(121514) 1999 UJ7: A primitive, slow-rotating Martian Trojan
Abstract
Aims: The goal of this investigation is to determine the origin and surface composition of the asteroid (121514) 1999 UJ7, the only currently known L4 Martian Trojan asteroid.
Methods: We have obtained visible reflectance spectra and photometry of 1999 UJ7 and compared the spectroscopic results with the spectra of a number of taxonomic classes and subclasses. A light curve was obtained and analysed to determine the asteroid spin state.
Results: The visible spectrum of 1999 UJ7 exhibits a negative slope in the blue region and the presence of a wide and deep absorption feature centred around 0.65 μm. The overall morphology of the spectrum seems to suggest a C-complex taxonomy. The photometric behaviour is fairly complex. The light curve shows a primary period of 1.936 d, but this is derived using only a subset of the photometric data. The asteroid may be in a non-principal axis rotational state, but our observational coverage is insufficient to draw definitive conclusions.
Conclusions: Although the observed spectral absorption is wider and deeper, this finding may be compatible with the 0.7 μm spectral feature exhibited by some Ch-type asteroids and could possibly be interpreted as diagnostic of the presence of hydrated minerals. The inferred composition of 1999 UJ7 as a primitive object can be consistent with a volatile-rich object originally accreted beyond the snow line of the solar system, and subsequently evolved to reach the inner regions of the solar system.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 2018
- DOI:
- 10.1051/0004-6361/201732466
- arXiv:
- arXiv:1809.02046
- Bibcode:
- 2018A&A...618A.178B
- Keywords:
-
- planets and satellites: individual: Mars;
- planets and satellites: individual: Trojan asteroids;
- techniques: imaging spectroscopy;
- techniques: photometric;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 8 pages, 5 figures