How exactly did the universe start and how did these processes determine its formation and evolution? This is what a recent study published in Physical Review Research hopes to address as a team of researchers from Spain and Italy proposed a new model for the events that transpired immediately after the birth of the universe. This study has the potential to challenge longstanding theories regarding the exact processes that occurred at the beginning of the universe, along with how these processes have governed the formation and evolution of the universe.

For the study, the researchers used a series of computer models to simulate the beginning of the universe that challenge the longstanding theory that the universe began with a period of rapid expansion known as “inflation”, with scientists estimating this occurred within the first fraction of a second of the universe’s existence. However, this inflation theory postulates that several variables were all involved in making this theory possible.

In contrast, this new model suggests that a longstanding phenomenon of general relativity called gravitational waves are responsible for the universe and all its components, including galaxies, stars, planets, and life on Earth. The team proposes these gravitational waves are part of a longstanding mathematical model called De Sitter space, which is named after the Dutch mathematician Willem De Sitter, who worked with Albert Einstein regarding the universe’s structure throughout the 1920s.

“For decades, we have tried to understand the early moments of the Universe using models based on elements we have never observed”, said Dr. Raúl Jiménez, who studies experimental sciences & mathematics at ICREA in Spain and is a co-author on the study. “What makes this proposal exciting is its simplicity and verifiability. We are not adding speculative elements but rather demonstrating that gravity and quantum mechanics may be sufficient to explain how the structure of the cosmos came into being”.

First proposed in 1893 and 1905 by Oliver Heaviside and Henri Poincaré, respectively, gravitational waves received a huge boost in attention in 1916 when Albert Einstein proposed them to be ripples in the space-time continuum as part of his general theory or relativity. Despite myriads of sources, including supernovae, black holes, and neutron stars, gravitational waves are incredibly difficult to detect and require very sensitive instruments. This is potentially why gravitational waves were not detected until September 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) observatory, which have locations in Washington and Louisiana.

The origin of the universe remains one of the biggest mysteries in science, as the Big Bang has long been theorized to have been the catalyst for the origin of the universe. Despite ongoing scientific breakthroughs and advancements, scientists remain puzzled regarding the origins of the universe, and especially what might have happened before the Big Bang.

Carl Sagan famously said, “The cosmos is within us. We are made of star-stuff. We are a way for the universe to know itself.”

We may never know exactly how the universe began and the processes responsible for you reading this article right now. But like the simplicity this study presents, perhaps this study is simply a way for us to know the universe itself a little bit better.

What new discoveries about the origins of the universe will researchers make in the coming years and decades? Only time will tell, and this is why we science!

• As always, keep doing science & keep looking up!

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Imagine looking up at the night sky and watching a star almost completely disappear, then reappear months later. That's exactly what happened with a distant star called ASASSN-24fw, leaving astronomers scratching their heads for months.

Located about 3,000 light years from Earth, this star pulled off an incredible disappearing trick between late 2024 and early 2025. For eight months, it dimmed by an astounding 97% before returning to its normal brightness. To put this in perspective, imagine a bright streetlight suddenly becoming as dim as a birthday candle.

It's not unheard of for stars to unexpectedly fade. Comparison of SPHERE images of Betelgeuse taken in January 2019 and December 2019, showing changes in brightness and shape

(Credit : ESO/M)

What made this event particularly puzzling was that the colour of the star's light remained unchanged during its dimming. This crucial clue told scientists that the star itself wasn't changing or dying, something else was blocking our view. After analyzing the data, researchers from The Ohio State University believe they've cracked the case. Evidence suggests it is likely that there is a cloud of dust in the form of a disk around it, according to lead researcher Raquel Forés-Toribio.

This isn't just any ordinary dust cloud though. The disk surrounding ASASSN-24fw is enormous, about 1.3 astronomical units (AU) across, even bigger than the distance between the Sun and our planet. The dust particles themselves are made of carbon or water ice, similar in size to large grains of dust found on Earth.

The mystery deepens further however since scientists suspect this star isn't alone; it likely has a smaller, cooler companion star orbiting nearby, making it what astronomers call a binary system. The second star, which is much fainter and less massive, may be driving the changes in geometry leading to the eclipses, explains Forés-Toribio. This hidden partner could be responsible for stirring up the dust disk, creating the conditions that led to the dramatic dimming event we witnessed.

Atacama Large Millimetre Array image of the dust disk around HL Tauri

(Credit : ALMA)

How rare is this phenomenon? Extremely. Chris Kochanek, a professor at Ohio State who co-authored the study, describes it as one in a million eclipsing. Even when researchers searched for similar events in their databases, they couldn't find anything quite like it.

The star was discovered by the All-Sky Automated Survey for Supernovae (ASAS-SN), a network of small telescopes that continuously monitor our night sky. Since its establishment more than a decade ago, ASAS-SN has collected about 14 million images and that keeps going up. Don't expect to see this show again anytime soon. Researchers calculate that the ASASSN-24fw system likely experiences an eclipse about once every 43.8 years, with the next one not expected to occur until around 2068.

This discovery reminds us that the universe still holds countless mysteries. As astronomer Krzysztof Stanek notes, The universe's capacity to surprise us is continuous. Each unusual event like this helps scientists better understand how stars and planetary systems form and evolve, pushing our theories to new limits.

Source : 

• Dusty structure explains near vanishing of faraway star

NASA's Perseverance rover has turned its attention to towering sand formations called megaripples at a site named Kerrlaguna on Mars. These windblown features, standing up to a metre tall, are providing new insights into how wind shapes the red planet today and could even help prepare for future human missions to Mars.

While Mars might seem like a frozen, static world, its landscape is actually being constantly reshaped by powerful winds. As NASA puts it, "On Mars, the past is written in stone, but the present is written in sand." This poetic description captures exactly what Perseverance has been studying lately, massive sand formations that tell the story of modern Martian weather.

NASA’s Perseverance Mars rover took this selfie over a rock nicknamed “Rochette,” on September 10, 2021, the 198th Martian day, or sol of its mission

(Credit : NASA/JPL Caltech)

After completing investigations at a geological contact zone called Westport, Perseverance attempted to climb steep slopes to reach a new rock exposure named Midtoya. However, the combination of treacherous terrain and rocky, unstable soil proved too challenging, forcing the rover team to retreat to smoother ground. The effort wasn't wasted though since Perseverance managed to study fascinating spherule rich rocks that had tumbled down from above, including a distinctive helmet shaped rock dubbed "Horneflya" that captured public attention online.

The rover then moved to Kerrlaguna, where the steep slopes give way to a field of megaripples. These aren't your typical beach type sand ripples, they're massive windblown formations that can tower up to one meter high. While that might not sound enormous, imagine sand dunes the height of a tall person scattered across an alien landscape.

The science team decided these features deserved a detailed mini-campaign of study. Usually, Perseverance focuses on ancient rocks that preserve evidence of Mars' distant past, but understanding the planet's current environment is equally important. These megaripples offer a window into how wind and weather continue to shape Mars today.

The Kerrlaguna feature on Mars is located in the Jezero Crater

(Credit : NASA)

Nearly a decade ago, Perseverance's predecessor, the Curiosity rover, studied an active sand dune in Gale crater and took a famous selfie there. However, the megaripples at Kerrlaguna appear inactive and dusty, representing a different type of Martian sand formation that's common across the planet's surface. These older, immobile features could reveal new insights about how wind and even trace amounts of water interact on modern Mars.

This self-portrait of NASA's Curiosity Mars rover shows the vehicle at the "Big Sky" site, where its drill collected the mission's fifth sample of Mount Sharp

(Credit : NASA)

During its investigation, Perseverance deployed multiple scientific instruments to thoroughly analyze the megaripples. Using SuperCam, Mastcam-Z, and MEDA instruments, the rover characterised the surrounding environment, measured the size and chemistry of individual sand grains, and looked for any salty crusts that might have developed over time.

This research serves a dual purpose beyond pure scientific curiosity. Understanding Martian soil composition and behaviour could prove crucial for future human missions to the red planet. Astronauts will likely need to use local Martian resources to help them survive, making detailed knowledge of soil properties and composition invaluable for mission planning.

The Kerrlaguna investigation also serves as preparation for a more ambitious study planned at Lac de Charmes, a location further along Perseverance's route that features an even more extensive field of larger sand formations. By studying these windblown features grain by grain, Perseverance continues to unlock the secrets of how Mars behaves today, complementing its discoveries about the planet's ancient past and helping pave the way for humanity's eventual arrival on one of our nearest planetary neighbours.

Source : 

• To see the world in a grain of sand: Investigating megaripples at Kerrlaguna on Mars

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Where is everybody?

For decades that question was merely a part of physics legend, the kind of thing grad students overhear when their advisors take them out to dinner. But the story behind that question is true, and it’s a good one. It was the late 1940’s, soon after the close of World War 2. The world was buzzing with reports of UFO’s, flying saucers, and aliens sticking their probes where the sun don’t shine.

Physicists can sometimes resemble real people, and like real people when they get together for lunch at work they like to chat about whatever’s in the news. And one time, famed physicist Enrico Fermi was visiting his colleagues at Los Alamos National Laboratory. Right down the road from Roswell. The conversation turned to UFO’s, and the group, including Fermi, started speculating wildly, quickly coming to the realization that the only feasible way that UFO’s could be aliens would be if faster-than-light travel was possible. But during the conversation, Fermi fell silent.

Sometime later, as the conversation shifted to other topics, Fermi suddenly blurted out, “Where is everybody?”

Everyone at the table immediately knew what we meant.

That lunchtime exclamation became the core what we call today the Fermi paradox. Here’s the basic deal: life is possible in the universe. Need proof? Hello, nice to meet you. It happened here on Earth, and the universe tends to not just do things only once. In fact, the default assumption in astronomy and cosmology is that we’re not special – we occupy no privileged position and we have no unique status (sometimes called Copernican principle for his removal of the Earth from the center of the universe). And indeed, nothing about our planet is all that remarkable: it’s just another lump of oxygen and carbon orbiting just-another-star. Heck, even our preliminary estimates suggest that there are something around 5 billion duplicates of the Earth in the Milky Way alone.

That’s 5 billion chances for life to arise under identical conditions.

So by that logic, the universe should be teeming with life. and not just regular life, intelligent life, and not just intelligent life, but space faring, and even space colonizing life! We can again point to ourselves as an example: we are right on the cusp of a sustained presence in space (like, in a real way), and it’s not hard to imagine that by extending our technology just a little bit, we could be one of those, I don’t know, star trek civilizations.

So if we could do it, then somebody else should be able to do it too.

You can even imagine throwing every technological hurdle in our way – nothing better than fusion-powered rockets, always constrained by the speed of light, limited lifespans, disease, warfare, anything that would and could slow down our progress, the works. But the fact is that our milky way galaxy is roughly 10 billion years old, and given that enormous amount of time, then space-faring civilizations have had more than enough eons to essentially spread throughout the entire galaxy, even doing it the slow way.

We should see advanced civilizations everywhere. We’re talking Dyson spheres, stellar engineering, or signatures of powerful engines. And while we do see many mysteries out in the universe – unexplained explosions or strange particles zipping by, we see no need to explain ANY observation in the solar system, galaxy, or universe, by invoking advanced alien civilizations. Even when our natural “dead” explanations don’t explain everything (cough FRBs, dark energy, hexagon on Saturn), we find no great pressure to say ALIENS DID IT.

Even leaving astronomical observations aside, given the abundance of life and intelligent civilizations, plus the raw amount of time they’ve had to poke around the galaxy, our solar system should have been visited MULTIPLE times by MULTIPLE species, either in person (or in-alien) or with their robotic craft. We should have monoliths and nanobots and space jockey skeletons everywhere, especially on the airless worlds that have maintained a record of impacts and events going back over four billion years.

So…where is everybody?

Hence the paradox: something in this line of reasoning has to give. We’ve got one, if not many – if not all – of these statements wrong. But which one?

Now, I would love to do an entire series on the fermi paradox and all its possible answers and what that means for current searches for life, but I’ll save that for a future date (and please, if more of you ask about it RIGHT NOW the sooner I’ll get to it).

But to slake your thirst for solving long-standing puzzles in physics, we’ll spend today jumping into one of the possible resolutions to the fermi paradox, the so-called GREAT FILTER.

Which sounds…kinda ominous. And…is…kinda ominous. But as we’ll see, it doesn’t HAVE to be ominous, but…sigh…it probably is.

• Check out Part 1 of the series here.

Now versions of the Great Filter argument had been around for decades (just like Fermi was not the first person to ask where everybody is), but the most comprehensive form of the argument comes from Robin Hanson in 1996, who is an economist. Now I know you’re thinking: an economist, really? But hey, who says astronomers get to have all the fun. Possible resolutions to Fermi’s paradox are less about physical theory and raw observations and more about statistics and probabilities, so hey economists, welcome to the party.

Here’s the simplest possible reduction of the great filter argument, the most distilled essence of the entire chain of reasoning to explain why we don’t see advanced space-faring civilizations roaming the galaxy: nobody makes it.

That’s it. nobody makes it to that stage. Question: where is everybody? Answer: nobody’s home. The logical chain that leads to Fermi’s paradox is broken in the assumption that intelligent space-faring civilizations are COMMON. According to the great filter answer, they’re not common at all, and so we shouldn’t be surprised when we don’t see anybody.

But wait, wait wait. Aren’t we on the cusp of achieving space colonization status? If the great filter is true, and nobody makes it to that level of sophistication, then…what does it mean for us? Is this…the end of the road?

Like I said, a little ominous.

Let’s breaks things down to see under what exact conditions things should start to feel a little spooky, and where we might be able to keep our blood pressure in a nice safe range.

The issue is that we don’t know exactly when or where the great filter actually happens. There are a lot of steps to go from “random planet with the right ingredients for life” to “vast interstellar empire”. For his part, ol robby hanson broke it down into 9 separate steps that life must go through to get from the little to the big leagues. These steps are: having the right star system to create the basic conditions for life, generating self-reproductive molecules (as in, abiogenesis), stepping up to basic cells with prokaryotic life, advancing to more complex and capable cells with eukaryotic life, achieving sexual reproduction, making the jump to multicellular life roaming around the world, achieving some vague sense of intelligence (like, say, mastering fire or using tools), then advancing to the status of a civilization with the POTENTIAL for space colonization, and finally, once all the pieces are in place, becoming a gigantic galaxy-spanning explosion of life.

We can debate the particulars of this classification scheme until the cows come home, but the point is that to get to make the galaxy your playground, you have to jump through a lot of hoops and pass a lot of tests. Some of those tests are early on, and some are a little later in the process. Sooooo the big question is: where’s the bottleneck? Where does the “Great filter” become so great? What stops nascent life from reaching the stage where we should be able to detect it? Is it at the beginning, with life-ready systems hard to come by? Somewhere in the middle, where life never gets a start or just spends billions of years swimming around in oceans, or is it towards the latter stages? And considering that WE OURSELVES ARE NEAR THE LAST STAGE, we’d really like to settle this question, because the location of the great filter means a lot for the future survival of our species.

Now I know there is an obvious bias in this argument: that life across the galaxy follows a similar path to us, which may or may not be true. But if we expand our definition of life, that makes fermi’s paradox even WORSE: there should be MORE evidence of life in that scenario, not less, so let’s stick with this restriction because it’s the most compatible with solutions to fermi’s paradox and move on.

So let’s talk about the early stages first, because…that makes sense. Maybe the great filter takes place at stage 1. Maybe the conditions for life are exceedingly rare. Well, to be perfectly honest, that doesn’t like that’s the case. Yes, I know that the Earth is the only known planet in the solar system, heck, the universe, where we know life can exist. But it seems based on our limited observations that life has had plenty of chances, even in our own solar system. We know for a fact that Mars once hosted liquid water oceans and a thick atmosphere, right around the same time that the early Earth did. Life happened here, and so it’s somewhat plausibly reasonable to assume that life got a start there. It just…kinda died. Same thing for Venus.

And we have to mention the icy moons of the outer planets, like Europa, Enceladus, and more. Under their icy shells those worlds host globe-spanning liquid water oceans, more liquid water than the Earth has! Those oceans just might be rich in minerals and nutrients..and might be homes for life.

I could go on. And I will. We see organic molecules, and even amino acids, in molecular clouds and on comets. The galaxy is swimming in the ingredients needed for our kind of life. So the basis, the stage 1, of just having the right conditions, seems to be very common indeed. No signs of a great filter here.

What about the next couple stages? You know, the bits about self-reproducing molecules and the evolution of single-celled organisms. Well, we don’t have much to go on here: we only have evidence for life on one single planet. But it’s still a data point that we can learn some lessons from. It’s not much – I’m definitely venturing into speculation territory here, so you’re welcome to make your own arguments – but it’s something. We know that life appeared basically ASAP once our planet cooled. Once the conditions for life were met – with the right ingredients, temperatures, and so on – life…happened. Life on Earth is almost as old as the Earth itself. So if we were forced to guess (and again it’s only a guess!) then a halfway decent reasonable guess is that the great filter is NOT in the earliest stages: if life has the right conditions, it probably shows up right away.

So where does that leave us?

• Check out Part 2 of the series here.

What about the middle stages? The march from single-celled organisms doing their single-celled thing to intelligent creatures that can wield tools and leave feedback reviews about them?

Well, again we still only have one data point, but we MIGHT be able to learn something about filters both small and great in those middle stages. And that’s the fact that intelligent life appeared very LATE on earth. Check this out, within 500 million years of our planet even forming, self-reproducing molecules and single-celled critters evolved. And here we are, intelligent creatures, only arising into consciousness within the past few hundred THOUSAND years. And guess what? We’re about to get cooked. No, that’s not a metaphor. As the sun ages it expands and brightens. It’s been doing so for…well, four and a half billion years already. That’s right, the first life to appear on the Earth knew a small, dimmer Sun than we do today. And it’s only going to get worse. Within about five hundred million years from now, the Sun will become so hot that the oceans will boil, plate tectonics will grind to a halt, and the greenhouse effect will spiral out of control, turning the Earth into another Venus: superheated and choking on its own acidic atmosphere. While life might – might - cling to a miserable existence in some crevice in that future hell-world, it’s definitely not going to be intelligent, let alone space-faring.

In other words, we are here, building our rockets, in the final stages where it’s even possible to do on the Earth. Now again, I have to sprinkle a lot of caution into these statements, but again maybe nature is trying to tell us something. Life itself appeared within the first chapter of the Earth’s viable history, and intelligent life appeared in the last.

So maybe that’s the answer: life is common, but intelligent life is not. Maybe that’s the Great Filter. Intelligence takes a lot of luck and stable evolutionary history (and maybe a few good whacks with an asteroid). So we shouldn’t expect other space faring civilizations because intelligence is a precious commodity in the cosmos (and on the Earth, yuk yuk).

How could we test this? Or, maybe “test” is too strong a world, but at least start to wrap the questions in some sort of statistics or probabilities. After all, so far we’re only going on one example. But we can imagine a future where we are able to find microscopic critters, maybe deep in the Martian crust, or swimming in the seas of Europa, or hanging out on some exoplanet. If we continue our searches and find simple life, but no signs of INTELLIGENT life, then this would be a major clue that the Great Filter is behind us: that we’re already on the other side and it’s all going to great.

Or not. “Not” is definitely still an option.

Until we have enough data to build statistics, and trust me that’s going to be a long way off so don’t hold your breath, then all we have is speculation. Which while not very scientifically rigorous is still really fun. What if the Great Filter is in front of us? What if it’s in our future? What if once life gains a foothold somewhere it has a universally decent chance of arising to intelligence, like it’s a foregone conclusion of the evolutionary process?

Well then, that means that maybe species simply destroy themselves. I mean, it’s not hard once you put your mind to it. The idea is that to travel interstellar, or even interplanetary, distances, you must be able to harvest, store, and use incredible amounts of energy, and develop a sophisticated technological base to do it. And if you can do that, then you can harvest, store, and use MORE THAN ENOUGH ENERGY to wipe every single living thing off the face of your home planet.

The best insurance against that is to have your favorite kind of living thing on multiple surfaces on multiple planets, but you will have to spend a certain amount of time – maybe centuries, maybe millennia – in a precarious balance, where you’re trying to climb the ladder to the stars without cutting yourself off at the knees. A species needs to use its technologies for good, not evil, for a very long time so that it can ensure its own survival. Meanwhile, during all that time slowly developing space travel and self-sustaining offworld habitats, a rogue state or actor or even the combined actions of the entire species can just...end it all.

And, like, THAT’S US. We can send robotic craft beyond the edges of the solar system. We can send crews to live months at a time in orbit. And…we can also wipe every living thing off the face of the earth. We have more than enough nuclear weapons to kill off all of humanity and trigger a mass extinction. If we pump enough carbon into the atmosphere, things can go haywire real quick and have the same effect. The same abilities that bring us to the stars can bury us in the dirt, which is real dark but kinda poetic.

Or maybe it takes so long that nature does the job for us, sending an unlucky rock in our direction or an ozone-killing blast from a gamma ray burst. Life may be hardy in general but individual species are not. Something – from nature or from ourselves – can kill us while we’re still in the cradle.

Remember, for the great filter argument to work, it has to be NEAR TOTAL. Which means…this is it. The end of the line. The last stop before galactic extinction. Goodbye everyone, hug your loved ones, and take one last bite of cheese, because the end of our species is right around the corner.

Wow, that got morbid.

The “Wow!” signal has been etched red marker in the memory of advocates for the search for extraterrestrial intelligence (SETI) since its unveiling in 1977. To this day, it remains one of the most enigmatic radio frequency signals ever found. Now a new paper from a wide collection of authors, including some volunteers, provides some corrections, and some new insights, into both the signal and its potential causes.

Data from 1977 was hard to parse, given the lack of modern computer systems, but volunteers from the Big Ear Observatory in Delaware, Ohio, where the original signal was collected, preserved the records after the observatory was shut down in 1998 and turned into a golf course. Using modern computing technology, the volunteers ran over 75,000 pages of original data through an optical character recognition routine, with visual help from human validators, allowing in-depth computational analysis of the original signal for the first time.

This more detailed analysis led to slight changes in three of the signal’s main characteristics. It narrowed the part of the sky the signal could have emanated from, with a corresponding increase in the statistical certainty of its location by two thirds. Its frequency was also tweaked slightly, but importantly, from 1420.4556 MHz to 1420.726 MHz. While that might not seem like much, the source would have to be spinning rapidly faster to create that much of a frequency difference.

Potentially the most interesting update to the signal was a new estimate of its flux density (i.e. its strength). In the language of radio astronomy, the new value is 250 Janskys (which are 10-26 watts per m2 per Hz), whereas previous estimates put it somewhere between 54 and 212 Janskys, so the signal was actually notably higher than original estimated.

Other minor errors, such as a 21 second clock offset didn’t have as much of an impact on the signal, but does on astronomer’s understanding of it. And probably the largest change was a correcting for a mislabeled channel in the filter bank that caused a recalculation of the frequency.

Ultimately, the signal remains as enigmatic as ever, though the paper does try to shed some light on potential sources. They definitively rule out any man-made sources, pointing out that there were no known TV stations operating in Ohio at that point in time, nor were there any satellites overhead that could have caused the signal. The moon was also on the other side of the planet at the time, so nothing bounced off of it.

How can thermoelectric generators (TEGs) help advance future lunar surface habitats? This is what a recent study published in Acta Astronautica hopes to address as a team of researchers from the Republic of Korea investigated a novel technique for improving power efficiency and reliability under the Moon’s harsh conditions. This study has the potential to help mission planners, engineers, and future astronauts develop technologies necessary for deep space human exploration to the Moon and beyond.

For the study, the researchers conducted a first-time analysis of how a novel TEG system could function under lunar surface conditions, specifically regarding the extreme temperature differences between the lunar day and lunar night, which ranges from 121°C (250°F) to -133°C (-208°F), respectively. Previous studies have hypothesized that drastic temperature ranges could enable greater efficiency for TEGs, also called a transient-state operation.

The goal of this study was to discuss how switching heat storage (HS) systems, also called multiple-HS systems, under lunar conditions could produce the transient-state operation. In the end, the researchers found the multiple-HS system under lunar conditions resulted in a 48.9 percent power generation increase, indicating the temperature range could benefit TEGs and a potentially long-term lunar habitat.

The study notes, “Deep space exploration, including missions such as the establishment of human bases, especially on the Moon and Mars, has garnered significant interest worldwide. As stated by scientists helming missions such as the Artemis project, a manned lunar base is an integral part of deep space exploration as it can serve as a base for future missions in the solar system. Consequently, production of sufficient power for maintaining such a base has become the focus of this research.”

The study discusses other potential power sources like Radioisotope Thermoelectric Generators (RTGs) but discourages their use for long-term missions due to the half-life decay of radioactive isotopes. Despite this, RTGs have successfully been used on instruments that were left on the lunar surface by the Apollo missions and are currently being used by NASA’s Curiosity and Perseverance rovers on Mars.

Going forward, NASA plans to use RTGs on the agency’s upcoming Dragonfly mission, which is currently slated to launch in July 2028. The researchers briefly mention how solar and nuclear power could be used as viable power sources on the Moon, with nuclear fission reactors previously being suggested for use on the lunar surface.

NASA’s Artemis program, specifically with the goal of establishing a long-term human presence on the lunar surface, enhances the relevance of this study. The continued development of new technologies on the lunar surface not only ensures a long-term human presence on the Moon but also establishes technologies that could be used on future crewed missions to Mars, as outlined in NASA’s Moon to Mars Architecture. Additionally, the use of a reliable power source on the lunar surface mitigates the need for bringing power sources from Earth, enhancing a practice called in situ resource utilization (ISRU), which uses available resources to maintain a successful mission. In this case, TEGs use the wide temperature range on the lunar surface for their power generation needs.

As humanity continues its journey towards developing long-term settlements beyond Earth, studies like this demonstrate a growing interest in using Earth-based technologies for improving life beyond Earth. Perhaps TEGs could serve as a starting point for powering long-term lunar habitats until a more advanced and reliable system is established.

How will thermoelectric power generation help advance lunar habitats in the coming years and decades? Only time will tell, and this is why we science!

• As always, keep doing science & keep looking up!

How do you tell how old an astronomical object is? I mean, the next time the Moon is in the sky, take a look at it. How would you even begin to answer that question?

I won’t leave you in suspense. Astronomers use a technique called crater counting and it’s pretty much exactly what it sounds like. The idea is that worlds like the Moon, Mercury, and many of the moons of the outer system are not active. They’ve been dead, in almost every sense of the word, for a very long time. And when a comet or asteroid strikes them, the crater they leave behind sticks around. There’s no air to blow it away. No water to wash it down. No plate tectonics to pull it under the surface.

And so craters just pile up, one after another, and often on top of each other. But not all dead worlds are created equal. Some of them were molten in the recent past, and lava is really good at covering up craters. So if you compare two worlds and count their craters, you can get a relative sense of which worlds solidified sooner.

And some had molten parts alongside the solid parts for some time. Planets and moons don’t always cool down all at once. There might be active volcanic regions over here and just plains of solid nothingness over there. So if you scan across the surface of a world, the places with more craters are probably going to be older (in the sense that they solidified in the more distant past) than the places were fewer craters.

For example, on the Moon we have those two broad regions: the dark basins, or mare, and the lighter-colored highlands. Just by looking at the craters you can tell that the maria are younger because they have fewer craters.

But…how old? If I see a world with tons of craters, how old it is? Not in a relative sense, as in this planet is older than this other one. But in an absolute sense. Like billions of years. Give me a number.

The Apollo missions held the key to unlocking crater records not just on the Moon, but across the solar system.

That’s because scientists have been able to apply radiometric dating to the moon rocks returned from the Apollo missions. If you’re not already familiar, radiometric dating is where you look at the abundances of various radioactive elements and compare their proportions to the numbers of elements that they decay into. Since we know the half-life of those elements, we can calculate the absolute age of that sample.

And since the Apollo missions visited many places on the Moon, we’ve been able to build a detailed accounting of which parts cooled and solidified when. For example, the edge of the Sea of Tranquility, the site of the Apollo 11 landing, is just over 3.5 billion years old, while some other regions in the highlands reach right up to 4 billion years old.

By far the youngest features on the Moon are some of the large impact craters. The Copernicus, Tycho, and Cone craters are all less than a billion years old. The youngest crater of all is probably the Giordano Bruno crater, named after the Italian renaissance smart/crazy guy, and is only 4 million years old. These craters are so young because the impacts carry so much energy that they’re able to erase everything in their vicinity, wiping the slate clean and starting the whole process over.

With these absolute numbers in hand, we can now calibrate crater counts across the entire solar system. Now we can look at regions of Mercury or Callisto and know how old they are, even though we’ve never been there, thanks to the Apollo missions and their geologic handiwork.

We also know thanks to the Apollo missions that the Moon is slowly slipping away from us. This was hypothesized all the way back in the early 1800’s when Sir Edmund Halley (of Halley’s comet fame) read through ancient eclipse records and realized we were slowly getting further and further apart. And we had a pretty good explanation for WHY the moon might be going away – the tides raised by the moon get carried in front of it by the spin of the Earth, and that extra gravitational tug pulls the moon into a higher orbit - but we had no good way of putting a precise number on this.

In 1962 Princeton graduate student James Faller proposed placing reflectors on the Moon’s surface. This would allow us to more easily bounce lasers back and forth from the Moon to here, and use that to measure a distance, the same way you can use one of those little laser measurement thingies to…measure distances.

While measurements had been taken before by just reflecting off the lunar soil, with the reflectors the measurements became much more accurate. We now know that the Moon is receding from the Earth at an average rate of 3.8 centimeters per year. Which isn’t very quick, but over the course of, you know, an eon or two, it really adds up.

In fact, in just a few hundred million years the combined effect of the Moon spiraling away from us and the Sun getting brighter and larger (different article) will mean that total solar eclipses will become impossible.

So enjoy them while they last.