A comet is a small Solar System body composed mainly of ice, dust, and organic compounds. As they approach the Sun, cometary ices sublimate, releasing gas and dust that form the glowing coma and distinctive tails—often extending millions of kilometers.
Comets originate from two primary reservoirs: the Kuiper Belt—home to short-period comets with orbits under ~200 years—and the distant Oort Cloud, which sends long-period comets with orbits spanning thousands of years. Occasionally, interstellar objects like ‘Oumuamua pass through our system, appearing comet-like.
They are “dirty snowballs” and among the most primitive remnants of the early Solar System, preserving original ices and organic material from 4.6 billion years ago.
Landmark missions include ESA’s Rosetta—with its lander Philae—which orbited and sampled Comet 67P/Churyumov–Gerasimenko (2014–2016). NASA’s Deep Impact struck Comet Tempel 1 in 2005 to analyze interior composition.
These missions discovered complex organic molecules, including amino-acid precursors, and supported the theory that comets may have delivered water and prebiotic compounds to early Earth.
Looking ahead, ESA–JAXA’s Comet Interceptor (launch planned for 2029) intends to perform a rapid flyby of a dynamically new or interstellar comet, using multiple spacecraft to sample both nucleus and coma environments.
Comets are studied across the electromagnetic spectrum—from radio to gamma rays—using telescopes and spacecraft to understand composition, internal structure, activity, and their roles in planetary formation, the evolution of the solar system, and the origin of life.
9 April 2026
As the crew of Artemis II travelled towards the Moon this week, Comet C/2026 A1 (MAPS) was expected to have its closest approach to the Sun on Monday. At this point, comet and Sun would be closer than half the distance separating the Earth and Moon. The comet did not survive; the featured video was made with 40 hours of data and shows the comet plunging toward the Sun, like a moth to a flame. Observing the comet so close to our bright star requires a coronagraph, an instrument that blocks the Sun and is used for studies of its corona. This composite video combines, starting from the outside, views from: the wider angle coronagraph (blue) and the narrower angle coronagraph (red), both on NASA's Solar and Heliospheric Observatory, and NASA's Solar Dynamics Observatory (black). We can see the comet approaching the sun, stretching, disappearing behind the coronagraph's occulting disk and reappearing as a cloud of debris that dissipates.