We present the first optical observations taken to characterize the near-Earth object 138175 ( 2000 EE104 ) .
This body is associated with Interplanetary Field Enhancements ( IFEs ) , thought to be caused by interactions between the solar wind magnetic field and solid material trailing in the orbit of the parent body .
Based on optical photometry , the radius ( in meters ) and mass ( in kilograms ) of an equal-area sphere are found to be r _ { n } = 250 ( 0.1 / p _ { R } ) ^ { 1 / 2 } and M _ { n } = 10 ^ { 11 } ( 0.1 / p _ { R } ) ^ { 3 / 2 } , respectively , where p _ { R } is the red geometric albedo and density \rho = 1500 kg m ^ { -3 } is assumed .
The measured colors are intermediate between those of C-type ( primitive ) and S-type ( metamorphosed ) asteroids but , with correction for the likely effects of phase-reddening , are more consistent with a C-type classification than with S-type .
No evidence for co-moving companions larger than \sim 40 ( 0.1 / p _ { R } ) m in radius is found , and no dust particle trail is detected , setting a limit to the trail optical depth \tau \leq 2 \times 10 ^ { -9 } .
Consideration of the size distribution produced by impact pulverization makes it difficult to generate the mass of nanodust ( minimum 10 ^ { 5 } kg to 10 ^ { 6 } kg ) required to account for IFEs , unless the size distribution is unusually steep .
Furthermore , impact pulverization timescales for source objects of the required size are much longer than the dynamical timescale .
While the new optical data do not definitively refute the hypothesis that boulder pulverization is the source of IFEs , neither do they provide any support for it .