How Jupiter acts as Earth's 'bodyguard' against cosmic threats

Countless asteroids and debris that travel through space pose potential dangers for Earth but a massive planet acts as our world's unseen guardian. Jupiter , the largest planet in the solar system, pulls in or deflects debris before it can venture too close to the blue marble. The phenomenon is caused by the gas giant’s immense gravitational pull, which is about 318 times that of Earth. Dimitra Atri, an astrophysicist at New York University Abu Dhabi, said the planet’s gravitational influence plays a significant role in maintaining the stability of our cosmic neighbourhood. “This gravitational powerhouse works as a protective shield for Earth by intercepting numerous space objects that could pose severe threats if they were to impact our planet,” he said. The planet, which is 11 times wider than the Earth , took most of the mass left over after the formation of the Sun, causing it to get more than twice the combined material of the other bodies in the solar system. Its gravitational influence attracts most objects flying through space, including asteroids and comets, that pose a threat to Earth and other planets. Dr Atri said one instance was the 1994 collision of a comet called Shoemaker-Levy9 with Jupiter. “The comet broke apart and collided with Jupiter and was observed extensively by professional and amateur astronomers around the globe.” The comet broke into 21 major fragments which struck the planet over several days, creating huge, dark scars in the planet's atmosphere. The plume from the resulting fireball rose to 3,000km above Jupiter's atmosphere, with the impact of each fragment generating seismic waves that rippled around the planet. Estimates suggested that each major impact released an enormous amount of energy measured at between 100,000 and several million megatonnes of TNT. The total energy released was more than the world's nuclear arsenal combined. If the comet had struck Earth instead, it could have created a global disaster, similar to the collision that wiped out the dinosaurs 65 million years ago. However, the incident allowed scientists to study such events and served as a stark reminder of how volatile space can be. Jupiter also plays a role in keeping the main asteroid belt – located between Mars and the gas giant – stable, which is where small pieces of debris come from. “The asteroid belt between Mars and Jupiter consists of numerous small rocky objects orbiting the Sun,” said Dr Atri. “While Jupiter's gravity might have prevented these asteroids from forming a planet, it also plays a crucial role in stabilising the belt. “Jupiter's gravitational influence helps to clear out debris and prevent large bodies from impacting Earth.” It absorbs fragments of these objects into its atmosphere or slings them out of the solar system entirely. While Jupiter does act as a “protector” of Earth and other planets, it cannot prevent every single piece of debris from potentially striking our planet. Comets from the Oort Cloud, a spherical shell of icy bodies surrounding the solar system, can survive Jupiter's gravitational pull. “Long-period comets originating from the Oort Cloud can have highly elliptical orbits that bring them close to the inner solar system without being significantly affected by Jupiter's gravitational pull,” said Dr Atri. The comet's paths can also be influenced by factors outside of Jupiter's influence, such as gravitational nudges from passing stars or galactic tides. Scientists have been studying Jupiter for many decades because it is probably the first planet that formed in the solar system. As a result, it is often used as a natural laboratory for studying planet formation and the dynamics of the solar system. Researchers also find the planet fascinating because of its immense size, powerful magnetic field and turbulent atmosphere. In 2023, Nasa's Juno mission revealed that the planet's magnetic field was even stronger and more irregular than expected, with a lumpy distribution. The James Webb Space Telescope, the world's most powerful space observatory, took its first test image of Jupiter after launching on Christmas Day, 2021. It beamed back newer, clearer images of the planet in 2022.