The Earth approaches aphelion.

The Earth will reach its aphelion, the furthest point in its orbit from the Sun, a distance of 1.017 AU (1.017 times the average distance between the Earth and the Sun) or 152 141 035 km, at 7.55 pm GMT on Thursday 3 July 2025. The Earth's orbit is slightly eccentric and slightly variable, leading to the distance between the Earth and the Sun varying by about 3.4% over time, reaching aphelion early in July each year and perihelion (the closest point on its orbit to the Sun) early in January. The exact distance at aphelion and perihelion each year varies, with this year's aphelion being slightly further from the Sun than last year (2024), when the Earth reached 152 099 970 km from the Sun on Friday 5 July, or next year, when it will only reacha distance of 152 087 778 km on Monday 6 July.

The difference between the Earth's perihelion (closest point to the Sun) and aphelion (furthest point from the Sun). Time and Date.

This is counter intuitive to inhabitants of the Earth's Northern Hemisphere, who often assume that the Earth is closest to the Sun in midsummer, when in fact it is at its furthest away. This is because the tilt of the Earth plays a far greater role in our seasons than the distance from the Sun, and the Northern Hemisphere has just passed its Summer Solstice, i.e. the point at which the North Pole was pointing as close to the Sun as it ever gets, so that the Northern Hemisphere is currently getting much more sunlight than the Southern. The Earth's surface receives about 7% less sunlight at aphelion to at perihelion, but this is far less than the seasonal variation caused by the tilt of the Earth (23% in each hemisphere).

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Ptychognathus dajie: A new species of Pom Pom Crab from East and Southeast Asia.

The genus Ptychognathus comprises 32 species of brackish-water Crabs found in estuaries and the lower parts of river systems across the Indo-Western Pacific region. They are known as Pom Pom Crabs in the aquarium industry because of the clusters of fine setae (hairs) on their claws (although they are widely traded as freshwater Crabs rather than brackish-water Crabs). Most species of Ptychognathus have very localised distributions, being found on a single island, estuary, or river system, although one species, Ptychognathus barbatus, is found over an extremely wide area, including Japan, Taiwan, China, the Philippines, Malaysia, Indonesia, and New Caledonia. However, as part of a PhD thesis completed in 2006, carcinologist Ngan Kee Ng, then a graduate student at the National University of Singapore, examined the systematics of Ptychognathus barbatus, concluding that the populations described under this name represented two, rather than a single, species. Ng went on the lead a highly successful research group, specialising in the study of Crabs, for many years, before passing away in 2022, but never formerly published her PhD thesis. This means that all taxonomic nomenclature presented in the thesis is considered unusable under the terms of the International Code of Zoological Nomenclature, even if specialists in the field believe it to be generally correct.

In a paper published in the journal ZooKeys on 27 June 2025, Jhih-Wei Hsu of the Department of Life Science at the National Chung Hsing University, Jose Christopher Mendoza, of the Lee Kong Chian Natural History Museum at the National University of Singapore, and Hsi-Te Shih, also of the Department of Life Science, and of the Global Change Biology Research Center at the National Chung Hsing University, build upon Ngan Kee Ng's work, to formally divide Ptychognathus barbatus into two, and describe a new species.

The new species is named Ptychognathus dajie, where 'dajie' means 'elder sister', a title often used for women in leadership roles in Chinese-speaking countries, in honour of Ngan Kee Ng. A genetic analysis of museum specimens suggests that this species is found in estuaries and tidally-influenced portions of rivers, in Malaysia, Japan, Taiwan, China, Philippines, Indonesia, and Thailand. Surprisingly, Ptychognathus dajie is not particularly closely-related to Ptychognathus barbatus, instead forming a sister species to Ptychognathus guijulugani, a species found on Negros and Mindanao islands in the Philippines, placing it close to the base of the Ptychognathus family tree.

A neighbor-joining tree for species of Ptychognathus, based on the COI gene. Probability values at the nodes represent support values. Only values greater than 50% are shown. Hsu et al. (2025).

Specimens of Ptychognathus dajie have almost square carapaces, slightly wider than they are long, with a glossy upper surface and a concave frontal margin. The lower part of the claw is covered by long, thin setae; claws are larger in males than in females. The largest male specimen found was 20.2 mm wide and 16.8 mm long, the largest female found was 16.8 mm wide and 14.5 mm long. Colour is extremeley variable, and tends to match the substrate upon which the Crabs live.

Ptychognathus dajie. (A), (B) Holotype male (13.2 × 11.6 mm, ZRC 2024.0072); (C), (D) Paratype female (10.6 × 9.2 mm, NCHUZOOL 17356); (E) Male (NCHUZOOL 17341); (F) Male (NCHUZOOL 17343); (G), (H) Males (NCHUZOOL 7342). (A), (C) Dorsal view; (B), (D) Ventral view; (A)–(D) Preserved specimens; (E)–(H) Colour in life. Hsu et al. (2025).

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Coesite in Australasian microtektites.

Tektites and microtektites (i.e. very small tektites) are pieces of glass formed as ejecta from impact events. They are found in strewn fields which may extend thousands of kilometres from the original impact site. Current models of their formation suggest that they form from the material being impacted, as a spray of droplets of material melted by the rapid heating of the impact of an asteroid or comet fragment at speeds of over 3 km per second. However, while we have a general picture of how these events unfold, much of the detail is unclear. For example, many tektites from the Australasian Strewn Field contain inclusions of material, which have for a long time been accepted as fragments of the original rock trapped within a matrix of glass melt. This view has recently been challenged by an alternative hypothesis, that the matrix material may be a condensate from rock which was vapourised during the impact, and that the most distant microtektites, from Antarctica, may have formed from material which was vapourised by heat from the atmospheric shock wave before the impacting object touched down. This would help to explain why the Antarctic tektites lack inclusions, whereas in those from close to the presumed impact site, in Southeast Asia, they may make up as much as 5% of the mass of the tektite.

In a paper published in the journal Geology on 3 June 2025, Luigi Folco, Enrico Mugnaioli, and Matteo Masotta of the Dipartimento di Scienze della Terra and the Centro per la Integrazione della Strumentazione  at the Università di Pisa, and Billy Glass of the Department of Geosciences at the University of Delaware, present the results of a study of four microtektites from the Australasian Strewn Field.

The Australasian Strewn Field covers about 15% of the Earth's surface, and formed about 800 000 years ago through the hypervelocity impact of a chondritic body. It is the youngest and largest of five known Cainozoic strewn fields, with the others  being the North American Strewn Field, which is about 34.86 million years old (Eocene), the Central European Strewn Field, which is about 14.7 million years old (Miocene), the Côte d'Ivoire Strewn Field, which is 1.07 million years old (Pleistocene), and the Central American Strewn Field, which is about 820 000 years old (Pleistocene). No crater has been found which can be linked to the Australasian Strewn Field, although high pressure phases have been found in tektites and other ejecta which strongly indicate that the formation of the field was linked to a crater-forming event, probably in Southeast Asia or the surrounding seas, or possibly in northwest China.

Several previous studies have established that Australasian microtektites show Australasian microtektites with distance from the presumed impact site. For this reason Folco et al. selected three microtektites from deep-sea locations close to the putative impact site, SO95-17957-2,04 and ODP 1144A,01 from the South China Sea, and ODP 769A,15_26 from the Sulu Sea, and one, FRO 2.9-1, from a site in the Transantarctic Mountains. These samples were analysed using a combination of optical microscopy, microanalytical scanning electron microscopy, dual beam microscopy, and microanalytical transmission electron microscopy coupled with three-dimensional electron diffraction.

The Australasian Strewn Field microtektites from deep-sea settings are spheroid in shape and dark brown in colour, with a transluscent laustre and numerous inclusions. They range from 350 to 700 µm in maximum elongation, and dominated by silica phases, compositional bands (schlieren), and vesicles. SO95-17957-2,04 and ODP 1144A,01 have normal composition, whereas ODP 769A,15_26 has a high nickel content (232 µg/g). The Antarctic specimen is a pale-yellow transparent sphere 485 µm in diameter with normal composition,  devoid of vesicles, with only one microscopic silica-rich inclusion,  a few tens of micrometres across with diffuse boundaries. This is considered to be fairly typical of Australasian microtektites from Antarctica, although it is the only Antarctic Tektite known with a silica-rich inclusion.

Micrographs of sectioned Australasian microtektite SO95-17957-2,04. (A) Microtektite is pale brown with teardrop shape. It shows folded schlieren (Sch), microscopic vesicles (V), and mineral inclusions (arrowed). Thick white arrow points to inclusion studied in this work. Optical microscope image, plane polarized light. (B) Same petrographic features as in A in backscattered electron (BSE) image. White rectangle outlines field of view of image in panel C. (C) Close-up BSE image of a quartz (Qtz) + lechatelierite (L) + coesite (Coe) inclusion. Silica phases in the inclusion can be distinguished by their different electron density contrast, which increases from lechatelierite to quartz to coesite. A diffusive boundary layer (Dbl) discontinuously surrounds the inclusion. Dashed line traces location of the dual beam microscopy section. Folco et al. (2025).

Examined under the scanning electron microscope, the microtectites from deep-sea environments were found to contain a inclusions which comprise a matrix of vesiculated lechatelierite (shock-fused quartz glass), with variable proportions of microscopic quartz grains and submicroscopic coesite grains (coesite is a form of silica dioxide which only forms at very high pressures). These inclusions are surrounded by diffusive boundary layers a few microns thick. The quartz grains tend to be arranged around the edge of the inclusions, and themselves be surrounded by grains of coesite, while the interior of the inclusions tends to be dominated by lechatelierite. The quartz grains tend to be anhedral and heavily fractured, while the coesite grains comprise  polycrystalline aggregates of nanoscopic crystals set in silica glass. Towards the interior of the inclusions, the coesite grains become smaller, and comprise a higher proportion of silica-glass. The interior part of the inclusions, while dominated by vesiculated lechatelierite, contain many of these low-coesite 'coesite grains'. All three of these microtektites have essentially the same structure, although ODP 769A,15_26 and ODP 1144A,01 are more vesiculated than SO95-17957-2,04.

The Austrolasian microtektite ODP 769A,15_26. (A) Optical microscope, plain polarised image of the sectioned spherule, showing dark brown colour, prolate shape, schlieren, microscopic vesicles and transparent to partly opaque mineral inclusions. (B) The same textural and compositional features seen under scanning electron microscope, back scattered electron imaging mode. The white rectangle outlines the area of the next panel. (C) Back scattered electron view of a quartz + lechatelierite + coesite inclusion. Silica phases in the inclusion can be distinguished by their different contrast, which increases from lechaterlierite to quartz to coesite. The dashed line marks the position of the dual beam film featured in the next panel. (D) Transmission electron microscope image of a dual beam section showing tens of submicroscopic anhedral coesite grains dispensed in vesiculated lechatelierite. Inset: a close-up view of one coesite grain showing characteristic (010) polysnthetic twinning. The dashed line in panel (C) traces the location of the DB section seen in panel (D). Abbreviations: sch, schlieren; V, vesicle: Qtz, quartz; Coe, coesite; L,  lachatelierite. Thin white arrows indicate inclusions; the thick white arrow indicates the coesite bearing inclusion studied in detail. Folca et al. (2025). 

At the edge of the inclusion in microtektite SO95-17957-2,04 studied with dual beam microscopy, coesite could be seen forming euhedral crystals which overgrow the quartz grains. Towards the lechatelierite core of the inclusion, the coesite can be seen to be segmented in submicroscopict abular grains by a fine network of silica glass veinlets producing the polycrystalline aggregates. These coesite grains show a tartan-like texture similar to that seen in microcrystalline coesite aggregates in silica glass found in shocked porous sandstones. The proportion of silica glass between the segments of coesite within the grains increases towards the core of the inclusion, where anhedral nanoscopic grains of coesite can be found floating free within the lechatelierite core. 

Transmission electron microscopy images of electron transparent dual beam microscopy section of quartz + lechatelierite + coesite inclusions from Australasian deep-sea sediment microtektites. (A) Whole section of coesite-bearing inclusion in microtektite SO95-17957-2,04. White rectangle outlines area featured in panel (B). (B) Textural relationships between quartz (Qtz), coesite (Coe), and lechatelierite (L). Few microscopic quartz relicts at periphery of inclusion are overgrown by euhedral coesite grains with polysynthetic (010) twinning. Toward the core of the inclusion dominated by lechatelierite, coesite is segmented by a network of silica glass veinlets producing polycrystalline aggregates, which then disaggregate with increasing amount of silica glass. White rectangle traces area featured panel (C). (C) Close-up view of euhedral coesite (top) adjacent to polycrystalline aggregate with subhedral outline (bottom). (D) Reconstruction of reciprocal space sampled by three-dimensional electron diffraction from a twinned coesite grain. This picture displays a view of the diffraction volume along hh0 vector. Projections of 00l* and hh0* vectors are indicated. (E) Nanoscopic anhedral coesite grain with embayed crystal boundaries embedded in lechatelierite in microtektite ODP 769A,15_26. (F) Several nanoscopic anhedral coesite grains dispersed in an area of about 2 µm² of lechatelierite in microtektite ODP 1144A,01. Broken-apart grains are arrowed. Vesicle (V). Folco et al. (2025).

Inclusions in the Transantarctic Mountains tektite, FRO 2.9-1, could be seen to be featureless glass undr the scanning electron microscope, with diffuse contact with the glass matrix of the tektite. This host matrix was composed largely of silica, with smaller amounts of aluminium oxide, iron oxide, magnesium oxide, titanium oxide, calcium oxide, potassium oxide, and sodium oxide. The transmission electron microscope confirmed that this composition did not vary through the tektite.

The Australasian microtektite ODP1144A,01. (A) Optical microscope, plane polarized image of the sectioned particle. It is a brown glass broken tear drop. Few microscopic vesicles, and faint schlieren and few mineral inclusions are visible. (B) The same textural and compositional features seen under the scanning electron microscope, back scattered electron imaging mode. The white rectangle outline the area of the next panel. (C) Back scattered electron close-up view of a highly vesiculated quartz + lechatelierite + coesite inclusion. Silica phases in the inclusion can be distinguished by their different contrast, which increases from lechatelierite, to quartz to coesite. The dashed line marks the location of the dual beam film featured in the next panel. (D) Transmission electron microscope image of a dual beam section showing a polycrystalline aggregate of submicroscopіс anhedral coesite grains set in lechatelierite. The dashed line in panel (C) traces the location of the dual beam featured in panel (D). Abbreviations: Sch, schlieren; V, vesicle; Qtz, quartz; Coe, coesite; L, lechatelierite. Thin white arrows indicate inclusions; The thick white arrow indicates the coesite bearing inclusion studied in detail in this work. Folco et al. (2025).

Coesite is a fairly common mineral in settings where quartz-bearing rocks have been subjected to shock metamorphism. Whether it occurs as a metastable phase in shocked rocks that have experienced peak pressures and temperatures much beyond its stability field (i.e. pressures in excess of 10 gigapascals and temperatures in excess of 2700°C) has been debated since the 1960s. There are three current models of coesite formation. The first suggests that coesite may form in a silica melt as pressure decreases rapidly following an impact event. The second model suggests that coesite forms within silica glass at very high pressures, without any melting actually occurring. The third model also sees coesite forming within solid quartz, although this time in porous sandstones as the peak of the pressure wave passes through. 

In the Australasian microtektites, coesite appears to be overgrowing quartz crystals, which Folco et al. interpret as a sign that they formed while the matrix was under high pressure, but still in a solid state. However, the adjacent polycrystalline aggregates consisting of submicroscopic elongated grains of coesite pervaded by silica glass veinlets do indicate that some melting has occurred, possibly of the coesite itself, and the nanoscopic anhedral coesite grains dispersed in the surrounding lechatelierite as evidence to significant melting and dispersal of coesite aggregates. In this scenario the coesite nanocrystals re relicts formed by the melting and dispersal of larger, pre-existing coesite crystals during the shock-metamorphism process.

The presence of coesite in the Australasian microtektites provides information about the location of the putative Southeast Asian impact site. Coesite forms at very high temperatures, but is unstable unless cooled rapidly; it has been estimated that after 10 seconds at very high temperatures then all coesite will have transformed into cristobalite. Since there is no cristobalite in the Australasian microtektites, it can be inferred that quenching was much more rapid in this instance, possibly aided by reactions such as the transformation of quartz and coesite melt into lechatelierite, which is endothermic (absorbs heat).

The abundant quartz and lechatelierite inclusions found in Australasian tektites are generally accepted to be indicative of a quartz-bearing target rock which underwent melting and fusion during the impact event. The boundary between these inclusions and the glass matrix of the microtektites shows varying levels of diffuseness, suggesting that these particles underwent varying levels of digestion into the matrix. The presence of coesite in tektites from deep-sea environments off Southeast Asia supports the idea that these tektites are from close to the impact site, and represent melt spherules formed by compression and depression of the impacted rock during crater formation. The absence of coesite from the Transantarctic Mountains tektite, FRO 2.9-1, could imply that this remained at higher temperatures for longer, allowing all coesite to be reabsorbed, possibly implying this tektite was exposed not just the heat from the origianal impact, but also from deceleration in ambient air or atmospheric re-entry. This would explain the near-total absence of inclusions in these tektites, and also the homogenous distribution of elements and isotopes observed. There is no structure in the microtektite indicative exposure of high pressure, which supports the idea that these more distant microtektites formed by rapid heating of the target rock prior to the actual impact.

The presence of pressure-related minerals and structures in microtektites from the South China and Sulu seas strengthens the argument for a Southeast Asian impact event.

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Neotrygon romeoi: A new species of Blue-spotted Maskray from Fiji.

Maskrays, Neotrygon spp., are a group of Stingrays, Dasyatidae, found in the Indian Ocean and west Pacific. They get their name from a distinctive coloured marking around the eyes, which resembles a mask, but have a number of other distinctive features, including short tails with well developed dorsal fins, small mouths with enlarged cuspid teeth, and large pectoral fins with a single row of thorns along their dorsal midline. All Maskrays were formerly thought to belong to a single widespread and somewhat variable species, Neotrygon kuhlii, but genetic studies have shown that there are in fact a range of species, with sixteen species described to date, nine of them since 2016, and thirteen of these belonging to a species-complex known as the Blue-spotted group.

In a paper published in the Journal of Fish Biology on 9 June 2025, Kerstin Glaus of the Institute of Marine Resources of The University of the South Pacific, William White and Helen O'Neill of the Australian National Fish Collection, Sarah Thurnheer of the Ecosystems and Landscape Evolution at Eidgenössische Technische Hochschule Zurich, and Sharon Appleyard, also of the Australian National Fish Collection, describe a new species of Maskray from Fiji.

Fiji has long been known to be home to a population of Blue-spotted Maskrays, which are the most widely traded Ray in local fish-markets, but which have never been the subject of a taxonomic study. Glaus et al.'s study was carried out using specimens purchased in Suva Fish Market on Viti Levu Island or obtained from local fishermen. No Rays were killed specifically for the study. A genetic analysis found that these specimens all belonged to a single species, and that this species was previously unidentified, and was a sister species to the previously described Neotrygon kuhlii from the Solomon Islands.

Glaus et al. name this new species Neotrygon romeo, in honour of the late Romeo Glaus, father of Kerstin Glaus, in recognition of his lasting inspiration, enduring support and deep respect for nature. Specimens of Neotrygon romeo have quadrangular disks, weakly convex at the front, and broader than they are long. They range from 310 to 397 mm in width and from 80.6 to 84.2 mm in length, or from 176.9 to 213.1 mm in length including the tail. A single row of thorns is present on the midline. There are two tail stings. Living specimens are beige-to-medium brown, with a slight greenish tinge. The disk has a sparse scaterring of spots, these having a white centre and a diffuse-edged dark-grey to blackishouter ring. There is also a scaterring of smaller, all black, spots. A dark 'mask' is present across the eyesm, and a pair of larger circular or irregular dark brown blotches behind the spiracules. The underside is white. The tail has a bluish tinge, and has irregular black and white bands towards the tip.

Dorsal (a) and lateral (b) view of preserved Neotrygon romeoi holotype (CSIRO H 9640–06, female 379 mm disc width) from Tailevu Province, east Viti Levu Island, Fiji. Scale bar is 50 mm. Glaus et al. (2025).

Neotrygon romeo appears to be common around the islands of Fiji, and is found on various substrates, including sandy-bottom areas, seagrass beds, muddy-sandy areas with and without sea-grass, and coral reefs, from the tidal zone to depths of about 23 m. Individuals are generally solitary, but have been spotted in groups of up to five. Glaus et al. recommend that due to the species restricted range, high catch rate, and unknown life-history, it should be considered for legal protection by Fiji's Endangered and Protected Species Act, which con-serves biodiversity by regulating trade, protection and management of species at risk or endemic to Fiji.

Live colouration of Neotrygon romeoi from around Fiji: (a) Lautoka, mixed rocky and sand habitat. (b) Near South Sea Island, rocky reef. Drawaqa Island, Yasawas on sand flat with some seagrass in about 18 m of water. (d) Suva foreshore, on seagrass in about 20 cm of water. (e) Mana Island, over seagrass. Leon Perrie, Jack Crosbie, Robert Macfarlane, Tom Vierus, and Floyd Hayes in Glaus et al. (2025).

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The Northern Solstice.

The Northern) Solstice will fall on Saturday 21 June this year (2025), the day on which the Sun rises highest in the sky and the longest day of the year in the Northern Hemisphere (where it is the Summer Solstice) and the day on which the Sun rises lowest in the sky and the shortest day in the Southern Hemisphere (where it is the Winter Solstice). Up until this date the days have been growing shorter in the Northern Hemisphere and longer in the Southern Hemisphere since the Southern Solstice in December last year (which is the Summer Solstice in the Northern Hemisphere and Winter Solstice in the Southern Hemisphere), but after it the situation will be reversed, with days growing steadily longer in the Northern Hemisphere and shorter in the Southern Hemisphere until the next Southern Solstice in December. 

The solstices are entirely a product of variation in the Earth's rotation on its axis, which is at an angle of 23.5° to the plain of the Earth's orbit about the Sun. This means that in December the Earth's Southern Pole is tilted towards the Sun, while the Northern Pole is tilted away from it. This means that around the Southern Solstice the Southern Hemisphere is receiving radiation from the Sun over a longer part of the than the Northern, and at a steeper angle (so that it to pass through less atmosphere to reach the planet), creating the southern summer and northern winter.

The tilt of the Earth at the Northern Solstice. Wikimedia Commons.

The solstices are fairly noticeable astronomical events, and tied to the seasons which govern the life cycles of life on Earth, and they have been celebrated under different names by cultures across the globe, but most notably by those at higher latitudes, who are more profoundly affected by the changes of the seasons.

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