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Staffing the moon base: How many astronauts should live in NASA’s lunar outpost?

The success of NASA's future moon base depends in large part on mission design, which should allow astronauts to work together well in a way independent from psychological training, a new study asserts.

The goal of the study was to identify "specific conditions" for mission success and to look for any "red flags" that may stand in the way, lead investigator Anamaria Berea, a computational social scientist at George Mason University (GMU), told Space.com via email. (The first author of the PLOS ONE study, which was published in May, was GMU's Raymond Vera.)

The team conducted the research using agent-based models, which are tools for computational simulations in fields ranging from the study of bird flocks to the spread of disease, Berea said. While a lot of modern-day AI "trains" or "learns" to extrapolate from information provided in a data set, agent-based modeling instead uses a data set to "understand emergent phenomena that don't have one single cause or direct cause," she said.

The study team considered scenarios for how many astronauts would be on the moon base and how often resupply missions would occur. In an "initial case," for example, the assumed mission duration was three months, with a single resupply run at Month 2 with food, water, air and a fresh group of astronauts.

Using a complex probability analysis known as a Monte Carlo simulation, the model astronauts in this scenario showed a productivity rate of about 20% against their expected tasks, "which is acceptable for a typical manufacturing process," the authors noted.

This productivity rate doesn't take into account anything unexpected that may crop up during the mission, the authors added. "The low task completion rate suggests that, on average, teams are having challenges to overcoming psychological stressors and environmental disruptions," they wrote.

Lessons from the International Space Station

NASA tracks productivity a little differently on the International Space Station (ISS). The agency uses a metric called "utilization," which largely refers to the amount of crew time and number of scientific investigations that are performed on the space station during an increment or expedition. As of 2014, the ISS program suggested that ideal utilization should be 35 hours per crew per week when there are three people working on the U.S. part of the space station, and 68.5 hours if there are four or more. (The Russian side of the ISS works largely independently in this respect.)

"NASA has generally met or exceeded this goal and set a high of 120 average hours per week devoted to research from October 2019 to April 2020," NASA's Office of the Inspector General (OIG), which has been tracking all of these productivity figures, stated in a report published in September 2024.

"Starting March 2022 through March 2023, the latest published data, we have seen utilization near 90 hours per week," the OIG noted. "In addition to the hours spent per week on research, the number of scientific investigations performed on-orbit has increased."

Figure 1 of the OIG report also shows both crew time and scientific investigations increasing, as a trend, between 2000 and 2023, suggesting that utilization of the space station is continuing to grow. And this is despite periodic and documented disruptions that required astronauts to take a step back from being productive, such as emergency ammonia leaks requiring spacewalks, the 9/11 disaster, or sheltering in place during brief contingencies such as space debris passing within a few miles of the station.

Not all crew time can be used for utilization even if all goes well, however, as the station requires normal maintenance like cleaning, and astronauts also need daily time for sleep, meals and a little relaxation. Additionally, utilization tends to increase with larger crews on the space station compared with smaller ones, as maintenance becomes less of a burden with more hands to take on these tasks.

But "lack of redundancy" in key supply items to the space station does pose a risk to utilization, the OIG has noted. As just one example, SpaceX Crew Dragon capsules and Roscosmos Soyuz spacecraft are the only two vehicles that bring astronauts to the station right now. "The lack of redundancy and limited capabilities of both cargo and crew transportation increase the risk to NASA's current and future ability to bring critical supplies, science, and crew to and from the station to maintain safe operations and full utilization of the ISS," the OIG wrote in the report.

An artist’s concept of astronauts working on the lunar surface.

An artist’s concept of astronauts working on the lunar surface. (Image credit: NASA)

Isolated environments

Those of us who have been on long car rides in a group, or who remember being in tight quarters with roommates or family during the pandemic, have some idea of what an isolated, confined environment (ICE) feels like: crowded, with limited resources, and possessing few connections with the outside world. Space serves as just one example of a true ICE; isolated research bases (like in Antarctica) or submarines have also been studied in the literature, according to a separate 2021 study in the journal Neuroscience & Biobehavioral Reviews.

Put simply, ICE refers to a location where humans must work to a high standard in isolated and often dangerous circumstances, with only long-distance support (if possible) from a mission control or its equivalent. And, as the new study points out, a moon base would be a complex example of an isolated environment — one featuring not only resident astronauts but also rovers, other robots and occasional visiting crews.

"The premise for our modeling approach came from trying to understand better the human factors involved in crewed space missions, particularly the deep-space ones, for which we don't have a lot of historical data," Berea said.

That's because only a handful of people have traveled beyond low Earth orbit — the two dozen who flew to lunar realms on Apollo missions in the late 1960s and early 1970s, and the four astronauts of NASA's Artemis 2 flight around the moon this past April.

"We ran various scenarios of space mission durations, number of astronauts, potentially unforeseen circumstances that can happen on the lunar surface or the habitat," she said. The model suggested the missions with the highest probability of success would include six astronauts working on the moon at a time, with fresh supplies coming from Earth every two weeks, and no extreme fluctuations in the environment from things like radiation or a micrometeorite impact.

"In contrast, the worst-case scenario consists of four astronauts on the moon at one time, only one month resupply window between Earth and moon, and moderate to high adverse environmental probabilities," Berea said. And, when asked if training is a factor in mitigating adverse effects, she did not necessarily agree that the years of work NASA and other agency astronauts put in would be more effective than shorter-duration training used for moon base analogs.

"People can be very, very well trained, but for long-duration or deep-space missions, there will always be a human factor involved," she said. "We looked at combinations of skills and personalities in a team of astronauts, and there is a fine line between having a team that is too small and a team that is too large, and there are synergies and emergent behaviors that come from people interacting with each other and with their environment.

"The team is more than the sum of its people," she continued. "The best ways to overcome these is not by more training, but by fine-tuning other aspects of the missions: the duration of the mission, the frequency of resupply missions, and the contingency plans for accidents and unforeseen conditions in extreme environments."

NASA, however, puts its ISS crews through many years of remote environment training long before they float through the space station hatch — and Artemis 2 commander Reid Wiseman told The New Yorker that extensive psychosocial training led to the obvious closeness seen live among his own four lunar crewmates despite tight quarters (and vent line issues that led to occasional toilet trouble).

That psychological intervention during training was by design. "Preparation starts by recruiting mentally healthy people and then providing training to help them deal with potential situations and issues," wrote the Canadian Space Agency of this training, citing NASA protocols. "Astronauts repeat this training often enough that they can anticipate their own reactions and those of their teammates. They also receive constant support from teams on the ground and have access to a variety of tools to help them deal with potentially difficult situations."

Berea noted, however, that psychology forms a part (but is not the focus) of her teams' simulation, including considering NASA TLX (task load index) scores and data, which measures coping and stress for astronauts. The researchers also considered case studies from analogs including Antarctic research missions and time aboard submarines or oil rigs, as some examples.

"We need to pay attention not only to the astronauts, but the team as a whole, and each team and space mission are unique. We will not be able to model these with statistics or AI," she said. "But what we can do is to make sure that before we send any human to live and work on the moon, that we understand well the complexity of interactions and scenarios they will face during the mission, and we can help with that."

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Earth may survive the sun’s death after all, new study suggests

For decades, astronomers have debated whether Earth's fate was tied to the sun's. When the star exhausts the hydrogen fuel that powers it about 5 billion years, it will swell into a red giant large enough to engulf Mercury and Venus — and, several studies have suggested, Earth as well.

New research, however, suggests our planet has a better chance of escaping that fiery end than previously thought. Using updated models of how aging stars interact with their planets, researchers found that the gravitational forces drawing Earth toward the expanding sun are weaker than older models predicted. That would give the planet more time to drift outward as the dying sun sheds its outer layers into space, potentially avoiding engulfment altogether.

The finding does not guarantee Earth's survival. Instead, researchers say it shifts the biggest uncertainty from how strongly the expanding sun tugs on planets to the poorly understood variable of how much mass the star will lose during its final stages of evolution.

"The largest uncertainty no longer comes from the tidal calculations, but from how much mass the future sun will lose," study lead author Mats Esseldeurs of the KU Leuven's Institute of Astronomy in Belgium said in a statement. "Observations of sun-like giant stars currently point towards Earth's survival, but we need better observations before we can be certain."

When stars like the sun exhaust their core hydrogen and balloon into massive red giants, they trigger a cosmic tug-of-war between expanding tidal forces pulling planets inward and shedding stellar weight pushing them outward, which ultimately decides whether nearby worlds are engulfed or saved.

This planetary push-and-pull unfolds in two stages. As the sun expands, gravitational tides act like a subtle brake, slowly draining Earth's orbital energy and pulling the planet inward. At the same time, the dying star sheds vast amounts of gas through powerful stellar winds, eventually losing about half its mass. As the sun grows lighter, its gravitational grip weakens, pushing the surviving planets outward into a wider orbit that could double their distance from the star, according to NASA.

"The fate of Earth depends on a delicate balance between these two effects," Esseldeurs said in the statement. "If tidal interactions dominate, Earth is engulfed. If mass loss dominates, Earth escapes to a wider orbit."

Previous studies reached different conclusions mostly because they treated those competing processes differently, Esseldeurs and his team argue. A few of those studies neglected tidal interactions altogether, while others relied on simplified prescriptions developed decades ago that predicted a much stronger inward pull, according to the study.

Instead of relying on those older formulas, the new study uses updated calculations of tidal forces based on the shifting internal structure and dynamics of aging stars — which the team says allowed it to precisely account for both tidal friction and shifting stellar winds — before testing the results against a range of possible mass-loss rates for the sun's final giant phase.

The results suggest that even with the weaker inward gravitational pull, Mercury and Venus are unable to outpace the expanding sun and are inevitably engulfed, while Earth and Mars migrate safely through both giant phases, leaving our planet to eventually settle into a broader orbit around the white dwarf remnant the sun will leave behind, the study found.

A diagram showing what the phases of the sun dying are.

A schematic evolution of the sun as it goes through its giant phases. The image showed the sun as it is today, going through its two giant phases, before ending its life as a white dwarf. The study showed that Mercury and Venus will be engulfed by the expanding sun, but Earth and Mars survive, ending up in a wider orbit. Sizes and distances are not to scale. (Image credit: Institute of Astronomy of KU Leuven)

The picture is far from settled, however. Because astronomers still cannot precisely observe how rapidly sun-like stars lose mass late in life, "the ultimate fate of the Earth remains uncertain," the researchers write in the new paper.

By factoring in real-world mass-loss rates from L2 Pup — a red giant star roughly 183 light-years away that was used as a proxy for our future sun due to its similar mass — the researchers confirmed that Earth will drift outward just quickly enough to avoid being swallowed, tipping the scales toward survival over destruction, the study notes.

For us humans, the finding offers academic comfort rather than practical salvation. Most scientists agree that as the sun ages, it will steadily grow hotter, boiling Earth's oceans and rendering the planet completely uninhabitable in about 1 billion years, long before the sun begins to expand.

Yet even if humans aren't around to witness it, tracking Earth's ultimate survival provides important context for how planetary systems evolve as their stars age, a framework that researchers say will be further refined by future observations of dying, sun-like stars.

"This will enable us to conduct population studies of the planetary orbital evolution around evolved stars," the researchers wrote in the paper, "and help us to constrain the future evolution of the Earth-sun system."

The study was published in June in the journal Astronomy & Astrophysics.

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The sun’s atmosphere is way hotter than its surface. Scientists may finally know why

The mystery of how the sun's corona, which is its outer atmosphere, reaches millions of degrees could have a surprising explanation: cosmic dust riding the magnetic waves carrying plasma on the solar wind.

"For decades, researchers have focused mainly on how electrons, ions, magnetic fields and plasma waves transport and dissipate energy in the solar atmosphere," said lead researcher Syed Ayaz of the University of Alabama in Huntsville in a statement. "Our work adds a new ingredient to this picture: dust grains."

The finding came courtesy of NASA's Parker Solar Probe, which has flown closer to the sun than any other spacecraft, skirting the corona at a distance of 6.1 million kilometers (3.8 million miles). If you've ever witnessed a total solar eclipse, or even seen a photograph of one, then you will be familiar with the corona — the ghostly tendrils of light that surround the eclipsed sun. Those tendrils are formed from plasma, or ionized gas, at temperatures in excess of a million degrees Fahrenheit, compared to the sun's visible surface, the photosphere, which radiates at about 9,932 degrees Fahrenheit (5,500 degrees Celsius). At those temperatures, the photosphere outshines the corona only because the plasma in the corona is so sparsely distributed. This is why the only time we can see the corona is during a total solar eclipse, when the photospheric glare is blocked.

Parker does not carry a cosmic dust detector, and that's because until now dust has not been considered a serious component of the solar atmosphere. Indeed, in the high temperatures of the solar corona it had been thought that dust could not survive for very long and would therefore have no impact.

However, Parker does host a bunch of antennas and magnetometers collectively referred to as the FIELDS experiment, designed to measure the electromagnetic field and radio emissions in the solar corona. The antennas kept picking up unexpected spikes in voltage, which according to Ayaz and his team are produced by clouds of charged particles created when tiny dust grains slam into Parker at high velocity.

These dust grains have accrued an electrostatic charge, which can interact with the electromagnetic field carried by the solar wind as it leaves the sun, which in turn can influence waves of plasma reverberating through that electromagnetic field called Alfvén waves.

There are two possible, competing ways in which dust can affect the Alfvén waves, which in turn could determine how energy is dumped into the corona, heating it. On one hand, the mass of the dust can act to provide extra inertia to the plasma as it rides the solar wind, allowing the plasma energy to be transported across wider distances. On the other hand, the electric charge on the dust grains can bolster the interactions between charged particles in the plasma, the Alfvén waves and the solar electromagnetic field.

An artist's impression of the Parker Solar Probe spacecraft facing and in close proximity to the sun. The disk of the star almost fills the frame, with swirling, fiery features and darker mottled spots present on its surface.

The Parker Solar Probe is seen in this illustration, right in front of the sun. (Image credit: NASA/Johns Hopkins APL/Steve Gribben)

"If dust mass dominates, [Alfvén] wave energy may travel farther into the corona," said Ayaz. "If dust-charge effects dominate, the energy may be released more locally as particle heating."

The balance between these two effects can therefore control where and when energy is deposited into the corona, focusing it in areas and causing temperatures there to rise dramatically.

Future solar missions are now going to have to start taking dust into account, said Ayaz, with dedicated detectors designed to measure dust's properties close to the Sun.

"The bigger question is fascinating," said Ayaz. "Is dust simply passing through the near-Sun environment, or is it helping shape how electromagnetic energy becomes heat and solar-wind motion?"

The new discovery was reported on July 1 in The Astrophysical Journal.

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More clues surface about the origins of interstellar comet 3I/ATLAS

More evidence that the interstellar comet 3I/ATLAS is much older than our solar system has come to light, along with clues that it formed on the outskirts of the protoplanetary disk belonging to its parent star long ago.

Earlier this year, researchers led by Martin Cordiner of NASA's Goddard Space Flight Center revealed that data from the James Webb Space Telescope (JWST) suggested that 3I/ATLAS is between 10 and 12 billion years old, based on the ratios of its carbon and deuterium isotopes. This would make it more than twice the age of our 4.6-billion-year-old solar system. Now, new results from the Ultraviolet and Visual Echelle Spectrograph (UVES) on the European Southern Observatory's Very Large Telescope support the JWST observations of carbon isotopes, and also introduce measurements of nitrogen isotopes that arrive at very interesting conclusions.

Isotopes are versions of atomic elements with different numbers of neutrons. For example, carbon-12 contains six protons and six neutrons, while carbon-13 contains six protons and seven neutrons. Meanwhile nitrogen-14 has seven protons and neutrons each, while nitrogen-15 has seven protons and eight neutrons.

These isotopes can form through subtly different processes, at different times and in different locations in the galaxy. The ratio of these isotopes in the gases released by comet 3I/ATLAS into its coma and tail as it neared the sun and grew warmer can therefore tell us much about its origin and history.

Consequently, interstellar objects such as 3I/ATLAS "are sort of fossils from a planetary formation process that happened very far away, but we get the chance to study from much closer," said astronomer Cyrielle Opitom of the University of Edinburgh in a statement.

Opitom led the team who got the chance to observe 3I/ATLAS with the VLT. They found that the ratio of carbon-12 to carbon-13 is higher than is found in comets in our solar system or indeed in the local interstellar medium. Carbon-13 is produced in greater abundances than carbon-12 over time, typically in red giant stars, so for there to be far more carbon-12 than carbon-13 tells us that 3I/ATLAS was born long ago before carbon-13 had a chance to build in abundance across the galaxy. This finding supports the JWST carbon isotope measurements.

Additionally Opitom's team, which was co-led by Jean Manfroid and Damien Hutsemékers of the University of Liège in Belgium, measured a ratio of nitrogen-14 to nitrogen-15 in 3I/ATLAS that is more than twice as large as the value measured in comets native to our solar system. In fact, the ratio is typical of that found on the outer edge of planet-forming discs around young stars, implying 3I/ATLAS formed a long way out from its parent star, perhaps in the equivalent of its Kuiper belt.

"Unlike comets from our solar system, this interstellar visitor carries unusually high carbon and nitrogen isotopic ratios," said team-member Aravind Krishnakumar, who is also of the University of Liège.

The results give us clues to how 3I/ATLAS found itself wandering the space lanes alone for billions of years. Models indicate that migrating giant planets can kick small bodies into interstellar space, but the location of 3I/ATLAS's birth far from that planetary action means that it is quite possible instead that it was snatched from its parent star by the gravity of a passing star and was subsequently hurled into deep space.

The JWST had also previously shown that 3I/ATLAS is rich in carbon monoxide and carbon dioxide relative to water, and also contains unexpectedly high abundances of nickel and iron and a very high abundance of methanol relative to hydrogen cyanide – all of which tells us that 3I/ATLAS formed in an environment with conditions and chemistry notably alien to our own solar system.

Unfortunately similar measurements were not possible with the other two known interstellar objects – 1I/'Oumuamua was not seen to outgas, while 2I/Borisov was too faint. However, 3I/ATLAS is a tantalizing indication that studies of more interstellar objects caught entering our solar system will be able to teach us about planet-forming conditions across both space and time in our Milky Way galaxy.

"3I/ATLAS is a really exciting opportunity to probe the composition of another planetary system, one that formed long before our Sun and solar system even existed," concluded Rosemary Dorsey, an astronomer from the University of Helsinki in Finland.

The findings were published on July 6 in the journal Nature Astronomy.

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‘Once-in-a-millennium’ asteroid flyby will be visible to much of the world in 2029

Three years before the skyscraper-size asteroid Apophis makes its very close (but safe) flyby of Earth, scientists have already begun charting exactly when and where billions of people can watch it sweep across the sky.

Speaking at an "Apophis T-3 Years" workshop held earlier this month at the University of Padua in Italy, retired cartographer Michael Zeiler and astronomer Rick Fienberg shared detailed visibility maps charting the asteroid's passage across Earth's skies.

According to their calculations, roughly 90% of the world's population — about 7.6 billion people — lives in regions where Apophis could, in principle, be seen with the naked eye on April 13, 2029. The actual viewing success will depend more on earthly considerations, however, including cloud cover and the extent of light pollution.

Known formally as 99942 Apophis, the space rock will not resemble a blazing meteor tearing through the sky. Instead, scientists say it will appear as a point-like speck of light gliding steadily across, which, at its closest approach, will appear to move by about the apparent width of the full moon every minute.

"It will definitely be noticeable," Fienberg told Space.com. "It's going to be moving more slowly than a satellite — it will cross the sky in hours, rather than minutes, and it will just be a point."

According to the new maps, the asteroid should remain visible to the naked eye for about seven hours, beginning over Australia at 11:00 a.m. EDT (15:00 UTC) and concluding over the North Atlantic at 6:00 p.m. EDT (22:00 UTC).

At 4:35 p.m. EDT (20:35 UTC), Apophis is expected to reach its greatest apparent brightness as it passes over Cameroon, offering prime viewing to an estimated 3.9 billion people across Africa, Asia, eastern South America and parts of Europe.

A diagram showing one of the points of peak brightness of Apophis.

One moment of peak brightness for Apophis (as seen from Earth) at the moment of closest approach at 5:45 p.m. EDT (21:45 UTC). The asteroid will be at a height lower than geosynchronous satellites. (Image credit: Eclipseatlas.com)

About an hour later, at 5:45 p.m. EDT (21:45 UTC), the asteroid will make its closest approach to Earth, passing about 19,700 miles (31,600 kilometers) above the North Atlantic — well inside the orbit of Earth's geostationary satellites. The event would be visible across much of South America, the United States, Africa and parts of Europe, reaching roughly 2 billion people.

"This is the first time we've been able to predict in human history an asteroid visibly passing by the Earth," Richard Binzel, a professor of planetary sciences at the Massachusetts Institute of Technology (MIT), said during the workshop. "That's part of a shared experience."

As excitement ramps up for the once-in-a-millennium spectacle, Binzel opened the workshop with three messages: "Apophis will safely pass the Earth. Apophis will safely pass the Earth. Apophis will safely pass the Earth."

That absolute certainty is the hard-won fruit of more than two decades of increasingly precise observations. When Apophis was discovered in 2004, early calculations suggested a 1-in-37 chance of an impact in 2029, making it the most potentially hazardous asteroid known at the time. Additional observations steadily refined the asteroid's orbit, eliminating any possibility of a collision in 2029 and also ruling out any impact threat for at least the next century, according to NASA.

With the impact threat removed, scientists now view the flyby as a rare opportunity to observe how Earth's gravity affects an asteroid during an exceptionally close encounter.

A diagram of the Earth showing a moment of closest approach.

A diagram of Earth showing where Apophis will be at the moment of closest approach on April 13, 2029. (Image credit: Eclipseatlas.com)

Our planet's gravity is expected to tug the asteroid into a new orbit around the sun without posing any future danger. During the flyby, however, those same gravitational forces may stretch and squeeze the asteroid enough to trigger landslides or expose pristine material hidden beneath its weathered surface. Or they may do almost nothing.

"We simply don't know what's going to happen," Binzel said during the workshop. "Apophis may go by and not care too much, or maybe we'll see something significant."

"That's why we have to look," he added. "We're gonna learn a lot either way."

At the workshop, scientists said they hope to monitor the flyby from observatories in Spain's Canary Islands, among other places, as its location in the Atlantic Ocean offers an ideal view of the asteroid's closest approach as well as favorable prospects for clear skies.

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Human flight was still 7 years away in 1776. Now, we’re headed back to the moon

Humanity has likely dreamed of flight since the very beginning, marveling at birds soaring overhead and trying to puzzle out their seemingly magical secret.

We made some halting steps over the centuries — getting kites aloft in ancient China, for example, and drawing up ambitious but unrealized flying machines during the Renaissance — but our boots were still firmly rooted on the ground when the United States of America was born on July 4, 1776.

Things changed just a few years later, however. In November 1783, a hot-air balloon designed by the Montgolfier brothers carried two men on a 25-minute flight over Paris, beginning our species' exploration of the heavens.

Another 120 years passed before we managed to fly with a powered, heavier-than-air craft, a milestone notched by the Wright brothers in North Carolina on Dec. 17, 1903. Remarkably, it took us less than half that long to make the jump from the sky to the final frontier, which cosmonaut Yuri Gagarin did for the first time on April 12, 1961.

Eight years later, Apollo 11 astronauts Neil Armstrong and Buzz Aldrin walked on the moon — a remarkable achievement that was the climactic moment of the Cold War space race between the United States and the Soviet Union.

Over the next three and a half years, five more Apollo missions landed on Earth's nearest neighbor, leaving behind flags, footprints and defunct machinery. Now, more than half a century later, our species is gearing up to go back — but this time, in a much different way.

NASA wants to build a base near the moon's south pole over the next decade or so, an ambitious project the agency is undertaking via its Artemis program. And this is not an end in itself; NASA believes the knowledge gained from establishing such an outpost will help humanity make the next giant leap — to Mars.

The ball is rolling on Artemis, with two successful missions already in the books. Artemis I launched an uncrewed Orion capsule to lunar orbit and back in late 2022, and Artemis II sent four astronauts on a loop around the moon this past April. Next up is Artemis III, which will test docking procedures with one or both of the Artemis program's lunar landers (SpaceX's Starship and Blue Origin's Blue Moon) in Earth orbit in 2027. If all goes well with that flight, Artemis IV will put astronauts down near the lunar south pole, possibly as soon as 2028. (That timeline is far from guaranteed, however, as much development work remains. For example, neither Starship nor Blue Moon has yet reached Earth orbit or been cleared to carry humans.)

This is all happening in the context of a new space race, this time with China. The nation plans to land astronauts on the moon by 2030 and has been ticking boxes that keep this timeline within reach. And China aims to build a base of its own — also near the moon's south pole, which is thought to be rich in water ice — in collaboration with Russia and other partners.

What does all of this mean for the United States? Well, the nation came of age industrially after the Wright brothers' historic flight and has been a leader in aerospace tech and exploration ever since. The U.S. can accomplish amazing things in the final frontier, especially when pushed by a rival, so the years just after its 250th birthday may be quite eventful indeed. Stay tuned!

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In 1776, the moon was a clock, a calendar and a streetlight — and it was 31 feet closer to Earth

After Americans declared independence on July 4, 1776, a waning gibbous moon rose in the night sky. To the people celebrating the birth of a new nation, it would have looked much the same as the moon we see today. But there was one subtle difference: 250 years ago, the moon was about 31 feet (9.4 meters) closer to Earth than it is now.

"The moon is currently drifting away from Earth at a rate of about 3.8 centimeters [1.5 inches] per year, which is coincidentally roughly the same speed at which human fingernails grow," says Seth McGowan, president of the Adirondack Sky Center & Observatory in Tupper Lake, New York.

That 31 feet may sound significant, but against the moon's average distance from Earth of 238,855 miles (384,400 km), it's effectively nothing. In fact, the moon's elliptical orbit causes its distance from Earth to vary by about 26,000 miles (43,000 km) every month as it moves between perigee, its closest point to Earth, and apogee, its farthest. "The tiny 31-foot shift over 250 years is entirely swallowed up by that massive monthly variance," says McGowan. But while the moon itself looked much as it does today, the world beneath it was very different.

How Americans used the moon in 1776

Colonial Americans depended on the moon in ways that are easy to forget in an age of electric light and digital clocks. Travelers planned journeys around how much moonlight would be available on a given night. Farmers and Indigenous peoples consulted lunar cycles to anticipate seasonal changes. Mariners tracked the moon's pull on the tides. Even military planners considered lunar illumination — during the Revolutionary War, a moonlit night could aid troop movement and navigation, but it could also expose an army's position to enemy forces. The moon helped people organize their activities in an era when daily life remained closely tied to the natural world.

One of the most popular publications of the colonial era was the almanac. Long before weather apps — or even standardized timekeeping — Americans turned to these annual guides for practical information about moon phases, moonrise and moonset times, eclipses, tides, and seasonal events. Publications such as Benjamin Franklin's "Poor Richard's Almanack" helped popularize the format decades before independence, while later titles, such as "The Old Farmer's Almanac," first published in 1792, continued the tradition.

What astronomers knew about the moon in 1776

By the time the Declaration of Independence was signed, astronomers already understood a surprising amount about Earth's nearest neighbor. More than 160 years earlier, Galileo's telescopic observations had revealed mountains, valleys, and craters on the lunar surface, overturning the ancient notion that heavenly bodies were perfect spheres. Isaac Newton's laws of motion and gravitation had since explained why the moon orbited Earth and why tides occurred.

While astronomers could predict eclipses and chart the moon's movements with impressive accuracy, they had never seen the moon's far side, had no idea how it formed, and couldn't say with confidence what it was made of. All of that would come centuries later — and there are still many lunar unknowns today.

How Apollo astronauts revealed the moon's slow escape

During the Apollo missions, we learned an extraordinary amount of new information about the moon, including the rate at which it's moving away from Earth. Apollo astronauts installed retroreflectors — special mirrors designed to bounce light directly back toward its source—on the lunar surface. Scientists then fired lasers at those reflectors to measure how long it takes the light to return, allowing them to calculate the Earth-moon distance with extraordinary precision. (Fun fact: We continue to use the retroreflectors today!) Those measurements revealed that the moon is receding from Earth at about 1.5 inches (3.8 cm) per year.

"The moon's gravity pulls on Earth's oceans, creating a tidal bulge," says McGowan. "Because Earth rotates faster than the moon orbits us, that ocean bulge pulls slightly ahead of the moon, acting like a cosmic gravitational leash that accelerates the moon into a higher, wider orbit. In doing so, the Earth's rotation slows ever so slightly — about 2.3 milliseconds per century. "Back in 1776, a day on Earth was about 5.75 milliseconds shorter than it is now," says McGowan.

This effect is imperceptible on human timescales, but over millions of years, it will have dramatic consequences. Eventually, the moon will appear too small in Earth's sky to completely cover the sun, ending the era of total solar eclipses and leaving only annular, or "ring of fire," eclipses in their place. The moon will never completely free itself from Earth, though — physics dictates that the drift will stop after about 15 billion years. And well before that, in about 5 billion years, the sun will expand into a red giant, consuming both the Earth and the moon entirely.

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NASA will send a soccer ball to the moon —if the US wins the World Cup

Jared Isaacman is doing his best to spur his country on to sporting glory.

The NASA chief announced on Tuesday (June 30) that the agency will send a FIFA World Cup 2026 soccer ball to the moon if the U.S. men's national team manages to win the tournament, which is going on right now.

"So, a little bit of motivation for the United States here on this one," Isaacman said during a livestreamed press event on Tuesday. "We're going to one-up Alan Shepard in the golf game on the lunar surface, and we're going to get the soccer ball there."

Shepard famously smuggled two golf balls and an improvised club onto the Apollo 14 mission, which he commanded. On Feb. 6, 1971, the NASA astronaut hit those balls on the moon, becoming the first person ever to play a sport on another world.

The soccer-ball plan, by contrast, would be a sanctioned affair; Isaacman and Carlos García-Galán, manager of NASA's Moon Base program, are both behind it.

"I don't know which lander it'll wind up going in," Isaacman said during Tuesday's event, the second of the agency's monthly updates about its plans to build a crewed outpost near the lunar south pole via its Artemis program.

Turning to García-Galán, he added, "I'll leave that to you guys, to handle the payload."

"We will take on that challenge," García-Galán replied. "It will be super exciting to do that if they win. Good luck."

a woman floating in zero gravity in a cramped laboratory spins a soccer ball using a power drill

NASA astronaut Jessica Meir spins a FIFA World Cup 2026 soccer ball in microgravity aboard the ISS. (Image credit: NASA)

The U.S. men's team will probably need some luck to win the World Cup, an every-four-year event that's currently being jointly hosted by the U.S., Canada and Mexico. The American men have won just two knockout-round games in the entire history of the tournament, and one of those came in 1930, during the first-ever World Cup.

The 2026 team has performed better than most of its predecessors to this point, however; the Americans won their four-team group to advance to the single-elimination stage, beating both Paraguay and Australia before losing a meaningless game to Turkiye. (The U.S. had already clinched the group win at that point.)

The U.S. plays Bosnia-Herzegovina in a Round of 32 match on Wednesday (July 1). To hoist the World Cup trophy, the Americans would have to win that game, then four more after that, likely against some perennial soccer powers.

If they make it to the quarterfinals, for example, they'll likely face Spain, which won the World Cup in 2010 — a potential matchup flagged by García-Galán, who's from Málaga.

The U.S. women's soccer team has enjoyed a great deal more success at the international level, winning four of the nine FIFA Women's World Cups to date. (The women's tournament, which is also held every four years, was first played in 1991.)

a soccer ball featuring the text 'fifa 26' sits near a window through which earth can be seen from space

The FIFA World Cup 2026 soccer ball on the International Space Station. (Image credit: NASA)

A moon mission wouldn't be the first trip off Earth for the official FIFA World Cup 2026 soccer ball. NASA also sent one of the balls to the International Space Station, where astronauts played with it in the Kibo module.

"We're working to inspire the next generation by showing how space exploration inspires innovation in sports science — and everyday life," the agency said via X on June 20, in a post that included video of the off-Earth action.

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Ocean-monitoring satellite spots wildfire smoke from space | Space photo of the day for July 1, 2026

White and gray smoke hovers over an Earth landscape.

Swirls of wildfire smoke can be seen over Canada. (Image credit: NASA)

Wildfires across the globe can be seen all the way from space. And one unexpected tool has come in handy to spot plumes of wildfire smoke: a satellite designed to study Earth's oceans.

What is it?

In this photo, we can see swirls of wildfire smoke over the Great Lakes in Canada. Fluffy white clouds float over the land and lakes, in contrast to the wisps of gray smoke, which float out from massive wildfires that ripped through North America.

The photo was snapped in May of last year by NASA's PACE (Plankton, Aerosol, Cloud, and ocean Ecosystem) satellite. This seems logical, as it is an Earth-monitoring satellite, but what's surprising is that the orbiting spacecraft was actually designed to study and monitor Earth's oceans and atmosphere. In fact, the image itself was captured by PACE's Ocean Color Instrument, which does "hyperspectral" imaging, meaning that it observes the planet in hundreds of different wavelengths of light (in visible, near-infrared and ultraviolet).

Why is it incredible?

This image, among others, shows the incredible versatility of space technologies like PACE. While wildfire monitoring isn't its explicit purpose, images and data from this mission could be incredibly helpful in deepening our understanding of wildfires and how they spread.

"The PACE satellite observes land too, and does it really well," Skye Caplan, terrestrial lead for the PACE mission at NASA's Goddard Space Flight Center in Maryland, said in a statement. "There is so much to explore with a new hyperspectral data set."

In fact, in addition to capturing wildfire smoke, as we can see in this image, PACE's Ocean Color Instrument can also spot changes in vegetation, burn scars and the charred aftermath of a wildfire. Images in the instrument's hundreds of wavelengths can reveal a variety of detailed information, such as how stressed, dry or even pigmented plants are on Earth's surface. This type of information could also be beneficial in identifying dry areas that could be at a higher risk of wildfires sparking.

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In 1776, the solar system only had 6 planets. Now, it has 8. Does it end there?

Over the past 250 years, the number of "planets" in our solar system has ranged from six to nine — and, briefly, even 11 — depending on what astronomers knew at the time and how they defined a planet. As the United States prepares to celebrate its 250th anniversary, that changing tally offers a unique lens on humanity's evolving understanding of the cosmos since 1776.

Throughout history, astronomers have discovered new worlds, identified entirely new classes of celestial objects and repeatedly revised the very definition of a planet. The result is a surprisingly complicated answer to one of astronomy's most basic questions: How many planets are there in our solar system?

"The change in the number of recognized planets well represents how science is done," Kevin Schindler, historian and public information officer at Lowell Observatory, told Space.com. "Scientists discover something — a planet, dinosaur fossil, or beetle, for example — study it and classify it. With further study, and by studying more examples, scientists learn more and update their understanding of the thing, sometimes reclassifying it."

When the United States declared independence in 1776, astronomers recognized just six planets: Mercury, Venus, Earth, Mars, Jupiter and Saturn. That changed only five years later when William Herschel discovered Uranus in 1781, expanding the known solar system and increasing the planet count to seven.

The tally grew again in 1801 with the discovery of Ceres, a world orbiting between Mars and Jupiter. Three similar objects were found soon afterward, and for a time astronomers considered all of them planets, briefly bringing the total to 11. However, as additional objects were discovered, scientists realized they represented a distinct population and those objects were reclassified as asteroids, reducing the planet count down to seven, Schindler explained.

Neptune's discovery in 1846 raised the total to eight, while Clyde Tombaugh's discovery of Pluto at Lowell Observatory in 1930 established the familiar nine-planet solar system. This changing planet count underscores a broader pattern in humanity's journey of exploration and discovery over the past 250 years.

"I think it shows that exploration and the thirst to understand the universe around us is ingrained in us, it's part of our DNA and we continue to want to learn," Schindler said. "Our founding fathers established the United States based on scientific principles such as reason and logic, observation, evidence-based analysis, and openness to debate different points of view and be open to change."

For much of the 20th century, the answer seemed settled: The solar system had nine planets. However, beginning in the late 1950s, advancing spacecraft technology allowed scientists to study planets, moons and smaller bodies up close, revealing worlds far more diverse and dynamic than could be seen through telescopes alone. Then, in the early 1990s, astronomers began discovering a growing population of icy worlds beyond Neptune.

"The discovery of Trans-Neptunian Objects (TNOs) — numerous objects similar to Pluto but with orbits extending much farther away from the sun — tells us a lot about our 'local' environment," astronomer Kyler Kuehn, director of science, technology and operations at Lowell Observatory, told Space.com in an email, emphasizing the impact discovering TNOs has had on the classification of Pluto.

An illustration of a rock in space with a star in the far distance.

An artist's interpretation of a trans-Neptunian object. (Image credit: Artwork: NASA, ESA, and G. Bacon (STScI); Science: NASA, ESA, and C. Fuentes (Harvard-Smithsonian Center for Astrophysics))

"While Pluto was the first TNO to be discovered, the fact that there could be millions of similar objects populating the outskirts of the solar system naturally leads to the question 'Why should we treat Pluto differently than any of the others?'" Kuehn said.

The growing number of TNO discoveries ultimately established that Pluto was part of the Kuiper Belt, a vast reservoir of icy bodies extending beyond Neptune's orbit. As a result, Pluto was no longer viewed as a unique outlier, but rather one member of a much larger population. This dramatically reshaped astronomers' understanding of the solar system, exposing a far more complex outer frontier than anyone in 1776 could have imagined.

"It doesn't fit into the relatively tidy structure of the solar system as understood in 1776," Schindler said. For 18th-century astronomers, "it likely wouldn't be a surprise to find new planets or a new class of planet-like bodies (asteroids), but the discovery of an entire new zone of bodies, which was more [chaotic], probably would have been a surprise, showing that the solar system is not nearly as tidy and stable as believed."

The debate surrounding Pluto's classification culminated in 2006, when the International Astronomical Union adopted a formal definition of a planet. Under that definition, a planet must orbit the sun, be massive enough to become nearly round under its own gravity and have "cleared the neighborhood" around its orbit. While Pluto met the first two requirements, it did not meet the third and was reclassified as a dwarf planet, dropping the official planet count from nine back down to eight.

Controversy over Pluto's classification continues today. Schindler said scientists who oppose Pluto's planethood typically favor a dynamical definition focused on how a body interacts with and dominates its orbital environment. Meanwhile, those who favor Pluto's return to planetary status generally support a geophysical definition based on an object's physical properties. In fact, Pluto's 2015 flyby by NASA's New Horizons spacecraft further fueled the debate by revealing a surprisingly complex world with mountains, glaciers and active geology.

"There has not been any resolution between the two sides," Schindler said, noting that public interest has also helped keep the debate alive.

Most recently, NASA Administrator Jared Isaacman added his voice to the conversation by saying he believes Pluto should once again be considered a planet and that the scientific community should revisit its classification.

A sphere in the foreground that is white-ish with a red splotch toward the bottom left. In the background, there is a purplish sphere with redness on its top.

A close up of Pluto (a red and white planet in the front) and its moon Charon (a darker reddish sphere) in the back in the darkness of space. (Image credit: NASA/JHUAPL/SwRI)

"Arguing about the technical definition of 'planet' doesn't actually change anything about the (dwarf) planet itself, but how we classify things can be extremely important to the kinds of questions we even think to ask, " Kuehn added. "Scientific definitions have changed and will continue to change over the course of decades and centuries as we learn more."

The changing planet count demonstrates the foundations of how science works. Schindler compared Pluto's reclassification to the dinosaur Brontosaurus, which was renamed Apatosaurus after further study before later regaining its original classification as scientists refined their understanding.

Therefore, future discoveries, both within our solar system and beyond it, could further reshape scientists' understanding of planetary systems and how planets are classified.

"That might lead us to a more useful definition of planet than anything we are even considering now," Kuehn said. Looking forward, "I think we will learn a lot more about the extreme edges of our solar system — we have barely scratched the surface."

Two hundred and fifty years ago, astronomers knew of only six planets. Today, the official count in our solar system stands at eight, as the debate continues over whether that number tells the whole story.

As the United States marks its 250th anniversary, the changing planet count serves as a reminder that discovery is never finished. Every new observation has the potential to reshape our understanding of the cosmos — just as it has since America's founding — and perhaps even change the answer to one of astronomy's oldest questions: How many planets are there in our solar system?