Hello Nature readers,
Today we investigate signs of microbial life on Mars, consider whether an infamous psychology study should be retracted and watch an AI-powered robot slam-dunk a miniature basketball.

Spotted Martian rocks hint at microbial life

Dark-rimmed ‘leopard spots’ in a rock studied by NASA’s Perseverance rover last year could be the remains of microbial activity on Mars. The rings aren’t a sure sign that microbes once thrived on the Red Planet; the only way to know for certain is to analyse a sample of the leopard-spotted rock here on Earth. Perseverance has a sample awaiting a ride off Mars for precisely that purpose. For now, the rings are being treated as ‘an intriguing signal’ of ancient Martian life, but far from a sure thing, said researchers at a conference yesterday.

Handful of genes influence brain ageing

Researchers have identified 64 genes that help to shape how quickly a person’s brain ages. The team analysed brain scans from nearly 40,000 people and calculated each person’s ‘brain age gap’ (BAG) — the difference between their predicted brain age and their chronological age. Using genetic data from just over 31,000 healthy participants from the cohort, the team homed in on 64 genes linked to BAGs, some with roles in blood clotting and cell death. They also pinpointed 13 potential drugs that have been explored in clinical trials that could be used to target these genes.

Ancient Europeans crossed the sea to Africa

A genomic study of people who lived more than 6,000 years ago hints that ancient European hunter-gatherers might have voyaged across the Mediterranean to Africa. Using DNA from bones or teeth from nine individuals found at archaeological sites in the eastern Maghreb region — present-day Tunisia and northeastern Algeria — researchers found that Stone Age populations who lived there were descended, in part, from Europeans. At that time, there were more islands poking above the waves in the narrow strait between what’s now Sicily and Tunisia, which could have eased the journey for ancient voyagers in simple boats.

Tiny anvil squishes metals atoms-thick

Researchers have forged relatively large sheets of metal that are just atoms thick. The team took inspiration from ancient copper forging techniques to squish molten droplets of metals such as bismuth, lead and tin into 2D sheets in a tiny sapphire anvil. This allowed them to study how the properties of super-thin sheets of the metals differ from 3D chunks of the same material. The team now have their sights on a new design that they hope will extend the technique to work with metals that have melting points above 500 ℃.

Retract the Stanford Prison Experiment?

While researching the infamous Stanford Prison Experiment for a book, social scientist Thibault Le Texier was struck by how quickly it all falls apart under scrutiny. The ethics of the mock jail study — which described undergraduate volunteers descending into sadism and breakdown — are questionable at best. Lead researcher Philip Zimbardo might have pinched the design of the study from junior team members without crediting them, and the results were sent to the media immediately, with no peer review in sight until 1973 — two years after the experiment concluded. The myriad problems Le Texier highlights raise a question, writes sociologist Augustine Brannigan: should the study be retracted? It might not even be possible — the journal that eventually published the paper no longer exists. “If Le Texier’s findings are credible, arguably the best outcome we can expect is more responsible reporting in contemporary textbooks,” Brannigan writes.

She solved the problem Darwin couldn’t

“Elisabeth Vrba’s meticulous studies of fossil and living mammals challenged the conventional view of evolution” writes palaeontologist Niles Eldredge. Among the achievements of Vrba, who has died aged 82, was a solution to a problem that Darwin grappled with throughout his career: “how could the great diversity of species over vast stretches on continental areas have occurred in the absence of obvious barriers that would cause reproductive isolation?” Vrba’s answer was that cataclysmic environmental changes can fragment and isolate habitats, and cause waves of extinction and evolution.