Inquiries about the moon’s twilight zone, and more reader feedback

Your letters and comments on the Aug. 5, 2017, issue of Science News

Locked up

Simulations suggest that heat from an infant Earth, the sun and the moon could have vaporized the moon’s metals into a thick atmosphere, Lisa Grossman reported in “Metallic air may have swaddled moon” (SN: 8/5/17, p. 7). One way to test the idea would be to look for a ring of extra sodium in rocks around the moon’s twilight zone, where sodium snow would have accumulated. This zone exists between the moon’s light and dark sides, which result from one side always facing Earth — a circumstance known as tidal locking.

Online reader Idhbk wondered if the early molten moon would have had a consistent face to show Earth at all. “I’m having trouble conceptualizing a ball of liquid being tidally locked,” the reader wrote. And if the surface was changing, would the sodium band be in the twilight zone where scientists expect?

Yes, a ball of magma can be tidally locked, says Prabal Saxena of NASA’s Goddard Space Flight Center in Greenbelt, Md. “A liquid body would have no rigidity and would be very responsive to locking,” Saxena says. The early moon’s roiling magma wouldn’t necessarily move the sodium band, either — the twilight zone would be in the same spot and would get more sodium deposits than other regions, Grossman says. But that’s only if the moon never showed Earth another side of itself.

Online reader Stargene asked if the moon’s tidal locking could have shifted over billions of years, and if such a shift might affect the sodium band’s location.

There’s no definitive answer on how the moon’s tidal locking evolved, says Saxena, but there are some theories. If the side of the moon facing Earth shifted as the two drifted apart, that could affect where the band may be found. Excess sodium would still end up in the twilight zone, but not the twilight zone as we know it today, Grossman says.

Light-hearted rodents

Light-harvesting bacteria can provide oxygen to rats’ blood-starved hearts, Tina Hesman Saey reported in “Photosynthesis treats ailing hearts” (SN: 8/5/17, p. 8). Researchers performed surgeries in the dark and under light to measure the bacteria’s activity.

 “How were the photosynthetic bacteria able to produce oxygen in the dark?” asked online reader Ivo Fernandes.

Bacteria did not produce oxygen in the dark, Saey says. Baseline oxygen levels around the heart increased during surgery in the dark because rats’ chest cavities were open to the air. Bacteria carried out photosynthesis only when bright lights were on, causing oxygen levels around the heart to shoot up.

Go the distance

A satellite sent entangled particles to two Chinese cities 1,200 kilometers apart, Emily Conover reported in “Quantum satellite sets distance record” (SN: 8/5/17, p. 14). The experiment brings scientists another step closer to developing a quantum internet, which would allow for ultrasecure communications.

Online reader Maia wondered how quantum communication would be ultrasecure.

“Quantum communication allows two people to share a secret string of random numbers by sending a series of entangled particles, with the surety that no one could have snooped on the random numbers,” Conover says. That’s because measuring entangled particles changes their properties. If anyone intercepts the particles, that action would leave telltale signs, and the pair would know their numbers had been compromised. “The string of numbers, in turn, serves as a secret code that can be used to encrypt further communications sent by normal means,” Conover says.

Patched up

Patches studded with microneedles safely and effectively delivered flu shots to a small group of U.S. adults, Aimee Cunningham reported in “Patch could someday replace flu shot” (SN: 8/5/17, p. 8).

Online reader Mark S. wondered how long the patch had to stay on to work.

The patch was effective 20 minutes after being applied, Cunningham says.

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