Daily briefing: Mars’s core is half the size of Earth’s

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Cells mimic embryo’s earliest stage yet

Scientists have used human stem cells to mimic the earliest stage yet of embryo growth. Multiple research groups independently report that they grew balls of cells that look like human blastocysts, which form about 4 days after an egg is fertilized by sperm. These experiments offer a window into a crucial time in human development and an opportunity to better understand pregnancy loss and infertility without experimenting on human embryos.

Nature | 6 min read

Reference: Nature paper 1, Nature paper 2, bioRxiv preprint 1 & bioRxiv preprint 2

First measure of the heart of Mars

NASA’s InSight spacecraft has revealed the size of Mars’s core by listening to seismic energy ringing through the planet’s interior. InSight’s measurement, taken from the Martian surface, suggests that the radius of the Martian core is 1,810–1,860 kilometres — roughly half of Earth’s. That’s larger than some previous estimates, meaning the core is less dense than had been predicted. The only other rocky planetary bodies for which scientists have measured the core are Earth and the Moon. Adding Mars will allow researchers to compare and contrast how the Solar System’s planets evolved.

Nature | 5 min read

Mystery bacteria might help plants in space

Three previously unknown strains of bacteria have been discovered growing on the International Space Station. All are members of the Methylobacteriaceae family, involved in nitrogen fixation and plant growth. Researchers suggest that the three new strains, and a fourth that was from a previously known species, could one day help to cultivate crops in space or on Mars.

CNN | 5 min read

Reference: Frontiers in Microbiology paper

COVID-19 coronavirus update

Has the pandemic peaked?

Global COVID-19 cases have fallen significantly since they peaked in early January. Scientists are asking whether this is the beginning of the end of the pandemic. It’s too soon to be sure — especially with the rise of new variants that threaten to circumvent vaccines. There are also many places that are still vulnerable because rates of immunity, either through vaccination or infection, are low. And the global trend does not reveal the true scale of infection in some parts of the world.

Nature | 7 min read

Next wave of vaccines tackle global needs

The next wave of vaccine developers are striking deals with producers and institutes in low- and middle-income countries. They are working on vaccines that combat fast-spreading variants, that are stable outside the fridge and that can be self-administered or more easily given. Nature Biotechnology enumerates these up-and-coming contenders and explores how they work.

Nature Biotechnology | 10 min read (thanks to everyone who let us know that that a glitch prevented some of you from reading this article in yesterday’s Briefing)

Features & opinion

To quell fake news, offer ‘carrots’ for truth

Social-media platforms should reward users for reliable, accurate and trustworthy posts, argues cognitive neuroscientist Tali Sharot. “As a neuroscientist who studies motivation and decision making, I have seen how even trivial rewards strongly influence behaviour,” writes Sharot. She points to Sweden — where drivers were offered prizes for obeying the speed limit, and average speed was reduced by 22% — and outlines how a reward system could overcome the appeal of sharing misinformation.

Nature | 5 min read

Hawaiian newspapers reveal past climate

In 1871, the Ke Au Okoa newspaper documented a major hurricane, including the exact time that flooding occurred and the changing wind directions. It’s one example of how the islands’ Hawaiian-language newspapers, which once numbered more than 100, offer a detailed historical record of extreme weather in the region. Language researcher Puakea Nogelmeier uncovered the data as part of a project to translate more than one million pages of newspaper archives. His team then collaborated with meteorologists to bring the information to light, eventually influencing climate legislation in the state.

Future Human | 8 min read

Reference: Bulletin of the American Meteorological Society paper