Hello Nature readers, welcome to your daily round-up of the top science news.
MASCOT took this image from about 20 metres above Ryugu's surface. The lander's shadow can be seen at the top right.Credit: MASCOT/DLR/JAXA
Hayabusa2 lands third rover on asteroid
A third lander has separated from Japan’s Hayabusa2 spacecraft and touched down on the asteroid Ryugu. It’s now racing to collect data on the asteroid’s temperature, magnetic field and surface composition. The rover has just 16 hours to complete its mission before its battery runs out. Hayabusa2’s fourth and final lander will touch down on the asteroid next July, before the mothership also lands on the surface to collect samples to bring back to Earth
Listen: Behind the scenes of Japan’s daring asteroid mission
Tantalizing hints of first exomoon
Astronomers have spotted what could be the first known moon to orbit an exoplanet. There had been earlier hints of this object, and new and better observations from the Hubble Space Telescope are making researchers more confident that the exomoon is real. Evidence suggests it’s about as big as Neptune, orbiting a planet roughly the size of Jupiter.
Reference: Science Advances paper
Historic agreement hands Central Arctic to scientists
The five Arctic countries and major fishing nations have signed a legally binding agreement to ban commercial fishing in part of the Arctic ocean that is being opened up by climate change. The accord includes the Arctic Five — Canada, Norway, Russia, Denmark (for Greenland and the Faroe Islands), and the United States — along with Iceland, Japan, South Korea, China, the European Union and the Inuit Circumpolar Council. The agreement will prevent commercial fishing in the Central Arctic Ocean for at least 16 years while scientific research is conducted to learn more about the area’s marine life and resources. The agreement is unprecedented, says former fisher and policy specialist Trevor Taylor. “Everywhere that we have fished in human history, we have fished first and asked questions later.”
FEATURES & OPINION
The rancorous rise of Reddit
A new book that traces the rise of Reddit reveals how the most powerful decentralizing technologies in history — the Internet and the web — have led to the greatest concentrations of power. From its beginnings as a scrappy start-up to its influence as a venue for the edgy, the story of Reddit tells the tale of how our world is changing.
Don’t execute a murderer who can’t remember
Vernon Madison can’t remember when he killed a police officer in 1985, because he has since had multiple strokes and developed vascular dementia. The state of Alabama argues that it doesn’t matter whether he remembers it, because he can still rationally conceptualize it: once the situation is explained to him, Madison understands that he was tried and will be executed. Madison’s intellectual disability means his execution doesn’t serve as justice or as a deterrent, argues a Nature editorial: the US Supreme Court should grant him mercy.
How to resolve the dark-matter crisis
There is a growing sense of crisis in the dark-matter particle community, say physicists Gianfranco Bertone and Tim Tait. We have failed to find evidence for the most popular candidates — WIMPs, axions and sterile neutrinos — despite the enormous effort that has gone into searching for them. Take a deep dive into the future of the field and how probing dark matter with astronomical observations might open new doors.
Possible solutions to the dark-matter problem.
