The Japanese spacecraft Hayabusa2 delivered samples of the asteroid Ryugu to Earth back in 2020, and since then, teams of scientists around the world have been carefully studying their composition.
Last year’s study stated that the Ryugu samples contain molecules important for life — «older than the Solar System itself» — while one recent analysis showed that some elements are likely to have originated directly from the Earth.
Ryugu — belongs to the most common category of asteroids (C-type asteroids or carbon asteroids); of all the asteroids found in the Solar System, 75% are carbonaceous. In fact, these are the debris left over from the formation of the Solar System, so they are quite interesting in terms of studying molecules that appeared almost 4.5 billion years ago.
The sample analyzed in the latest study is part of a larger rock weighing 5.2 grams, and was found to contain «filamentous» microorganisms very similar to Earth’s prokaryotic bacteria.
Scientists have long debated whether life on Earth originated directly on our planet or whether it came «from the heavens». Previous analyses of meteorites found on Earth have shown that some of these space rocks contain the five nucleotide bases essential for organic life — but the question of whether they were «contaminated» with these elements after falling to Earth remained open. The Hayabusa2 mission was one of the first to try to find the answer.
Initially, scientists from the UK, having received the sample from their Japanese colleagues, scanned the stone with X-rays and found no signs of bacteria on its surface. However, three weeks later, they tried again — they moved the sample into resin and used a scanning electron microscope, eventually seeing strands of organic matter on the surface.
The growth rates, shapes, and sudden appearance of the bacteria were very similar to those found on Earth — and again raised the question of post-landing contamination. The findings in the article, in addition to demonstrating the importance of following strict sample examination procedures, also emphasize the incredible adaptability of terrestrial bacteria, which rapidly absorb organic material from everywhere, regardless of the planet.
«The presence of microorganisms in meteorites has been used as evidence of extraterrestrial life, but the potential for terrestrial contamination makes their interpretation highly controversial», the researchers write. «The discovery highlights that terrestrial bioorganisms can quickly colonize extraterrestrial specimens, even if measures are taken to control pollution».
The article was published in the journal Meteorics and Planetary Science.
Source: livescience