American Scientist

In this roundup, associate editor Nicholas Gerbis summarizes notable recent developments in scientific research, selected from reports compiled in the free electronic newsletter Sigma Xi SmartBrief: www​.smartbrief.com/sigmaxi/

Seeking Alien Life? Think Purple

Purple bacteria dominated Earth for much of its existence; maybe it’s time for surveys seeking life on distant planets to look beyond the usual green chlorophyll and seek something a little more lilac. To that end, a team led by Cornell University researchers used purple bacteria grown in oxygen and anoxic lab conditions to develop an online database of such spectral fingerprints. They then simulated the reflectance spectra of Earthlike planets covered with purple biota, including ocean worlds, snowball planets, frozen worlds, and planets with conditions akin to modern Earth, where such bacteria dwell in and around shallow waters, coasts, marshes, and even deep-sea hydrothermal vents. Many purple bacteria thrive in oxygen-free environments like those found on Earth until about 2.3 billion years ago. Their photosynthesis relies on biopigments that absorb light in the near-infrared and red wavelengths emitted by the commonest stars: cool red dwarfs. The authors recommend that exoplanet surveys use a variety of spectra, because some purple biopigment signatures closely resemble those of atmospheric water and ozone. (See Perspective, "Alien Life Is No Joke.") They say the technique is also suitable for worlds unlike Earth, such as hot, ocean-covered planets with hydrogen-dominated atmospheres.

Coelho, L. F., et al. Purple is the new green: Biopigments and spectra of Earth-like purple worlds. Monthly Notices of the Royal Astronomical Society 530:1363–1368 (April 16).

Metal Shreds and Green Energy

Researchers have found a highly efficient way to make hydrogen from water, with the added benefit that it upcycles some of the millions of tons of metal shavings, or swarf, produced as waste by industrial machining processes each year. The process, which uses swarf’s built-in nanotexture to grab and hold catalytically active particles, such as platinum and cobalt, could help meet rising demand for climate-friendly hydrogen technologies while also mitigating the large carbon and waste footprints of some manufacturing sectors. The Nottingham, England, team found that platinum-on-titanium arrangements excelled at splitting water molecules to produce hydrogen gas, whereas cobalt-on-nickel configurations efficiently split water to make oxygen. Making hydrogen required no solvents or reagents, and took only one-tenth as much platinum as typical commercial catalysts do. The authors also built a 1.6-volt full-cell electrolyzer that produced hydrogen and oxygen at a 2:1 ratio and wasted no electricity on unwanted reactions.

Thangamuthu, M., et al. From scrap metal to highly efficient electrodes: Harnessing the nanotextured surface of swarf for effective utilization of Pt and Co for hydrogen production. Journal of Materials Chemistry A 2024 (April 16). doi:10.1039/D4TA00711E.

Whale Clicks Speak Volumes

The vocalizations of sperm whales (Physeter macrocephalus) may convey far more meaning than once thought, according to data from individuals recorded near the Caribbean island of Dominica between 2005 and 2018. Analysis by a team led by Pratyusha Sharma of the Massachusetts Institute of Technology suggests the whales’ patterns of clicks and gaps, or codas, are less like mechanical Morse code and more akin to music, complete with meaningful shifts in rhythm, tempo, rubato, and ornamentation. The findings aren’t conclusive, but could mean that humans are not alone in developing a highly complex and contextual system of vocal communication in which sounds and “words” take on various meanings through ordering, reordering, and context, and in which phrases gain nuance through inflections. Experts cannot yet fully decode the ideas and shades of meaning conveyed by these clicks, creaks, clangs, and silences, but their intricate patternings are consistent with the social and behavioral complexity on display in sperm whale societies, which conduct group decision-making and engage in complex social and foraging behavior. Notably, past research has shown that different whale “clans” in overlapping geographical areas use different repertoires of codas, not unlike human dialects.

Sharma, P., et al. Contextual and combinatorial structure in sperm whale vocalizations. Nature Communications 15:3617 (May 7).

Lost Nile Branch Fed Pyramids

New research suggests that today’s landlocked Egyptian pyramids once lay along waterways that provided access for religious ceremonies and transport for construction materials. A team led by Eman Ghoneim of the University of North Carolina Wilmington found signs of a 64-kilometer branch of the Nile River that once flowed past 31 monuments, including the Giza complex, through a channel ranging from 2 to 10 kilometers west of the river’s modern course. The find relied on technologies, such as ground-penetrating radar, that can sense beyond today’s silt, sand, and farmland to reveal ancient riverbeds and stream deposits. Parts of the lost branch (named Ahramat, from the Arabic term for pyramids) likely served as sections of later canals, such as the Bahr Yusef, a vital irrigation and water management channel dating to Egypt’s Middle Kingdom. As the waters migrated eastward, possibly because of tectonic tilting, the overall branch was abandoned, perhaps silting up as streamflow slowed and filling with windblown sand. The findings fill in gaps in existing evidence and seem to fit ancient Egyptians’ tendencies to situate key cities and monuments near the Nile and its branches. Indeed, many pyramid complexes feature causeways that lead to the now-buried riverbed.

Ghoneim, E., et al. The Egyptian pyramid chain was built along the now abandoned Ahramat Nile Branch. Communications Earth & Environment 5:233 (May 16).

Beethoven's Heavy Metal Hair

Spectral analysis of two locks of Ludwig van Beethoven’s hair reveals the presence of high levels of lead, arsenic, and mercury in the German composer’s body. The finding reignites speculation as to the possible causes of Beethoven’s many ailments. Using a Centers for Disease Control and Prevention formula to convert his hairs' lead levels (which measured 64–95 times higher than normal) to an equivalent blood concentration, a team led by Nader Rifaia of Harvard Medical School found enough of the heavy metal to cause digestive and kidney disorders as well as hearing loss. They say such a quantity of lead, which Beethoven likely ingested via eating, drinking, and medical treatments, would not have killed him, but might have exacerbated existing medical conditions. The researchers did not comment on the effects of detected arsenic and mercury, which respectively measured 13 times and four times higher than normal. If this story sounds as familiar as Beethoven’s Ninth Symphony, or echoes like the “da-da-da-dum” of his Fifth, it’s likely because a hair-lead link was previously put forward in 2007. That finding fell flat, however, when a 2023 genomic analysis of other samples showed that the older study’s famed “Hiller lock” was not Beethoven’s hair, and in fact belonged to a female. The new study’s locks have a male chromosome pattern, show DNA damage in tune with an early 19th century origin, and share mitochondrial genomes and a unique mutation that indicate they came from the same person. Moreover, one lock has an unbroken chain of custody dating back to April 1826, when Beethoven himself hand-delivered the hairs to fellow pianist Anton Halm.

Rifai, N., et al. High lead levels in 2 independent and authenticated locks of Beethoven’s hair. Clinical Chemistry hvae054 (May 6).