Dr Christine Joblin of the CNRS and her colleague Dr Hassan Sabbah of the University of Toulouse III – Paul Sabatier highlight the ability of the AROMA molecular analyser to understand the origin of large carbonaceous molecules in cosmic environments.
The James Webb Space Telescope (JWST, NASA/ESA/CSA) has just revealed its amazing capabilities to study the Universe at infrared wavelengths. Among the data, we expect unprecedented information about large carbonaceous molecules that are key species in star- and planet-forming regions.2 These molecules are dominated by the family of polycyclic aromatic hydrocarbons (PAHs) – well-known terrestrial pollutants that are major by-products of combustion processes. It remains to be understood why these PAHs are so abundant in astrophysical environments (they typically contain 10% of the carbon).
What are the mechanisms that recycle carbon in space and (preferentially) form these molecules? So far, the research has been mainly guided by our knowledge of flame chemistry and the proposal that astro-PAHs are produced at the end of the life of carbon-rich stars, in hot and dense envelopes in which the formation of dust and molecular species, such as PAHs, is favoured. Still, as of today, we have no clear observational diagnosis to demonstrate this scenario. In addition, the individual PAHs that have been identified so far (indene C9H8 and cyano-naphthalene C10H7CN)4,5 are present in the TMC-1 dark molecular cloud and are most likely products of very low temperature gas-phase chemistry.
The PAH model
Over the past decade, the unambiguous detection of C60 buckminsterfullerene and its C60+ cation in a variety of astrophysical environments has been a major achievement. It has allowed support for the PAH model. This model, proposed in the 1980s, explains that all the strong aromatic infrared bands observed in emission come from radiative cooling of PAHs heated by ultraviolet photon absorption. We now know that other carriers, such as fullerenes, must be included. Compared to PAHs, the formation of fullerenes requires more extreme conditions – in particular, higher temperatures. This issue motivates studies to propose formation scenarios for C60 in astrophysical environments. These include processing of grains by heat, shocks or high-energy ions and UV photo-processing of large PAHs.6,7
In this paper, we present our approach to address the question of the formation of astro-PAHs and fullerenes from an experimental point of view. This approach is based on two pillars. The first pillar is to use a variety of reactors to produce samples that can be considered as laboratory analogues of stardust. Although it is impossible to mimic the physical and chemical conditions of dying stars, a new machine, Stardust,8 has been built in Madrid (ICMM/CSIC) to advance in this field by offering features not available in other experimental setups, such as the controlled production of (e.g, carbon, silicon) atoms to drive the chemistry.
Cold plasmas are also used as an alternative method to study the impact of complexity on chemistry. In particular, we study the role of metal (e.g., iron) atoms in the formation of dust and large carbonaceous molecules with our colleagues from LAPLACE (CNRS/ Université Toulouse III-Paul Sabatier).9 The second pillar consists of studying samples of extra-terrestrial matter (meteorites) that are rich in carbon. This is the case of carbonaceous chondrites like Murchison and Allende but also of the polymict ureilite meteorite Almahata Sitta (AhS). These two pillars share the common interest of probing the carbonaceous molecular content of samples that may be in the form of dusty deposits or bulk materials, as illustrated in Fig. 1. This topic motivated the development of the Astrochemistry Research of Organics with Molecular Analyzer (AROMA) setup.
Fig. 1: Different types of samples analysed with the AROMA setup. On the left, atomic force microscopic image of Stardust analogues showing the presence of carbon nanoparticles8 and a scanning electron microscope image of dusty plasma analogues showing organosilicon dust decorated with silver nanoparticles.9 In the middle, small fragments of the AhS meteorite observed with a digital microscope12 and image of one of the Hayabusa2 sample container (Yada et al., DOI: 10.1038/s41550-021-01550-6). On the right, picture of the emission of soot particles (Source: COLOA Studio/Shutterstock) and asphaltenes from oil pipelines (Credit: Schlumberger). The structures of the PAH prototype, C16H10 pyrene and C60 fullerene are shown at the bottom
AROMA: the molecular analyzer
The AROMA setup10 has been developed in the framework of the Nanocosmos ERC Synergy project.1 The construction was done by Fasmatech, a young Greek company, following the requirements of our scientific and engineering team. The main objective is to trace the molecular content of various solid samples, especially in large molecules such as polycyclic aromatic hydrocarbons, carbon clusters and fullerenes.
AROMA, as shown in Fig. 2a, consists of three main components: the ion source, the ion trap, and the mass analyzer.
In the ion source, millimetre-sized samples are positioned on an XY manipulator and subjected to laser desorption/ionisation (LDI) techniques. LDI techniques, using a single laser step, are powerful tools for directly probing non-volatile organic species in native or artificial matrices without the need for tedious extraction procedures. In the case of high molecular weight compounds, such as biomolecules, a matrix-assisted LDI (MALDI) technique is typically used. The specificity of AROMA is the use of the L2MS technique, in which the desorption and ionisation processes are separated in time and space and performed with two different lasers. A pulsed infrared laser is used to desorb neutral molecules, followed after a few microseconds by a pulsed ultraviolet laser to selectively ionise the molecules of interest.13 L2MS offers a much higher sensitivity than one-step LDI to the targeted molecules (e.g., in our case, PAHs and fullerenes). In addition, AROMA offers the possibility to isolate and trap ions of a specific mass and to study their fragmentation by collisions with a gas or by absorption of photons from a tuneable laser. Both techniques help us to elucidate the molecular structures of the dominant species. Finally, the ions are mass separated using a high-resolution time-of-flight mass spectrometer (104 resolving power).
Fig. 2: (a) Mass spectrum recorded from a bulk sample of the Murchison meteorite. Some of the identified peaks are shown with their mass-to-charge ratio (m/z), associated chemical formula and possible molecular structure. (b) Schematic representation of the AROMA setup highlighting all its components
Fig. 2 shows an example of a mass spectrum recorded for a few mg of crushed powder from the Murchison meteorite. It plots the intensity of the ion signal as a function of the mass-to-charge ratio. This allows us to unequivocally assign a chemical formula to each detected peak and associate it with a pure carbon (Cx) or hydrocarbon (CxHY) species. Other elements, especially in atomic form, may also be present (for example, Na, Al, K, Fe, etc.). Our assignment accuracy approaches 0.01 at a mass/charge ratio m/z ~300. This is our limitation to assign with high confidence organic compounds with N, O and S atoms in their chemical formula. Eventually, hundreds of peaks are identified in the mass spectra with notable discrepancies between different samples. The latter can be used to trace the chemical history of each sample and are not a bias of our analysis.
For example, in the analysis of terrestrial soot samples,11 we were able to track the evolution of carbonaceous molecular families, as a function of height above the burner (Z) and demonstrate efficient thermal processing of the large PAH population to produce hydrogenated carbon clusters (HC clusters) and then fullerenes (see Fig. 3a). To recover this chemical information, large mass spectrometry datasets must be reduced to relevant parameters such as molecular families. For this, our methodology consists in calculating double bond-equivalent (DBE) values, which are representative of the unsaturation level of the molecules. The different ranges of DBE values allow us to disentangle the molecular families: PAHs, HC clusters, aliphatic species (very rare in our samples because the ultraviolet laser is not adapted to their ionisation), carbon clusters and fullerenes.
Fig. 3: Compositional diversity in the four molecular families (PAHs, HC clusters, C clusters, and fullerenes) obtained after DBE analysis. (a) Soot samples collected at different heights above the burner11 and analogues produced with the Stardust machine using atomic carbon and different gases (H2 from8 and C2H2 from Santoro et al, DOI: 10. 3847/1538-4357/ab9086 ). (b) Murchison, Allende and two AhS meteorite fragments10,12
Fig. 3 illustrates the method and shows the results of molecular family analysis for several samples, including terrestrial soot, stardust analogues (Fig. 3a), and several meteorites (Fig. 3b). PAHs dominate the molecular composition of carbonaceous chondrites (Murchison and Allende). In contrast, the two AhS fragments, AhS#04 and AhS#48, show a greater diversity of molecular families, which have been shown to originate from different cosmic reservoirs.
All mass spectra associated with published work are publicly available in the AROMA database. The database provides the ability to calculate and plot DBE values, and to perform molecular family analyses. We are also developing a method to assess the similarity between recorded mass spectra and how it can be used to provide faster investigation and additional information about the chemical history of a sample.
Amazing results and perspectives
Initially seen as an analytical tool to support the Stardust machine, AROMA has now become a key facility to contribute to our understanding of the origin of large carbonaceous molecules in cosmic environments. In the term cosmic, we include astrophysical environments (e.g., evolved stars as stardust factories) but also our Solar System, via extra-terrestrial samples that we can access in the laboratory.
In connection with the Stardust machine, the most important result we have obtained so far is the near absence of aromatics formed in the chemistry of atomic carbon with molecular hydrogen. This casts doubt on the possibility of forming abundant PAHs by gas-phase chemistry in the envelopes of evolved stars.
But the result that opens up the greatest prospects is certainly the unexpected but firm detection of fullerenes, from C30 to at least C100, in the Almahata Sitta (AhS) polymict ureilite meteorite. We are now in a rather unique position to search for fullerenes in a variety of extra-terrestrial samples. In particular, we were recently fortunate to receive two grains from the asteroid Ryugu that were carried by JAXA’s Hayabusa2 sample return mission. Ryugu is a C-type asteroid that is considered one of the most pristine objects in the Solar System. The analysis of this type of object will allow us to circumvent the problem of meteorite alteration linked to the shocks during their ejection and to the heating during their entry into the Earth’s atmosphere, as well as to a possible terrestrial contamination. We believe that this work can give us new insight into the origin of fullerenes in astrophysical environments.
We also expect a big step forward with the next JWST results, including the identification of individual species among the molecular families studied by AROMA: fullerenes, PAHs, C clusters, as well as new information on the chemical relationship between these families and with the dust particles.
The prospect of changing our view of the cosmic carbon cycle has never been closer and it is quite exciting. In addition to the fantastic challenges that JWST and Hayabusa2 have met, innovation will also be required on the laboratory side. A major advance that we hope to address in our research activity is the possibility to couple the L2MS technique to an OrbitrapTM mass analyser that offers very high mass resolution and thus opens new perspectives to trace the origin of organic matter in samples of cosmic interest.
Acknowledgements
This research was supported over the period 2014-2021 by the ERC under the European Union’s Seventh Framework Programme ERC-2013-SyG, Grant Agreement no. 610256, Nanocosmos.
2: Early Release Science of JWST: “Radiative feedback from massive stars”: Berné, O, Habart, E, Peeters, E, et al., Publ. Astron. Soc. Pac. 134 (1035) (2022), id.054301; https://arxiv.org/abs/2201.05112
3: “Astro-PAHs from space missions to laboratory astrophysics”; Joblin, C, The Innovation Platform issue 8 (2021), p.228-231; https://www.innovationnewsnetwork.com/astro-pahs-space-missions-to-laboratory-astrophysics/15527/
4: Observation of indene in the dark molecular cloud TMC-1: Cernicharo, J, et al., Astron. & Astrophys. 649 (2021), id.L15, 12 pp.; https://doi.org/10.1051/0004-6361/202141156
5: Observation of cyanonaphthalene in the dark molecular cloud TMC-1: McGuire, B. A., et al., Science 371 (2021), 1265–1269; https://arxiv.org/pdf/2103.09984.pdf
6: Discussion about formation scenarios of C60 in planetary nebulae: Cami, J., et al., Galaxies 6 (4) (2018), p. 101; https://www.mdpi.com/2075-4434/6/4/101
7: Scenario to form C60 from large PAHs: Berné, O, Tielens, A G G M, Proc. Natl. Acad. Sci. U.S.A. 109 (2012), 401-406; https://doi.org/10.1073/pnas.111420710
8: Stardust machine and the (non)formation of aromatics in evolved stars: Martínez, L, Santoro, G, Merino, P, et al., Nature Astron. 4 (2020), 97-105; https://hal.archives-ouvertes.fr/hal-03085475
9: Role of metals in (star)dust chemistry investigated in cold plasmas: Bérard, R, et al., Front. astron. space sci. 8 (2021), 654879; https://hal.archives-ouvertes.fr/hal-03227179
10: AROMA setup: Sabbah, H, et al., Astrophys. J. 843 (2017), id. 34, 8 pp.; https://arxiv.org/ftp/arxiv/papers/1705/1705.09974.pdf
11: Analysis of soot samples with AROMA: Sabbah, H, et al., Proc Combust Inst 38 (2021), 1241–1248; https://doi.org/10.1016/j.proci.2020.09.022
12: Detection of fullerenes in the Almahata Sitta meteorite: Sabbah, H, et al., Astrophys. J. 931 (2022), id.91; https://iopscience.iop.org/article/10.3847/1538-4357/ac69dd
13: First presentation of the L2MS technique and its application to extra-terrestrial samples: Spencer, M K, Hammond, M R, and Zare, R N, Publ. Astron. Soc. Pac. 105 (2008), 18096-18101; https://doi.org/10.1073/pnas.0801860105
Please note, this article will also appear in the eleventh edition of our quarterly publication.
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
