Zodiacal light

Parts of this article (those related to the hypothesized origin of the zodiacal cloud - Mars dust, rather than comets or asteroids) need to be updated. Please help update this article to reflect recent events or newly available information. (March 2021)

Zodiacal light is a faint glow of diffuse light in the sky scattered by interplanetary dust, particularly a zodiacal cloud, along the ecliptic, and therefore the zodiac. It is mostly only visible in very dark conditions across the night sky along the whole ecliptic as the zodiacal band,^[2] backscattered slightly brighter from an oval area of the band directly opposite to the light source as the gegenschein (or counterglow) and brightest as a triangle-shaped area at the horizon around the light source as false dawn, mostly just before or after the Sun rises or sets.^[3][4][5][6]

Zodiacal light contributes^[7] to the natural light of the sky, though since zodiacal light is very faint, it is often outshined and rendered invisible by moonlight or light pollution.

The interplanetary dust in the Solar System forms a thick, pancake-shaped cloud called the zodiacal cloud which straddles the ecliptic plane. The particle sizes range from 10 to 300 micrometres, implying masses from one nanogram to tens of micrograms.^[8][9]

The Pioneer 10 and Helios spacecraft observations in the 1970s revealed zodiacal light to be scattered by the interplanetary dust cloud in the Solar System.^[10][11] Analysis of images of impact debris from the Juno spacecraft shows that the distribution of the dust extends from Earth's orbit to the 4:1 orbital resonance with Jupiter at 2.06 AU, and suggests that the dust is from Mars.^[12] However, no other dedicated dust instrumentation on Pioneer 10, Pioneer 11, Galileo, Ulysses, and Cassini found an indication that Mars is a significant source of dust besides comets and asteroids.^{[10][13][14][15]}