Category: Other Worlds and Tech

A little over a year ago, NASA released a statement on a find made by the Mars 2020 rover Perseverance as it continued to explore an ancient river outflow delta within Jezero Crater on Mars. It related to an unusual arrowhead-like rock NASA dubbed “Cheyava Falls”, and which showed both white veins of calcium sulphate – minerals that precipitate out of water – running across it, and tiny mineral “leopard spots”, whitish splotches ringed by black material.

These spots, together with black marks referred to as ”poppy seeds”, are common on Earth rocks when organic molecules react with hematite, or rusted iron, creating compounds that can power microbial life. “Cheyava Falls” was the first time such formations had been located and imaged on Mars, and marked the rock, roughly a metre in length and half a metre wide to become the target for more detailed study before the rover eventually moved on.

This study resulted in more discoveries hinting at the potential for organic processes to have perhaps once been at work within the rock, as I noted in Space Sunday: Mars Rocks and Space Taxis. However, the matter was complicated both because “leopard spots” can also be the result of an abiotic chemical reaction rather than the result of any organic interaction, and the further examination of the rock revealed the presence of olivine mineral.

The latter is no friend to organics, as it generally forms within magma at temperatures deadly to organic material. This suggest it and the phosphates and other organic-friendly minerals within the rock may have been deposited at temperatures which would have killed off any organics present long before they could have resulted in the “leopard spots” forming, leaving the latter’s formation purely a matter of inorganic reactions.

But the matter is complicated, and for all of its capabilities, the science laboratory aboard Perseverance is limited in how much it can do. What is really required is for the samples gathered from “Cheyava Falls” to be returned to Earth and subject to far more extensive study – something which in the current political climate in the United States, isn’t going to happen in the near-term.

Considerable caution needs to be taken when discussing matters of microbial life on Mars. The planet is a highly complex environment, and while there are many indicators that it may have once been a far warmer, wetter and cosier environment which may have formed a cradle for the basics of life, that period might also have been extremely brief in terms of the Mars’ very early history. And therein lies another twist with “Cheyava Falls”; the rock appears to have formed some time after that period in the planet’s history.

If nothing else, the likes of ALH84001 – the meteorite fragment discovered in the Allen Hills of Antarctica in 1984 and shown to have originated on Mars – encourage a lot of caution is required when it comes to trying to determine whether or not something is indicative of organic interactions having once been present on Mars.

In that particular case, the team studying the fragment in 1996 reported they may have found trace evidence of past microscopic life from Mars. Unfortunately, their findings were over-amplified by an excited press to the point where even in the face of increasingly strong evidence that what they had discovered – what appeared to be tiny fossilised microbes embedded in the rock – was actually the result of entirely inorganic processes, members of the science team involved in the ALH84001 study became increasingly adamant they had for evidence of long-dead Martian microbes. It wasn’t until around 2022 that the debate over this piece of rock was apparently settled (see: Space Sunday: pebbles, ALH84001 and a supernova).

With this in mind, an international team set out to subject the data and images gathered from “Cheyava Falls” and its immediate surroundings, referred to as “Bright Angel”, and where other samples were taken for analysis by the rover, in an attempt to try to identify the processes at work which may have resulted in the formation of the “leopard spots” and “poppy seeds”. They published their findings on September 10th, 2025 – and those findings are potentially eyebrow-raising.

On Earth, all living organisms obtain energy through oxidation-reduction (redox) reactions, the transfer of electron particles from chemicals known as reductants to compounds named oxidants. An example of this is mitochondria found in animal cells which transfer electrons from glucose (a reductant) to oxygen (an oxidant). Some rock dwelling bacteria use other kinds of organic compound instead of glucose, and ferric iron instead of oxygen.

Ferric iron can be similarly reduced, resulting in water-soluble ferrous iron, which can be leached away or reacts to form new, lighter-coloured minerals, resulting in the “leopard spot” deposits very similar to those found on “Cheyava Falls”. In particular, these latter reactions can result in two iron-rich minerals, vivianite (hydrated iron phosphate) and greigite (iron sulphide). Again, on Earth the formation both of these minerals can involve organic interactions with microbes – and both vivianite and greigite appear to be present within the “Cheyava Falls” samples analysed by Perseverance.

However, as noted, above “leopard spots” – and by extension vivianite and greigite – can be formed through purely aboitic reactions. The most common means for this occurs when rock containing them is formed, due to the transfer of electrons from any organic matter (which is not necessarily living organisms) trapped in the rock to ferric iron and sulphate. But this process requires very high temperatures in order to occur – and given the age of “Cheyava Falls”, the required temperatures were unlikely to have played a role in its formation. However, the presence of living microbes in the rock could result in the spots and the phosphate and sulphide minerals found within them.

Given this, the research team focused on trying to find non-biological interactions which might produce the minerals in question – and they were unable to do so.

The combination of these minerals, which appear to have formed by electron-transfer reactions between the sediment and organic matter, is a potential fingerprint for microbial life, which would use these reactions to produce energy for growth.

– NASA statement of the mineral composition found within samples of the “Cheyava Falls” rock

So, does this mean evidence of ancient microbes having once existed on Mars? Well – not necessarily; nor do the research team suggest it is. As they note in their paper, while no entirely satisfying non-biological explanation accounts for the full suite of observations made by Perseverance, it doesn’t mean that there isn’t one; it’s just that while the rover’s on-board analysis capabilities are extensive, they are also limited. In this case, those limits prevent the kind of in-depth examination and analysis of the “Cheyava Falls” rock sample which might definitively determine whether or not microbial interaction or some currently unidentified inorganic process is responsible for the deposits.

The only way either of these options might be identified is for the samples to be returned to Earth so they can be subjected to in-depth investigation. But again, as noted, that’s unlikely to happen any time soon. A major flaw with the Mars 2020 mission has always been that the samples it gathers can only be returned by a separate Mars Sample Return (MSR) mission. This has proven hard to put together thanks to the complexities of the mission being such that its design has cycled through several iterations and suffered spiralling costs, reaching US $11 billion by 2024 – with the timescales constantly being pushed back to the period 2035-40.

More recently, there have been more modest proposals put forward for the MSR mission, such as that from Peter Beck’s Rocket Lab, which offered a simplified approach to collecting the Perseverance samples in 2030/31 at  a cost capped at US $4 billion. However, that is currently off the table as the entire idea of any MSR project is currently facing cancellation under the Trump Administration’s proposed cuts to NASA’s 2026 budget. Whether it remains so has yet to be seen.

Following the publication of the new “Cheyava Falls” study, NASA acting Administrator, Sean Duffy, has voiced a belief MSR could be carried out “better” and “faster” than current proposals – but failed to offer examples of how. Further, it’s not clear if his comment was a genuine desire to retrieve the Perseverance samples or bluster in response to China’s Tianwen 3 mission. Slated for launch in 2028, this is intended to obtain its own samples from Mars and return them to Earth by 2031.

New Study Complicates Search for Life on Enceladus

Enceladus, may be a small icy moon orbiting Saturn and just 500 km in diameter, but it has been the subject of intense speculation over the years as a potential location for life beyond Earth. Like Jupiter’s larger moon Europa, Enceladus has been imaged by space probes giving off plumes of water vapour through geysers, suggesting that under its icy surface it might have a liquid or semi-liquid ocean, warmed by tidal forces created by Saturn and its other moons.

These geysers have been shown to contain organic molecules, suggesting that the moon’s ocean might be habitable. However, new research presented during a planetary science conference hosted by Finland provides strong evidence for many of the organic molecules detected in the geysers are actually formed by interactions between radiation from Saturn’s magnetic field and the moon’s surface icy surface.

Specifically, a team based at Italy’s National Institute for Astrophysics recreated conditions on the surface of Enceladus in miniature using an ice chamber and freezing samples of water, carbon dioxide, methane and ammonia – all constituents found within the ice covering Enceladus – down to -253ºC. Each sample was then bombarded with high-energy “water-group ions,” the same charged particles trapped around Saturn that constantly irradiate Enceladus, with the interaction monitored using infra-red spectroscopy.

In all five cases, the samples outgassed carbon monoxide, cyanate, and ammonium in varying amounts. These are the exactly the same core compounds as detected within the water plumes of Enceladus as detected by NASA’s Cassini spacecraft in the early 2000s. Further, the five experiments all additionally produced more complex organics – carbamic acid, ammonium carbamate and potential amino acid precursors including methanol and ethanol, as well as molecules like acetylene, acetaldehyde and formamide – all of which were also detected in small quantities within the plumes escaping Enceladus, but which have never been recorded on the moon’s surface.

That all five samples produced broadly similar results in both basic and complex compounds can be taken as a strong indicator that the presence of those compounds within the Enceladus geysers could be as much due to the interaction of radiation from Saturn with the surface of the moon as much as anything organic that might be occurring in any ocean under the moon’s ice.

Although this doesn’t rule out the possibility that Enceladus’ ocean may be habitable, it does mean we need to be cautious in making that assumption just because of the composition of the plumes. [While] many of these products have not previously been detected on Enceladus’ surface, some have been detected in Enceladus’ plumes. This leads to questions about whether plume material is formed within the radiation-rich space environment or whether it originates in the subsurface ocean.

– Grace Richards, Enceladus study lead for EPSC-DPS2025.

The study also notes a further complication: the timescales necessary for radiation to drive these chemical reactions are comparable to how long ice remains exposed on Enceladus’ surface or in its plumes. This further blurs any ability to differentiate between any actual ocean-sourced organics with Enceladus’ plumes (if present) from those produced by the demonstrated surface-born interactions.

As with the “Cheyava Falls” rock samples, potentially the only way of really determining whether or not some of the organics in the geysers on Enceladus have a sub-surface / oceanic source is to go and collect samples. Again, this is not going to happen any time soon.

Currently, NASA has no current plans for a robotic surface mission to Enceladus;  while the European Space Agency has outlined a complex mission to explore several of Saturn’s moons – Titan, Rhea, Dione, Tethys, Enceladus and Mimas, and which will release a lander vehicle to the south polar region of Enceladus in order to study the geysers and collect samples for in-situ analysis. However, if approved, this mission will not take place until the 2050s. The same goes for a three-part mission outlined by China’s Deep Space Exploration Laboratory (DSEL) to specifically map the surface of Enceladus and use a lander / robot drilling system in an attempt to drill down 5 km through the moon’s ice and directly sample the moon’s ocean at the ice-ocean boundary and seek out potential biosignatures. As such, any answers on the potential habitability (or otherwise) of any potential ocean within Enceladus are going to be a long time coming.

On Wednesday, August 26th, 2025, SpaceX undertook the 10th integrated flight test (IFT) of its Starship / Super Heavy combination. Overall, the flight achieved all of its stated goals, which should be taken as a step forward – to a degree.

Those goals were broadly the same as the previous failed launches: place a Starship vehicle into a sub-orbital trajectory, carry out a deployment of eight Starlink satellite simulators, attempt a brief restart of one the vehicle’s Raptor engines and test a number of different materials for possible use as future heat shield elements to help protect a Starship vehicle through atmospheric (re-)entry.

The launch itself came at 23:30 UTC on August 26th, some two days later than planned, and following two scrubbed attempts. The first of these was due to an unspecified issue with ground systems, which prevented the original planned launch on August 24th. The second scrub came on August 25th, the result of poor weather around the Boca Chica launch facility and along the route of initial ascent.

While not a hindrance to this particular flight, both of these issues illustrated a weakness in the entire idea of “rapid reusability” for the Starship / Super Heavy, in which boosters and Starship craft are supposed to be turned around on the pad within hours following a flight, and then re-launched – an idea utterly dependent upon ground systems (and those on the vehicles) not having significant issues and the weather cooperating with the launch schedule 100% of the time.

Anyway, on August 27th, everything came together and the stack of booster and ship lifted-off more-or less on time at 23:30 UTC. The initial ascent through Max-Q was largely smooth, although one of the booster’s 33 Raptor motors did fail a minute and a half into the flight – an event which did not impact the booster’s performance.

At 2 minutes 36 seconds, MECO (most engines cut-off) was reached, the two rings of Raptor engines on the booster shutting down, leaving only the gimballed three central motors running. Two seconds later, the six motors on the Starship ignited, and a hot-staging occurred, the Starship separating from the booster, the latter immediately vectoring away from the Starship in it “boost-back” burn. This is normally required to put the booster on a descent back towards the launch facility for capture by the launch tower. As no such capture was planned for this flight, the boost-back instead put the booster into a free-fall, engine-first drop back towards the Gulf of Mexico and a planned splashdown.

At 6 minutes 20 seconds after launch the booster performed a final landing burn. This comprised an initial firing of the inner 13 motors of of the booster before quickly cutting back to three motors. Normally, this would be the 3 centre engines on the booster, which can be gimballed to provide directional thrust.

However, for this flight only two of the gimballed motors were used, together with one of the motors on the inner ring of 10 fixed engines. This was to test the booster’s ability to hold station and steer itself in the event of one of the three central motors being out-of-use during the final descent during an actual post-launch capture attempt. As a result, this final burn offered an impressive demonstration of the booster’s hover capability, as it came to a halt at around twice its length above the surface of the Gulf of Mexico. The motors were then shut down, leaving the booster to drop unpowered into the water, exploding on impact.

Following separation, the Starship vehicle continued on into its sub-orbital trajectory. Just under 19 minutes after launch, the payload slot designed specifically for Starlink deployments and of no use for anything else, cranked open successfully, allowing the deployment of the eight Starlink simulators to commence. The entire deployment of the 4 pairs of satellite simulators took some 7 minutes to complete from initial slot opening to slot closure.

The final element of the sub-orbital part of the flight was the re-lighting of a single Raptor motor. This was literally just a re-ignition and shutdown, shortly before the vehicle commenced it atmospheric re-entry. The latter utilised a much higher angle of attack that has been seen with previous flights. In part, this was to test whether such an approach would decrease the plasma flow over the forward aerodynamic flaps, which on previous flights have suffered major issues of burn-through and failure.

This, coupled with alterations made to the positioning of the forward flaps for the “Block 2” vehicle design, appeared to work; the forward flaps survived the re-entry period pretty much unscathed. However, the choice angle of attack exposed the stern of the vehicle – the engine skirt and stern flaps – to greater dynamic forces and plasma flow, and as re-entry proper commenced, there was a sudden energetic event within the engine bay. The exact cause of the event is unclear at the time of writing, but it resulted in part of the engine skirt being blown out and the port side aft aerodynamic flap suffering damage.

As a result, the affected flap suffered a degree of burn-through that might not otherwise have occurred. Fortunately, this did not result in a complete failure with the flap, or affect the vehicle’s control, but the overall event could be indicative of potential vulnerabilities related to high angle of attack re-entry profiles and the need for SpaceX to further refine re-entry parameters to avoid excessive damage at either end of the ship.

That said, the vehicle did go on to complete its descent through the atmosphere, the aerodynamic flaps fully able to maintain the vehicle’s attitude and pitch through to the final kilometre of the descent. At this point the flaps folded back against the vehicle’s hull as the centre motors were re-lit and the vehicle performed a “flip up” manoeuvre, pointing its motors towards the sea as it performed a powered splashdown, prior to toppling over and exploding.

These final moments of the flight were captured from a remotely operated camera mounted on a buoy deployed by SpaceX at the target landing site – the Starship vehicle actually coming down within metres of its intended splashdown point. This footage revealed strange discolouring across the vehicle’s heat shield: white around the nose and payload bay and vivid orange around the cylinder of the propellant tanks. SpaceX later indicated that both were the result of testing different materials or possible future heat shield use.

In the case of the white decolourisation, it was stated that some of the alternate material tiles had failed to prevent the insulation between them and the hull of the vehicle form becoming  heated to the point where it melted and flowed out over the heat shield. The orange was later blamed on a single metal tile fitted high on the vehicle’s main cylinder, which was super-heated by the nearby re-entry plasma, spreading oxidised metal particles over the heat shield.

Whilst the flight did meet all of its primary goals, IFT-10 is, in reality, something of a qualified success, further demonstrating the continued prioritisation of SpaceX goals – developing a system for deploying Starlink satellites over meeting contracted obligations for NASA: namely developing and prototyping the Human Landing System (HLS) required by the Artemis programme and moving forward with the not insignificant issue of large-scale cryogenic propellants between orbiting Starship vehicles, again a vital requirement for Artemis 3 and Artemis 4. Of the latter, the SpaceX CEO will only commit to stating the company will solve this “eventually” – despite the fact the company is expected to have HLS flight-tested and ready for Artemis 3 and to have solved the propellant transfer issue within the next two years if NASA is to avoid further delays to Artemis.

Nancy Grace Roman Passes Test Deployments

NASA’s latest space telescope – the infra-red Nancy Grace Roman Space Telescope (shortened as the Roman Space Telescope or RST) took two more significant steps forward in early August when the Solar Array Sun Shield (SASS) that will both provide the telescope with power and shield its electronics and instruments from excess solar heat, together with the Deployable Aperture Cover (DAC), which both protects the telescope primary optics aperture during launch and then shade the aperture for receiving too much sunlight and spoiling observations.

The tests were carried out on August 7th, and 8th, respectively at NASA’s Goddard Space Centre, where the telescope has been undergoing integration and testing. They were carried out using a rig able to simulate the microgravity conditions the telescope will be in during an actual deployment.

The first test was to confirm four of the telescopes six solar panels would fold out from their stowed launch positions on either side of telescope’s body. Spring-loaded, each panel unfolded over a 30-second period after being triggered by non-explosive actuators. To help dampen the effect of each panel’s deployment, there was a 30-second pause between each deployment, after which, the panels were examined by engineers to confirm the panels had correctly deployed and ready for operation.

Following this, the DAC’s deployment mechanism was successfully tested, the cover successfully unfolding to provide the noted shadow protection over the optic’s aperture to prevent sunlight entering it, and must do so without itself snagging or blocking the telescope’s field of view.

Intended to operate in a halo orbit around the Sun-Earth L2 position, the 4-tonne telescope has a stated primary mission encompassing a search for extra-solar planets using gravitational microlensing;  probing the chronology of the universe and growth of cosmic structure with the end goals of measuring the effects of dark energy, the consistency of general relativity, and the curvature of space-time.

A further aspect of RST’s mission will be as part of a growing network of ground and space-based observatories tracking and understanding potentially dangerous asteroids and comets that could threaten our planet. From its Sun-Earth L2 halo orbit, the telescope will use its sensitive near infrared vision to study near Earth objects (NEOs), the asteroids and comets whose orbits bring them close to our planet. Not only will RST be able to identify NEO for tracking by other telescopes and observatories, it will be able to determine their size, shape, composition and exact orbital paths, allowing the potential for a possible collision with Earth and the likely results to be fully assessed. This aspect of the mission will particularly see the RST work in collaboration with another new facility – the Earth-based Vera C. Rubin Observatory in Chile, which has also featured in these pages.

While the US-led Project Artemis programme is suffering continued delays in its attempt to return humans to the Moon – the Artemis 2 lunar orbital mission originally set for late 2024 being delayed until April 2026, while Artemis 3, the first mission to land on the Moon appears increasingly unlikely to meet its planned mid-2027 launch date due a number of reasons, perhaps most notably the current non-existence of the SpaceX lunar landing vehicle and much of the technology required for it to actually work – China’s project to deliver humans to the Moon and establish an operational base there is continues to roll along at a pace suggesting it will be more than ready to meet its initial goal of delivering two taikonauts to the surface of the Moon by 2030.

As I’ve previously covered in this column, China’s route to the Moon – managed by the China National Space Agency (CNSA) – is a lot less technically complicated than Artemis. In some ways it harkens back to NASA’s own Project Apollo of the 1960s and 1970s; at its core, it relies on sending two pairs of vehicles directly to the Moon. The first is the Mengzhou (“Dream Vessel”) crew vehicle, China’s “next generation” vehicle intended to both ferry crews to and from the Tiangong space station (up to 6 at a time) and to and from the Moon (3 at a time). Supported by a service module, Mengzhou is at an advanced stage of development and testing, and could start crewed flights to orbit in 2027.

The other half of the equation is the lunar lander. Called Lanyue (“embracing the Moon”) takes its cues from the Apollo Lunar Module. Designed to carry a crew of two to and from the lunar surface, Lanyue is a two-stage vehicle comprising the actual lander together with a propulsion module.

For lunar missions both Mengzhou and Lanyue are designed to be launched separately and directly to the Moon by China’s in-development Long March 10 booster, with the two craft docking in lunar orbit to allow the transfer of two of the crew to the lander, which will then be assisted in its lunar descent by the propulsion module used to power it to the Moon, before the lander separates to make its powered landing.

This week CNSA took a further significant step towards the goal of a human landing on the Moon by 2030 with the first powered test of Lanyue’s descent motors using a full-scale structural test article of the lander. Whilst only 30 seconds in length, the tethered test successfully demonstrated the integration and performance of key systems, simulating descent, guidance, control and engine shutdown, all of which are critical to undertaking a successful lunar landing.

The full sized test article was hoisted into the air within a special test stand which then lowered the vehicle at a rate consistent with a fall towards the Moon, the test article firing its primary braking / propulsion motors and using its attitude control thrusters, allowing engineers to assess the effectiveness of both systems in maintaining vehicle control. The test concluded with a verification of the craft’s landing and take-off systems and lunar surface contact propulsion shutdown procedures.

For our manned space missions, we must ensure that astronauts land on the lunar surface very smoothly, which necessitates high standards for the lander’s cushioning and performance. Every bit of weight has to play a role in several functions, so we have to achieve ultimate in integrated design and lightweight construction.

– Huang Zhen China National Space Agency (CNSA)

Lanyue still has a multitude of tests to undergo, but given the relatively short development time frame and with several test articles and prototypes already undergoing  tests, including simulations of launch vibrations and stresses on the craft, investigations into the craft’s response to the thermal environment of cislunar space, it is not unfair to say its overall development is fairly advanced, potentially putting that “by 2030” deadline well within reach.

Artemis 2 Update

Despite its delays in terms of its original timescales as noted above, Artemis 2 is making progress. The Orion Multi-Purpose Crew Vehicle (MPCV), mated to its European-built Service Module (ESM) was transferred from NASA’s Multi-Payload Processing Facility (MPPF) to the Launch Abort System Facility (LASF).

Whilst at the MPPF, Orion and its Service Module were loaded with propellants, high-pressure gases, coolant and other essential fuels for its upcoming flight. In addition, the crew for Artemis 2 – NASA astronauts Reid Wiseman, Victor Glover and Christina Koch and Canadian Space Agency (CSA) astronaut Jeremy Hansen – carried out the first on-board tests of their flight pressure suits (aka the Orion Crew Survival System suits) with Orion’s life support and communications systems for a variety of simulated ground and flight conditions.

Now it is at the LASF, Orion will be mated to its 13.4-metre launch abort system tower. This is the system which tops the SLS and Orion stack during launch and the initial ascent to orbit. It is designed to propel the crew capsule away from the launch vehicle in the event of an emergency, and steer the capsule from any potential danger, allowing the crew to return to Earth under the Orion’s parachute system.

Once the installation of the Launch Abort System is complete, Orion will be moved to the Vehicle Assembly Building (VAB), where it will be stacked atop its Space Launch System (SLS) launch vehicle. The rocket itself is currently going through its final assembly within the VAB. Once Orion is mated to it, the two vehicles will go through a series of final integration tests in readiness for their launch.

The Artemis 2 mission is currently scheduled for a no later than April 2026 launch date, and will comprise six key phases:

• Launch to a Low-Earth orbit for initial vehicle check-out on arrival in orbit prior to an orbital boost.
• 24-hour eccentric orbit with an apogee above that of typical communications satellites, where further vehicle check-outs are performed and proximity operations with the (detached) upper stage of the SLS launch vehicle.
• TLI (trans-lunar injection) – firing the service module’s main engines to put it on a course for a Moon rendezvous.
• Lunar fly-by – passing around the Moon with a closest approach of around 7,400 km, during which the crew will continue to monitor and test Orion’s systems.
• Earth return trajectory – Orion will use the Moon’s gravity to swing it into a free-return trajectory to Earth.
• Re-entry and splashdown in the Pacific Ocean.

In all, the mission is expected to last some 10 days.

Hubble Images 3I/ATLAS – and guess what? It is a Comet

A couple of Space Sundays back, I wrote about 3I/ATLAS, the third known interstellar traveller to pass through our solar system, and the (frankly silly) idea that that it is an alien probe, possibly sent here on a spy mission.

In that piece (see: Space Sunday: daft alien theories and a space shuttle) I noted that some of the claims about the object being “alien technology” were due to the fact that as an interstellar comet (as initial analysis suggested was the case), it “had no tail”; this despite the fact the object was already developing a gaseous cloud of ejected dust as it started to get warmed by the Sun.

Well, guess what? As it continues to close on Sun in is inward journey through the solar system, 3I/ATLAS has started to develop a tail – and it has been imaged by the Hubble Space Telescope. Given the images were captured at a time when 3I/ATLAS was 3.8 AU from the Sun – some four times the average distance between Earth and the Sun – the fact that it is starting to evidence a tail indicates it is rapidly becoming active under the Sun’s influence.

Tails generally form on comets as they close on the Sun, when the heat and energy of the latter directly affects the surface of the latter, causing it to outgas volatiles – dust, water vapour, etc., – in sufficient quantities that they are caught in the solar wind to form a trail of matter pointing away from the Sun.

Given 3I/ATLAS is still a long way from the Sun, to see it start to form a tail of outgassed material – even if relatively weak in visual terms – would suggest that it has a lot of volatile materials within it which are already being dramatically affected by the Sun’s energy. What’s more, it is entirely possible that this tail will become more pronounced as the object continues to approach the Sun and reaches perihelion.

However, not only does the appearance of this tail on 3I/ATLAS further undermine claims that it is “alien technology”, it offers a means for astronomers to better understand its composition and likely size. Using Hubble’s exceptional resolution, a research team from UCLA led by David Jewitt has been able to estimate how much material 3I/ATLAS is losing now, putting the amount at between 6 and 60 kilos per second at its current distance from the Sun – or roughly the amount of a small car even few minutes – a not significant amount.

The team also attempted to estimate the likely size of the nucleus of the object; no easy task, given the surrounding cloud of outgassed dust. To achieve this, they instead analysed the brightness distribution of the surrounding dust cloud (coma), and concluded 3I/ATLAS has a likely less than 2.8 km across, assuming it reflects only 4% of the light that hits it (similar to charcoal), but unlikely to be less than 0.32 km in diameter.

This size constraint is crucial because it helps astronomers understand the object’s composition and history. Different materials require different amounts of solar heating to begin sublimating, so by observing when and how vigorously 3I/ATLAS becomes active, it’s possible to make educated guesses about what it’s made of. Further, through this analysis of the Hubble images and data, it is possible for astronomers to gain insight into the nature of 3I/ATLAS, and by extension, the stellar system from which it originated, as objects like 3I/ATLAS carry with them the chemical signatures and physical characteristics shaped by alien environments billions of kilometres away – although sadly, it will be extremely difficult to determine where the object actually originated.