This image shows the nuclei of comets Tempel 1 and Hartley 2, as imaged by NASA's Deep Impact spacecraft, which continued as an extended mission known as EPOXI.
Tempel 1 is five times larger than Hartley 2. Visible jets are easily seen in images of Hartley 2, but required extensive processing to be seen in images of Tempel 1.
Tempel 1 is 7.6 kilometers (4.7 miles) in the longest dimension. Hartley 2 is 2.2 km (1.4 miles) long.
The Tempel 1 image was built up from more than 25 images captured by the impactor targeting sensor on July 4, 2005. The Hartley 2 image was obtained by the Medium- Resolution Imager on Nov. 4, 2010.
For more information about EPOXI visit http://www.nasa.gov/epoxi and http://epoxi.umd.edu/.