The Southern Delta Aquariid Meteor Shower.

The Southern Delta Aquariid Meteor Shower is visible between roughly 12 July and 23 August each year, and is expected to peak on Tuesday 30 July this year, producing up to 25 meteors per hour. Best viewing this year is predicted to be between 3.00 am (this will be in local time wherever they are viewed from, as the time reflects the orientation of the planet to the rest of the Solar System) and dawn, when the radiant point of the shower (point from which the meteors appear to radiate), which is close to the star Delta Aquarii (hence the name) will be highest in the sky. This year the peak of activity will fall a few days before the new moon on 4 August, and the Moon will be in the constellation of Taurus, rising slightly after midnight on 30 July, so light interference should be minimal.

The radiant point of the Southern Delta Aquariid Meteor Shower. EarthSky.

Meteor streams are thought to come from dust shed by comets as they come close to the Sun and their icy surfaces begin to evaporate away. Although the dust is separated from the comet, it continues to orbit the Sun on roughly the same orbital path, creating a visible meteor shower when the Earth crosses that path, and flecks of dust burn in the upper atmosphere, due to friction with the atmosphere.

The Earth passing through a stream of comet dust, resulting in a meteor shower. Not to scale. Astro Bob.

The Southern Delta Aquariids are thought to be caused by the Earth passing through the trail of Comet 96P/Machholz 1, where it encounters thousands of tiny dust particles shed from the comet as its icy surface is melted (strictly sublimated) by the heat of the Sun. 96P/Machholz is a short period, Jupiter Family Comet, crossing our orbit every 5.24 years, but the trail of particles shed by it forms a constant flow.

How the passage of the Earth through a meteor shower creates a radiant point from which they can be observed. In The Sky.

96P/Machholz 1 was discovered by amateur astronomer Donald Machholz from Loma Peak in California on 12 May 1996. The name 96P/Machholz implies that it was the first comet discovered by Machholz and was the 96th periodic comet discovered (a periodic comet is a comet which orbits the Sun in less than 200 years). 

Comet 96P/Machholz 1 imaged on 4 April 2007 by the SECCHI inner Heliospheric Imager on the STEREO Ahead space-based observatory. NASA/Wikimedia Commons.

96P/Machholz1 has an orbital period of 1931 days (5.29 years) and a highly eccentric orbit tilted at an angle of 58.1° to the plain of the Solar System, that brings it from 0.12 AU from the Sun at perihelion (12% of the distance between the Earth and the Sun, considerably inside  the orbit of Mercury, and closer to the Sun than any other known periodic comet); to 5.95 AU from the Sun at aphelion (5.96 times as far from the Sun as the Earth or slightly more than the distance at which Jupiter orbits). As a comet with a period of less than 20 years, 96P/Machholz 1 is considered to be a Jupiter Family Comet.

The orbit and position of 96P/Machholz 1 on 30 July 2024. JPL Small Body Database.

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Remains of Early Christian community uncovered in Bahrain.

Traces of an Early Christian community have been discovered by archaeologists in the village of Samahij on the north coast of Muharraq Island, Bahrain, according to a press release issued by the University of Exeter. The remains comprise a large building with eight rooms beneath the remains of a later mosque, with the site yielding radiocarbon dates from the mid fourth century to the mid eighth century AD. At this time Christian communities belonging to the Nestorian Church, or Church of the East, are known from historical records to have been found around the Persian Gulf, although very few archaeological remains associated with these communities have been found to date, making the discovery of the site significant.

The approximate location of the Samahij archaeological site. Google Maps. 

The excavations were carried out by a team of British and Bahraini archaeologists led by Timothy Insoll of the Institute of Arab and Islamic Studies at the University of Exeter and Salman Almahari of the Bahrain Authority for Culture and Antiquities, between 2019 and 2023, and a museum showcasing the discoveries is planned to open in 2025.

The building uncovered had stone walls with plastered internal walls. It was possible to identify the places where doors and fixed benches had been attached by sockets and holes in the walls and floor. One room had clearly been used as a kitchen with several hearths made from the bases of amphorae or other large storage vessels.

The Samahij archaeological site. University of Exeter.

Food remains from the site are still being analysed, but suggest the people here enjoyed a diet including pork, fish, shellfish, and several plant crops. Other finds include beads made from carnelian, a semi-precious stone likely to have originated in India, as well as ceramics which are clearly of Indian origin, indicating the community were part of a trade network that reached the sub-continent. Other items include spindle whorls, copper needles, and glassware, including wine glasses, copper coins thought to come from the Sasanian Empire, which had its centre in modern Iran and incorporated much of the Persian Gulf area.

The site has been identified as Christian on the basis of three plaster crosses and gratfiti scratched in the plaster walls, which includes the Early Christian Chi-Rho and Fish symbols. During the late pre-Islamic period the site would have formed part of the Nestorian Diocese of Meshmahig or Mašmahig (which may be related linguistically to Samahij). 

The Church of the East effectively split from the 'Church of the West' (i.e. the Roman church) in 410 AD, becoming the official Christian church of the Sasanian Empire, which at this time was at war with the Roman Empire in the west. This de facto separation was made official in 424, with the name 'Nestorian Church' becoming prevalent after 431, when the theologian Nestorius, who was Arch-Bishop of Constantinople, was condemned for heresy by the Council of Ephesus, for claiming that Mary should be described as the Mother of Christ but not the Mother of God, and sought refuge in the Sassanian Empire, becoming an important theological thinker and eventually a saint of the Church of the East. 

These changes do not appear to have been universally accepted throughout the area claimed by the Church of the East, with a Bishop of Meshmahig being excommunicated in 410 AD, and another being condemned for challenging the unity of the church in the seventh century. Christianity ceased to be a major political power around the Persian Gulf  with the rise of Islam in the seventh century, but the Church of the East still survives today as the Assyrian Church of the East, which is based in the city of Erbil in northern Iraq, and has over 400 000 followers, mostly living in Iraq, Turkey, Syria, Iran, and India, the Ancient Church of the East, which is based in Bagdad, and has about 75 000 followers, mostly in Iraq and India, the Chaldean Catholic Church, which is also based in Bagdad and has over 490 000 followers, mostly in Iraq, but with substantial communities in the United States, Canada, and Australia, and the Syro-Malabar Church, based in Kerala State, India, with about 4..53 million followers, mostly in Kerala and Sri Lanka. 

Early Christian archaeological sites are also known from other areas around the Persian Gulf, including Iran, Kuwait, the United Arab Emirates and eastern Saudi Arabia, although none of these are in locations still inhabited today, and most are younger than the Samahij site, further emphasising the importance of this locality.

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Local transmission of Dengue Fever recorded in Iran for the first time.

The transmission of Dengue Fever within Iran has been demonstrated for the first time in June 2024, according to a press release issued by the World Health Organization on 22 July 2024. The Ministry of Health and Medical Education of Iran reported to cases of the disease had been confirmed by Polymerase Chain Reaction testing at the Pasteur Institute in Bandar Abbas, both in patients from the city of Bandar-Lengheh in Hormozgan Province who had never travelled outside of Iran, and who can therefore be confirmed to have acquired the infection within the country. By 17 July 2024 twelve cases had been confirmed in Bandar-Lengheh among people who had no history of travel outside the country.

This development is not entirely unexpected, as the number of imported cases within Iran has remained steady at about 20 per year between 2017 and 2023, and the Aedes aegypti and Aedes albopictus Mosquitoes, which act as vectors for the disease, are both present in Sistan and Balouchistan, Hormozgan, Bushehr, Khuzastan, and Gilan provinces. In 2024 the number of cases in the country has risen sharply, with 137 reported between 15 May and 10 July.

Dengue is a viral infection transmitted to humans through the bite of infected Mosquitoes and is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas. The primary vectors that transmit the disease are Aedes aegypti Mosquitoes and, to a lesser extent, Aedes albopictus.  These mosquitoes are also vectors of Chikungunya, Yellow Fever and Zika viruses. Dengue is widespread throughout the tropics, with local variations in risk influenced by climate parameters as well as social and environmental factors.

Colour print of the Dengue Mosquito Aedes aegypti (then called Stegomyia fasciata, today also Stegomyia aegypti). To the left, the male, in the middle and on the right, the female. Above left, a flying pair in copula. Emil August Goeldi (1905)/Wikimedia Commons.

Infection with the Dengue Virus can cause a wide spectrum of disease. Ranging from subclinical disease (people may not know they are even infected) to severe flu-like symptoms in those infected. Although less common, some people develop Severe Dengue, which can be any number of complications associated with severe bleeding, organ impairment and/or plasma leakage. Severe Dengue has a higher risk of death when not managed appropriately. Severe Dengue was first recognised in the 1950s during Dengue epidemics in the Philippines and Thailand. Today, Severe Dengue affects most Asian and Latin American countries and has become a leading cause of hospitalisation and death among children and adults in these regions.

Dengue is caused by a Virus of the Flaviviridae family of positive-strand RNA Viruses and there are four distinct, but closely related, serotypes of the Virus that cause Dengue (Dengue Fever Virus-1, Dengue Fever Virus-2, Dengue Fever Virus-3 and Dengue Fever Virus-4). Recovery from infection is believed to provide lifelong immunity against that serotype. However, cross-immunity to the other serotypes after recovery is only partial, and temporary. Subsequent infections (secondary infection) by other serotypes increase the risk of developing Severe Dengue.

A transmission electron micrograph showing Dengue Virus virions (the cluster of dark dots near the centre). Centers for Disease Control and Prevention/Wikimedia Commons.

Dengue has distinct epidemiological patterns, associated with the four serotypes of the Virus. These can co-circulate within a region, and indeed many countries are hyper-endemic for all four serotypes. Dengue has an alarming impact on both human health and the global and national economies. Dengue Fever Virus is frequently transported from one place to another by infected travellers; when susceptible vectors are present in these new areas, there is the potential for local transmission to be established.

The incidence of Dengue has grown dramatically around the world in recent decades. A vast majority of cases are asymptomatic or mild and self-managed, and hence the actual numbers of dengue cases are under-reported. Many cases are also misdiagnosed as other febrile illnesses.

One modelling estimate indicates 390 million Dengue Virus infections per year, of which 96 million manifest clinically (with any severity of disease). Another study on the prevalence of dengue estimates that 3.9 billion people are at risk of infection with dengue viruses. Despite a risk of infection existing in 129 countries, 70% of the actual burden is in Asia.

The number of dengue cases reported to the World Health Organization increased over 8 fold over the last two decades, from 505 430 cases in 2000, to over 2.4 million in 2010, and 5.2 million in 2019. Reported deaths between the year 2000 and 2015 increased from 960 to 4032, affecting mostly younger age group. The total number of cases seemingly decreased during years 2020 and 2021, as well as for reported deaths. However, the COVID-19 pandemic might have also hampered case reporting in several countries.

The overall alarming increase in case numbers over the last two decades is partly explained by a change in national practices to record and report Dengue to the Ministries of Health, and to the World Health Organization. But it also represents government recognition of the burden, and therefore the pertinence to report Dengue disease burden.

Before 1970, only 9 countries had experienced Severe Dengue epidemics. The disease is now endemic in more than 100 countries in the World Health Organization regions of Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. The Americas, South-East Asia and Western Pacific regions are the most seriously affected, with Asia representing about 70% of the global burden of disease.

Not only is the number of cases increasing as the disease spreads to new areas including Europe, but explosive outbreaks are occurring. The threat of a possible outbreak of Dengue now exists in Europe; local transmission was reported for the first time in France and Croatia in 2010 and imported cases were detected in 3 other European countries. In 2012, an outbreak of Dengue on the Madeira islands of Portugal resulted in over 2000 cases and imported cases were detected in mainland Portugal and 10 other countries in Europe. Autochthonous cases are now observed on an annual basis in few European countries.

Iran forms part of the World Health Organization's Eastern Mediterranean Region, which is considered to be at high risk to Dengue Fever epidemics, with many countries having fragile healthcare systems due to conflict and political instability, while other countries where healthcare systems are considered to be stronger are sufferering increased rains due to climate change, leading to a proliferation of the Aedes aegypti and Aedes albopictus Mosquitoes which act as vectors for the disease. 

The countries of the World Health Organization's Eastern Mediterranean Region. Özturk et al. (2024).

Iran is particularly threatened by the presence of both types of Mosquito and a climate favourable to the spread of the disease, as well as a large numbers of visitors from countries where the disease is endemic. The discovery that the disease is being transmitted in the country at this time is particularly alarming as it comes shortly before the annual Arba'in Pilgrimage, which this year will take place in August, with potentially millions of Shiite Muslims from around the world visiting the Shrine of Husayn ibn Ali in the city of Karbala in central Iran.

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Curiosity rover detects elemental sulphur on Mars.

NASA's Curiosity Rover has detected crystals of elemental sulphur on the surface of Mars, the first time sulphur has been detected as a pure element on the planet. The crystals were observed at a location within Gale Crater called Convict Lake on 7 Jun 2024, and form a patch about 12 cm across. The crystals are thought to have been exposed by the rover itself driving over a rock and crushing it several days previously.

A patch of minerals including crystals of pure elemental sulphur on the surface of Mars. The image has been colour enhanced to for the benefit of Human eyes; the rover used an X-ray spectrophotometer to detect the element. NASA/JPL/CalTech/Malin Space Science Systems. 

The presence of sulphur on Mars is hardly surprising not surprising. The element is one of the most common in the universe and has been detected on all planets in the Solar System, as well as meteorites, asteroids, and comets. But most sulphur previously found on Mars has been in the form of sulphate salt evaporites, which formed as lakes and other bodies of water dried out on the surface of the planet long ago.

On Earth, sulphur deposits typically take the form of sulphates (the oxidised form of the mineral) or sulphites (the reduced form) with elemental sulphur forming in sedimentary rocks through the actions of sulphur-reducing micro-organisms in anaerobic (i.e. oxygen free) environments, and in volcanic rocks by the reaction of gaseous hydrogen sulphide and sulphur dioxide. The geology of Gale Crater is dominated by sedimentary deposits, including evaporites, but is generally low in sulphates. 

It is possible that the Convict Lake rock is of volcanic origin, and reached the Gale Crater locality as ejecta. However, the images of the rock resemble the surrounding sedimentary rocks, making it more likely that it is local in origin. This makes it likely that the sulphur has been derived from an original sulphate source in some way, although this does not necessarily imply the presence of sulphur reducing micro-organisms, as in the oxygen-free atmosphere of Mars, abiotic reducing reactions impossible on Earth become far more likely.

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Re-dating the oldest known figurative cave art.

The rock-art left behind by prehistoric cultures has the potential to provide us with insights into the lives of these long-vanished peoples. Dating this art is notoriously difficult. In the past few decades the predominant approach has been the analysis of uranium and its decay products within flowstone layers partially covering ancient art. Flowstone is formed by the deposition of calcium carbonate onto surfaces by evaporating water; typically water that has flowed through limestone deposits then run out onto a surface such as a cave wall or cliff face before evaporating. The most obvious examples of this are stalagmites and stalactites, though many caves have an interior surfaces covered by flowstone. Where these flowstone deposits occur in caves with paintings they will often overlay the artwork, which means that if the flowstone can be dated, then a minimum age for the art can be established (as the art cannot be younger than the flowstone that overlays it).

This method has been used to date ancient art in many parts of the world, including Western Europe, Island Southeast Asia, and Russia. Notably, a hand-stencil in Spain has been dated to 64 800 years before the present, which implies that it must have been made by a Neanderthal artist, although the reliability of the data used in this study has been questioned. The oldest date we currently have for figurative cave art comes from Sulawesi, Indonesia, where an image of a Warty Pig, Sus celebensis, at Leang Tedongnge in the Maros-Pangkep karst has been given a minimum age of 45 500 years.

The methods used to date flowstone samples to date have relied upon dissolving a sample to form a solution, something which will tend to homogenise the sample, averaging the age of multiple layers overlaying a piece of art, and therefore producing a younger age estimation for the art than if the oldest of these layers could be isolated. 

In a paper published in the journal Nature on 3 July 2024, a team of scientists led by Adhi Agus Oktaviana of the School of Humanities, Languages and Social Science at Griffith University, the Pusat Riset Arkeometri of the Badan Riset dan Inovasi Nasional, the Griffith Centre for Social and Cultural Research, and the Center for Prehistory and Austronesian Studies, and Renaud Joannes-Boyau of the Geoarchaeology and Archaeometry Research Group at Southern Cross University, present the results of a study which used laser-ablation uranium-series dating to provide more accurate dates for the Leang Tedongnge image, as well as other examples of cave art in the same region. 

The laser-ablation method enables the targeting of an area 44 μm in diameter, within a laboratory environment. This enables far smaller samples to be collected than with previous methods, which typically involved grinding a sample from the rockface with a rotary tool. With the laser ablation method it is possible to take a polished thin section of rock, and target points upon that, which is both cheaper and less destructive than traditional methods, as well as far more accurate, as it enables specifically targeting the layer of rock directly overlaying the pigment.

Map of the study area. (a) The Indonesian island of Sulawesi, showing the location of the southwestern peninsula (area inside rectangle). (b) South Sulawesi, with the limestone karst area of Maros-Pangkep indicated by blue shading. The locations of cave sites with dated Late Pleistocene rock art were as follows: 1, Leang Bulu’ Sipong 4; 2, Leang Karampuang; 3, Leang Tedongnge; 4, Leang Timpuseng. Oktaviana & Joannes-Boyau et al. (2024).

At the Leang Bulu’ Sipong 4 site in the Maros-Pangkep karst, a 4.5 m wide panel on the rear wall of a cave depicts a number of Human, or Therianthrope (Human-Animal hybrid) figures, interacting with Warty Pigs and Anoas (Dwarf Buffalo), Bubalus sp.. The figures are holding some form of objects, possibly spears or ropes. The artwork may depict a hunting scene, or possibly a visual representation of a myth.

Dated rock art panel at Leang Bulu’ Sipong 4. (a) Photostitched panorama of the rock art panel. Ther, Therianthrope. (b) Tracing of the dated rock art panel showing the results of laser-ablation uranium-series dating. (c) Transect view of the rock art sample BSP4.5 after removal from the artwork, highlighting the paint layer and the three integration zones (ROIs) and associated age calculations. (d) Laser-ablation-multicollector inductively coupled plasma mass spectrometry imaging of the BSP4.5 thorium²³²/uranium²³⁸ isotopic activity ratio. Oktaviana & Joannes-Boyau et al. (2024).

The imigary at Leang Bulu’ Sipong 4 is covered by four distinct speleothems (flowstone deposits), which have previously been dated to minimum ages of 35 100 years, 43 900 years, 40 900 years, and 41 000 years. The new data obtained by Oktaviana & Joannes-Boyau et al. revises these dates to minimums of 27 600 years, 39 600 years, 39 500 years, and 48 000 years. Most of these ages are similar or older to the previously obtained ages, though one younger date was obtained, possibly because Oktaviana & Joannes-Boyau et al. were careful to avoid areas showing clear signs of post-depositional alteration. 

Since the speleothems overlie the rock art, the oldest speleothem must still be younger than the art, giving a minimum age. The art was previously dated to a minimum of 43 900 years old, but Oktaviana & Joannes-Boyau et al.'s data raises that minimum age to 48 000 years, an increase of over 4000 years, older than the previous oldest dated art at Leang Tedongnge.

At the Leang Karampuang site, again in the Maros-Pangkep karst, a ceiling panel depicts three Human or Therianthrope figures interacting with an Animal, probably another Warty Pig, although the preservation here is poor due to surface exfoliation (flakes breaking off the surface of the limestone), and extensive overlying coralloid growths (small nodes of calcite, aragonite or gypsum that form on surfaces in caves). The image executed in red, and comprises the large, Pig-like Animal, 92 x 38 cm, in side view, with an infill pattern of stripes or lines, consistent with depictions of Pigs and other Animals elsewhere in South Sulawesi. There are other Pig depictions within the Leang Karampuang cave, although it is uncertain if they are the same age as the dated example. The Pig is surrounded by three Humanoid figures. The largest of these is 42 v 27 cm and lacks legs; it has both arms extended and appears to have a rod-shaped object in its left hand.  The second figure measures 28 x 25 cm and is located directly in front of the Pig, with its head in front of the Pig's snout. The final figure, measuring 35 x 5 cm, is upside-down relative to the other figures, with its legs splayed out away from the Pig and one hand reaching towards the Pig's head. A possible fourth figure may have once been present between the first and third figures. There are also at least three hand stencils on the same panel, two which appear to be contemporary with the Pig, plus one darker one which is partially overlain by the Pig, and presumably, therefore, pre-dates it.

Oktaviana & Joannes-Boyau et al. collected samples from four coralloid growths, one overlying each of the figures, plus one from the Pig. The oldest date came from the coralloid overlying the second figure, with a minimum age of 51 200 years. The minimum dates from the first and third figures were 18 700 years and 44 000 years respectively, while the coralloid growth from the Pig yielded a minimum age of 31 900 years. Thus, if the figures and Pig do represent a single piece of artwork, as seems likely, then the whole scene can be assumed to have a minimum age of 51 200 years, making it the oldest known piece of figurative art in the world. 

Dated rock art panel at Leang Karampuang. (a) Photostitched panorama of the rock art panel. (b) Tracing of the rock art panel showing the results of laser-ablation uranium-series dating. (c) Tracing of the painted scene showing the Human-like figures (H1, H2 and H3) interacting with the pig. (d) Transect view of the coralloid speleothem, sample LK1, removed from the rock art panel, showing the paint layer and the three integration zones (ROIs), as well as the associated age calculations. (e) Laser-ablation-multicollector inductively coupled plasma mass spectrometry imaging of the LK1 thorium²³²/uranium²³⁸ isotopic activity ratio. Oktaviana & Joannes-Boyau et al. (2024).

Oktaviana & Joannes-Boyau et al.'s method shows that the Leang Bulu’ Sipong 4 art is over 4000 years older than the previously determined age, with a minimum age of 48 000 years, while the Leang Karampuang art is at least 51 200 years old. These dates significantly increase the maximum known age of figurative art. The oldest known art dates from the Middle Stone Age of southern Africa, between 75 000 and 100 000 years ago, but this comprises geometric marks carved into ochre nodules. Figurative art is presumed to have arisen within Africa, and from there to have been carried around the world by migrating Humans, but there is currently no evidence for this, and it cannot be excluded that this form of expression arose in another region and then spread back to Africa.

The South Sulawesi art also challenges to long-standing preconceptions about cave art, which have come about largely from studies based upon the extensive European rock-art record. These are that Humans and/or Human-like figures did not appear in rock art until the very end of the Pleistocene, and the other is that narrative compositions were absent from early rock art. 

Three of the oldest dated rock art panels in the world come from South Sulawesi, Leang Karampuang, at least 51 200 years old, Leang Bulu’ Sipong, at least 48 000 years old, and Leang Tedongnge, at least 45 500 years old, all include figures, and all appear to involve interactions between the figures and one-another and/or Animals which imply a narrative context. Another piece of cave art, at Leang Timpuseng, dated to at least 35 300 years before the present, depicts a Pig standing in a painted line, presumably representing a ground surface. This depiction of composed scenes presumably had some communicative function, allowing the telling of a story through a narrative interpretation of the art, probably in conjunction with oral storytelling. Thus, this cave-art can also be interpreted as evidence of the emergence of a consistent form of mythology, many thousands of years before any such evidence appears in Europe.

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