Smart 1

The ESA Smart-1 spacecraft (see http://www.esa.int/esaMI/SMART-1/index.html) was launched in Sept. 2003 for ESA's first mission to the Moon.
Smart1
The Smart 1 spacecraft (artists impression). Source: ESA
On Sept. 3rd, 2006, after a highly successful mission, the spacecraft reached the end of its life when it was deliberately impacted onto the lunar surface. The path of the spacecraft over the lunar surface is shown in the figure below. The impact was observed via telescopes from the Earth. However, the impact crater which resulted was too small to be seen from the Earth so has never been imaged.
To estimate what the impact crater looks like, staff at ESA asked the University of Kent to do impact simulations using our two-stage light gas gun. The impact on the Moon was at a very shallow angle (approximately 1) and a speed of 2kms-1. Professor Mark Burchell, an undergraduate student (Rowena Robin-Williams who was working on her final year project) and Experimental Officer Michael Cole, carried out a series of impacts using sand targets in the gun. A report on the results is on the ESA web site at http://www.esa.int/esaSC/SEM8SH7LURE_index_0.html
Shallow angle impacts result in non-circular craters, so this new crater should be easy to spot on the lunar surface when high enough resolution pictures are available.
The location of the impact on the lunar surface is shown in the figure below. The planned orbits of the spacecraft over the surface are shown as a series of parallel, near vertical, lines. It was predicted in advance that on one of these the altitude of the spacecraft would have dipped so low it would hit the surface. The actual impact point occurred where the red diamond appears.

Smart 1 trajectory over the lunar surface. The impact point is show as a red diamond. Source: ESA.
During the impact, a series of telescopes on Earth were observing the expected impact region. The explosion produced a flash of light which was visible and can be seen in the figure below.

Three views of the impact region on the moon, closely separated in time. The impact flash is visible in the centre image (images taken at the Canadian-French-Hawaii Telescope). Source: ESA.
But what does the impact crater look like? The crater itself is too small to be seen from the Earth. So the only images are those made in the laboratory at Kent. One possible shape is shown in the figure below.

A laboratory impact made in sand at shallow angle using the Kent two stage light gas gun. The impact direction was from the bottom. An elongated crater results at the 2 incidence as shown here. At shallower angles, multiple craters result in a 'snow-man' like appearance. Source: Kent.
A preliminary report on the results is available in the LPSC abstract: 'Laboratory Simulations of Smart-1 impact on the moon.' Robin-Williams R., Burchell M.J. 38th Lunar and Planetary Science Conf., Abstract 1651, 2007. More details of earlier Kent work on hypervelocity impacts at oblique angles are available in the following papers:

Rock targets:
  • Oblique Incidence Hypervelocity Impacts on Rocks. M.J. Burchell and L. Whitehorn, Monthly Notices of the Royal Astronomical Society 341, 192-198, 2003.
  • Azimuthal Impact Directions from Oblique Impact Crater Morphology, D. Wallis, M.J. Burchell, A.C. Cook, C.J. Solomon and N. McBride, Monthly Notices of the Royal Astronomical Society, 359, 1137 - 1149, 2005.
Ice targets:
  • Scaling of Hypervelocity Impact Craters in Ice with Impact Angle, I.D.S. Grey, M.J. Burchell and N.R.G. Shrine, J. of Geophysical Research E., 107(E10), 5076, doi:10.1029/2001JE001525, 2002.
Metal targets:
  • Crater Ellipticity in Hypervelocity Impact On Metals, M.J. Burchell and N. Mackay, J. of Geophys. Res. 103 E, 22761-22774, 1998.
Aerogel targets:
  • Capture of Hypervelocity Particles in Aerogel: in Ground Laboratory and Low Earth Orbit. M.J. Burchell, R. Thomson and H. Yano, Planetary and Space Science 47, 189-204, 1999.