ~10% of amorphous water ice. Additionally, we
used the IFU-reconstructed images to measure the relative astrometric position
of the largest satellite Hi`iaka and determine its orbital elements. An orbital
solution was computed with our genetic-based algorithm GENOID and our results
are in full agreement with recent results.Comment: Accepted for publication in A&
The spectrum of (136199) Eris between 350 and 2350 nm: Results with X-Shooter
X-Shooter is the first second-generation instrument for the ESO-VLT. It as a
spectrograph covering the 300 - 2480 nm spectral range at once with a high
resolving power. These properties enticed us to observe (136199) Eris during
the science verification of the instrument. The target has numerous absorption
features in the optical and near-infrared domain which has been observed by
different authors, showing differences in their positions and strengths.
We attempt at constraining the existence of super-volatiles, e.g., CH4, CO
and N2, and in particular try to understand the physical-chemical state of the
ices on Eris' surface.
We observed Eris in the 300-2480 nm range and compared the newly obtained
spectra with those available in the literature. We identified several
absorption features, measuring their positions and depth and compare them with
those of reflectance of pure methane ice obtained from the optical constants of
this ice at 30 K to study shifts in their positions and find a possible
explanation for their origin.
We identify several absorption bands in the spectrum all consistent with the
presence of CH4 ice. We do not identify bands related with N2 or CO. We
measured the central wavelengths of the bands and find variable shifts, with
respect to the spectrum of pure CH4 at 30 K. Conclusions. Based on these
wavelength shifts we confirm the presence of a dilution of CH4 in other ice on
the surface of Eris and the presence of pure CH4 spatially segregated. The
comparison of the centers and shapes of these bands with previous works suggest
that the surface is heterogeneous. The absence of the 2160 nm band of N2 can be
explained if the surface temperature is below 35.6 K, the transition
temperature between the alpha and beta phases of this ice. Our results,
including the reanalysis of data published elsewhere, point to an heterogeneous
surface on Eris.Comment: 15 pages, 5 figure
Similar origin for low- and high-albedo Jovian Trojans and Hilda asteroids?
International audienceHilda asteroids and Jupiter Trojans are two low-albedo (p(v)similar to 0.07) populations for which the Nice model predicts an origin in the primordial Kuiper Belt region. However. recent surveys by WISE and the Spitzer Space Telescope (SST) have revealed that similar to 2% of these objects possess high albedos (p(v) \textgreater= 0.15), which might indicate interlopers - that is, objects not formed in the Kuiper Belt among these two populations. Here, we report spectroscopic observations in the visible and / or near infrared spectral ranges of twelve high-albedo (p(v) \textgreater 0.15) Hilda asteroids and Jupiter Trojans. These twelve objects have spectral properties similar to those of the low-albedo population. which suggests a similar composition and hence a similar origin for low-and high-albedo Hilda asteroids and Jupiter Trojans. We therefore propose that most high albedos probably result from statistical bias or uncertainties that affect the WISE and SST measurements. However, some of the high albedos may be true and the outcome of some collision induced resurfacing by a brighter material that could include water ice. Future work should attempt to investigate the nature of this supposedly bright material. The lack of interlopers in our sample allows us to set an upper limit of 0,4% at a confidence level of 99.7% on the abundance of interlopers with unexpected taxonomic classes (e.g., A-, S-, V-type asteroids) among these two populations
Ultraviolet to near-infrared spectroscopy of the potentially hazardous, low delta-V asteroid (175706) 1996 FG3
Context. Primitive near-Earth asteroids (NEAs) are important subjects of
study for current planetary research. Their investigation can provide crucial information
on topics such as the formation of the solar system, the emergence of life, and the
mitigation of the risk of asteroid impact. Sample return missions from primitive asteroids
have been scheduled or are being studied by space agencies, including the
MarcoPolo-R mission selected for the assessment study phase of ESA M3
missions.
Aims. We want to improve our knowledge of the surface composition and
physical nature of the potentially hazardous, low delta-V asteroid (175706) 1996 FG3,
backup target of MarcoPolo-R. This intriguing object shows an as-yet
unexplained spectral variability.
Methods. We performed spectroscopic observations of 1996 FG3 using the
visible spectrograph DOLORES at the Telescopio Nazionale Galileo (TNG),
and the UV-to-NIR X-Shooter instrument at the ESO Very Large Telescope (VLT).
Results. We find featureless spectra and we classify 1996 FG3 as a
primitive Xc-type in the Bus-DeMeo taxonomy. Based on literature comparison, we confirm
the spectral variability of this object at near-infrared (NIR) wavelengths, and find that
spectral variations exist also for the visible spectral region. Phase reddening cannot
explain such variations. Obtained with the same observational conditions for the whole
0.3–2.2 μm range, our X-Shooter spectrum allowed a proper comparison with
the RELAB meteorite database. A very good fit is obtained with the very primitive C2
Tagish Lake carbonaceous chondrite (pressed powder), confirming 1996 FG3 as a suitable
target for a sample return mission from primitive NEAs.
Conclusions. We hypothesize a compacted/cemented surface for 1996 FG3,
like that observed by the Hayabusa mission on (25143) Itokawa, with the possible presence
of regions showing different degrees of surface roughness. This variegation could be
related to the binary nature of 1996 FG3, but to check this hypothesis further
observations are necessary