Fireball meteor over Lake Michigan.

The American Meteor Society has received reports of a bright fireball meteor being seen over Lake Michigan at about 11.40 pm local time on Sunday 19 June 2022 (about 3.40 am on Monday 20 June, GMT). People witnesses observing the event from Iowa, Illinois, Indiana, Michigan, Minnesota, Missouri, Ohio, and Wisconsin, and reported it moving roughly south to north. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry.

The 19 June 2022 Lake Michigan fireball seen from Crest Hill, Illinois. Neil Boing/American Meteor Society.

Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as an luminous object. However, this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).

Heat map showing areas where sightings of the meteor were reported (warmer colours indicate more sightings), and the apparent path of the object (blue arrow). American Meteor Society. 

These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.

Witness reports can help astronomers to understand these events. If you witness a fireball-type meteor over the US you can report it to the American Meteor Society here. 

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Evidence for photosynthetic oxygen production in a Neoarchean lake.

The photosynthetic production of oxygen has been a driving force in the evolution of the Earth's surface throughout much of the planet's history. However, quite when this process began remains a mystery. Oxygen has been present in the Earth's atmosphere since the Great Oxidation Event, 2.4 billion years ago, which provides a latest possible date for the onset of photosynthesis, but opinions are divided as to whether this marks the onset of oxygen production by the biological organisms, which then rapidly changed the face of the Earth, or whether photosynthesis had been occurring long before this, but been masked as a signal in the geological record by abundant reducing compounds in Archean environments, which prevented oxygen from building up in the atmosphere. 

Theoretically, if oxygen production did start long before the Great Oxidation Event, then this should have led to the development of local 'oxygen oases', areas where oxygen production was able to overpower any local redox buffering to produce localised oxidative conditions, which might have been preserved in the rock record. Many Archean continental sedimentary deposits show signs of oxidative weathering, despite having apparently been laid down under a reducing atmosphere. A possible cause of this could have been the local production of oxygen in lake environments. A modern analogue for this has been observed in lakes in Antarctica, where photosynthetic Cyanobacteria produce oxygen in benthic microbial mats, beneath an anoxic water column. 

Microbial mats produce distinctive sedimentary structures called Stromatolites; these form when layers of micro-organisms create biofilms on the surface of sediments in shallow water environments. Typically such films are buried by sediments periodically, with a new biofilm forming on the surface. Over time this builds up to a distinctive structure with layers of organic and inorganic material. Since these structures record the environment in which pre-Great Oxidation Event photosynthesis was likely to have occurred, Archean lacustrine Stromatolites have become a target for scientists searching for evidence of such activity.

In a paper published in the journal Geology on 9 May 2022, Dylan Wilmeth of the Department of Earth Sciences at the University of Southern California, and the Laboratoire Géosciences Océan at the Institut Universitaire Européen de la Mer, Stefan Lalonde, also of the Laboratoire Géosciences Océan at the Institut Universitaire Européen de la Mer, William Berelson, also of the Department of Earth Sciences at the University of Southern California, Victoria Petryshyn of the Environmental Studies Program at the University of Southern California, Aaron Celestian, again of the Department of Earth Sciences at the University of Southern California, and the Natural History Museum of Los Angeles County, Nicolas Beukes of the Department of Geology at the University of Johannesburg,  Stanley Awramik of the Department of Earth Science at the University of California, Santa Barbara, John Spear of the Department of Civil and Environmental Engineering at the Colorado School of Mines, and Taleen Mahseredjian and Frank Corsetti, again of the Department of Earth Sciences at the University of Southern California, present evidence for the presence of oxygen within microbial mats in a 2.74 billion-year-old palaeolake in the Hartbeesfontein Basin of South Africa.

The Hartbeesfontein Palaeolake formed in a half-graben structure within the Ventersdorp Continental Rift. ItTH has been identified as a lacustrine deposit on the basis of frequent, meter-scale facies shifts and intercalation with subaerial volcanic deposits. The palaeolake deposits also contain numerous Stromatolites, preserved as chert, many of which show exquisitely preserved microbial structures. Also present in the Stromatolites showing this high quality preservation are numerous rounded fenestrae (holes), which are interpreted as having been formed by gas bubbles produced by the activities of microbes living within the mats. These fenestrae are evenly distributed across the structures. Microbes living within mats of this sort can potentially produce a range of gasses (e.g. methane), so the presence of the fenestrae does not necessarily indicate the production of oxygen. 

Hartbeesfontein Basin (South Africa) Stromatolite textures. (A) Location map. Black square in inset represents map location. (B) Domal stromatolitic chert; hammer head is 2 cm tall. Wilmeth et al. (2022).

Wilmeth et al. used Rare Earth Element data to investigate the possible presence of oxygen within the Hartbeestfontein Stromatolites, in particular the distribution of cerium. Cerium levels were found to be anomalously high around fenestrae, and anomalously low in the surrounding laminae, which Wilmeth et al. believe is evidence of the element being scavenged onto oxides forming around the bubbles.

Fenestral oxides. (A), (B) Bubble fenestra with extensive oxides along bottom margin viewed in plane-polarized and reflected light. (C), (D) Fenestral (fen.) oxide viewed in reflected light. (E) Schematic of manganese (Mn) and cerium (Ce) oxidation and sorption onto fenestral oxides during mat growth. Qtz strom., quartz Stromatolite layers. Wilmeth et al. (2022).

Three distinctive assemblages of oxides could be observed within the Hartbeestfontein Stromatolites; within the bubble fenestrae, within the laminae, and on erosional surfaces. The fenestrae oxides appear orange and white under reflected light, and are found at the contact between the walls of the fenestrae and the megaquartz filling of the interior, implying that they were deposited early, before the emplacement of the quartz cement. Examination of this oxide layer with an electron microprobe found it to be rich in manganese, and the minerals goethite and titanite, whereas the oxide layers in the Stromatolite laminae were formed of  haematite and goethite, and are black, red, and yellow in colour, often with a metallic lustre. Oxides on recent erosional surfaces are reddish-orange in colour, and dominated by iron compounds.

Laminar and surficial oxides. (A), (B) Laminar oxides viewed under reflected light. Note the difference between laminar and fenestral oxides. (C) Laminar oxide with dissolution zones filled by orange goethite shown in reflected light. (D) Electron microprobe analysis backscatter image of laminar oxide with dissolution zones. (E) Schematic of laminar versus fenestral oxides during mat growth. (F) Surficial oxides formed by recent weathering. Qtz cem., quartz cement. Wilmeth et al. (2022).

All of the oxides present within the Hartbeestfontein Stromatolites are thought to have derived from minerals present in the original Archean microbial mats. However, these deposits have since undergone both  greenschist-grade metamorphism and weathering at the surface, so interpreting the original conditions must be done with care. For example, the haematite minerals present in the laminae of the Stromatolites were probably originally deposited as ferrihydrite or goethite.

Rare Earth Elements such as Cerium tend to be fairly immobile once deposited in rock formations, and not prone to redistribution by metamorphic processes. This makes them a useful tool for geologists wishing to understand the depositional conditions under which ancient strata were laid down. Furthermore, any available cerium within the water column will rapidly be incorporated into any manganese or iron oxides forming.

Cerium anomalies which are believed to have been formed after deposition are known, though these are due to the precipitation of cerium from water running over or through the rock. In the case of the Hartbeestfontein Stromatolites, the raised cerium levels can be observed around fenestrae that were enclosed within chert and recovered from drill cores, making this scenario highly unlikely. 

The presence of areas of both raised cerium (around fenestrae) and lowered cerium (within laminar layers), suggests that a radox boundary was present within the original Stromatolites, and therefore presumably the surrounding water column. Disolved cerium is scavenged from water and deposited onto iron or manganese oxides under oxidising conditions, but dissolves back into solution under reducing conditions. This would imply a shifting redox boundary within the ancient Hartbeestfontain Palaeolake, shifting above and below the microbial mats in response to changing local conditions. 

The deposition of cerium oxides around fenestrae withoin the Hartbeestfontain Stromatolites appears to be indicative of oxgen formation by microbes within the mats from which the Stromatolites formed. Given the highly reducing conditions thought to have been present within most Archean environments, this oxygen is likely to have been consumed by redox reactions long before it was able to make any meaningful impact on the wider lake environment, let alone the world beyond, but nevertheless the presence of these oxides tells us that ancient microbes had begun to produce oxygen by this time.

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Tartarocyon cazanavei: A new species of Amphicyonid 'Beardog' from the Faluns bleus deposits of Aquitaine, France.

Amphicyonids, or Beardogs, are an extinct group of Carnivoran Mammals known from the Eocene to Pleistocene of Europe, Asia, Africa and North America. Opinions on their relationship to other Carnivorans vary, with some palaeontologists feeling they are more closely related to Dogs and others that they are more closely related to Bears. Amphicyonids were for the most part large animals, including the earliest specimens, and most species are interpreted as having had either a hypercarnivorous diet (diet with a very high proportion of meat, similar to that of modern Cats), or to have been bone-crushing durophages (similar to modern Hyenas). The first Amphicyinids appear in the fossil record in Europe during the Eocene, with the group reaching North America during the Early Miocene.

In a paper published in the journal PeerJ on 15 June 2022, Floréal Solé of the Royal Belgian Institute of Natural Sciences,  Jean-Francois Lesport, an independent researcher from Sainte-Hélène in France, and Antoine Heitz and Bastien Mennecart of the Naturhistorisches Museum Basel, describe a new species of Amphicyonid Beardog from the Middle Miocene Faluns bleus deposits of Aquitaine, France.

The Faluns bleus deposits record a marine transgression in Aquitaine during the Serravallian (Middle Miocene, 13.82-11.63 million years ago). These deposits have produced a plethora of marine fossils laid down in a shelly sandstone, which have been studied by palaeontologists since the 1830s. The deposits are thought to represent a nearshore environment with a subtropical climate, and are most noted for their numerous Mollusc fossils.

The new species is described from a single mandible found by Jean-Francois Lesport and Philippe Renard in 1993, within a micro-conglomerate within the Faluns blues. This specimen has been donated to the Natural History Museum of Bordeaux by Jean-Francois Lesport, and is available to other researchers under the specimen  number MHNBx 2020.20.1; in addition the specimen has been 3D surface scanned, and to make a model which can be downloaded from here.

The new species is named Tartarocyon cazanavei, where 'Tartarocyon' is a combination of 'Tartaro', a legendary man-eating giant supposed to have lived in the Southwestern French Pyrenees (i.e. the area where the fossil was found), and 'cyon', the Greek for 'Dog', while 'cazanavei' honours Alain Cazanave, who owned the location where the fossil has found, and helped with it's extraction.

The specimen is a single right mandible with the second, third, and fourth premolars present, as well as the alveoli of the incisors, canine, first canine, and first, second, and third molars. There are diastemata (gaps) between the canine and first premolar, first and second premolars, second and third premolars, and third and fourth premolars, with that between the second and third premolars being the largest.

Holotype (MHNBx 2020.20.1) of Tartarocyon cazanavei from Sallespisse (MN7/8, Southwest France), in occlusal, lingual, and labial views. Scale bar is 5 cm. Solé et al. (2022).

Most of the features used to determine relationships within the Amphicyonidae are associated with the molars, which are not preserved in MHNBx 2020.20.1, making it hard to determine how Tartarocyon cazanavei is related to other members of the group, although it's tooth numbering makes it likely that it is a member of the Subfamily Thaumastocyoninae.

Solé et al. estimate that Tartarocyon cazanavei had a body mass of 194.91 kg. This is large for a Amphicyonid, comparable to Amphicyon major, Amphicyon pannonicus, Magericyon spp., and Megamphicyon carnutense, although smaller than the very largest species, such as Megamphicyon giganteus, Amphicyon gutmanni, Amphicyon eppelsheimensis, and Amphicyonopsis serus.

Amphicyonids have been divided into four dietary groups; omnivores, mesocarnivores, bone-crushing durophages, and hypercarnivores. Hypercarnivores show a reduction in the number of premolars and molars, which is not the case with Tartarocyon cazanavei, ruling this out as an ecological role for the species. Mesocarnivory in Amphicyonids is known only in smaller species, and is associated with closely appressed premolars and teeth with high crowns and blunt cuspids; this can also be ruled out for Tartarocyon cazanavei. Omnivory in Amphicyonids is also associated with small species, making it unlikely Tartarocyon cazanavei was an omnivore. Durophageous Amphicyonids typically have complete sets of molars and widely spaced premolars, making it highly likely that Tartarocyon cazanavei was a durophage. Furthermore, most such species were of comparable size to Tartarocyon cazanavei, further supporting this hypothesis. 

Reconstruction of Tartarocyon cazanavei feeding on a stranded Dolphin by the Serravallian Sea. Little is known of the inland environmental conditions where Tartarocyon lived. This illustration thus combines all the data from the site la Crousquillière in Sallespisse including the intertidal dark deposits, the abundance of the Molluscs, and the mandible of Tartarocyon in the high-tide line. Denny Navarra in Solé et al. (2022).

The survival of different ecological groups of Amphicyonids in Europe has been linked to climatic and environmental change. Smaller, mesocarnivorous forms largely disappeared at the end of MN5 (about 13.7 million years ago), which may have been related to the related to the Middle Miocene Climatic Transition, during which the climate cooled significantly, and became more arid. From this point on the majority of Amphicyonids were either hypercarnivores or durophages, with only a small number of omnivorous species. 

Amphicyonids were also impacted by the Vallesian Crisis, about 9.7 million years ago. This was marked by a spreading of more open, grassland environments, and a subsequent loss of many dense, woodland environments. This again seems to have reduced diversity within the group, with only large hypercarnivorous and durophageous forms surviving.

Body mass and diet distribution of Amphicyonids during the Miocene. Solé et al. (2022).

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Aulacoseira wyomingensis: A new species of freshwater Diatom from a seep near Casper, Wyoming.

Diatoms are single celled algae related to Kelp and Water Moulds. They are encased in silica shells with two valves. During reproduction the cells divide in two, each of which retains one valve of the shell, growing a new opposing valve, which is slightly smaller and fits flush within the older valve. This means that the Diatoms grow smaller with each new generation, until they reach a minimum size, when they undergo a phase of sexual reproduction, giving rise to a new generation of full-sized cells. Members of the Family Aulacoseiraceae have elongate valves with many spines; these spines being able to  interdigitate with other members of the species, enabling them to form long chains. The family currently contains four genera, Aulacoseira, which is known from fossils dating back as far as the Cretaceous and still extant, with a global distribution, Eosira, which is known only from the Eocene of North America, Miosira, which is know from the Miocene of Europe, and Alveolphora, which is known from Miocene and Pliocene deposits across the Northern Hemisphere.

In a paper published in the journal Taxonomy on 8 June 2022, Jeremy Greifenstein, Rachel Shea, and John Patrick Kociolek of the Department of Ecology and Evolutionary Biology at the Museum of Natural History of the University of Colorado Boulder describe a new species of Aulacoseira from a small seep near Casper, Wyoming.

The new species is named Aulacoseira wyomingensis, where 'wyomingensis' means 'from Wyoming'. The new species is described from a series of specimens extracted from a sample collected on 22 August 2021. These Diatoms are cylindrical in shape, and while they can adhere together, chains of longer than two Diatoms have been observed.

Aulacoseira wyomingensis. Scanning electron microscopy. External girdle views of entire frustules. Valves have striae that are disorganised. Column has small ridges. Cingulum is composed of numerous ligulate elements. Spines are small in length and shield-like. Valve on the right in (C) appears to be incompletely formed. Scale bars are 5 µm. Greifenstein et al. (2022).

The valves of Aulacoseira wyomingensis are 7-14 μm in diameter, with faces covered by large areolae (openings) up to 1 μm in diameter. The sides are covered by striations, these having smaller areolae. The central part is covered by ridges. 

Aulacoseira wyomingensis. Scanning electron microscopy. Internal views. (A) Valve view showing areolae and interior of valve. Scale bar is 2.5 µm. (B) Side view showing part of valve interior and exterior. Scale bar is 2.5 µm. (C) Valve view of interior showing ringleiste. Scale bar is 2.5 µm. (D) High magnification view of single areola showing fine hymenate occlusion over opening. Scale bar is 0.3 µm. (E) Side view showing part of the valve interior and exterior. Scale bar is 2.5 µm. Greifenstein et al. (2022).

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Eruptions on Mount Balusan, Luzon Island, the Philippines.

Mount Balusan, a 1565 m high stratovolcano (cone shaped volcano made up of layers of ash and lava) on southern Luzon Island, the Philippines, erupted slightly after 10.35 am local time on Sunday 5 June 2022, producing an ash column that rose slightly over 1 km above its summit and drifted to the west. Ashfall was reported in several nearby villages, and following the event, the Philippine Institute of Volcanology and Seismology recorded gas emissions from both the volcano's main crater and a vent on its northwest summit.

An ash column produced by Mount Balusan on 5 June 2022. Rissa Bonita/AFP/Getty Images.

The volcano erupted again slightly after 3.35 am on Sunday 12 June, this time producing an ash column only 500 m high, but again leading to ash falls in several local communities. The eruptions are believed to have been phreatic in nature, i.e. caused by hot magma encountering liquid water somewhere within the volcano, causing the water to vaporise instantly and explosively. The ashfalls have affected about 16 000 people, covering homes and crops and polluting water sources, with 418 people living in the communities closest to the volcano being evacuated as a precaution against further, more violent action.

Ash covering villages and plantations near Mount Balusan following an eruption on Sunday 12 June 2022. Sorsogon Provincial Information Office.

The geology of the Philippines is complex, with the majority of the islands located on the east of the Sunda Plate. To the east of this lies the Philippine Sea plate, which is being subducted beneath the Sunda Plate (a breakaway part of the Eurasian Plate); further east, in the Mariana Islands, the Pacific Plate is being subducted beneath the Philippine Sea Plate. This is not a smooth process, and the rocks of the tectonic plates frequently stick together before eventually being broken apart by the rising pressure, leading to Earthquakes in the process. Material from the subducting Philippine Plate is heated by the temperature of the Earth's interior, causing lighter minerals to melt and the resultant magma to rise through the overlying Sunda Plate, fuelling the volcanoes of the Philippines.

Subduction beneath the Philippines. Yves Descatoire/Singapore Earth Observatory.

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Human burials in a high altitude cave system in western Tibet.

Caves have been inhabited by Humans throughout the history of our species, but have also been widely used for other purposes, often mystical rather than practical in nature. One widespread use of caves has been as a burial site for the dead, both in natural and Human created spaces within caves. Such burials have been recorded at several places within the Nepalese part of the Tibetan Plateau, but to date have not been recorded from Tibet itself.

In a paper published in the journal Antiquity on 7 April 2022, Hongliang Lu and Ziyan Li of the School of Archaeology and Museology at Sichuan University, Chilie Ciren of the Tibet Autonomous Region Institute of Cultural Relics Conservation, Doudou Cao, also of the School of Archaeology and Museology at Sichuan University, and of the Department of Archaeology at the University of Cambridge, Xuan Gao, again of the School of Archaeology and Museology at Sichuan University, and Linhui Li, also of the Tibet Autonomous Region Institute of Cultural Relics Conservation, describe the discovery of an ancient burial site at the Sding Chung cave system in western Tibet.

The cave system is located on a mountain slope between the Gangdise and Himalayan Mountain ranges at an altitude of 5000 m. It is thought to have formed when part of the rock body collapsed following water dissolution (essentially as a sinkhole), but is now dry. The cave system is made up of two sets of branching tunnels, connected by a 14 m deep shaft. Both layers contained extensive collections of Human and Animal remains, as well as a few artefacts, which were spread out over the floors of the caves.

The location of the Sding Chung site. Ziyan Li in Lu et al. (2022).

Lu et al. divided the system into twelve units, collecting all artefacts from each of these, as well as taking samples of both the Human and Animal remains, although the majority of these were left in situ. More material was taken from the upper cave than the lower, due to unsafe conditions in the lower cave, and more Human remains were collected than Animal ones, with a preference for collecting skulls. The Human and Animal material was concentrated in a few branch caves, with little material found within the connecting tunnels. 

The landscape of Sding Chung. F Deng in Lu et al. (2022).

The floors of the three larger branches of the upper cave system (SG2, SG3, NG4) had a dense covering of Human and Animal remains, as well as a smaller number of artefacts. With the exception of two individuals found with the pelvis and vertebra attached by soft tissues, the Human remains were disarticulated and intermingled, although it is unclear whether this was done at the time of deposition or by later Human activities (which could have been associated with either ritual practices or looting). The most frequently encountered Human remains were crania, pelvises and limbs, although it is unclear if this was a product of collecting bias (these are generally the largest and most visible parts of a Human skeleton), or reflects a ritual practice in which more of these elements were deposited in the cave. A total of 526 Human bone and bone-fragment samples were identified in the upper caves, representing at least 34 individuals.

Plan and section views of the Sding Chung cave system. Kaiqi Zhang & Ziyan Li in Lu et al. (2022).

The most abundant Animal bones in the caves were those of Caprids (Goats), with those of Bovids, Equids, and Felids also present. Moat of these were found in a single branch cave (SG2). Some of the Animal remains were in the form of articulated limbs, often with skin and other soft tissues still present. At least three overlapping Equid skeletons were present. At least some of the Animal carcasses appear to have been transported to the caves intact. The artefacts found include bronze, ceramic, wooden and Bamboo items, and well as pieces of fabric.

(a) View from the tunnel of the upper cave; (b) the shaft tunnel; (c) scattered skeletons in LG1R; (d) piled Human skulls in LG1R. Hongliang Lu & Ziyan Li in Lu et al. (2022).

The lower caves had a much denser layer of Human and Animal skeletal remains. One of the cave recesses contained a pile of skulls, which appeared to have come from 10-15 individuals, five of which could be observed to have suffered notable injuries, though it is unclear at this time whether these injuries happened before or after death. The lower caves were found to contain 218 observable Human bones and bone fragments, representing at least 26 individuals.

Selected artefacts from Sding Chung: (1) wooden cup; (2) bronze goblet; (3) ceramic shard; (4) textile; (5) fragments of Bamboo weaving; (6) wooden stick. Hailun Xu & Xuan Gao in Lu et al. (2022).

The majority of the Animal bones in the lower caves were skulls, which Hu et al. presume is the result of deliberate selection by the people who placed them there. Once again Caprids were the most common Animals, with Bovids, Equids, and Canids also present. Artefacts were much less common in the lower cave system, and mostly comprise fragments of wood, which Hu et al. speculate may represent fragments of coffins.

The relationship between the remains in the upper and lower caves is unclear. If they can be assumed to represent different sets of individuals, then the minimum total number of individuals present would be 60. However, if some individuals have contributed skeletal remains to both levels, then the minimum total number of individuals present is only 54. It is also quite possible that other remains are present but buried or covered by rock debris or sediment and have not yet been discovered, in which case it is quite possible the caves hold over a hundred sets of Human remains. The Animal remains appear to represent at least 350 individuals.

Hu et al. carried out a limited excavation within the upper part of the Sding Chung cave system, uncovering a 1 m x 1 m area in branch NG1, close to the entrance. This produced a cluster of Bamboo objects, beneath which was a 20 cm ash layer, within which were found numerous burnt Animal bones, two Human bones, one intact bronze goblet, one bamboo cup, several ceramic shards, some wooden sticks, and debris from metal artefacts.

Hu et al. took twelve samples for radiocarbon dating from Human and Animal bones, Bamboo and textiles, from three locations in the upper cave system and one in the lower caves. All of these yielded dates between 300 BC and 300 AD. 

A number of prehistoric burial sites have been found in the Western Himalayas in recent years, although the majority of those being artificial cave or shaft tombs located close to settlements. A notable exception to this has been the cave burials of Mustang District in Nepal. The Sding Chung burials are at a notably higher altitude than most previous burial sites, and appear to represent a previously unknown funerary tradition, possibly involving people living in lowlands but carrying their dead to a higher (and hidden) burial site.

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