A space probe that penetrates the surface of a planet, moon, or other body in space, such as a comet. The craft must be able to survive a great impact and still transmit data relating to the subsurface being explored. In 1999, NASA lost contact with its ambitious Mars Polar Lander which carried two penetrators that were to be fired in to Mars's soil, but its twin Mars Exploration rovers that landed in 2003 had rock abrasion tools and used their wheels to scrape the surface. ESA's Rosetta spacecraft, launched on 2 March 2004, and reached the comet 67P/Churyumov–Gerasimenko on 6 August 2014. NASA's Deep Impact mission, fired an impactor into the nucleus of comet Tempel 1 in July 2005, excavating a crater, Japan's Lunar-A scheduled to drop two penetrators into the Moon was cancelled in 2007.