Unlike on Earth, where terrains are commonly dated using natural radioactivity of rocks, scientists have largely constrained the chronology of Mars by counting impact craters on its surface.

“The idea behind crater dating is not rocket science; the more craters, the older the surface,” says SwRI’s Dr. Simone Marchi, who published a paper about these findings accepted for publication in The Astronomical Journal. “But the devil is in the details. Craters form when asteroids and comets strike the surface. The rate of these cosmic crashes over the eons is uncertain, hampering our ability to convert crater numbers to terrain ages. I took a fresh look at this and built on recent developments in the way we understand the earliest evolution of the solar system.”

Scientists have used radiometric ages of precious lunar rocks brought back by the Apollo missions to calibrate a lunar crater chronology. This lunar chronology is then extrapolated to Mars, and this is where things get tangled with the earliest evolution of the solar system. Our understanding of the time evolution of lunar and Martian impact rates has greatly improved in recent years. The present model improves upon how the critical Moon-to-Mars extrapolations are done.

“For this paper, I looked particularly at the Jezero Crater because that is the landing site for the Mars 2020 Perseverance rover,” Marchi said. “These surfaces could have formed over 3 billion years ago, as much as 500 million years older than previously thought. NASA plans to have Perseverance gather and package surface samples that can be collected by a future mission for return to Earth for radiometric dating. That could provide vital ground-truth data to better calibrate our chronology models.”

Jezero Crater has a diameter of about 30 miles located within the 750-mile-wide Isidis Basin, created by an earlier impact. The latter cut a wide portion of the Borealis Basin’s rim, perhaps the largest and oldest impact basin on Mars. This coincidence of nested craters is of particular interest as samples from these terrains may return information about the timing of these consecutive impacts.

Furthermore, Jezero Crater hosts clay-rich terrains and a fluvial delta, indications that the crater once hosted a lake. This makes the Jezero Crater an ideal place to fulfill the Mars 2020 mission’s science goal of studying a potentially habitable environment that may still preserve signs of past life. As such, understanding the timeline of these surfaces is particularly important.

The new model also provides a revised age for Isidis Basin, now estimated to be 4-4.2 billion years old, providing an upper limit for the formation of Jezero Crater and water activity at this location on Mars.

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The Marsoulas Cave, between Haute-Garonne and Ariège, was the first decorated cave to be found in the Pyrenees. Discovered in 1897, the cave bears witness to the beginning of the Magdalenian (2) culture in this region, at the end of the Last Glacial Maximum. During an inventory of the material from the archaeological excavations, most of which is kept in the Muséum de Toulouse, scientists examined a large Charonia lampas (sea snail) shell, which had been largely overlooked when discovered in 1931.

The tip of the shell is broken, forming a 3.5 cm diameter opening. As this is the hardest part of the shell, the break is clearly not accidental. At the opposite end, the shell opening shows traces of retouching (cutting) and a tomography scan has revealed that one of the first coils is perforated. Finally, the shell has been decorated with a red pigment (hematite), characteristic of the Marsoulas Cave, which indicates its status as a symbolic object.

To confirm the hypothesis that this conch was used to produce sounds, scientists enlisted the help of a horn player, who managed to produce three sounds close to the notes C, C-sharp and D. As the opening was irregular and covered with an organic coating (3), the researchers assume that a mouthpiece was also attached, as is the case for more recent conches in collection of the Musée du quai Branly — Jacques Chirac. 3D impressions of the conch will enable this lead to be explored and verify whether it can be used to produce other notes.

The first carbon-14 dating of the cave, carried out on a piece of charcoal and a fragment of bear bone from the same archaeological level as the shell, provided a date of around 18,000 years. This makes the Marsoulas conch the oldest wind instrument of its type: to date, only flutes have been discovered in earlier European Upper Palaeolithic contexts; the conches found outside Europe are much more recent.

In addition to immersing us in the sounds produced by our Magdalenian ancestors, this shell reinforces the idea of exchanges between the Pyrenees and the Atlantic coast, more than 200 kilometres away.

Further information:

– Listen to the sound of the Marsoulas conch: https://soundcloud.com/cnrs_officiel/marsoulas-shell-conch-sound/s-234KE5bFZO1

– See the 3D model: https://sketchfab.com/3d-models/triton-700k-0bddff3405144c7b8f91f902e28bcc9b

Notes

(1) The laboratories involved are the Travaux et recherches archéologiques sur les cultures, les espaces et les sociétés (CNRS/Université Toulouse — Jean Jaurès/Ministère de la Culture), the Maison des sciences de l’homme et de la société de Toulouse (CNRS/Université Fédérale de Toulouse) and the Laboratoire d’archéologie moléculaire et structurale (CNRS/Sorbonne Université).

(2) Covering a period between around 21,000 and 14,000 years BP, it is characterised by worked animal bones and antlers and extensive exchange networks. The Altamira and Lascaux caves are the most famous examples.

(3) As the quantity is limited, analyses have not been able to identify its nature.

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The findings, which are published today in the journal Nature, may aid future efforts to understand why some embryos fail to form in the earliest stages of development, and lead to new clinical efforts in treating infertility or early miscarriages.

An embryo is fragile in the first hours after its formation. Rapid cell division and environmental stress make them prone to cellular errors, which in turn cause the sporadic death of embryonic stem cells. This is assumed to be one of the major causes of embryonic developmental failure before implantation.

Living organisms can remove cellular errors using immune cells which are dedicated to carry out this function, but a newly-formed embryo cannot create these specialised cells. To find out whether embryos can remove dying cells before the formation of an immune system, the researchers used high resolution time-lapse imaging technology to monitor zebrafish and mouse embryos, two established scientific models used to study vertebrate development.

They found that epithelial cells — which collectively form the first tissue on the surface of an embryo — can recognise, ingest and destroy defective cells. It is the first time this biological process, known as epithelial phagocytosis, has been shown to clear cellular errors in newly formed vertebrate embryos.

“Long before the formation of the organs, one of the first tasks performed by a developing embryo is to create a protective tissue,” says Dr. Esteban Hoijman, first and co-corresponding author of the paper.

According to Dr. Hoijman, epithelial phagocytosis was a surprisingly efficient process thanks to the presence of arm-like protrusions on the surface of epithelial cells. “The cells cooperate mechanically; like people distributing food around the dining table before tucking into their meal, we found that epithelial cells push defective cells towards other epithelial cells, speeding up the removal of dying cells,” he adds.

“Here we propose a new evolutionarily conserved function for epithelia as efficient scavengers of dying cells in the earliest stages of vertebrate embryogenesis,” says Dr. Verena Ruprecht, group Leader in the Cell & Developmental Biology program at the CRG and senior author of the paper. “Our work may have important clinical applications by one day leading to improved screening methods and embryo quality assessment standards used in fertility clinics.”

According to the authors, the discovery that embryos exhibit an immune response earlier than previously thought warrants further exploration on the role of mechanical cooperation as a physiological tissue function, which remains poorly understood, in other important biological processes such as homeostasis and tissue inflammation.

The study is published today in the journal Nature. The team was led by the CRG in Barcelona in collaboration with the Pompeu Fabra University (UPF) and the Institute of Photonic Sciences (ICFO), as well as the University Paris-Diderot.

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3D LiDAR can provide accurate imaging and mapping for many applications; it is the “eyes” for autonomous cars and is used in facial recognition software and by autonomous robots and drones. Accurate imaging is essential for machines to map and interact with the physical world but the size and costs of the technology currently needed has limited LIDAR’s use in commercial applications.

Now a team of researchers from Pointcloud Inc in San Francisco and the University of Southampton’s Optoelectronic Research Centre (ORC) have developed a new, integrated system, which uses silicon photonic components and CMOS electronic circuits in the same microchip. The prototype they have developed would be a low-cost solution and could pave the way to large volume production of low-cost, compact and high-performance 3D imaging cameras for use in robotics, autonomous navigation systems, mapping of building sites to increase safety and in healthcare.

Graham Reed, Professor of Silicon Photonics within the ORC said, “LIDAR has been promising a lot but has not always delivered on its potential in recent years because, although experts have recognised that integrated versions can scale down costs, the necessary performance has not been there. Until now.

“The silicon photonics system we have developed provides much higher accuracy at distance compared to other chip-based LIDAR systems to date, and most mechanical versions, showing that the much sought-after integrated system for LIDAR is viable.”

Remus Nicolaescu, CEO of Pointcloud Inc added, “The combination of high performance and low cost manufacturing, will accelerate existing applications in autonomy and augmented reality, as well as open new directions, such as industrial and consumer digital twin applications requiring high depth accuracy, or preventive healthcare through remote behavioural and vital signs monitoring requiring high velocity accuracy.

“The collaboration with the world class team at the ORC has been instrumental, and greatly accelerated the technology development.”

The latest tests of the prototype, published in the journal Nature, show that it has an accuracy of 3.1 millimetres at a distance of 75 metres.

Amongst the problems faced by previous integrated systems are the difficulties in providing a dense array of pixels that can be easily addressed; this has restricted them to fewer than 20 pixels whereas this new system is the first large-scale 2D coherent detector array consisting of 512 pixels. The research teams are now working to extend the pixels arrays and the beam steering technology to make the system even better suited to real-world applications and further improve performance.

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