67P/Churyumov–Gerasimenko

67P/Churyumov–Gerasimenko is a Jupiter-family comet originating from the Kuiper belt. It is best known as the destination for the European Space Agency's landmark Rosetta mission, which in 2014 became the first spacecraft to orbit a comet and deploy a lander to its surface. The mission provided unprecedented data on the comet's composition, structure, and activity, revolutionizing our understanding of these primitive solar system bodies.

Discovery and naming

The comet was discovered on 20 September 1969 by Klim Churyumov and Svetlana Gerasimenko at the Alma-Ata Observatory in the Kazakh Soviet Socialist Republic. Churyumov identified the object while examining a photographic plate taken by Gerasimenko of another comet, 32P/Comas Solà, at the Byurakan Observatory in Armenia. Following the established International Astronomical Union convention for periodic comets, it was named after its co-discoverers. Its orbital history suggests it was likely captured into its current path by the gravitational influence of Jupiter relatively recently, within the last few centuries.

Physical characteristics

The comet has a distinctive bilobate, or "rubber duck," shape, consisting of two lobes connected by a narrow neck. Measurements from the OSIRIS camera aboard Rosetta determined its larger lobe measures approximately 4.1 × 3.3 × 1.8 km, while the smaller lobe is about 2.6 × 2.3 × 1.8 km. The surface is extremely dark, with an albedo of about 6%, and is dominated by diverse terrains including smooth plains, brittle fractured regions, and large cliffs. Key features include the Imhotep region, a relatively flat dusty plain, and the active pits of the Seth region.

Orbit and rotation

67P follows an elliptical orbit around the Sun with a period of about 6.45 years, taking it from a perihelion just outside the orbit of Earth to an aphelion near the orbit of Jupiter. Its orbit is inclined by 7.04 degrees to the ecliptic. The comet's rotation period was approximately 12.4 hours at the start of the Rosetta mission but was observed to change slightly due to non-gravitational forces from outgassing. Its orbital dynamics are heavily influenced by gravitational interactions with the giant planet Jupiter, which is characteristic of the Jupiter-family comet classification.

Exploration by Rosetta

The European Space Agency's Rosetta probe, launched in 2004 aboard an Ariane 5 rocket, rendezvoused with the comet in August 2014 after a complex journey involving gravity assists from Earth and Mars. In November 2014, Rosetta deployed the Philae lander, which achieved the first-ever controlled touchdown on a comet nucleus, though it ultimately came to rest in a shadowed area. The Rosetta orbiter conducted close-range observations for over two years, studying the comet through its perihelion in August 2015, before its controlled impact on the surface in September 2016, ending the mission.

Scientific findings

Data from instruments like ROSINA, VIRTIS, and MIRO revealed the comet's composition is rich in organic compounds, including the amino acid glycine and phosphorus, key ingredients for life. The ALICE spectrometer detected that water vapor outgassing from the comet had a different deuterium-to-hydrogen ratio than water on Earth, challenging the idea that such comets were a primary source of terrestrial water. The CONSERT experiment provided evidence of a highly porous, homogeneous interior structure. Observations of dramatic outbursts and collapsing cliffs, like those at the Aswan site, provided direct insight into cometary activity and erosion processes.

Category:Comets Category:Rosetta (spacecraft) mission Category:Jupiter-family comets