Uracil, a building block of life, has been found on the asteroid Ryugu.

Yasuhiro Oba and colleagues discovered the precursor to life in samples collected from the asteroid and returned to Earth by Japan’s Hayabusa2 spacecraft, the team reports March 21 in Nature Communications.

“The detection of uracil in the Ryugu sample is very important to clearly demonstrate that it is really present in extraterrestrial environments,” says Oba, an astrochemist at Hokkaido University in Sapporo, Japan.

Uracil had been previously detected in samples from meteorites, including a rare class called CI-chondrites, which are abundant in organic compounds. But those meteorites landed on Earth, leaving open the possibility they had been contaminated by humans or Earth’s atmosphere. Because the Ryugu samples were collected in space, they are the purest bits of the solar system scientists have studied to date (SN: 6/9/22). That means the team could rule out the influence of terrestrial biology.

Oba’s team was given only about 10 milligrams of the Ryugu sample for its analysis. As a result, the researchers were not confident they would be able to detect any building blocks, even though they’d been able to previously detect uracil and other nucleobases in meteorites (SN: 4/26/22).

Nucleobases are biological building blocks that form the structure of RNA, which is essential to protein creation in all living cells. One origin-of-life theory suggests RNA predated DNA and proteins and that ancient organisms relied on RNA for the chemical reactions associated with life (SN: 4/4/04).

The team used hot water to extract organic material from the Ryugu samples, followed by acid to further break chemical bonds and separate out uracil and other smaller molecules.

Laura Rodriguez, a prebiotic chemist at the Lunar and Planetary Institute in Houston, Texas, who was not involved in the study, says this method leaves the possibility that the uracil was separated from a longer chain of molecules in the process. “I think it’d be interesting in future work to look at more complex molecules rather than just the nucleobases,” Rodriguez says.

She says she’s seen in her research that the nucleobases can form bonds to create more complex structures, such as a possible precursor to the nucleic acid which may lead to RNA formation. “My question is, are those more complex structures also forming in the asteroids?”

Oba says his team plans to analyze samples from NASA’s OSIRIS-REX mission, which grabbed a bit of asteroid Bennu in 2020 and will return it to Earth this fall (SN: 10/21/20).

A relict glacier near Mars’ equator. Image credit: Lee et al. / LPSC 2023 / NASA.

Advertisement

“What we’ve found is not ice, but a salt deposit with the detailed morphologic features of a glacier,” said lead author Dr. Pascal Lee, a planetary scientist with the SETI Institute and the Mars Institute.

“What we think happened here is that salt formed on top of a glacier while preserving the shape of the ice below, down to details like crevasse fields and moraine bands.”

The relict glacier is estimated to be 6 km (3.7 miles) long and up to 4 km (2.5 miles) wide, with a surface elevation ranging from 1.3 to 1.7 km (0.9-1.1 miles).

The presence of volcanic materials blanketing the region hints of how the sulfate salts might have formed and preserved a glacier’s imprint underneath.

When freshly erupted pyroclastic materials come in contact with water ice, sulfate salts like the ones commonly making up Mars’ LTDs may form and build up into a hardened, crusty salt layer.

“This region of Mars has a history of volcanic activity,” said co-author Sourabh Shubham, a graduate student at the University of Maryland.

“And where some of the volcanic materials came in contact with glacier ice, chemical reactions would have taken place at the boundary between the two to form a hardened layer of sulfate salts.”

“This is the most likely explanation for the hydrated and hydroxylated sulfates we observe in this LTD.”

Over time, with erosion removing the blanketing volcanic materials, a crusty layer of sulfates mirroring the glacier ice underneath became exposed, which would explain how a salt deposit is now visible, presenting features unique to glaciers such as crevasses and moraine bands.

“Glaciers often present distinctive types of features, including marginal, splaying, and tic-tac-toe crevasse fields, and also thrust moraine bands and foliation,” said co-author Dr. John Schutt, a geologist at the Mars Institute.

“We are seeing analogous features in this light-toned deposit, in form, location, and scale. It’s very intriguing.”

The glacier’s fine-scale features, its associated sulfate salts deposit, and the overlying volcanic materials are all very sparsely cratered by impacts and must be geologically young, likely Amazonian in age, the latest geologic period which includes modern Mars.

“We’ve known about glacial activity on Mars at many locations, including near the equator in the more distant past,” Dr. Lee said.

“And we’ve known about recent glacial activity on Mars, but so far, only at higher latitudes.”

“A relatively young relict glacier in this location tells us that Mars experienced surface ice in recent times, even near the equator, which is new.”

“It remains to be seen whether water ice might still be preserved underneath the light-toned deposit or if it has disappeared entirely.”

“Water ice is, at present, not stable at the very surface of Mars near the equator at these elevations.”

“So, it’s not surprising that we’re not detecting any water ice at the surface.”

“It is possible that all the glacier’s water ice has sublimated away by now.”

“But there’s also a chance that some of it might still be protected at shallow depth under the sulfate salts.”

The scientists presented their findings March 16 at the 54th Lunar and Planetary Science Conference 2023 (LPSC 2023).

_____

Pascal Lee et al. A Relict Glacier near Mars’ Equator: Evidence for Recent Glaciation and Volcanism in Eastern Noctis Labyrinthus. LPSC 2023, abstract # 2998

17th century scientist Christiaan Huygens set his sights on faraway Saturn, but he may have been nearsighted.

Huygens is known, in part, for discovering Saturn’s largest moon, Titan, and deducing the shape of the planet’s rings. But by some accounts, the Dutch scientist’s telescopes produced fuzzier views than others of the time despite having well-crafted lenses.

That may be because Huygens needed glasses, astronomer Alexander Pietrow proposes March 1 in Notes and Records: the Royal Society Journal of the History of Science.

To make his telescopes, Huygens combined two lenses, an objective and an eyepiece, positioned at either end of the telescope. Huygens experimented with different lenses to find combinations that, to his eye, created a sharp image, eventually creating a table to keep track of which combinations to use to obtain a given magnification. But when compared with modern-day knowledge of optics, Huygens’ calculations were a bit off, says Pietrow, of the Leibniz Institute for Astrophysics Potsdam in Germany.

One possible explanation: Huygens selected lenses based on his flawed vision. Historical records indicate that Huygens’ father was nearsighted, so it wouldn’t be surprising if Christiaan Huygens also suffered from the often-hereditary affliction.

Assuming that’s the reason for the mismatch, Pietrow calculates that Huygens had 20/70 vision: What someone with normal vision could read from 70 feet away, Huygens could read only from 20 feet. If so, that could be why Huygens’ telescopes never quite reached their potential.