Untitled What are Hycean worlds, a proposed new habitat for life?
A little bit more than 124 light years from Earth, circling an otherwise uninteresting star in the constellation of Leo, sits a planet called K2-18 b. It is one of thousands of exoplanets spotted by Kepler, a space telescope that was launched in 2009 and is designed for the task. In 2019 observations by the Hubble Space Telescope suggested the planet might have water in its atmosphere; they were taken as evidence that, if it were a planet like the Earth, it might be habitable.
On September 11th there was further astronomical hubbub, if also a few worries about potential hype, when a team led by Nikku Madhusudhan of the University of Cambridge announced that observations made with the more sensitive James Webb Space Telescope (JWST) suggested K2-18 b might be what is called a 'Hycean world'. What off Earth is that?
Though the term (which is pronounced with a soft c) has a classical ring to it, it was introduced into astronomy by Dr Madhusudhan just two years ago, a portmanteau of 'hydrogen ocean'. It describes a kind of planet which is unknown in the solar system—but which might be both common and habitable elsewhere.
Observations of exoplanets typically provide astronomers little more than an orbit, a mass and a radius. If the radius and mass match something seen in the solar system they can guess what the object's inner structure may be: an exoplanet the size and mass of the Earth is probably rocky. But with a radius 2.6 times that of the Earth, and a mass around nine times higher, K2-18 b is considerably bigger than any of the inner solar system's rocky planets. But it is also much smaller than the giants which hold sway in the outer solar system: just half the mass of Neptune, less than 3% the mass of Jupiter.
With no nearby analogues to guide them, astronomers work out the structure of exoplanets from first principles: what physically self-consistent arrangement of shells of different densities can provide the right answer? The idea of a Hycean world is Dr Madhusudhan's suggestion for an answer which would apply to planets like K2-18 b. It imagines a core of rock and iron about the size of Earth that is covered by an ocean thousands of kilometres deep, topped off with a relatively thin atmosphere composed of light gas, presumably hydrogen. Give such a planet a mass like that of K2-18 b and it will have a radius like that of K2-18 b. It will also have a planet-covering, island- and continent-free ocean in which, in principle, life could thrive.
JWST is sensitive enough to detect tiny flickers of starlight that have passed through the planet's uppermost atmosphere—and they are consistent with such a picture. Models predict the atmosphere of such a planet should contain carbon dioxide and methane, and both were found. There was also a tentative identification of dimethyl sulphide, a molecule which on Earth is only made by life, most notably by plankton. That does not mean that it is produced by life on K2-18 b. But the almost-observation is bound to pique interest.
The sorts of processes which would produce methane in such an atmosphere should also produce ammonia, and this was not seen. But that is a Hycean feature, not a bug. Ammonia would dissolve in an underlying ocean in a way that methane would not, so only methane remains in the atmosphere.
None of this, though, proves K2-18 b to be a true Hycean world. The depth of the atmosphere in Dr Madhusudhan's model is very important. If it is just a bit too thick, the resulting greenhouse effect would make liquid oceans impossible. Instead the lower reaches would consist of water in a very hot, high pressure, 'supercritical' state that is utterly uninhabitable. Sceptics say the existence of Hycean worlds is only possible given fine tuning which provides an atmosphere thick enough not to be lost to space but thin enough not to set off a runaway greenhouse effect in its depths. The new observations offer little—other than the absence of ammonia—to rule out the possibility that K2-18 b is just such a sauna hell world.
Happily K2-18 b is not going anywhere, other than regularly round and round its parent star. There will be ample opportunities for further observations. Those should be able to show whether K2-18 b really is a habitable Hycean waterworld, and whether it really does have evocative traces of dimethyl sulphide in its atmosphere. If it does, you can expect to hear the word Hycean a lot more in years to come.
First Published: 2 May 2025, 11:17 PM IST
Hashtags
Try Our AI Features
Explore what Daily8 AI can do for you:
Comments
No comments yet...
Related Articles
Hindustan Times
5 hours ago
- Hindustan Times
The Alzheimer's drug pipeline is healthier than you might think
OF ALL THE medical challenges that scientists have faced, Alzheimer's disease, the most common form of dementia, has been one of the trickiest. Between 1995 and 2021 private money spent on Alzheimer's research totalled $42.5bn, but more than 140 trials failed to deliver a single drug capable of slowing the disease. Yet the tide may be turning. There are two working drugs, offering modest benefits, on the market. A new review paper suggests more could soon follow. There are 182 clinical trials for Alzheimer's treatments under way in 2025—an 11% increase on the previous year—testing 138 different drugs, of which 12 are set to complete their final 'phase 3' trials this year. Moreover this pipeline includes medicines aimed at a diverse range of targets in the brain, reflecting an increasingly sophisticated understanding of the molecular processes behind Alzheimer's and dementia more broadly. For decades, the theory that has dominated Alzheimer's research, and drug pipelines, is known as the amyloid hypothesis. It argues that the primary cause of the disease is the accumulation of plaques of beta-amyloid proteins in the brain. These would lead to a cascade of negative effects including neuronal dysfunction, brain-cell death and neuroinflammation. The amyloid hypothesis was supported by genetic evidence, which showed mutations in key genes within families to be linked to early onset of the disease. The success of the two drugs already treating Alzheimer's—lecanemab and donanemab, which arrived on the market in 2023 and 2024, respectively—proves that a connection exists. Both help to clear amyloid from the brain, and offer modest help to a subset of patients for whom the drug is thought to be safe and useful. They slow the progression of the disease by about one-third, according to clinical trials, meaning patients can retain their quality of life for longer. The excitement generated by these drugs was tinged, however, with a feeling that they were not much to show for decades of effort. The singular focus on amyloid was probably misplaced. James Rowe, a professor of cognitive neurology at the University of Cambridge, says that although amyloid accumulation is a critical 'early trigger' for the disease, by the time patients arrive at his clinic there are other neural processes accelerating the illness. These include the accumulation of a misshapen version of a protein called tau; increased metabolic stress on brain cells; neuroinflammation; and degeneration of the brain's blood supply. A more nuanced understanding of Alzheimer's is at last being reflected in drug development. That is the conclusion of Jeffrey Cummings at the University of Nevada, Las Vegas, and colleagues in a review published on June 3rd in the journal Translational Research & Clinical Interventions. Academic experts, and investors, agree. Dame Kate Bingham is the managing partner of SV Health Investors, a venture-capital firm based in London that in 2015 started the first fund dedicated to discovering new treatments for dementia in 2015. At the time the drug pipeline for Alzheimer's was mainly focused on tackling amyloid. She says the growing diversity of potential targets today gives her increased optimism. Fully one-third of the new drugs are repurposed, which means they are already approved for use in other conditions and are being redeployed to Alzheimer's. The appeal of this approach is that the drugs already have known safety and toxicity profiles, and can be approved quickly and developed cheaply. One of the more well-known is semaglutide, a diabetes and weight-loss drug whose anti-inflammatory and metabolic benefits have led to its being tested as a treatment for mild cognitive impairment. The drug piromelatine, meanwhile, works on melatonin and serotonin receptors in the brain, which help regulate sleep. As healthy sleep is thought to increase the rate at which amyloid and other waste proteins are cleared, improving it may slow the progression of Alzheimer's. Then there is AR1001 (also known as mirodenafil), which was originally developed for erectile dysfunction and is being tested for its neuroprotective properties. The drug increases levels of a molecule in the brain called cGMP which, in turn, activates pathways that support the survival of nerve cells and improve connections between brain cells. Drugs in this category are known to improve blood flow, so the drug might also have an impact on the brain's vascular health. Another repurposed drug is nabilone, which interacts with the cannabinoid receptors in the body. (The most well known molecule of this kind is tetrahydrocannabinol, the active compound in cannabis). It was originally developed to treat nausea and vomiting in those undergoing cancer chemotherapy. It is now being tested as a potential treatment for agitation and behavioural problems in those with Alzheimer's. Guanfacine, a drug that improves attention and executive function in those with ADHD, is also being tested to see if it can offer similar benefits. Repurposed drugs do not necessarily have a higher chance of success in late-stage trials than those with a novel mechanism. Dame Kate argues that innovative approaches that use new molecular targets, rather than repurposing, will have the greatest impact on the disease. One area of innovation centres around drugs that can tackle inflammation in the brain. Particular attention is being paid to brain cells called microglia, which play a central role in the brain's immune response and, most probably, its fight against Alzheimer's. Microglia have been described as acting as the brain's fire service, police and binmen, because they respond to emergencies, maintain order and clear up debris. A number of drugs are trying to target the protein TREM2 on the surface of microglia in the hope of boosting their activity. Combinations of drugs are also being tested. For example, it is hoped that a pairing of dasatinib, a cancer drug, and quercetin, a molecule derived from plants, will clear ageing and dysfunctional cells. Drug combinations that target different pathways and components of an illness have made big inroads into other complex and intractable diseases such as cancer and HIV. Some of the errors of the past have been corrected. Dr Rowe says that early attempts to design amyloid-clearing drugs did not remove enough amyloid, or did so too slowly. The patient selection in trials was also poor, with many patients included who—it later turned out—did not have Alzheimer's at all. Today's trials still have blind spots, warns Antonella Santuccione-Chadha, the founder of the Women's Brain Foundation, a non-profit that studies how sex affects brain and mental health. Many still fail to differentiate patients by sex, she says. Yet women are twice as likely to develop Alzheimer's, a difference that cannot be explained solely by their longer lifespans, and the disease seems to progress differently in their brains. At any given stage of the disease, tau proteins spread farther in women than in men, says Dr Chadha. It would help the trials—and patients—if more people were tested for Alzheimer's earlier on, so that they could be enrolled to try the new drugs. A single register of those with the disease would also be useful, making it easier for patients to find trials, and for drug companies to find patients. Much, therefore, remains to be done. But for those suffering from a horrible and as yet insurmountable disease that steals so many minds, there is also some much needed hope. Curious about the world? To enjoy our mind-expanding science coverage, sign up to Simply Science, our weekly subscriber-only newsletter. Get 360° coverage—from daily headlines to 100 year archives.
NDTV
a day ago
- NDTV
As Race To Replace Space Station Heats Up, California Company Bets On Haven-1
As the International Space Station (ISS) approaches its retirement, the race to build the next generation of space stations is heating up, particularly in the commercial sector. Leading the charge is Max Haot, the CEO of VAST Space, a company dedicated to creating a commercial space station named Haven-1. In an exclusive interview with NDTV, Mr Haot shared insights into the unique aspects of Haven-1, the competition with other entities like Axiom and India, and the potential for collaboration with ISRO. "We're going through an era where the current International Space Station is one of the most expensive objects ever created by humans, about $150 billion," Mr Haot said. "And we are now transitioning to an era where the commercial space stations are run by commercial entities, not by the government. The two key criteria are safety and dramatically lowering the cost." NASA is running a competition called the Commercial Low Earth Orbit (LEO) Destination (CLD) program, where in July 2026, they are expected to pick one or two winners to develop the replacement for the ISS. Mr Haot emphasised VAST Space's unique strategy: to build a commercial space station before NASA makes its decision. "No one has ever built a commercial space station yet. And we want to build one before NASA makes the decision." The space station, named Haven-1, integrates with the Crew Dragon spacecraft of SpaceX and is set to launch on a single Falcon 9 rocket in May 2026. "It is a single module space station that can house a crew of four with important science, Starlink internet, sleeping berths, and all the consumables to live there on a two-week mission. It will be in orbit for three years. During that time, we will have four two-week missions with the Dragon spacecraft," he said. Mr Haot explained that the main reason for building Haven-1 is to win the NASA competition to develop a much larger space station composed of nine modules. "We believe that if we are selected in July 2026, we will have the first module up for NASA and other international partners in orbit by the end of 2028, a year ahead of what NASA requires. More importantly, it will allow NASA and its partners to test the replacement with a two-year overlap before the retirement of the ISS." When asked about the cost, Mr Haot highlighted the significant reduction compared to the ISS. "VAST is investing a billion dollars by the time we fly Haven-1 next year, in private funding and some of our customer revenue. We've developed all the facilities, all the technologies. We have about 850 people in our California, Los Angeles facility." He emphasised the efficiency of vertical integration in reducing costs and speeding up development. "We can make the next module not only quicker - in two and a half years instead of three - but at a much lower cost because we build everything from the primary structure to a lot of the systems in-house." The competition in the commercial space sector is fierce, with Axiom Space being a notable contender. Axiom plans to link its module to the ISS, but Mr Haot believes VAST Space has an edge. "They started a long time before us, but I think the facts are telling us they're going much slower. Their stated strategy is to launch that module in 2027. If we achieve our goal, we're already at least one year earlier than them." Mr Haot pointed out the strategic advantage of building a free-flyer space station that does not rely on the ISS. "We are building a free flyer, which does not need the ISS and can be standalone, regardless of what happens to the ISS." India is also entering the space station race with plans to launch its first module of the Bhartiya Antariksha Station by 2028. Mr Haot sees potential for collaboration rather than competition. "Absolutely. India might have more interest in training more astronauts before its space station. That could be an interesting discussion - to maybe bring an Indian astronaut to Haven-1."
India Today
a day ago
- India Today
Sun will be thrown out: When will Milky Way Galaxy collide with Andromeda?
Astronomers had predicted over a century ago the fate of the Milky Way Galaxy. It is on a collision course with its next-door Andromeda research indicated that the collision was predicted to be so violent that it would toss the Sun out of its orbit destroying planets like Earth and the entire Solar System. A new study now claims that isn't the of data from the Hubble Space Telescope and the European Space Agency's (ESA) Gaia space telescope reveal that the collision is far less inevitable than astronomers had previously suspected. 'We have the most comprehensive study of this problem today that actually folds in all the observational uncertainties," the lead author of the paper, Till Sawala said. The details have been published in the journal Nature Astronomy. These galaxy images illustrate three possible encounter scenarios between our Milky Way and the neighbouring Andromeda galaxy. (Photo: Nasa) WHEN WILL THE COLLISION HAPPEN? Astronomers estimate that there is a 50-50 chance that the mega collision of the two galaxies could happen in the next 10 billion years based on computer simulations using the latest observational using the latest and most precise observational data available, the future of the Local Group of several dozen galaxies is uncertain. Intriguingly, we find an almost equal probability for the widely publicized merger scenario, or, conversely, an alternative one where the Milky Way and Andromeda survive unscathed,' said team mentioned that 'Even using the latest and most precise observational data available, the future of the Local Group of several dozen galaxies is uncertain. Intriguingly, we find an almost equal probability for the widely publicised merger scenario, or, conversely, an alternative one where the Milky Way and Andromeda survive unscathed,' said Sawala. The team mentioned that predicting the long-term future of galaxy interactions is highly uncertain, but the new findings challenge the previous consensus and suggest the fate of the Milky Way remains an open considered 22 different variables that could affect the potential collision between our galaxy and our neighbour.'Because there are so many variables that each have their errors, that accumulates to rather large uncertainty about the outcome, leading to the conclusion that the chance of a direct collision is only 50% within the next 10 billion years. The Milky Way and Andromeda alone would remain in the same plane as they orbit each other, but this doesn't mean they need to crash. They could still go past each other,' said new result, however, also still leaves a small chance of around 2% for a head-on collision between the galaxies in only 4 to 5 billion years. Trending Reel
