Antarctica's Blood Falls and the Hill Tracts' 'Blood Fruit' in Focus

Two very different red things were being talked about in Bangladesh at the start of June 2026. One is Blood Falls, a stream of salty, iron-rich water that seeps from the tongue of Taylor Glacier in Antarctica and stains the white ice a rusty red. The other is a wild climber of the Chittagong Hill Tracts whose ripe fruit is filled with blood-red juice and which hill people and traders call rokto fol, or blood fruit. A Jagonews24 feature published on 3 June 2026 brought the two together. This report sets out what scientists had established about the Antarctic falls by that date, and what researchers, agriculture officials and traders had said about the fruit, whose demand in Rangamati, Chattogram and Dhaka had risen after posts on social media.

Blood Falls is not in West Antarctica, as some accounts say, but in Victoria Land in East Antarctica. It is an outflow of salt water tinted by iron from the end of Taylor Glacier, which flows onto the ice-covered surface of West Lake Bonney in Taylor Valley, one of the McMurdo Dry Valleys. Taylor Glacier is about 65 kilometres long. It is an outlet glacier of the East Antarctic Ice Sheet, flowing from the polar plateau of Victoria Land into the western end of Taylor Valley, where a small section of it ends in Lake Bonney.

The McMurdo Dry Valleys are a series of largely snow-free desert valleys on the coast of Victoria Land, west of McMurdo Sound and the Ross Sea. Together they cover about 4,500 square kilometres and form the largest ice-free region of Antarctica. They are classed as a cold desert, among the coldest and driest places on Earth: precipitation averages around 100 millimetres a year, almost all as snow, and katabatic winds, cold dense air pulled downhill by gravity, scour away snow and moisture. The mountains around the valleys hold back the ice of nearby glaciers. Even so, the region holds more than 6,000 lakes and ponds, fed for a few weeks each summer by meltwater streams from the glaciers. The valleys lie within the McMurdo Dry Valleys Antarctic Specially Managed Area, in which activity is managed under the Antarctic Treaty system.

Lake Bonney, into which the falls seep, is a saline lake with a permanent ice cover about 3.7 to 4.6 metres thick. It is 7 kilometres long and up to 900 metres wide, and a channel only 50 metres wide divides it into East Lake Bonney (3.32 square kilometres) and West Lake Bonney (0.99 square kilometres). The lake was first visited by the British National Antarctic Expedition of 1901 to 1904 and was named during Robert Falcon Scott's expedition of 1910 to 1913 after Thomas George Bonney, professor of geology at University College London.

The red deposit was found in 1911 by the geologist Thomas Griffith Taylor, after whom the glacier and the valley are named. Taylor was born in England in 1880, moved with his family to New South Wales in Australia at the age of 13 and studied at the University of Sydney. Scott appointed him senior geologist of the Terra Nova Expedition of 1910 to 1913. In January 1911 Taylor led a geological party to the coast west of McMurdo Sound, in the area between the Dry Valleys and the Koettlitz Glacier, and his team produced the first maps and geological interpretations of large parts of the region.

The glacier itself had been seen earlier, by the British National Antarctic Expedition of 1901 to 1904, which took it for part of the Ferrar Glacier. Taylor's Western Journey party of the 1910 expedition found that the upper and lower parts of what was then called the Ferrar Glacier were two glaciers joined side by side, and Scott named the upper one after Taylor. The early explorers thought the red colour came from red algae. Later work showed that it comes from iron, not algae.

The water does not leave the glacier red. It comes out clear and turns crimson within moments. The brine beneath the glacier holds dissolved ferrous iron (iron in its reduced, more soluble form) and almost no oxygen. When it reaches the surface and meets the air, the iron is oxidised, much as iron rusts, and poorly soluble iron oxides and hydroxides are left on the ice, staining it red.

A study published on 30 May 2022 in Frontiers in Astronomy and Space Sciences, by Elizabeth Sklute, Jill Mikucki, Darby Dyar, Peter Lee, Ken Livi and Sarina Mitchell, analysed samples from the falls with a wide range of laboratory techniques. It found the deposits to be dominated by the carbonate minerals calcite and aragonite, with quartz, feldspar, halide and clay minerals, and found no strong evidence of crystalline iron oxide. Instead, it found iron- and chlorine-rich amorphous nanospheres. The authors concluded that the red colour arises when dissolved iron in the subglacial fluid is oxidised on contact with air and forms nanospheres of amorphous, mixed-valent iron material, with the colour also influenced by other ions in them.

Johns Hopkins University explained the finding in June 2023. Ken Livi, a research scientist in its department of materials science and engineering, not a physicist, as earlier reports had it, examined solids from the water with transmission electron microscopes. He found an abundance of tiny iron-rich nanospheres, about one hundredth the size of a human red blood cell. "As soon as I looked at the microscope images, I noticed that there were these little nanospheres and they were iron-rich, and they have lots of different elements in them besides iron: silicon, calcium, aluminum, sodium, and they all varied," Livi said in the university's release.

He said the nanospheres had been missed because earlier work assumed a mineral was responsible. "In order to be a mineral, atoms must be arranged in a very specific, crystalline, structure. These nanospheres aren't crystalline, so the methods previously used to examine the solids did not detect them," he said. The samples came from the most recent Antarctic expedition of Jill Mikucki, a University of Tennessee microbiologist who had studied Taylor Glacier and Blood Falls for years, and were sent to Johns Hopkins with the astronomer Darby Dyar of Mount Holyoke College.

The salt water comes from a subglacial pool of unknown size under about 400 metres of ice, several kilometres from the small outlet at the falls. It is thought to be ancient seawater left from a time when the sea reached into the valley; as pure ice formed and pushed out its salt, the trapped water became a brine with two to three times the salinity of average seawater. Unlike most Antarctic glaciers, which are frozen to their beds, Taylor Glacier is thought not to be frozen to the bedrock beneath this brine, probably because of the salt.

In April 2017 a team led by Jessica Badgeley, with Erin Pettit, Chris Carr, Slawek Tulaczyk, Jill Mikucki and W. Berry Lyons, reported in the Journal of Glaciology how the brine reaches the falls. Using radio echo sounding, they mapped a zone of brine inside the ice upstream of Blood Falls, elongated in the direction of ice flow. They estimated that more than 13 per cent of the ice volume was brine within 2 metres of the centre of this zone, and that brine could still be detected up to 45 metres away along some lines. The authors inferred a network of crevasses at the base of the glacier through which pressurised brine is pushed into the ice and routed towards the falls. The brine stays liquid, even though the mean annual air temperature there is minus 17 degrees Celsius, because freezing releases latent heat and because of its high salt content.

In December 2014 Mikucki and colleagues used a probe called IceMole, designed by a German collaboration, to melt into the glacier and sample the brine that feeds the falls directly. The samples showed a brine at minus 7 degrees Celsius, rich in iron (3.4 millimoles per litre) and containing about 8 per cent sodium chloride. Earlier accounts that a lake lay in the area about 2 million years ago, and that University of Alaska Fairbanks researchers found the falls had flowed for 1.5 million years, mix up two separate findings: the 2009 estimate of how long the brine had been sealed off, described below, and the 2017 study of how the brine moves.

In April 2009 Jill Mikucki and colleagues reported in the journal Science that an active community of microbes cycles sulphur in the sulphate-rich, ancient marine brine beneath Taylor Glacier, using ferric iron as the final acceptor of electrons in place of oxygen. Because there is no photosynthesis under the ice, the supply of organic carbon is very limited, and the result is a brine that is free of oxygen but not sulphidic. The authors wrote that these linked processes let the microbes grow in long isolation, and that the system shows how similar oceans starved of organic matter, such as those of the Neoproterozoic era, could have built up dissolved iron.

Mikucki has said that water samples from the falls contained at least 17 different types of microbes and almost no oxygen. The same 2009 work estimated that the subglacial pool was sealed off between 1.5 and 2 million years ago, turning it into a kind of time capsule. From the brine sampled in 2014, scientists isolated a cold-loving, salt-tolerant bacterium of the genus Marinobacter; other bacteria identified there include Thiomicrospira and Desulfocapsa species. "There are microorganisms that have been existing for potentially millions of years underneath the saline waters of the Antarctic glacier. These are ancient waters," Livi said in 2023.

Researchers value the site because it is the only known place in Antarctica where material from beneath a glacier comes to the surface where it can be studied, without drilling deep boreholes that could contaminate an untouched environment. Livi came to the problem as a specialist in planetary materials: Mikucki's team had analysed Blood Falls samples with the same kinds of instruments used by rovers on Mars. "Our work has revealed that the analysis conducted by rover vehicles is incomplete in determining the true nature of environmental materials on planet surfaces," he said, adding that a transmission electron microscope would be needed but could not yet be placed on Mars.

Blood Falls lies inside one of the most studied polar deserts. The McMurdo Dry Valleys Long Term Ecological Research project was established in 1992 as part of the US National Science Foundation's LTER programme to study how physical, chemical and biological processes shape the ecosystems of the valleys' soils, streams, glaciers and ice-covered lakes. Its automatic weather network includes stations on the shores of Lake Bonney and on Taylor Glacier, and Lake Bonney is one of the project's main study lakes. A green alga, Chlamydomonas priscuii, is known only from this lake.

The red falls are therefore a well-documented natural phenomenon rather than a mystery without an answer. Earlier accounts that tourists crowd the valley to see them are not supported by the sources: the falls lie in a remote part of the Dry Valleys, inside the specially managed area, and the work described here was done by scientific field teams.

In Bangladesh, meanwhile, a wild fruit of the Chittagong Hill Tracts had been drawing attention since spring. Prothom Alo reported on 15 May 2026 that demand for the fruit had multiplied after food vloggers posted videos and pictures of it on Facebook, and some doctors posted videos about its qualities. Seen from a distance, its bunches look like hanging grapes; the fruits are somewhat larger, green when unripe and blood red when ripe, with a sour-sweet taste. Bengali speakers in the plains call it rokto fol (blood fruit); the Chakma call it rosko and the Tripura taithak (also reported as taichok); other names include rokto gota and lalgula, and in Hindi it is called khoon phal.

Jagonews24 reported that at the start of the 2026 season the fruit had sold for more than Tk 400 a kilogram in markets in Dhaka and Chattogram. Prothom Alo's May report gave prices from Rangamati: a fruit seller at Banarupa bazar said a kilogram fetched Tk 600 to 700 at the start and end of the season and Tk 300 to 400 in the middle, that he sold 40 to 50 kilograms a day, and that on some days 300 to 400 kilograms were sent outside Rangamati. The deputy director of the Department of Agricultural Extension (DAE) in Rangamati told the paper that the fruit had sold for Tk 700 to 800 a kilogram the previous year and for Tk 250 to 400 that year, as more fruit had come to market: more than twice as much as the year before.

The same official said there was still no formal record of production, as the fruit comes mainly from hill forests, and that the DAE had no formal programme for it, though individual growers were being encouraged. He said the plant is a climber whose stem becomes woody, that its fruit season runs from the last week of April to June, and that plants grown from vines brought in from the forest begin fruiting within four to five years. A farmer in Naniarchar upazila told Prothom Alo that he had planted vines from the forest on his land 12 to 15 years earlier and now had about 15 plants yielding 300 to 400 kilograms a year. Two years earlier, in June 2024, Prothom Alo had reported vines being sold for Tk 200 to 300 each at Banarupa and other Rangamati markets so that buyers could raise seedlings, and a DAE deputy director had said that research was needed before commercial cultivation.

The blood fruit is Haematocarpus validus, a woody climber of the moonseed family, Menispermaceae, a family of about 81 genera and 440 species found mostly in the lowland tropics. Indian researchers describe it as an underutilised fruit of tropical Asia. According to Down To Earth (1 November 2018), it is popular among tribal communities in the north-eastern states of India, the Andaman and Nicobar Islands and Bangladesh. In Bangladesh it grows in natural forests of the Chittagong Hill Tracts, the country's only extensive hill area, about 13,184 square kilometres in the south-east, now divided into Rangamati, Khagrachhari and Bandarban districts. The plant flowers once a year and its main fruiting season is April to June. The fleshy part between skin and seed is full of red juice, which gives the fruit its name, and fruits from the Andaman Islands are generally darker than those from elsewhere.

Laboratory studies published before 2026 describe what the fruit contains. A 2019 study by Pooja Bohra and colleagues at ICAR-Central Island Agricultural Research Institute in Port Blair, in the Journal of Food Science and Technology, found pulp with total soluble solids of 17 degrees Brix, an acidic pH of 3.01, total phenolics of 13.44 milligrams gallic acid equivalent per 100 grams of fresh pulp, and 8.76 milligrams of total anthocyanins (red pigments) per gram of fully ripe pulp, with pelargonidin the main anthocyanin. The authors called it a potential candidate for the food and dye industries. A 2021 study in the same journal reported that the fruit is rich in iron (57.29 milligrams per 100 grams of dry weight), has a very high ratio of potassium to sodium, and contains quinic acid. Prothom Alo's May report also cited a study of fruit from five hill areas of Meghalaya, published in 2025 in the Journal of Agriculture and Food Research, which found up to 1.5 per cent protein and up to 1,890 milligrams of potassium per 100 grams, high levels of polyphenols and flavonoids, the sweetest and highest-yielding fruit at about 300 metres in the West Garo Hills, and no harmful effects in a toxicity test on rats.

Posts on social media promoted the fruit as boosting immunity, aiding weight loss and protecting the heart and skin. These claims come from posts and vendors, not from any health authority, and the studies above measured what the fruit contains, not its effect on people's health. The DAE official quoted in May said no major scientific study of its nutritional value had yet been done in Bangladesh. Anyone thinking of using the fruit for a health condition should ask a doctor.

Because the plant grows wild and its fruit has long been gathered from forests, researchers have warned about its survival. Down To Earth reported in November 2018 that indiscriminate harvesting had affected natural regeneration and that the species was considered critically endangered. Researchers from ICAR-Central Island Agricultural Research Institute in Port Blair, the ICAR Research Complex for North Eastern Hill Region at Barapani and the College of Agriculture in Tripura developed a standard nursery protocol for raising it. Working with fruit from the Middle Andaman Islands and Tripura, they found that the seeds had dormancy problems that had to be treated to raise healthy seedlings in numbers. The findings were published in Current Science in September 2018.

Pooja Bohra, a member of that team, told Down To Earth: "We are already distributing seedling to farmers in Andaman and Nicobar Islands to promote commercial scale cultivation." The team said the gene pool in the Andaman Islands could be lost to natural calamities and that promoting cultivation could help conserve the species. In a later study, published in July 2020 in the Current Agriculture Research Journal, Bohra, Ajit Arun Waman and R. Karthika Devi found that sowing seeds in vermicompost raised germination to 69 per cent, significantly better than sand or soil mixed with vermicompost. Researchers have also studied the fruit's red pigment as a natural food colour and dye for handicrafts.

In Bangladesh, the Rangamati DAE deputy director told Prothom Alo in May 2026 that the plant should be regarded as endangered and that conservation was urgent, even as hill farmers were bringing vines from the forest to plant on their own land. Jagonews24 noted that the DAE had no documented information on the fruit, and that with rising demand some farmers had begun to grow it commercially.

Photo: National Science Foundation/Peter Rejcek / Wikimedia Commons (public domain). The top picture shows Blood Falls flowing from Taylor Glacier into Lake Bonney, Antarctica, in November 2006; the tent at left gives a sense of scale.

Sources: Jagonews24, Prothom Alo, Down To Earth, Science, Journal of Glaciology, Frontiers in Astronomy and Space Sciences, Johns Hopkins University (via Futurity), Journal of Food Science and Technology, Current Agriculture Research Journal, McMurdo Dry Valleys LTER, Banglapedia, Wikipedia