Explained: How Jupiter Trojan asteroids will help NASA understand evolution of solar system

The spacecraft's first encounter will be with an asteroid that lies in the main belt that can be found between Mars and Jupiter. 

This asteroid is named 'Donald Johnson' after the paleoanthropologist who discovered the fossilised remains of "Lucy".


By: Explained Desk | New Delhi |
Updated: October 13, 2021 

NASA's Lucy spacecraft is seen at the AstroTech facility, 

Wednesday, Sept. 29, 2021, in Titusville, Fla. 

(AP Photo/John Raoux)

NASA is set to launch ‘Lucy’ next week, its first mission to explore the Jupiter Trojan asteroids. These asteroids are believed to be the remnants of the early solar system, and studying them will help scientists understand its origins and evolution, and why it looks the way it does.

The solar-powered mission is estimated to be over 12 years long, during the course of which the spacecraft will visit eight asteroids covering a distance of about 6.3 billion km to deepen the understanding of the “young solar system”.

The mission is named after ‘Lucy’, a 3.2 million-year-old ancestor who belonged to a species of hominins (which include humans and their ancestors).

The spacecraft’s first encounter will be with an asteroid that lies in the main belt that can be found between Mars and Jupiter. This asteroid is named ‘Donald Johnson’ after the paleoanthropologist who discovered the fossilised remains of ‘Lucy’.

When will ‘Lucy’ be launched?

The spacecraft will launch from the Cape Canaveral Space Force Station, Florida on an Atlas V 401 rocket during a 21-day launch period that will start on October 16, 2021. Subsequently, the spacecraft will fly by the Earth twice in order to use the planet’s gravitational field to assist it on its journey to the asteroids.

What is the aim of this mission?

NASA says that as per some planet formation and evolution models, the Trojan asteroids are believed to be formed from the same material that led to the formation of planets nearly 4 billion years ago when the solar system was formed.

Therefore, the mission is designed to understand the composition of the diverse asteroids that are a part of the Trojan asteroid swarms, to determine the mass and densities of the materials and to look for and study the satellites and rings that may orbit the Trojan asteroids.

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Where and what are the Trojan asteroids?

Asteroids are divided into three categories.

First, those found in the main asteroid belt, between Mars and Jupiter. This region is estimated to contain somewhere between 1.1-1.9 million asteroids.

The second group is that of trojans (the name comes from Greek mythology), which are asteroids that share an orbit with a larger planet. NASA reports the presence of Jupiter, Neptune and Mars trojans. In 2011, they reported an Earth trojan as well.

The Jupiter asteroids can be found in what are referred to as “swarms” that lead and follow the planet Jupiter along its orbit around the Sun. ‘Lucy’ will reach the first swarm of these asteroids that precede Jupiter by August 2027.

The third classification of asteroids is under Near-Earth Asteroids (NEA), which has orbits that pass close to the Earth. Those that cross the Earth’s orbit are called Earth-crossers. More than 10,000 such asteroids are known, of which over 1,400 are classified as potentially hazardous asteroids (PHAs).