Monday, March 25, 2024

Signs of life detectable in single ice grain emitted from extraterrestrial moons

UNIVERSITY OF WASHINGTON

Enceladus — IMAGE:
AN ARTIST’S RENDITION OF SATURN’S MOON ENCELADUS DEPICTS HYDROTHERMAL ACTIVITY ON THE SEAFLOOR AND CRACKS IN THE MOON’S ICY CRUST THAT ALLOW MATERIAL FROM THE WATERY INTERIOR TO BE EJECTED INTO SPACE. NEW RESEARCH SHOWS THAT INSTRUMENTS DESTINED FOR THE NEXT MISSIONS COULD FIND TRACES OF A SINGLE CELL IN A SINGLE ICE GRAIN CONTAINED IN A PLUME.
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CREDIT: NASA/JPL-CALTECH

The ice-encrusted oceans of some of the moons orbiting Saturn and Jupiter are leading candidates in the search for extraterrestrial life. A new lab-based study led by the University of Washington in Seattle and the Freie Universität Berlin shows that individual ice grains ejected from these planetary bodies may contain enough material for instruments headed there in the fall to detect signs of life, if such life exists.

“For the first time we have shown that even a tiny fraction of cellular material could be identified by a mass spectrometer onboard a spacecraft,” said lead author Fabian Klenner, a UW postdoctoral researcher in Earth and space sciences. “Our results give us more confidence that using upcoming instruments, we will be able to detect lifeforms similar to those on Earth, which we increasingly believe could be present on ocean-bearing moons.”

The open-access study was published March 22 in Science Advances. Other authors in the international team are from The Open University in the U.K.; NASA’s Jet Propulsion Laboratory; the University of Colorado, Boulder; and the University of Leipzig.

The Cassini mission that ended in 2017 discovered parallel cracks near the south pole of Saturn’s moon Enceladus. Emanating from these cracks are plumes containing gas and ice grains. NASA’s Europa Clipper mission, scheduled to launch in October, will carry more instruments to explore in even more detail an icy moon of Jupiter, Europa.

To prepare for that mission, researchers are studying what this new generation of instruments might find. It is technically prohibitive to directly simulate grains of ice flying through space at 4 to 6 kilometers per second to hit an observational instrument, as the actual collision speed will be. Instead, the authors used an experimental setup that sends a thin beam of liquid water into a vacuum, where it disintegrates into droplets. They then used a laser beam to excite the droplets and mass spectral analysis to mimic what instruments on the space probe will detect.

Newly published results show that instruments slated to go on future missions, like the SUrface Dust Analyzer onboard Europa Clipper, can detect cellular material in one out of hundreds of thousands of ice grains.

The study focused on Sphingopyxis alaskensis, a common bacterium in waters off Alaska. While many studies use the bacterium Escherichia coli as a model organism, this single-celled organism is much smaller, lives in cold environments, and can survive with few nutrients. All these things make it a better candidate for potential life on the icy moons of Saturn or Jupiter.

“They are extremely small, so they are in theory capable of fitting into ice grains that are emitted from an ocean world like Enceladus or Europa,” Klenner said.

Results show that the instruments can detect this bacterium, or portions of it, in a single ice grain. Different molecules end up in different ice grains. The new research shows that analyzing single ice grains, where biomaterial may be concentrated, is more successful than averaging across a larger sample containing billions of individual grains.

A recent study led by the same researchers showed evidence of phosphate on Enceladus. This planetary body now appears to contain energy, water, phosphate, other salts and carbon-based organic material, making it increasingly likely to support lifeforms similar to those found on Earth.

The authors hypothesize that if bacterial cells are encased in a lipid membrane, like those on Earth, then they would also form a skin on the ocean’s surface. On Earth, ocean scum is a key part of sea spray that contributes to the smell of the ocean. On an icy moon where the ocean is connected to the surface (e.g., through cracks in the ice shell), the vacuum of outer space would cause this subsurface ocean to boil. Gas bubbles rise through the ocean and burst at the surface, where cellular material gets incorporated into ice grains within the plume.

“We here describe a plausible scenario for how bacterial cells can, in theory, be incorporated into icy material that is formed from liquid water on Enceladus or Europa and then gets emitted into space,” Klenner said.

The SUrface Dust Analyzer onboard Europa Clipper will be higher-powered than instruments on past missions. This and future instruments also will for the first time be able to detect ions with negative charges, making them better suited to detecting fatty acids and lipids.

“For me, it is even more exciting to look for lipids, or for fatty acids, than to look for building blocks of DNA, and the reason is because fatty acids appear to be more stable,” Klenner said.

“With suitable instrumentation, such as the SUrface Dust Analyzer on NASA’s Europa Clipper space probe, it might be easier than we thought to find life, or traces of it, on icy moons,” said senior author Frank Postberg, a professor of planetary sciences at the Freie Universität Berlin. “If life is present there, of course, and cares to be enclosed in ice grains originating from an environment such as a subsurface water reservoir.”

The study was funded by the European Research Council, NASA and the German Research Foundation (DFG). Other co-authors are Janine Bönigk, Maryse Napoleoni, Jon Hillier and Nozair Khawaja at the Freie Universität Berlin; Karen Olsson-Francis at The Open University in the U.K.; Morgan Cable and Michael Malaska at the NASA Jet Propulsion Laboratory; Sascha Kempf at the University of Colorado, Boulder; and Bernd Abel at the University of Leipzig.

This image shows red streaks across the surface of Europa, the smallest of Jupiter’s four large moons. The upcoming Europa Clipper mission will send instruments to investigate this moon. New research shows that one of these instruments destined for the next mission could find traces of a single cell in a single ice grain ejected from the planetary body’s interior.

NASA

The drawing on the left depicts Enceladus and its ice-covered ocean, with cracks near the south pole that are believed to penetrate through the icy crust. The middle panel shows where authors believe life could thrive: at the top of the water, in a proposed thin layer (shown yellow) like on Earth’s oceans. The right panel shows that as gas bubbles rise and pop, bacterial cells could get lofted into space with droplets that then become the ice grains that were detected by Cassini.

ESA

Enceladus Bubbles (IMAGE)

UNIVERSITY OF WASHINGTON

The left panel shows the kilometers-thick icy crust believed to encapsulate Saturn’s moon Enceladus. Filling the crack is salty water with a proposed thin layer (shown orange) at its surface. The right panel shows that as gas bubbles rise and pop, they combine with organic material and get lofted into the spray.
CREDIT
Postberg et al. (2018)/Nature

JOURNAL

Science Advances

DOI

10.1126/sciadv.adl0849

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Cells

ARTICLE TITLE

How to identify cell material in a single ice grain emitted from Enceladus or Europa

ARTICLE PUBLICATION DATE

22-Mar-2024

Tudor era horse cemetery in Westminster revealed as likely resting place for elite imported animals

Isotopic biographies reveal horse rearing and trading networks in medieval London

UNIVERSITY OF EXETER

Analysing horse bones — IMAGE:
EXETER RESEARCHERS ANALYSING BONES RECOVERED FROM THE HORSE CEMETERY.
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CREDIT: UNIVERSITY OF EXETER

Archaeological analysis of a near unique animal cemetery discovered in London nearly 30 years ago has revealed the international scale of horse trading by the elites of late medieval and Tudor England.

Using advanced archaeological science techniques, including studying chemical composition, researchers have been able to identify the likely origins of several physically elite horses and the routes they took to reach British shores during the formative years of their life.

These animals – akin to modern supercars – were sourced from a variety of locations across Europe specifically for their height and strength and imported for use in jousting tournaments and as status symbols of 14th- to 16th-century life. They include three of the tallest animals known from late medieval England, standing up to 1.6 metres or 15.3 hands high, which while quite small by modern standards would have been very impressive for their day.

The skeletons of the horses were recovered from a site under the modern-day Elverton Street in the City of Westminster, which was excavated in advance of building works in the 1990s. In medieval times, the cemetery would have been located outside the walled City of London but was close to the royal palace complex at Westminster.

The research, led by the University of Exeter, and funded by the Arts and Humanities Research Council, is published in the latest edition of Science Advances.

“The chemical signatures we measured in the horse’s teeth are highly distinctive and very different to anything we would expect to see in a horse that grew up in the UK,” said Dr Alex Pryor, Senior Lecturer in Archaeology and lead researcher. “These results provide direct and unprecedented evidence for a variety of horse movement and trading practices in the Middle Ages. Representatives for the King and other medieval London elites were scouring horse trading markets across Europe seeking out the best quality horses they could find and bringing them to London. It’s quite possible that the horses were ridden in the jousting contests we know were held in Westminster, close to where the horses were buried.”

In the first experiment of its kind to be conducted on medieval horse remains, the researchers took 22 molar teeth from 15 individual animals and drilled out portions of the enamel for isotope analysis. By measuring isotope ratios of the elements strontium, oxygen and carbon present within the teeth and comparing the results with known ranges in different geographies, the team was able to identify the potential origin of each horse – and accurately rule out others, including prime European horse-breeding centres such as Spain and southern Italy.

Dr Pryor said that at least half of the horses had diverse international origins, possibly Scandinavia, the Alps and other northern and eastern European locations. The results, the researchers conclude, were consistent with the breeding patterns of royal stud farms, where horses would reside until their second or third year, before they would either be broken and trained or sent elsewhere to be sold.

Physical analysis of the teeth revealed wear suggestive of heavy use of a curb bit, often employed with elite animals, especially those groomed for war and tournaments after the 14th century. Bit wear on two of the mares also suggested they were used under saddle or in harness and for breeding. And analysis of the skeletons revealed many of them to be well above average size, with several instances of fused lower thoracic and lumbar vertebrae indicative of a life of riding and hard work.

“The finest medieval horses were like modern supercars – inordinately expensive and finely tuned vehicles that proclaimed their owner’s status,” added Professor Oliver Creighton, a medieval specialist at the University of Exeter and part of the research team. “And at Elverton Street, our research team seem to have found evidence for horses used in jousting – the sport of kings, in which riders showcased their fighting skills and horsemanship on elite mounts.

“The new findings provide a tangible archaeological signature of this trade, emphasising its international scale. It is apparent that the medieval London elite were explicitly targeting the highest quality horses they could find at a European scale.”

The paper, Isotopic biographies reveal horse rearing and trading networks in medieval London, can be accessed via Science Advances.