Comet Hartley 2 was discovered by Malcolm Hartley. He discovered this comet in 1986 at the Siding Spring Observatory in Australia. Comet Hartley 2 is a small periodic comet with an estimated diameter between 1.2 and 1.6 kilometers. This comet has a peanut type shape to it. It has an orbital period of about 6.46 years.

On November 4, 2010, during the EPOXI mission, a spacecraft by the name of Deep Impact got as close as 430 miles of Comet Hartley 2. This makes Comet Hartley 2 the smallest comet in history to be visited. In 2005 the Deep Impact actually visited another comet by the name of Comet Tempal 1. That makes Deep Impact responsible for the visitation of 2 of the 5 comets ever visited. Deep Impact was traveling at approximately 27,500 miles per hour during the spacecrafts visit with Comet Hartley 2. During the visit NASA scientists actually describe Comet Hartley 2 as being extremely active compared to previous comets. These scientists also noted that the rays coming from Comet Hartley 2 were made up of basketball and golf ball sized chunks of dust and what is described as fluffy ice. These chunks were ejected by jets of carbon dioxide. It is presumed that the CO2 ice actually dates back to the beginning of our solar system.

Some other interesting findings during the EPOXI mission concluded that Comet Hartley 2 spins on one axis and at the same time continually tumbles around another axis. The surface of this comet consists of glittering, blocky objects that reach somewhere around 165 feet high and 260 feet wide. In terms of comparison they are the size of a 16 story building.

On October 20, 2010 Comet Hartley 2 passed within .12 astronomical units which is equivalent to within 11,000,000 miles of Earth. If you lived in North America this comet was visible around midnight during early November 2010. Eight days after Comet Hartley 2 passed by Earth it came to perihelion which means closest approach to the sun. Comet Hartley 2 is again expected to come to perihelion around April 20, 2017. Even though Comet Hartley 2 passed so close to Earth it has not yet been the cause of a meteor shower. This is suppose to change in 2062 and 2068 as the 1979 dust trail and more recent dust trails move in and out of Earths orbit. The Minor Planet center has designated Comet Hartley 2 as 103p Hartley.