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A closeup photo of a round metal container filled with what looks like crushed ice and three shiny metal balls.

Milling ordinary ice with steel balls disrupted its crystalline structure and led to a novel, denser version of solid water. (Alexander Rosu-Finsen, Christoph Salzmann)

New type of ice discovered

Scientists have made a new form of ice that has never been seen before. It was produced by shaking normal ice in a container filled with stainless steel balls at –200 °C, which disrupted the ice’s crystalline structure. There are already heaps of types of ice: depending on how it freezes, water can solidify in any of 20 regular arrangements. And two types of disordered, or ‘amorphous’, ice were already known: one denser, and one less dense, than water. The new ice — called medium-density amorphous ice — seems to have the same density and structure of liquid water. The discovery could help scientists to better understand water’s mysterious properties, as well as geophysical processes on icy moons.

Nature | 4 min read

Read more: Water might be so unusual because it’s actually two liquids in one (Chemistry World | 11 min read, from 2020)

Reference: Science paper

How long does COVID immunity last?

How quickly does immunity from vaccination, infection with SARS-CoV-2, or a combination of the two, wane? Studies from Portugal, Israel, Sweden and Qatar have offered clues, but the real answer is: it’s complicated. ‘Hybrid’ immunity gained from vaccination and infection provides some protection against reinfection for around eight months, longer than immunity acquired from a booster alone. But the emergence of new variants makes it hard to determine the role of immune evasion. One study suggests that immunity against reinfection could last up to three years — if the virus does not mutate. The data make it difficult to predict when new surges of infections might occur — or when to schedule booster shots.

India pledges US$4 billion for green energy

India’s government has committed 350 billion rupees (US$4.25 billion) to a green-energy transition, with the goal of reaching net-zero emissions by 2070. The country aims to become a leading producer and exporter of ‘green hydrogen’, a fuel produced using renewable energy. Policy analysts in India applauded the net-zero target, but said it was unclear how the country would make the steep emissions cuts needed to achieve it. India is the world’s third-biggest emitter of greenhouse gases.

Nature | 3 min read

Features & opinion

Science urgently needs a plan for ChatGPT

The artificial intelligence (AI) chatbot ChatGPT shows how science “now faces a reckoning induced by AI technology infringing on its most dearly held values, practices and standards”, argue five researchers who specialize in psychology, cognition and AI. The authors delve into the complexities of accuracy and misinformation, how to bestow attribution and credit, and how AI might ultimately remake the scientific enterprise.

Nature | 15 min read

Futures: Deus exed

An artificial intelligence seeks to reinvent its role at the top of a misguided religion in the latest short story for Nature’s Futures series.

Nature | 4 min read

Five best science books this week

Andrew Robinson’s pick of the top five science books to read this week includes a witty, richly illustrated look at European ice-age life and an intriguingly human collection of articles about computer coding.

Nature | 3 min read

Podcast: mummification mix

Pots from a 2,500-year-old embalming workshop have revealed ancient Egyptians’ mummification recipes. In the first chemical analysis of labelled embalming components, scientists discovered local animal fats, plant oils and beeswax — as well as two plant resins that must have come from distant parts of Africa and southeast Asia. “It’s something totally new because we had no idea that Egyptians would have imported some products from so far away,” archaeologist Maxime Rageot tells the Nature podcast.

Nature Podcast | 30 min listen

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Quote of the day

“If my theory is correct, it makes the philosophical problem of creation disappear, in a way.”

A lost television interview with cosmologist and priest Georges Lemaître, who first proposed the idea of an expanding Universe, has been rediscovered by a Belgian broadcaster. (Science Alert | 4 min read and 20 min video)Read the full English transcript of the interview on the arXiv.