BangaloreAnother boost to the hypothesis that comets and asteroids deposited the building blocks of life on Earth millions of years ago. A team of scientists has discovered the presence of a basic amino acid, crucial for making RNA, in samples collected from the near-Earth asteroid Ryugu, adding to growing evidence that the ingredients for life on Earth may have been present. Could have come from outer space.
Asteroid samples collected by a Japanese-led space mission called Hayabusa2 have revealed the presence of various organic molecules, including uracil, one of the four nucleobases of ribonucleic acid (RNA). RNA is a molecule that is present in all living cells and plays an important role in converting the instructions in DNA into proteins.
The latest findings are detailed in a paper, ‘Uracil in the carbonaceous asteroid (162173) Ryugu,’ published on March 21. in the magazine nature communication,
Initial analysis of samples brought back from this asteroid containing carbon was done last month published in the journal Science, Scientists reported finding several organic molecules, including 15 amino acids – the building blocks of proteins. The authors proposed that these compounds would have been created on the asteroid by the reaction of surface ice with sunlight.
“These molecules may survive on the surfaces of asteroids and be transported throughout the Solar System,” the February paper, titled ‘Soluble organic molecules in a sample of the carbonaceous asteroid (162173) Ryugu’, said.
Hayabusa2 was launched in 2014 and returned samples to Earth in December 2020 after traveling 95,000 km from Ryugu.
The samples were collected from two sites on the asteroid that have had different geological histories, but were untouched since formation. The samples, the researchers said in the March paper, allowed them to analyze “ancient extraterrestrial material without uncontrolled exposure to Earth’s atmosphere and biosphere.”
The Hayabusa 2 mission was led by the Japan Aerospace Exploration Agency (JAXA) in collaboration with the German Space Center (DLR) and the French Space Agency (CNES). It was supported by the National Aeronautics and Space Administration (NASA) and the Australian Space Agency (ASA).
extra-terrestrial beginning?
To find out where life originated and how it came to Earth, astrophysicists are looking for primordial organic compounds in celestial bodies.
Among such compounds are the five nucleobases, the nitrogenous compounds that form the basis of RNA and DNA – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U).
The burning question is whether these life-forming compounds formed on Earth, or if they were delivered by carbon-rich asteroids that hit Earth as meteorites.
There has been mounting evidence for the latter over the past few years.
In a study published in nature communication Last April, Japanese planetary scientists had Confirmed The presence of all five primary nucleobases – A, G, C, T, and U – in three meteorites, suggesting that life and Earth’s constituents may have had an extra-terrestrial origin.
The findings from Hayabusa2 also point in the same direction.
The first analysis of samples from the asteroid Ryugu published last month revealed a variety of “prebiotic molecules,” including those that form in the presence of water.
The latest analysis, published this March, is even more exciting because it shows the presence of uracil, the nucleobase denoted by U, and found in RNA.
The researchers also found nicotinic acid, also known as niacin, which is a form of vitamin B3.
The researchers theorize in their paper that these compounds may have been released when the sun’s UV light broke down chemicals on the asteroid’s surface.
Hayabusa asteroid mission
Hayabusa2 was the successor to Hayabusa1, a mission that retrieved samples from asteroid Itokawa and returned them to Earth in 2010. Both missions, named after the Japanese word for peregrine falcon, were led by JAXA.
Hayabusa1 was the first controlled landing on an asteroid and the first ascent from a Solar System body other than the Moon. However, the asteroid dust samples were too small, reportedly due to technical issues. An analysis later revealed the presence of minerals such as olivine and plagioclase.
This time, Hayabusa2 “successfully delivered a total of 5.4 grams of ancient samples collected during the two touchdown operations” to Ryugu, the study said.
The mission was launched in 2014, with a 2018 rendezvous with the asteroid.
Ryugu’s closest approach to Earth is at a distance of 95,0000 km, and the asteroid orbits the Sun in the asteroid belt between Mars and Jupiter.
Once there, Hayabusa2 deployed two rovers and a lander and influencers fired Creating an artificial pit to take samples from below the surface. The mission lifted off in February 2019 and delivered samples via the landing capsule on 6 December 2022.
Hyabusu2 is currently on an extended mission to another asteroid, 1998 KY26.
Notably, JAXA shared a portion of its asteroid sample with NASA, in exchange for some samples from another near-Earth asteroid, Bennu, when Osiris-Rex The mission delivers them later this year. Bennu, it was reported in 2018, showed signs that there was once water in it.
(Edited by Asawari Singh)
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