News Excerpt:

According to data reported in a 2021 paper by a group of researchers from Denmark and the U.S., dust particles struck the solar panels attached to the Juno spacecraft.

Key highlights of the study:

• The 2021 paper reported a peak in the number of dust particles impacting Juno at 1.5 AU. 
• A scientist (Dr. Pabari) at the Physical Research Laboratory (PRL), Ahmedabad, used this data to calculate the flux of dust between 1 and 5 AU. He found the flux at 1.5 AU to be 10-times higher than at other distances.
• The flux is the number of dust particles flowing through a given area per second.
• ‘AU’ stands for ‘astronomical unit’, which is the distance between the Earth and the Sun. Mars is at a distance of 1.52 AU, and Jupiter is at 5.2 AU from the Sun.
• Scientists have known that this dust is the source of zodiacal light. 
• But the scientist at PRL, Ahmedabad, compared the flux of dust in the vicinity of Mars and the number of particles escaping the two moons of Mars and concluded that these moons could be the dust source. 
• He also found no other phenomenon in the neighbourhood of this area that could release as much dust.

• Dr. Pabari found that micrometeorites fly into Mars’s moons just as they do into the Earth. 
• In the case of Earth, they burn up and disintegrate in the atmosphere. 
• But Deimos and Phobos (Mars’s moons) don’t have atmospheres, meaning most micrometeorites slam into their surfaces and kick up small dust clouds.
• These dust particles can easily escape Phobos and Deimos because of the moons’ low gravity. (The more gravity a planetary body has, the more spherical its shape. Deimos and Phobos are not at all spherical.) 

• • The smaller of these dust particles escape into space, whereas Mars’s gravity pulls in the larger ones. 
    • The latter collects in the form of a dust ring around Mars. 
    • Over time, they drift closer towards or away from the planet but stay in orbit.

About Mars’s moons:

Mars’s two moons are called Deimos and Phobos. In Greek mythology, Mars is the god of war, and the planet’s moons are named for his twin sons, the gods of dread and panic, respectively. The American astronomer Asaph Hall discovered both of them in 1877.

• Phobos:
  • Phobos is the bigger of Mars’s two moons. 
  • It is drifting closer to Mars at a rate of six feet per century. 
  • Eventually, astronomers expect it to crash into the planet or break up into a ring around it.
  • The most prominent feature of Phobos is a 10-km-wide crater named in honour of Hall’s wife, Angeline Stickney.  
  • On its day-side, the temperature on Phobos is around -4 degrees C, while just a few kilometres away on the night side, the temperature often drops to an even lower -112 degrees C. 
  • This large temperature difference (around 108 degrees C) arises because the surface of Phobos is covered with fine dust that lacks the ability to hold heat. 
  • Phobos also has no atmosphere that can trap heat.
• Deimos:
  • Deimos is the smaller of the two Martian moons and is less irregular in shape.
  • Astronomers believe its actual surface is buried under almost 100 metres of dust.
  • Like Phobos, Deimos is a small, lumpy, heavily cratered object. 
  • Its craters are generally smaller than 1.6 miles (2.5 kilometres) in diameter and lack the grooves and ridges seen on Phobos. 
  • When impacted, dust and debris will leave the surface of the moon because it doesn't have enough gravitational pull to retain the ejecta. 
    • However, the gravity from Mars will keep a ring of this debris around the planet in approximately the same region that the moon orbits. 
    • As the moon revolves, the debris is redeposited as a dusty layer on its surface.