Life on Earth may have come from space, say Japan scientists studying samples from asteroid 300 million km away

The black particles from an asteroid some 300 million km away look unremarkable, like pieces of charcoal, but they hold the components of life itself. Scientists in Japan have discovered the chemical compound uracil, one of the building blocks of RNA, in just 10 milligrams of material from the asteroid Ryugu, according to new research. They found niacin as well, which is also called Vitamin B3 or nicotinic acid and is vital for the metabolism. The finding lends weight to a long-standing theory that life on Earth may have been seeded from outer space when asteroids crashed into our planet carrying fundamental elements. It is some of the latest research from analysis of 5.4 grams of rocks and dust gathered by the Japanese Space Agency’s Hayabusa-2 probe from the asteroid Ryugu. Hayabusa-2 was launched in 2014 and returned to Earth’s orbit in late 2020 with a capsule containing the samples from the asteroid, which landed in Australia’s remote outback. The precious cargo was divided between international research teams and has already yielded several insights, including that some of life’s building blocks, amino acids, may have been formed in space. The first drop of water discovered in a near-Earth asteroid has also been found among the samples. The new research, published on Tuesday in the journal Nature Communications, went looking for another foundation of life: the nucleobases of RNA. Samples from far-distant asteroid leave Japan scientists ‘speechless’ Scientists have long pondered about the conditions necessary for life to arise after Earth formed about 4.5 billion years ago. The new findings fit well with the hypothesis that bodies like comets, asteroids and meteorites that bombarded early Earth seeded the young planet with compounds that helped pave the way for the first microbes. Key organic molecules had previously been detected in carbon-rich meteorites found on Earth. But there was the question of whether these space rocks had been contaminated by exposure to the Earth’s environment after landing. “Our key finding is that uracil and niacin, both of which are of biological significance, are indeed present in extraterrestrial environments and they may have been provided to the early Earth as a component of asteroids and meteorites,” said astrochemist Yasuhiro Oba of Hokkaido University in Japan, lead author of the research. While DNA, the famed double helix, functions as life’s genetic blueprint, single-strand RNA is an all-important messenger, converting the instructions contained in DNA for implementation. Like DNA, it is made up of bases: adenine, guanine, cytosine, and uracil. Testing the Ryugu samples was a multiphase process that began by putting them in hot water, like “brewing coffee or tea”, Oba said. Acid was then applied to extract molecules that were analysed by extremely sensitive tools capable of detecting the minute quantities of uracil present. We expect it plays a role for prebiotic evolution and possibly the emergence of the first life Yasuhiro Oba, astrochemist The discovery offers “strong evidence that one of the RNA components has been provided to the Earth even before the emergence of life”, Oba said. “We expect it plays a role for prebiotic evolution and possibly the emergence of the first life.” Oba said uracil and niacin were found at both landing sites on Ryugu, which is about a half-mile (900 metres) in diameter and is classified as a near-Earth asteroid. The concentrations of the compounds were higher at one of the sites than the other. The sample from the site with the lower concentrations was derived from surface material more susceptible to degradation induced by energetic particles darting through space, Oba said. The sample from the other site was mainly derived from subsurface material more protected from degradation, he added. Valentine’s Day asteroid not likely to hit Earth after all, scientists say Oba hopes to analyse new samples collected from space in coming years, including Osiris-REx’s material from the asteroid Bennu, expected to arrive this year. Yoshinori Takano, a scientist at the Japan Agency for Marine-Earth Science and Technology and co-author of the Ryugu research, said he was also keenly awaiting the Martian Moons eXploration project, set to launch from Japan next year and return around 2029. It will collect samples from Phobos, one of the moons of Mars. “I am sure it will be very hotly watched by organic cosmochemists for the next 10 years,” Takano said. Asteroids are rocky primordial bodies that formed in the early solar system. The researchers suggest that the organic compounds found on Ryugu may have been formed with the help of chemical reactions caused by starlight in icy materials residing in interstellar space. Additional reporting by Reuters