Mini-Moons and Quasi-Moons
Context:
Recently, an asteroid by the nomenclature 2025 PN7 has been spotted, which is said to be a quasi-moon and could be smallest of its kind.
UPSC Relevance: Science and technology
PYQ:
Q) The group of small pieces of rock revolving round the sun between the orbits of Mars and Jupiter are called:
a) Meteors
b) comets
c) meteorites
d) asteroids
Q) Consider the following statements regarding asteroids:
1. Asteroids are rocky debris of varying size orbiting the sun
2. Most of the asteroids are small, but some have diameters as large and 1000 km
3. The orbit of asteroids lies between the orbits of Jupiter and Saturn
Which of these statements are correct:
a)1, 2 and 3 are correct
b)2 and 3 are correct
c)1 and 2 are correct
d)1 and 3 are correct
About Asteroids:
- Asteroids are remnants of planetary formation that failed to coalesce because of the gravitational interference of Jupiter. They circle the Sun in a zone lying between Mars and Jupiter. The circular chain of asteroids is called the asteroid belt. It lies between 2.3 and 3.3 AU from the Sun.
- Asteroids (planetoids ― another term for an asteroid) are composed mainly of refractory rocky and metallic minerals, with some ice. They range in size from hundreds of kilometres across to microscopic.
- Ceres (2.77 AU) is the largest asteroid (946 km in diameter), a protoplanet, and a dwarf planet. It has a mass large enough for its own gravity to pull it into a spherical shape. All asteroids, except Ceres , are classified as small Solar System bodies.
Mini-moons and Quasi-moons:
Mini-Moons:
- Mini-moons are asteroids that fail to escape Earth’s gravity and end up orbiting the planet for some time.
- They are usually very small and hard to detect — only four mini-moons of Earth have ever been discovered, and none are still orbiting Earth.
- These events are relatively frequent, with similar occurrences happening every few decades.
How does Earth capture Mini Moons?
- Mini moons are captured from the Near-Earth Object (NEO) population, which consists of asteroids and other celestial bodies that pass close to Earth.
- NASA classifies any space object that comes within 120 million miles (190 million kilometres) of our planet as a near-Earth object, while objects within 4.7 million miles (7.5 million kilometres) are considered potentially hazardous
Quasi-moons:
A quasi-moon is a term used to describe an asteroid or space rock that orbits the sun in a similar time frame as Earth but is only slightly influenced by Earth’s gravitational pull. It appears to accompany Earth during its yearly journey around the sun but is not a natural satellite like the moon.