The solar system was a very different place around 4.6 billion years ago. The sun, still a protostar, accreted enough material to reach a high enough temperature and pressure for hydrogen fusion at its core, thus becoming a star, encompassing around 99 per cent of all mass in the original solar nebula.
Concurrently, material further out in the protoplanetary disk was clumping up to form planets in distinct orbits around the newly formed star. Leftover material, which could not coalesce to form planets due to a number of reasons, aggregated, for the most part, in distinct locations in the solar system, namely in the asteroid belt between Mars and Jupiter, as well as in the Kuiper belt and beyond, located in the outer reaches of the solar system beyond the orbit of Neptune.
The clumps of rock and ice, which we now call asteroids or Kuiper belt objects, are thus leftover fragments from the early stages of formation of the solar system. These have remained in orbit around the sun as frozen relics, presenting an opportunity for a look at the material that would have been present in the original solar nebula and that could have been delivered to the surface of planets like Earth via asteroid impacts.
101955 Bennu is one such asteroid, forming part of the Apollo group of asteroids, which are near-Earth asteroids that cross our planet’s path in their orbits. Asteroids such as 101955 Bennu likely collided with Earth in the past, particularly during the hypothesised Late Heavy Bombardment period around four billion years ago.
The clumps of rock and ice, which we now call asteroids or Kuiper belt objects, are thus leftover fragments from the early stages of formation of the solar system
It is indeed theorised that all ocean water was originally brought to Earth via collisions of comets and asteroids in the early history of the formation of our planet. It is thus also possible that such impactors might have also brought other materials with them, such as the building blocks of life, to our planet.
A mission to collect a sample from asteroid Bennu, termed OSIRIS-REx, was launched in September 2016, rendezvousing with the asteroid in December 2018 and landing on the asteroid in October 2020, before starting its journey back home in May 2021.
The spacecraft did not land on Earth itself however, swinging past Earth only to make the Bennu sample delivery before changing its name to OSIRIS-APEX and heading out to yet another asteroid, Apophis.
The sample was returned to Earth only last month, but preliminary analysis of the collected asteroid sample shows evidence of water and carbon content.
Further studies will reveal the exact content of the retrieved samples, in a bid to better understand the kind of material that might have been brought to primordial Earth by such asteroids and perhaps identify their role in the origin of life on our planet.
Josef Borg completed a PhD in astronomy at the Institute of Space Sciences and Astronomy, University of Malta, and is currently a researcher at the Faculty of Health Sciences at the University of Malta. He is also Malta’s representative on the European Astrobiology Network Association (EANA) council.
Sound Bites
• Quartz crystals have been detected by JWST in an exoplanet’s atmosphere. WASP-17b is a hot Jupiter-type planet, with a scorching atmospheric temperature of 1,500ºC at the daytime side of the of the planet – located just under eight million kilometres away from its host star. As light from the host star passes through the puffed-up atmosphere of the exoplanet, some of that light will be absorbed by molecules in the atmosphere, dependent on the actual molecules themselves. JWST’s MIRI instrument detected the presence of pure quartz crystals in this manner, and like Jupiter, most of the atmosphere of WASP-17b is made up of hydrogen and helium.
For more soundbites, listen to Radio Mocha every Saturday at 7.30pm on Radju Malta and the following Monday at 9pm on Radju Malta 2 https://www.fb.com/RadioMochaMalta/.
DID YOU KNOW?
• The Apophis asteroid, measuring some 366 metres across, will make a close encounter with Earth in 2029. The asteroid will reach a closest approach distance of just over 32,000 kilometres on April 13, 2029, at which point the OSIRIS-APEX mission spacecraft is intended to use Earth’s gravity to enter in orbit around the near-Earth asteroid.
• The total mass of asteroids in the asteroid belt amounts to around four per cent of the mass of the moon. Even though there are millions of small asteroids in the asteroid belt, the total mass of all these asteroids is indeed only a small fraction of the mass required to form larger bodies such as moons and planets. Approximately half of this mass is accounted for by the four largest bodies in the belt, namely Ceres (which is now classified as a dwarf planet), Vesta, Pallas and Hygiea.
For more trivia, see: www.um.edu.mt/think.