In July 2005, NASA's Deep Impact spacecraft visited Tempel 1 and sent a projectile - an 800 pound block of copper - into the comet. NASA essentially was doing a bit of space excavation, hoping to dig out a crater in order to get a view of the materials below the surface of the comet. The mission was a success. Maybe too successful - the resulting dust kicked up by the explosion - something akin to nearly 5 tons of TNT going off - and the probe couldn't get really good images. The objective of the Stardust-Next probe was to record the results from that experiment.
So it was that during its Valentine's Day flyby, the NASA probe came within 110 miles of the comet, as it passed by the other side of Tempel 1. In doing so, the Stardust probe charted territory that has never been imaged before. In this photo, the widest of the banded slopes is about a mile. The lowest terrace has a couple of circular features that are about 500 feet in diameter. The inset on the right shows a closer view. (You can read more about the latest Tempel 1 mission here.
On the left, the image from Deep Impact shows a dark mound inside a yellow circle. That's the area targeted by the 2005 impactor. The image on the right obtained by the Stardust spacecraft shows the mound flattened by the impactor. According to NASA, "the outer circle annotated on the right-hand image shows the outer rim of the crater and the inner circle shows the crater floor."
The surface of the comet has undergone changes in the last six years. Cliff erosion in some places has been as much as 100 feet since Deep Impact's 2005 visit (top right image). The middle left of the image show depressions that have merged together over time.
Before-and-after comparison of the part of comet Tempel 1 hit by the impactor from the Deep Impact spacecraft in 2005.
Another before-and-after comparison of the area where the 2005 impactor fell. The left-hand image includes an arrow pointing to the exact spot where the impact occurred. The right-hand image shows the plume of material kicked up by the impact that obscures the surface
Different views of Tempel 1 seen by the Deep Impact spacecraft (left) and the Stardust spacecraft (right).