I teach a university course called Hormones and Behaviour. What surprises students is that biological sex is not produced by a single switch. What surprises me is that many students have never been taught this before. It is basic biology, but it helps explain life.

Sex emerges through a sequence of events before birth and continues at puberty. Chromosomes help direct the formation of gonads, the body parts that usually become ovaries or testes. Gonads make hormones. The body then has to respond to those hormones. In most people, these steps flow in the same direction. But in rare cases, they do not.

These cases are known as disorders, more recently differences, of sex development (DSDs). They are not new but they provide a useful way to understand how bodies develop. DSDs can affect hormone production. Some affect the body’s response to hormones. Some affect chromosomes or gonad development. Two people can have a DSD, yet have very different bodies, medical needs and life experiences.

Each condition reveals what can happen when one step in the normal sequence is altered. Here are five ways sex development can take a different path.

Congenital adrenal hyperplasia

This DSD affects around one in 16,000 births.

The adrenal glands, which normally produce small amounts of male hormones, even in females, are hyperactive in this condition.

A baby with two X chromosomes and ovaries can therefore be born with external genitals that look male.

Complete androgen insensitivity syndrome

In contrast, a child with complete androgen insensitivity syndrome (CAIS), can have XY chromosomes and internal testes that make testosterone, but their body cannot respond to that testosterone.

This lack of a response to testosterone keeps the developing fetus in its “default” female state, leading to female external genitals at birth.

Someone with CAIS will develop breasts at puberty. Since their external anatomy is typically female, people with CAIS are usually raised as girls and may only be diagnosed later, often when their periods do not start.

CAIS is estimated to affect one to five in 100,000 live born females.

5-alpha-reductase deficiency

Another condition, called 5-alpha-reductase deficiency, shows how sex development does not finish at birth.

The body needs an enzyme called 5-alpha-reductase to turn testosterone into a stronger version of the hormone before birth. When a genetic mutation inactivates this enzyme, an XY baby may be born with genitals that are read as female and may be raised as a girl. At puberty, however, the normal surge of conventional testosterone masculinises the body.

The condition is rare worldwide and its exact incidence is unknown, partly because conditions affecting sex development have often been surrounded by silence.

In parts of the Dominican Republic, where this condition is known as guevedoces, studies have reported surprisingly high local rates. A rare genetic mutation is more common in these isolated populations, about one in 90 males.

More recently, some of these communities have begun to recognise guevedoces at birth and raise them as boys.

Sex chromosomes disorders

Usually, females receive one X chromosome from their father and one X from their mother, and are therefore XX, while males receive one X chromosome from their mother and the Y chromosome from their father. However, a person with Klinefelter syndrome, affecting one in 500-1,000 male births, has XXY chromosomes, causing smaller testes, scant body hair, lower testosterone and reduced fertility. It is often never diagnosed.

On the other hand, Turner syndrome, or the loss, in females, of one of the two X chromosomes, affects one in 2,500 female births and impairs growth, puberty and fertility. It can affect physical appearance, for instance a wide neck and broad chest and often comes with health conditions such as hearing loss and kidney problems.

Swyer syndrome is rarer: a person has XY chromosomes but with a mutation in the Y chromosome that disrupts the signal that normally drives testes formation. The gonads do not develop into testes, testosterone remains low and the external and internal anatomy is typically female.

These are the clearer examples. Milder sex differences can result from mutations that reduce, rather than completely inactivate, an enzyme or hormone response. For example, non-classic congenital adrenal hyperplasia, where some enzyme activity remains. Their effects may be less obvious, and their incidence is often unknown because many cause subtler changes or are never diagnosed.

What this does and does not tell us

None of this is new. These conditions have been known to scientists for decades. But now genetic testing can identify the mutation behind some cases.

Specialist clinics and patient groups have pushed for clearer information for parents, better psychological support for patients and greater caution around irreversible childhood surgery when it is not medically urgent. Recent patient-centred research shows that clear information, good communication and psychological support are central to good care for people with DSDs. It’s unclear whether increased awareness has improved people’s lives, but the direction is clear: better information, specialist care and long-term support matter.

The lesson is not that sex is meaningless or endlessly fluid. These rare conditions do not provide a simple answer to every argument about sex and gender.

However DSDs do show sex is not a single event. Just like the growth of our body, it is a process. When chromosomes, gonads, hormones and the body’s response to them all follow the usual sequence, the result often looks simple. When one link changes, the body may no longer fit the binary pattern many of us were taught at school.

For the people affected, this is not an abstract puzzle. Some need lifelong hormone treatment. Some face infertility. Some discover their condition only as teenagers or adults. Chromosomes or sex designation at birth may explain part of the biology behinds DSDs. It does not explain what it feels like to grow up, go through puberty, seek fertility treatment or decide who needs to know.

Jean-Michel Fustin is a Medical Research Council-funded Senior Research Fellow in the Division of Integrative Physiology at The University of Manchester. He contributes the level-3 course Hormones & Behaviour.

In the early hours of Wednesday morning August 5 the upper stage of a Falcon 9 rocket crashed into the Moon in an uncontrolled collision.

No damage was caused, other than the creation of a new crater several metres in diameter, but the event highlights the increasing problem of space junk left in orbit when it has completed its intended purpose.

Natural impacts occur on the Moon daily. On average, Nasa estimates that 33 metric tonnes of meteoroids (space rocks) hit Earth every day, but most of this burns up in the atmosphere before hitting the ground. A smaller proportion make it through and reach the surface as meteorites.

Most of the human-made space debris that falls back to Earth also burns up on its way through the atmosphere. The Moon has no atmosphere, so any debris – either natural or human-made – on a collision course will hit the surface.

First identified and reported as an upcoming collision months ago, the object in this case was the upper stage of the SpaceX Falcon 9 rocket on a mission to ferry two robotic landing craft to the lunar surface. These were Blue Ghost Mission 1, manufactured by Texas-based firm Firefly Aerospace and Hakuto-R, built by the company ispace, which is headquartered in Tokyo, Japan.

The first stage of the rocket did what it was designed to do, took the second – or upper – stage and the payload of spacecraft into low Earth orbit, detached, and returned safely to a landing pad on Earth to be refurbished for reuse.

The upper stage engines then ignited and took the spacecraft on their intended trajectory to the Moon. However, once it had released the spacecraft, its job was complete and it was left in a high elliptical orbit around the Earth.

In a statement, SpaceX said that, for most missions, the company carries out a controlled de-orbit of the Falcon 9 second stage, so that it safely re-enters Earth’s atmosphere over the ocean. However, the company added that for payloads headed to the Moon, like this one, the de-orbit manoeuvre is not always possible.

On August 5, 2026, its orbit coincided with the position of the Moon and it crashed into the lunar surface, generating a new crater and excavating a large amount of lunar rock and dust. South Korea’s Danuri spacecraft, which entered orbit around the Moon in December 2022, has taken images of the impact site, showing traces of material (ejecta) thrown out across the lunar surface.

With an estimated mass of four tonnes (its exact mass depended on how much unspent fuel was left on board) it was travelling at 2.43 km/s (1.51 miles per second) at the point of impact. This is far slower than most space rocks in the solar system, but fast enough to do some serious damage if it had hit anything of value.

While this was an accidental impact, astronomers made plans to observe the event to advance our understanding of crater formation on the Moon. Given that we know the size, shape and mass of the rocket body, studying the resulting crater will help us better understand the lunar surface and its impact history.

Seismometers (to measure ground motion) deployed during the Apollo landings in the 1960s and 70s, helped us understand the frequency of meteorite impacts on the Moon. But we can only estimate the properties of the impacting object after the crater has formed.

This, as well as other accidental – and deliberate – impacts can help us better understand lunar surface material. As part of an international campaign to observe the impact, the University of Manchester’s Jodrell Bank Observatory used the 76-metre Lovell Telescope as the receiving element in a bistatic radar experiment, where the transmitter and receiver are separated by a large distance.

Radio transmissions from Nasa’s Deep Space Network station near Madrid were directed towards the impact region, while the Lovell Telescope listened for faint radar echoes reflected from the resulting plume of dust and debris excavated from the lunar surface. The observations also included tracking the Falcon 9 upper stage during its final approach to the Moon.

Detecting radar returns from an impact plume at lunar distance is extremely challenging, although the Lovell Telescope has previously demonstrated its radar receiving capability on similarly demanding experiments, both for tracking and characterising objects in orbit and detecting radar echoes from a near-Earth asteroid.

Developing these techniques will be increasingly important for monitoring hazards and protecting future infrastructure and human activity in space.

Keeping space free of clutter is becoming increasingly important, both in low Earth orbit where there are now more than 16,000 active satellites but more than 1.2 million pieces of debris larger than 1cm in size, and around the Moon where more infrastructure is planned.

With several countries aiming to put humans on the Moon for long duration missions, the problem of space debris and impacts will become increasingly pressing. There is also the risk of accidentally destroying sites of historical and cultural importance – such as Neil Armstrong’s first footprint at the Apollo 11 landing site.

Space treaty

The Outer Space Treaty provides the basic framework for international space law. It states that “states shall be liable for damage caused by their space objects”. This applies on the Moon as much as it does around Earth. So, hypothetically, if a US rocket part hit a Chinese lunar base, the Chinese would expect the US to take responsibility, and vice versa.

This principle applies to collisions in low Earth orbit too, as well as to falling debris that survives re-entry. Commercial companies are developing methods of catching and removing defunct satellites and other hazardous pieces of debris before they can cause a collision or crash.

Increasing awareness of this problem is pushing companies and nations to improve how they dispose of their rockets and satellites once they reach the end of their operational lifetime. There are some regional regulations on the disposal of such material, but it is currently far from universal.

In its statement, SpaceX said: “For higher energy missions like those to a lunar transfer orbit, nearly all performance on the vehicle is devoted to successfully placing the payload in the intended orbit, and a controlled disposal manoeuvre is not always possible.”

The company added: “We actively work to be as responsible as possible with hardware left in space to ensure space safety, including for more complex missions. In this case, solar activity and gravity led the second stage toward the Moon.”

Nasa’s Artemis II mission, which carried four astronauts on a loop around the Moon in April 2026, showed that there is significant public interest in sending humans back to the Moon.

This incident illustrates a significant risk that future lunar missions will need to address, both in terms of keeping astronauts and infrastructure safe from old debris, but also looking towards a future where governments and (increasingly) private companies are more responsible with their equipment once it has completed its mission.

Right now, there are no humans on the Moon so there is no risk to life. On this occasion, there were no landers or other equipment in the projected impact location.

But as more and more missions head to the Moon, increasing numbers of spent rocket parts will end up on potential collision courses with the Moon – if we are planning to build a base and have it crewed long term, the last thing you want is for it to be accidentally damaged by a piece of space junk.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

The moment of first contact with extraterrestrials is a staple of science fiction. It usually involves a frantic scientist having a Eureka moment, realising in a single dramatic instant that Earth is being visited by creatures from light-years away.

Aliens are in the public consciousness once again thanks to Steven Spielberg’s latest film, Disclosure Day, which follows a whistleblower’s attempts to reveal extraterrestrial visitations to the world.

In reality, the discovery of extraterrestrial intelligence is far more likely to emerge as a faint anomaly in astronomical data, followed by a slow, painstaking process of verification, peer review and intense international deliberation. There might be no single Eureka moment, and no lone scientist with the answer.

As our telescopes have advanced, so too has the complexity of the world we live in. That is why a committee of the International Academy of Astronautics (IAA) has just voted to accept a major overhaul of the “post-detection protocols” – the scientific code of conduct for what happens after we find evidence of life beyond Earth.

The IAA body that has approved the changes is the Search for Extraterrestrial Intelligence (Seti) Committee. Seti is the collective term for scientific projects dedicated to searching for signs of intelligent alien life in the universe.

The previous version of these principles was adopted way back in 2010. To put that in perspective, in 2010, the “fake news” era hadn’t quite arrived, social media was in its infancy, and the broader idea of “technosignatures”, looking for signs of alien technology such as waste heat from giant structures in space, was still largely on the fringes of mainstream astronomy.

Today, the field has exploded. We are no longer just listening out for artificial radio signals from a few select stars. Projects like Breakthrough Listen have globalised the search, and we now observe the entire electromagnetic spectrum for any sign of advanced technology.

Furthermore, the information landscape has become a minefield. In an era of deepfakes and instant global connectivity, a single unverified claim could trigger global panic or widespread misinformation before scientists have even had a chance to check their data.

At the heart of the 2026 update is a commitment to scientific rigour. The new protocols make it clear: we do not shout “alien” the moment we see a strange blip in our data. If a researcher detects a candidate signal, which could be an artificial radio signal, or something else, such as a sign of alien technology, the first step isn’t a post on social media; it’s a quiet, rigorous attempt to prove themselves wrong. The discovery must be independently authenticated by multiple organisations using different instruments.

Only when a consensus is reached that the signal is truly credible is it brought to the world. This isn’t about secrecy for secrecy’s sake. There is no obligation to disclose verification efforts while they are ongoing, precisely to avoid embarrassing and damaging false alarms.

However, once a discovery is confirmed, the protocols demand full transparency. The data, the analysis methods, and the code used must be made open to the entire global scientific community and, indeed, the general public for replication.

Should we talk back?

One significant addition to the 2026 declaration is the focus on researcher safety. We’ve seen in recent years how scientists at the centre of high profile news stories can become targets for harassment or “doxxing”, where malicious individuals post the scientist’s personal details online. The new guidelines urge institutions to protect their researchers from negative professional repercussions and physical or digital harassment.

The protocols also address the “trash” of our own making: radio frequency interference (RFI). The radio frequency bands that Seti scientists use to listen for E.T. are increasingly polluted – from below by mobile networks, radar and poorly shielded electronics, and from above by the growth of satellite “mega-constellations” like Starlink.

The declaration calls for extraordinary international efforts to protect the frequencies where a signal is detected, ensuring our “communication channel” isn’t drowned out by our own technology.

The most controversial part of Seti isn’t the searching; it’s the messaging. Known as Meti (Messaging Extraterrestrial Intelligence), the idea of intentionally sending signals to other worlds splits the community. As enshrined in the earlier declarations, the 2026 Declaration remains firm on one point: no response should be sent until there has been a broad, international consultation.

Deciding how to represent Earth to an alien civilisation is a choice that belongs to all of humanity, not a single institution or individual. These consultations must take place through the United Nations or other broadly representative global bodies.

The discovery of intelligent life beyond Earth would stand as one of the most transformative events in human history. To help manage the profound aftermath, the IAA SETI Committee is establishing a permanent Post-Detection Sub-Committee.

This body will not simply be a room full of astronomers; it will include international experts in ethics, law, social sciences and communications to advise on the complex, long term societal implications of contact.

The new protocols themselves are designed to be living documents, supplemented by a separate Code of Conduct and Best Practices Guidelines that will be periodically reexamined and updated to reflect the “best practice” of the day.

The revised declaration has recently been formally adopted by the IAA Board of Trustees and over the rest of the year it will be filed with other appropriate organisations for their endorsement.

The next goal will be to present the finished framework to the wider scientific community at the International Astronautical Congress in Turkey in August 2026. Beyond that, the Committee hope that the new protocols will also be reviewed and noted by the UN.

By establishing these rigorous rules now, we ensure that if, or when, that signal finally arrives, the world is prepared to listen, verify, and respond as one planet.

Michael Garrett led a task group that included Professor Kathryn Denning (York University, Canada), Professor Carol Oliver (University of New South Wales, Australia) and Mr. Les Tennen (Law Offices of Sterns and Tennen, USA, and Full member and Legal Counsel of the International Academy of Astronautics Board of Trustees). This group drafted the updated 2026 protocols.