Near-IR imaging of Asteroid 4 Vesta

The Keck Observatoryʹs adaptive optics (AO) system has been used to observe Asteroid 4 Vesta during its 2003 closest approach to Earth. Broadband K ′ - and L ′ -band images, centered at 2.1 and 3.6 μm, respectively, are presented here. The sharpness of the images was improved by applying a deconvolution algorithm, MISTRAL, to the images. The K ′ - and L ′ -band images at spatial resolutions of 53 km ( 0.055 ″ ) and 88 km ( 0.085 ″ ), respectively, display albedo features on the surface of the asteroid that can also be seen in the HST images (673 nm) presented by Thomas et al. [1997. Impact excavation on Asteroid 4 Vesta: Hubble Space Telescope results. Science 277, 1492–1495] and Binzel et al. [1997. Geologic mapping of Vesta from 1994 Hubble Space Telescope images. Icarus 128, 95–103] at the same latitudes and longitudes. While we cannot determine the morphology of these features, we can speculate that some of the albedo features may be impact craters filled with dark material. Spectra, centered at 1.65 and 2.1 μm, were also obtained. Spectra were corrected for the solar flux and are similar to those published by Gaffey [1997. Surface lithologic heterogeneity of Asteroid 4 Vesta. Icarus 127, 130–157], along the same wavelength range.