Color-Changing Chameleon Comet

Rosetta mission data has revealed how comet 67P/Churyumov-Gerasimenko undergoes color changes as it moves through space. The European Space Agency's VIRTIS instrument tracked the comet over two years, showing that its nucleus appeared redder when far from the Sun due to dust-covered surfaces. As it approached the Sun, sublimation exposed fresh ice, making the nucleus bluer. Meanwhile, the surrounding coma followed an opposite pattern, appearing bluer when far from the Sun but redder near perihelion, as dust grains dominated the expelled material.

Key Findings

• The comet's nucleus was redder when distant due to dust accumulation.

• As it neared the Sun, sublimation exposed fresh ice, turning the nucleus bluer.

• The coma followed an inverse trend, appearing bluer when far but redder near perihelion due to expelled dust.

• These changes were linked to the frost line, where solar heating triggers ice sublimation.

• The study provides new insights into cometary evolution, showing how surface composition shifts dynamicallyover time.

Comet 67P/Churyumov-Gerasimenko exhibits dynamic color changes throughout its journey in space, revealing important details about its surface evolution. As it moves away from the Sun, its nucleus appears redder due to accumulated dust, while its coma looks bluer. However, as it approaches the Sun, sublimation exposes fresh ice, turning the nucleus blue, while the coma shifts to a redder hue due to expelled dust grains.

These color transformations are linked to the frost line, the boundary where solar heating triggers sublimation of volatiles. This process not only alters the comet's appearance but also influences its activity cycle, shedding light on how comets evolve over time. Scientists used Rosetta's VIRTIS instrument to monitor these changes over two years, providing unprecedented insights into the relationship between thermal cycles, surface composition, and color dynamics.

This study enhances our understanding of cometary aging and behavior, highlighting how space environments shape their physical properties. It also emphasizes the need for long-term observations to track these evolutionary processes in other comets.

European Space Agency (2020). Rosetta data reveals process behind color-changing chameleon comet. Phys.org.