The smallest comet that has been visited by a spacecraft is Hartley 2. This comet was discovered in 1986 and is officially known as 103P/Hartley. It has an eccentricity of 0.694, which means its orbit is highly elliptical, and it takes about 6.46 years to complete one orbit around the sun.
Hartley 2’s orbit is inclined at an angle of 13.6 degrees relative to the plane of Earth’s orbit. This inclination gives it a unique trajectory compared to other comets. It also means that its closest approach to Earth, known as the Minimum Orbit Intersection Distance (MOID), is about 0.072 astronomical units (AU), which is equivalent to approximately 10,800,000 kilometers.
One interesting fact about Hartley 2 is its small size. It is considered to be one of the smallest comets that has been studied up close. When the spacecraft Deep Impact visited Hartley 2 in November 2010, it provided valuable data and images of the comet’s nucleus.
During its close encounter with Hartley 2, Deep Impact captured stunning images that revealed the comet’s irregular shape and surface features. The nucleus of Hartley 2 was found to be roughly 2.2 kilometers long and 0.4 kilometers wide. This makes it significantly smaller than other comets that have been observed.
The visit to Hartley 2 allowed scientists to study the composition and structure of the comet in more detail. They discovered that the surface of Hartley 2 is covered in a layer of fine dust and ice, which gives it a bright appearance. The spacecraft also detected the presence of various gases, such as water vapor, carbon dioxide, and methane, emanating from the comet.
The study of Hartley 2 provided valuable insights into the formation and evolution of comets. Scientists were able to observe jets of gas and dust erupting from the comet’s nucleus, which indicated the presence of active surface processes. These observations helped to refine our understanding of how comets interact with the sun and how they release gas and dust as they approach it.
The visit to Hartley 2 by the Deep Impact spacecraft marked a significant milestone in the study of comets. It provided a unique opportunity to explore one of the smallest comets up close and gather valuable data about its composition and behavior. This information has contributed to our broader understanding of the solar system and the processes that shape celestial bodies like comets.