  In this paper we present the observational campaign carried out at ESO NTT
and VLT in April and May 2006 to investigate the nature and the structure of
the Near Earth Object (144898) 2004 VD17. In spite of a great quantity of
dynamical information, according to which it will have a close approach with
the Earth in the next century, the physical properties of this asteroid are
largely unknown. We performed visible and near--infrared photometry and
spectroscopy, as well as polarimetric observations. Polarimetric and
spectroscopic data allowed us to classify 2004 VD17 as an E-type asteroid. A
good agreement was also found with the spectrum of the aubrite meteorite Mayo
Belwa. On the basis of the polarimetric albedo (p_v=0.45) and of photometric
data, we estimated a diameter of about 320 m and a rotational period of about 2
hours. The analysis of the results obtained by our complete survey have shown
that (144898) 2004 VD17 is a peculiar NEO, since it is close to the breakup
limits for fast rotator asteroids, as defined by Pravec and Harris (2000).
These results suggest that a more robust structure must be expected, as a
fractured monolith or a rubble pile in a "strength regime" (Holsapple 2002).

Astrophysics