In the aftermath of the collision of Deep Impact with Comet Tempel-1, one of the scientists in the control room cried, "I can't believe they pay us to have this much fun!" If this report in New Scientist is anything to go by, the experience has given NASA scientists a taste for using their space probes as ordnance:
A plan to drop a quarter-tonne copper ball through Mars's atmosphere and study the ejecta it blasts away from the planet's surface on impact is to be proposed to NASA.
…The idea behind THOR (Tracing Habitability, Organics, and Resources) is to fly an observer spacecraft to Mars and, hours before it reaches the planet, release an "impactor" ball. It could be up to 230 kilograms in mass and would be aimed at a region about 40° north or south of the equator.
The impactor, likely to be a giant copper sphere, would crash to the surface at more than 4 kilometres per second, blasting a crater about 10 metres deep.
The concept is very similar to Deep Impact, in that the observer spacecraft would analyse the debris thrown up by the impact with spectrometers, allowing scientists to get a peek at the composition of the Martian sub-surface. The main aim of this experiment is to test for the existence (or not) of low-latitude ice, although it might also detect organic compounds which might give hints of life (which, if it’s there, will surely appreciate having a quarter-tonne of copper dropped on its head from orbit). It’s quite a cool idea, in mad sort of way.