Shaken-but-not-stirred remnants of Earth’s earliest years still exist nearly 4.6 billion years later.

Researchers traced the shadowy footprints of an isotope that hasn’t existed for over 4.5 billion years to much younger lava rocks from the Pacific and Atlantic oceans. That suggests that reservoirs of the ancient mantle may be hidden deep inside the planet, geochemist Hanika Rizo and colleagues report May 13 in Science.

Earth formed about 4.6 billion to 4.5 billion years ago as planetary bodies collided, disintegrating and melting to accrete into one mass like a hot, rocky lint ball. Geologists have assumed that any relics of this bumpy beginning were mixed beyond recognition.
Instead, Rizo’s team found a surprise: Some modern flood basalts have unusually high concentrations of tungsten-182. That’s significant because that isotope forms only from radioactive decay of hafnium-182. And hafnium-182 only existed during Earth’s first 50 million years. “These isotopes had to be created early,” says Rizo, of the University of Quebec in Montreal.
It is “spectacular” that some of Earth’s earliest materials may still be preserved, says Matthias Willbold, a geochemist at the University of Manchester in England. “We may have to revise our view of the Earth’s internal structure.”

Rizo and colleagues measured the tungsten-182 in flood basalts from two locations: Canada’s Baffin Bay, part of the 60-million-year-old North Atlantic Igneous Province, and near the Solomon Islands, part of the 120-million-year-old Ontong Java Plateau in the Pacific Ocean. “Flood basalts are not normal eruptions,” Rizo says. “They are capable of tapping into the deep mantle.”
Her team found that levels of tungsten-182 in the lavas varied, suggesting that the deep sources of these younger rocks were different pieces of Earth’s oldest material, each with their own isotopic signature and history. These results also show that the ancient remnants have somehow escaped being mixed by convection currents.

Geophysicists have identified two large “blobs” in the deep mantle, called large low-shear velocity provinces. Those blobs “could be candidates” for the remnants of the ancient mantle, Rizo says.

What builds up can also tear down, a new study of bacteria suggests.

Bacteria build biofilms, communities of the microorganisms encased in a protective goo that shields the microbes from antibiotics and immune system attacks. But the very enzymes bacteria use to construct that shield can also destroy some of its molecules and strip away the protection, researchers report May 20 in Science Advances.

“We’re weaponizing the bacteria against themselves,” says P. Lynne Howell, a structural microbiologist at the Hospital for Sick Children in Toronto. Howell and colleagues studied Pseudomonas aeruginosa bacteria, which can cause pneumonia and other infections and is particularly problematic for people with the lung disease cystic fibrosis.
The researchers discovered that two enzymes, PelAh and PslGh, which the bacteria use to build two different sugar polymers, can degrade those same polymers. That delete function, supplied by parts of the enzymes known as glycoside hydrolase domains, normally helps correct mistakes or prevents buildup of the sugar chains inside bacterial cells, Howell says.

In laboratory tests, synthetic versions of the glycoside hydrolase domains applied to P. aeruginosa cultures stopped the bacteria from forming new biofilms and melted existing ones. Stripping away sugar polymers did not kill the bacteria but did make them more vulnerable to antibiotics and immune cells. Human lung cells grown in dishes containing the enzymes suffered no harm, suggesting the enzymes wouldn’t damage human tissues.

Animal tests are needed to determine whether the enzymes are safe and can fight biofilm infections in the body, Howell says. Similar enzymes from other bacteria and fungi may also fight biofilm infections caused by those organisms, she says.

Giant pandas have better ears than people — and polar bears. Pandas can hear surprisingly high frequencies, conservation biologist Megan Owen of the San Diego Zoo and colleagues report in the April Global Ecology and Conservation.

The scientists played a range of tones for five zoo pandas trained to nose a target in response to sound. Training, which took three to six months for each animal, demanded serious focus and patience, says Owen, who called the effort “a lot to ask of a bear.”

Both males and females heard into the range of a “silent” ultrasonic dog whistle. Polar bears, the only other bears scientists have tested, are less sensitive to sounds at or above 14 kilohertz. Researchers still don’t know why pandas have ultrasonic hearing. The bears are a vocal bunch, but their chirps and other calls have never been recorded at ultrasonic levels, Owen says. Great hearing may be a holdover from the bears’ ancient past.