Bibcode
Pinilla-Alonso, N.; Licandro, J.; Gil-Hutton, R.; Brunetto, R.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 468, Issue 1, June II 2007, pp.L25-L28
Advertised on:
6
2007
Revista
Número de citas
22
Número de citas referidas
21
Descripción
Context: Recent results suggest that there is a group of trans-Neptunian
objects (TNOs) (2003 EL{61} being the biggest member), with surfaces
composed of almost pure water ice and with very similar orbital
elements. These objects provide exciting laboratories for the study of
the processes that prevent the formation of an evolved mantle of
organics on the surfaces of the bodies in the trans-Neptunian belt
(TNb). Aims: We study the surface composition of another TNO that
moves in a similar orbit, (145453) 2005 RR{43}, and compare it with the
surface composition of the other members of the group. Methods:
We report visible and near-infrared spectra in the 0.53-2.4 μm
spectral range, obtained with the 4.2 m William Herschel Telescope and
the 3.58 m Telescopio Nazionale Galileo at the “Roque de los
Muchachos” Observatory (La Palma, Spain). Scattering models are
used to derive information about its surface composition. We also
measure the depth D of the water ice absorption bands and compare with
those of the other members of the group. Results: The spectrum of
2005 RR{43} is neutral in color in the visible and dominated by very
deep water ice absorption bands in the near infrared (D= 70.3 ±
2.1% and 82.8 ± 4.9% at 1.5 μm and 2.0 μm respectively). It
is very similar to the spectrum of the group of TNOs already mentioned.
All of them present much deeper water ice absorption bands (D >40 %)
than any other TNO except Charon. Scattering models show that its
surface is covered by water ice, a significant fraction in crystalline
state with no trace (5% upper limit) of complex organics. Possible
scenarios to explain the existence of this population of TNOs are
discussed: a giant collision, an originally carbon depleted composition,
or a common process of continuous resurfacing. Conclusions: 2005
RR{43} is member of a group, may be a population, of TNOs clustered in
the space of orbital parameters that show abundant water ice and no
signs of complex organics and which origin needs to be further
investigated. The lack of complex organics in their surfaces suggests a
significant smaller fraction of carbonaceous volatiles like CH4 in this
population than in “normal” TNOs. A carbon depleted
population of TNOs could be the origin of the population of carbon
depleted Jupiter family comets already noticed by A'Hearn et al. (1995).