astrobiology

A Japanese research team has identified the five nucleic bases (adenine, guanine, cytosine, thymine, and uracil)—which form the building blocks of DNA and RNA—in samples from the asteroid Ryugu, according to a study published in Nature Astronomy, which compares the composition of these samples with those from the asteroids Bennu and Orgueil. “The detection of various nucleic bases in asteroid and meteorite materials demonstrates their widespread presence throughout the solar system and reinforces the hypothesis that carbonaceous asteroids contributed to the prebiotic chemical inventory of the early Earth,” the authors write.

Amino acids are the building blocks of proteins. These are known as the building blocks of life, but they cannot replicate themselves. To do so, they need the instructions provided by RNA. How this relationship began is still a mystery. Now, a British team has shown how it could have started from relatively simple conditions. According to the researchers, who published their findings in the journal Nature, ‘understanding the origin of protein synthesis is fundamental to understanding where life comes from.’

The research article A bacterium that can grow by using arsenic instead of phosphorus was one of the big science stories because it discussed the possibility of arsenic-based life. However, it has been the subject of criticism until now. After nearly 15 years of debate and failed attempts by other groups to replicate the findings, Science has now decided to retract the article, despite finding no evidence of fraud or misconduct on the part of the authors, who disagree with the decision.

Using data from the James Webb Space Telescope (JWST), a group of astronomers has detected the chemical fingerprints of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in the atmosphere of exoplanet K2-18b, which orbits its star in the habitable zone. The detection has been published in The Astrophysical Journal Letters. 

The red colour of Mars corresponds to a type of ferrihydrite that is the dominant form of iron oxide in Martian dust, although previous studies have attributed it to anhydrous haematite. The persistence of ferrihydrite, whose formation requires water, suggests that it formed during a cold, wet period, followed by a transition to the planet's current arid environment. The result, based on ESA and NASA space data and new laboratory experiments, is published in Nature Communications.

US researchers have published a model showing that ice in the mid-latitudes of Mars could allow photosynthetic life to develop. Its thickness and composition would attenuate harmful ultraviolet radiation, but allow sufficient visible light to pass through. The work is published in the journal Communications Earth & Environment.

ESA's ExoMars and Mars Express missions have for the first time detected ice near the equator of Mars, specifically in the Tharsis volcanoes, an area of the planet where it was thought impossible to exist. According to the researchers, who publish the results in the journal Nature Geoscience, such findings are important for habitability and future human exploration. 

Fifteen years ago, the European Space Agency's (ESA) Mars Express probe revealed the presence of large deep deposits on Mars, in an area called the Medusae Fossae Formation (MFF), located at its equator. Now, new data from the probe's MARSIS radar indicate that the deposits are deeper than previously thought - up to 3.7 kilometers thick - and include both ice-rich and dusty layers. The results are published in Geophysical Research Letters.

A Japanese research team has announced in Nature Communications that it found uracil, a component necessary to form RNA, in a small sample collected from the asteroid Ryugu. According to the authors, these results indicate that these molecules of prebiotic interest were commonly formed on asteroids like Ryugu, and reached the early Earth with the impact of these bodies. The sample was collected by the Japan Aerospace Exploration Agency's Hayabusa2 robotic spacecraft, which returned to Earth in December 2020.

Based on a model, a study theorises that Mars may have been habitable for microorganisms 3.7 billion years ago, according to the journal Nature Astronomy.