This Moment in Science History for 09-11-2024

On September 11, 1985, the International Cometary Explorer (ICE) spacecraft made history by becoming the first spacecraft to visit a comet. Originally named the International Sun-Earth Explorer-3 (ISEE-3), the spacecraft was launched in 1978 to study the interaction between the Earth's magnetic field and the solar wind.

However, after completing its primary mission, NASA decided to repurpose the spacecraft for a daring cometary encounter. The target was Comet Giacobini-Zinner, a periodic comet that orbits the Sun every 6.6 years.

To achieve this feat, the spacecraft had to perform a series of complex maneuvers, using the Moon's gravity to slingshot itself into the correct trajectory. The journey to the comet took approximately four years.

On September 11, 1985, ICE successfully flew through the comet's tail at a distance of about 7,800 kilometers (4,850 miles) from the nucleus. The spacecraft collected valuable data on the comet's composition, as well as its interaction with the solar wind.

The encounter provided scientists with the first direct measurements of a comet's environment, including the detection of organic molecules, which are the building blocks of life. The data gathered by ICE helped scientists better understand the nature of comets and their role in the formation of the solar system.

The success of the ICE mission paved the way for future cometary encounters, such as the European Space Agency's Giotto mission to Halley's Comet in 1986 and NASA's Deep Impact mission, which successfully impacted Comet Tempel 1 in 2005.

Today, the study of comets remains an active area of research, with ongoing missions like ESA's Rosetta spacecraft, which orbited Comet 67P/Churyumov-Gerasimenko from 2014 to 2016, providing unprecedented insights into these fascinating celestial objects.