Patriofelis (Rom-u)
Patriofelis (Patriofelis Leidy, 1870)
Order: †Oxyaenodonta
Family: Oxyaenidae
Temporal range: during the Miocene (North America)
Dimensions: length - 1,8 m, height - 70 сm, weight - 30 - 100 kg
A typical representative: Patriofelis ferox
In North America during the Miocene, some 45 million years ago, the cat-like creodont Patriofelis hunted in the conifer forests. About the size of a modern-day jaguar, Patriofelis had short legs, a long tail, and broad paws. The paws suggest that the creodont may not have run fast, but could have been a good swimmer. Modern jaguars often hunt in the rivers. At the very least, Patriofelis was probably an ambush hunter.
Game in Nevada and Oregon was plentiful. Small horses started to travel in herds, taking advantage of the receding forests. Could Patriofelis lay in wait near watering holes, picking off unwary prehistoric horses and other herbivores.
One theory about Patriofelis' habits suggest that it led a semi-aquatic life. A specimen found in the Bridger Lake sediment had very well-worn teeth. Bridger Lake once swarmed with turtles. If so, the turtles may have been a staple part of Patriofelis' diet! To support this theory, coprolites containing fragments of turtle shells have been found in the Bridger Lake sediment. Patriofelis definitely had jaws robust enough to dine on turtles.
Patriofelis' predecessor Oxyaena, was a good climber but it looks like Patriofelis preferred the water to the trees. If Patriofelis continued in the water, it may have evolved into modern pinnipeds. So, the "father of cats" may actually have been more like the "father of seals!" The largest Patriofelis - Patriofelis ferox - was about the size of a small black bear, with a disproportionately large skull. The skull is also broad and short and have some aspects similar to that of a sea lion's skull. However, unlike a sea lion, Patriofelis had a small brain case inside its huge, thick skull. Patriofelis ulta was about a third smaller. Both species had broad, plantigrade feet and long bodies and tails. Some of the sketches of Patriofelis resemble an otter on steroids more than a feline.
Un fossile de Nouvelle-Écosse est le premier exemple de soins parentaux
A partnership between a Nova Scotia fossil hunter and Carleton University researchers has yielded the earliest fossil evidence of a parent caring for its offspring — a skeleton of a 300-million-year-old animal that appeared to be concealing and protecting a juvenile in a den.
The two creature were “synapsids” — commonly known as mammal-like reptiles. While prehistoric synapsids were lizard-like in appearance, they belong to the evolutionary line that eventually led to mammals. The larger of the pair — the parent — was about 30 centimetres long from the tip of the nose to the end of its tail. The juvenile was about a third of that size.
These particular synapsids were likely hiding inside the trunk of tree when they were apparently trapped by a sudden flood. The two skeletons were discovered in 2017 by Brian Hebert, who has been searching for fossils in Nova Scotia for 30 years.
Hebert was combing a section of the east coast of Cape Breton Island near Sydney when he found the fossils in a lithified tree stump from the Carboniferous Period, a time in which the area was covered by a swampy forest, millions of years before the rise of dinosaurs.
Hebert has often found such tree stumps in his searches, but many are empty. Even those with skeletons inside had only one skeleton.
“The tree was not a well-preserved tree, but everything inside was amazingly well-preserved,” he said of the find he made in 2017. “I knew it was something special as soon as I opened it.”
Paleontologist Hillary Maddin, who analyzed the finding with the Carleton University team, said Hebert’s finding predates the previous oldest record of this behaviour by 40 million years. The adult’s tail is wrapped around the juvenile’s hind limbs in a manner common among denning animals.
It is likely the parent was carnivorous, while the juvenile ate insects. “The bugs were quite big back then,” said Maddin.
It is not common to see fossils this well-preserved, she said. “This fossil is just so beautifully articulated,” she said.
Parental care is common in mammals — all mammal offspring require nourishment from their mothers. Some other animals, including birds, some amphibians, reptiles and even fish also care for their young.
Parental care requires animal parents to make an investment, or divert resources away from themselves, to give their young a better chance of survival, said Maddin. Prolonged care of offspring after birth can have the highest cost to parents.
How parental care has evolved as a behavioural strategy is a question not yet answered. Understanding of how parental care evolved can only be done by studying fossils. So far, most evidence of prehistoric parenting has been limited to finding groups of individuals of different ages of the same species.
There are evolutionary advantages and disadvantages to parental care, said Maddin. Some animals demonstrate extended care for their young and some don’t. Some just ditch their offspring, while others protect them until they are better able to care for themselves.
“This confers some sort of advantage to this animal,” said Maddin.
The findings of the Carleton team have been published in the journal Nature Ecology & Evolution. It has created a stir worldwide.
Reaction to the published article has bad been “pretty crazy,” said Maddin. The story has appeared in more than 70 general interest publications and on more than 50 national news broadcasts. “It really kind of exploded.”
Are these two lizard-like animals apparently cuddling together the first example of mother love? Not in the way that humans think of it, said Maddin. Some modern animals not considered intelligent, such as some shrimp and crabs, also demonstrate parental care, she said.
“It’s quite a common strategy. This is just the first example we have seen of it.”
Hebert said fossil hunters have been searching Nova Scotia for almost 200 years. Storm surges can erode cliffs, exposing more finds.
“There’s an untapped resource of amazing fossils to be found,” he said.
Roncellia perceensis
Marc R. Haensel:
The largest trilobite you've never heard of: Roncellia perceensis from the Lower Devonian of Percé, Quebec. MHC-00639.
With a pygidium nearly 15cms wide, I'd imagine the complete trilobite to be over 40cms long!
Dinosauroïde
Imaginez ma surprise de tomber nez à nez avec ce cher dinosauroïde 40 ans plus tard dans l'entrepôt du musée de la nature, situé à Gatineau! J'ai été complètement émerveillé de rencontrer cette créature qui avait captivé mon imagination lorsque j'étais enfant. En espérant que ce magnifique modèle sera à nouveau exposé au public afin d'éveiller la fascination de nouvelles générations!
Pour plus d'info: https://cdnsciencepub.com/doi/10.1139/cjes-2020-0172
La théorie du "stoned ape" de Terence McKenna
There seems to have been a profound difference in cognitive abilities between early Homo sapiens and our immediate predecessor, Homo erectus. Sure, erectus stood upright — a big, um, step forward — but with the emergence of Homo sapiens, we see traces of art, pictography, and tool usage, and we believe humankind made its first forays into language.
In the early 1990s, psychedelic advocate and ethnobotanist Terence McKenna published his book Food of the Gods in which he surmised that Homo sapiens‘ cognitive leap forward was due to their discovery of magic mushrooms. The scientific community never took McKenna’s theory very seriously, considering it mostly trippy speculation — these days, his ideas have largely been relegated to the spacier corners of Reddit. Now, however, the idea has acquired a new advocate, psilocybin mycologist Paul Stamets, who’s suggesting McKenna was right all along.
The stoned ape
In McKenna’s Stoned Ape hypothesis,” he posited that as humans began to migrate to new areas, at some point they came upon psychedelic mushrooms growing in cow droppings, as is their wont, and then ate them. After ingesting them, and more specifically the psilocybin they contained, their brains kicked into overdrive, acquiring new information-processing capabilities, and a mind-blowing expansion of our imaginations in the bargain. Many modern users of psychedelics claim the world never looks the same again after such an experience. As McKenna put it, “Homo sapiens ate our way to a higher consciousness,” and, “It was at this time that religious ritual, calendar making, and natural magic came into their own.”
The return of the stoned ape
Regarding this theory, Stamets presented “Psilocybin Mushrooms and the Mycology of Consciousness” at Psychedelic Science 2017. In his talk he sought to rehabilitate McKenna’s hypothesis as a totally plausible answer to a longstanding evolutionary riddle. “What is really important for you to understand,” he said, “is that there was a sudden doubling of the human brain 200,000 years ago. From an evolutionary point of view, that’s an extraordinary expansion. And there is no explanation for this sudden increase in the human brain.”
Why not mushrooms? Stamets portrayed a group of early humans making their way through the savannah and happening across “the largest psilocybin mushroom in the world growing bodaciously out of dung of the animals.” It needn’t have been unusually large to have its effect, of course. In any event, he invited the crowd to suspend their disbelief and admit that McKenna’s idea constitutes a “very, very plausible hypothesis for the sudden evolution of Homo sapiens from our primate relatives,” even if it’s an unprovable one.
The audience’s response was reportedly enthusiastic, though it’s fair to note that these were people attending a conference on psychedelic science, and thus pre-disposed toward such chemicals’ importance.
Just tripping?
Certainly, there’s general agreement on the mystery Stamets cited, if not so much on timing details. And consciousness, the “hard problem” even in its modern form, is an area rife with unanswered questions. What is consciousness, anyway? Is it a simple enough thing that it could have a single root cause as McKenna and Stamets say? Many experts suspect our brains gained new capabilities as the result of early community ties and the requirements of social interaction, but when?
Anthropologist Ian Tattersall tells Inverse that the where seems obvious enough: Africa, “For it is in this continent that we find the first glimmerings of ‘modern behaviors’. . . But the moment of transformation still eludes us and may well do so almost indefinitely.”
There are other researchers who’ve studied early humanity’s use of drug plants but who are skeptical of the stoned ape notiion. Elisa Guerra-Doce, an expert in the field, considers the idea too simplistic, potentially a reduction of a complex evolutionary process into a single “aha” — or maybe “oh, wow” — moment. She’s also troubled by there being little evidence of such a pivotal moment, or of drug use at all, so early in the archeological record.
Amanda Feilding of the psychedelic think tank Beckley Foundation says, however, that the stoned ape theory is at the very least a valid reminder that humans have always been drawn to and fascinated by mind-altering substances: “The imagery that comes with the psychedelic experience is a theme that runs through ancient art, so I’m sure that psychedelic experience and other techniques, like dancing and music, were used by our early ancestors to enhance consciousness, which then facilitated spirituality, art, and medicine.”
Just how early our love affair with hallucinogenic states began may have something to say about the plausibility of McKenna’s hypothesis, but, alas, we don’t know when that would have been. And, as the saying about the 1960s goes, even if any of these people were still around to ask, anyone who was really there wouldn’t be able to remember.
Eusmilus (Mario Lanzas)
A wonderful reconstruction of the prehistoric nimravid - mammalian predators better known as "false saber-toothed cats" - Eusmilus, by the talented artist Mario Lanzas. Anyone who is already familiar with nimravids knows that Eusmilus looks like one of the famously called saber-toothed cats, but for those who don't know; nimravids like Eusmilus evolved down a separate genetic line, they found themselves living in a world where there was a predatory niche open for cat-like predators. Growing large, they developed enlarged upper canine teeth that were almost as long as their skulls, fossil evidence suggests that nimravids went along derived evolutionary pathways; resulting in conical teeth, dirk teeth, and scimitar teeth, with that their evolutionary paths then split in two, leading to saber-toothed and conical-toothed forms that convergently evolved with those of true felids tens of millions of years later. Meaning, despite Eusmilus having long saber teeth and looking like a saber-toothed cat, nimravids were actually a so-called "false saber-tooth" that only bore this resemblance due to convergent evolution. There are only three valid species of Eusmilus known; the type species E. bidentatus (Filhol, 1873), along with E. villebramarensis (Peigne and Brunet, 2003), and lastly, E. adelos (Barrett, 2021) the largest species in the genus. Ironically, Eusmilus' name means "true saber" - despite having the nickname 'false saber-tooth' - or "early knife," depending on the translation. Eusmilus is classified as Eukaryota, Animalia, Chordata, Mammalia, Carnivora, Feliformia, Nimravidae, and Hoplophoninae.
Fossils of Eusmilus have been unearthed throughout Europe and North America. It lived during the Paleogene Period, Late Eocene to Early Oligocene Epochs, Priabonian to Rupelian Ages 37.2 - 28.4 million years ago. Most Eusmilus species had a long body, and compared to modern leopards their legs were short, but despite that were about as tall as leopards, reaching a shoulder height of 60 - 70 centimeters (24 - 28 inches). Some specimens reached 2.5 meters (8 feet) long, E. adelos was comparable to African lion proportions, reaching a weight of 111 kilograms (244.7 lbs), and thus was the largest of the holplophonine nimravids. Eusmilus would have been a hunter of medium to large sized animals; much like rhinoceratids, tapirids, anthracotheriids, or upon the diversity of ‘oreodont', equid, and camelid taxa. Their enlarged canines were the primary killing tools employed by Eusmilus, and analysis of the skeleton supports this. The muscle attachment points on the skull show that Eusmilus actually had weak jaw closing muscles, but this was to allow for a wide jaw opening angle. To properly use their saber teeth, Eusmilus could open their jaw to an impressive ninety degrees wide, thirty degrees more than a modern African lion (Panthera leo).
Curiously, Eusmilus possessed fewer teeth than other mammalian carnivores, only 26 instead of the usual 44 teeth. To help compensate for the weak bite force, the neck and shoulders evolved to allow for powerful downward thrusts that drove the saber-teeth through its victim without the need for using the jaw muscles. Once punctured into a critical area such as the neck, death would come in a matter of minutes at most for the prey. Unfortunately, nimravids most likely went extinct due to general faunal turnover that saw a major reduction in diversity of numerous prey taxa, such as equids, camelids, antilocaprids and dromomerycids, from about 7.5 to 6.8 million years ago. The second image shows the partial skeleton of Eusmilus adelos specimen USNM 12820, with shaded known elements. Cranial abbreviations: fr frontal, na nasal, mp mastoid process, (A) cn carnassial notch, mc main cusp of P3, pa paracone, pcc posterior cingular cusp of P3, ps parastyle; (B - D) bis brachialis insertion site, lg lateral groove of ulna, rn radial notch, sln semilunar notch, (E - G) ce capitular eminence of radius, rt radial tuberosity, (H - J) dpc delto-pectoral crest, of olecranon fossa, sc supinator crest (brachial flange), remnants of bridge enclosing epicondylar foramen. Eusmilus adelos skeletal reconstruction by Dhruv Franklin. Photo credit: Paul Zachary Barrett, 2021.
La côte Est des États-Unis s'enfonce
In many parts of the U.S. East Coast, rising seas driven by melting ice and the thermal expansion of warming water is only part of what threatens coastal areas. The land is also sinking. This geologic two-step is happening rapidly enough to threaten infrastructure, farmland, and wetlands that tens of millions of people along the coast rely upon, according to a NASA-funded team of scientists at Virginia Tech’s Earth Observation and Innovation (EOI) Lab.
The researchers analyzed satellite data and ground-based GPS sensors to map the vertical and horizontal motion of coastal land from New England to Florida. In a study published in PNAS Nexus, the team reported that more than half of infrastructure in major cities such as New York, Baltimore, and Norfolk is built on land that sank, or subsided, by 1 to 2 millimeters per year between 2007 and 2020. Land in several counties in Delaware, Maryland, South Carolina, and Georgia sank at double or triple that rate. At least 867,000 properties and critical infrastructure including several highways, railways, airports, dams, and levees were all subsiding, the researchers found.
The findings follow a previous study from the EOI Lab, published in Nature Communications, that used the same data to show that most East Coast marshes and wetlands—critical for protecting many cities from storm surge during hurricanes—were sinking by rates exceeding 3 millimeters per year. They found that at least 8 percent of coastal forests had been displaced due to subsidence and saltwater intrusion, leading to a proliferation of “ghost forests.”
(...) Part of the reason that the Mid-Atlantic is sinking more rapidly than the northeastern U.S. is because the edge of the massive Laurentide ice sheet, which covered much of northern North America during the height of the most recent Ice Age, ran through northern Pennsylvania and New Jersey. Ice-free lands to the south of that line, especially in the Mid-Atlantic, bulged upward while ice-covered lands to north were pushed downward by the weight of the ice, Shirzaei explained. When the ice sheet started retreating 12,000 years ago, the Mid-Atlantic region began sinking gradually downward—and continues to do so today—while the northeastern U.S. and Canada began rising as part of a rebalancing process called glacial isostatic adjustment.
While the edge of the Laurentide ice sheet never got close to northern Florida, that region has relatively high rates of uplift due to another geologic process—the gradual dissolution and lightening of karst landscapes due to the infiltration of groundwater.
La gravité ‘'manquante'' du Canada expliquée
Extraits de cet article:
Les hommes et les femmes qui habitent dans le nord du Canada, autour de la Baie d’Hudson, ressentent un peu moins que leurS congénères l’attraction terrestre. Concentrant l’attention des satellites jumeaux de la mission GRACE sur cette zone, des chercheurs présentent désormais un schéma et une explication détaillés de cette anomalie du champ gravitationnel de la Terre.
La gravité étant étroitement liée à la répartition des masses à la surface de la Terre, le champ gravitationnel de notre planète varie légèrement d’un endroit à un autre. Les premières cartographies établies dans les années 60 ont révélé qu’au nord du Canada la gravité était anormalement faible. La Laurentide, l’ancienne calotte glaciaire qui recouvrait le nord de l’Amérique il y a 20.000 ans, et qui mesurait jusqu’à trois kilomètres d‘épaisseur, a été rapidement rendue responsable.
Les travaux de l’équipe de Mark Tamisiea (Harvard-Smithsonian Center for Astrophysics, USA), publiés dans la revue Science du 10 mai, confirment le rôle du rebond post-glaciaire. Comprimée pendant l‘Age de glace, la croûte terrestre a commencé à remonter lorsque la glace a fondu. Cependant, ce rebond est très lent et même si la gravité augmente progressivement les chercheurs estiment qu’il faudra encore 300.000 ans avant que les effets de la période glaciaire disparaissent.
Les données des satellites GRACE révèlent que l’ancienne calotte Laurentide comptait deux énormes dômes de glaces, un de chaque côté de l’actuel baie d’Hudson, qui ont provoqué une élévation du niveau des eaux de 60 mètres lorsqu’ils ont fondu.
Cependant, d’après Tamisiea et ses collègues, le rebond post-glaciaire n’explique qu’une partie de l’anomalie du champ gravitationnel. Le reste serait dû aux mouvements de brassage au sein du manteau terrestre.
Se déplaçant en formation à 500 km au-dessus de nos têtes, les deux satellites de la mission GRACE fournissent une cartographie très précise du champ de gravitation de la Terre. Les variations de la gravité modifient la vitesse de déplacement des satellites. Or la distance qui les sépare est constamment mesurée par des instruments qui détectent les écarts au micron près. Les satellites ont été lancés en mars 2002 pour une mission de cinq ans.
(...) That’s right: Canada actually has less gravity than it’s supposed to. The reasons for the shortage have puzzled scientists for decades.
Gravity isn’t uniform all over the Earth’s surface. It’s a result of mass, which means the varying density of the Earth at different locations can affect how much you weigh there.
(...) Satellite data collected by GRACE—the Gravity Recovery and Climate Experiment—has recently solved this mystery. During the last ice age, Canada was covered by a vast glacier called the Laurentide Ice Sheet. This sheet was two miles thick over northern Quebec and stretched as far south as modern-day New York and Chicago.
Ice is heavy, so five million square miles of it pushed down on the rock underneath, squishing it like a Nerf ball. When the ice began to melt, about 21,000 years ago, the Earth began to spring back, but, like a Nerf ball, it takes a while. To this day, the Earth in the Hudson Bay region is still deformed, with lots of rock-mass having been pushed outward by all the ice. Less mass means less gravity.
Extraits de cet article:
For more than 40 years, scientists have tried to figure out what's causing large parts of Canada, particularly the Hudson Bay region, to be "missing" gravity. In other words, gravity in the Hudson Bay area and surrounding regions is lower than it is in other parts of the world, a phenomenon first identified in the 1960s when the Earth's global gravity fields were being charted.
Two theories have been proposed to account for this anomaly. But before we go over them, it's important to first consider what creates gravity. At a basic level, gravity is proportional to mass. So when the mass of an area is somehow made smaller, gravity is made smaller. Gravity can vary on different parts of the Earth. Although we usually think of it as a ball, the Earth actually bulges at the Equator and gets flatter at the poles due to its rotation. The Earth's mass is not spread out proportionally, and it can shift position over time. So scientists proposed two theories to explain how the mass of the Hudson Bay area had decreased and contributed to the area's lower gravity.
One theory centers on a process known as convection occurring in the Earth's mantle. The mantle is a layer of molten rock called magma and exists between 60 and 124 miles (100 to 200 km) below the surface of the Earth . Magma is extremely hot and constantly whirling and shifting, rising and falling, to create convection currents. Convection drags the Earth's continental plates down, which decreases the mass in that area and decreases the gravity.
A new theory to account for the Hudson Bay area's missing gravity concerns the Laurentide Ice Sheet, which covered much of present-day Canada and the northern United States. This ice sheet was almost 2 miles (3.2 km) thick in most sections, and in two areas of Hudson Bay, it was 2.3 miles (3.7 km) thick. It was also very heavy and weighed down the Earth. Over a period of 10,000 years, the Laurentide Ice Sheet melted, finally disappearing 10,000 years ago. It left a deep indentation in the Earth.
To get a better idea of what happened, think about what happens when you lightly press your finger into the surface of a cake or a piece of really springy bread. Some of it moves to the sides and there's an indentation. But when you remove your finger, it bounces back to normal. A similar thing happened with the Laurentide Ice Sheet, the theory proposes -- except the Earth isn't so much "bouncing" back as it is rebounding very slowly (less than half an inch per year). In the meantime, the area around Hudson Bay has less mass because some of the Earth has been pushed to the sides by the ice sheet. Less mass means less gravity.
So which theory is correct? It turns out that both of them are. Convection and the ice sheet's rebound effect are both causing some of the decrease in gravity around Hudson Bay. First, we'll consider the ice sheet theory.
To calculate the impact of the Laurentide Ice Sheet, scientists at the Harvard-Smithsonian Center for Astrophysics used data gathered by the Gravity Recovery and Climate Experiment (GRACE) satellites between April 2002 and April 2006. The GRACE satellites are highly sophisticated machines, orbiting about 310 miles (500 km) above the Earth and 137 miles (220 km) apart. The satellites can measure distances down to a micron, so they can detect minor gravitational variations. When the lead satellite flies over the Hudson Bay area, the decrease in gravity causes the satellite to move slightly away from the Earth and from its sister satellite. This shift in distance is detected by the satellites and used to calculate the change in gravity. Any shifts detected can also be used to create maps of gravitational fields.
The GRACE data allowed scientists to create topographical maps approximating what Hudson Bay looked like during the last ice age, when it was covered by the Laurentide Ice Sheet. These maps revealed some interesting features about the area, including two bulging areas on the western and eastern sides of Hudson Bay where the ice was much thicker than the rest of the sheet. Gravity is now lower there than in other parts of the gravity-depleted bay.
Another important finding came from the GRACE data: It turns out that the ice sheet theory only accounts for 25 percent to 45 percent of the gravitational variation around Hudson Bay and the surrounding area. Subtracting the "rebound effect" from the area's gravitational signal, scientists have determined that the remaining 55 percent to 75 percent of gravitational variation is likely due to convection.
The Hudson Bay area is going to have less gravity for a long time. It's estimated that the Earth has to rebound more than 650 feet to get back to its original position, which should take about 5,000 years. But the rebound effect is still visible. Although sea levels are rising around the world, the sea level along Hudson Bay's coast is dropping as the land continues to recover from the weight of the Laurentide Ice Sheet.
While the mystery surrounding Canada's gravitational anomalies has been put to rest, the study has wider implications. Scientists involved in the Harvard-Smithsonian Center study were amazed that they were able to see how the Earth looked 20,000 years ago. And by isolating the influence of the ice sheet's rebound effect, researchers better understand how convection affects gravity and how continents change over time. Finally, the GRACE satellites have provided scientists with data on many ice sheets and glaciers. By examining climate change that took place thousands of years ago, scientists may gain a better understanding of how global warming and rising sea levels are affecting our planet today and what impact they will have on our future.
L'étude de Tamisiea, Mitrovica et Davis:
The free-air gravity trend over Canada, derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission, robustly isolates the gravity signal associated with glacial isostatic adjustment (GIA) from the longer–time scale mantle convection process. This trend proves that the ancient Laurentian ice complex was composed of two large domes to the west and east of Hudson Bay, in accord with one of two classes of earlier reconstructions. Moreover, GIA models that reconcile the peak rates contribute ∼25 to ∼45% to the observed static gravity field, which represents an important boundary condition on the buoyancy of the continental tectosphere.
Possible découverte d’un astéroïde minganois sur Google Maps
Une équipe de scientifiques français étudie un possible cratère d’astéroïde sur la Côte-Nord, jamais identifié auparavant. À quelque 100 kilomètres au nord du village de Magpie, les premiers indices de son existence ont été découverts par un curieux internaute en quête d’aventure.
Joël Lapointe promenait candidement son curseur dans Google Maps sur des chemins forestiers afin de planifier ses vacances en camping lorsqu’un détail lui a accroché l'œil.
"Je vois quelque chose de rond et d’un peu effacé, comme une espèce de fosse d’une quinzaine de kilomètres de diamètre", décrit-il. Quelque chose dans la courbe lui semble suspect. À l’intérieur de cette fosse-là, un autre anneau de petites montagnes d’à peu près huit kilomètres de diamètre, et puis au centre : le lac Marsal.
"Ça, c’est bien trop concentrique pour que ça soit naturel!", s'est-il dit.
M. Lapointe s’est donc tourné vers des chercheurs professionnels. Il a envoyé des courriels à des centres d’ici et d’ailleurs pour enfin attirer l'attention de la Meteorotical Society. C’est à travers cette société vouée à l’étude des matériaux extraterrestres fondée en 1933 que le dossier du lac Marsal tombe sur le bureau du géophysicien Pierre Rochette.
Quelques mois plus tard, M. Rochette reçoit des échantillons envoyés spécialement par le Service géologique du Canada : "Les roches que j’ai récupérées sont des roches qui ont été fondues", commente-t-il. Son équipe et lui sont à la recherche de preuves précises, qui prouveraient qu’un météorite est entré en collision avec la Terre.
"Cela pourrait être des roches volcaniques, mais notre hypothèse, c'est qu'elles ont été fondues par l'impact. Alors, pour vraiment apporter la preuve que ça a été fondu pour un impact, il faut trouver les preuves de très haute pression", indique le chercheur.
Les analyses sont encourageantes, assure M. Rochette, mais elles ne sont pas encore conclusives. "On a reçu dix échantillons et l’un d’entre eux contient un minéral qu'on appelle le zircon, qui est très souvent utilisé pour prouver les impacts", explique-t-il. "Le zircon, c’est un minéral très résistant qui, sous l’effet d’un impact, se transforme."
La découverte d'un impact d'une telle puissance serait majeure, affirme Pierre Rochette. "Pour creuser un cratère de 15 kilomètres de diamètre, en gros, il faut un astéroïde de deux kilomètres de diamètre." Le dernier astéroïde découvert de cette dimension l’a été en 2013, selon le scientifique. "Ça fait un bail."
Si les analyses d’échantillons confirment qu'un astéroïde est bel et bien tombé en Minganie, Pierre Rochette et son équipe prévoient un voyage dans la région pour en tirer de plus amples leçons. "L'idée, c'est d'aller en hydravion sur le lac, qui est vraiment au centre du cratère", prévoit-il. "Et il se trouve qu’en suivant différents plans d'eau, on peut naviguer sur une dizaine de kilomètres à l'intérieur du cratère."
Cette expédition est prévue en 2025.
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