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doi: https://doi.org/10.1038/d41586-024-01703-3
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Nature, Published online: 14 June 2024; doi:10.1038/d41586-024-01702-4
Data recorded at an observatory in Chile do not fit with a black hole, a supernova, a pair of merging stars or anything else.
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Download the Nature Podcast 12 June 2024
In this episode:
A comprehensive suite of biomedical data, collected during the first all-civilian spaceflight, is helping researchers unpick the effects that being in orbit has on the human body. Analysis of data collected from the crew of SpaceX’s Inspiration4 mission reveals that short duration spaceflight can result in physiological changes similar to those seen on longer spaceflights. These changes included things like alterations in immune-cell function and a lengthening of DNA telomeres, although the majority of these changes reverted soon after the crew landed.
Collection: Space Omics and Medical Atlas (SOMA) across orbits
Researchers have discovered why 2019 was so awash with Painted Lady butterflies, and the meaning behind gigantic rock engravings along the Orinoco river.
Research Highlight: A huge outbreak of butterflies hit three continents — here’s why
Research Highlight: Mystery of huge ancient engravings of snakes solved at last
A huge trial of hybrid working has shown that this approach can help companies retain employees without hurting productivity. While a mix of home and in-person working became the norm for many post-pandemic, the impacts of this approach on workers’ outputs remains hotly debated and difficult to test scientifically. To investigate the effects of hybrid working, researchers randomly selected 1,612 people at a company in China to work in the office either five days a week or three. In addition to the unchanged productivity, employees said that they value the days at home as much as a 10% pay rise. This led to an increase in staff retention and potential savings of millions of dollars for the company involved in the trial.
Research article: Bloom et al.
Editorial: The case for hybrid working is growing — employers should take note
Germany balks at the $17 billion bill for CERN’s new supercollider, and working out when large language models might run out of data to train on.
Nature News: CERN’s $17-billion supercollider in question as top funder criticizes cost
Associated Press: AI ‘gold rush’ for chatbot training data could run out of human-written text
Subscribe to Nature Briefing, an unmissable daily round-up of science news, opinion and analysis free in your inbox every weekday.
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HOUSTON, TEXAS
NASA astronaut Kate Rubins was having a hard time seeing in the eerie twilight of the Moon’s south pole this month.
Rubins made her way carefully through the deep shadows on the lunar surface, her path dimly lit by lights on her spacesuit’s helmet. She was hunting through the volcanic landscape for geological treasure — Moon rocks that she could pick up and bring back to Earth, which would reveal secrets of this frozen world. As the first person to set foot on the Moon in more than half a century, Rubins was making good progress on her historic foray — despite the piles of cow manure along the way.
The rock-strewn plain wasn’t really the Moon but was, in fact, the high desert of northern Arizona. Rubins and astronaut Andre Douglas were participating in the biggest dress rehearsal yet for the next time NASA plans to send people to the Moon’s surface, a mission known as Artemis III. If all goes to plan, Rubins or one of her colleagues will be stepping onto the actual Moon a little over two years from now. So NASA is training its astronauts to make the most of their precious time there — given that no human has set foot on the lunar surface since the last Apollo crew blasted off in 1972.
The $93-billion plan to put astronauts back on the Moon
“There’s a lot we need to relearn or figure out,” says Juliane Gross, a planetary scientist at NASA’s Johnson Space Center (JSC) in Houston, Texas, who will oversee the Artemis samples when they come back to Earth. “And so we’re charting the way while we sail it.”
“We’re baking in that scientific rigour very early on that these missions are going to need,” Rubins later told Nature.
During the moonwalking simulation two weeks ago, Gross and other scientists gathered at JSC. It was a massive undertaking that linked astronauts in the field in Arizona with mission controllers and a science team in Houston — working together in real time to choreograph what the astronauts should do on the mock lunar surface. Leading scientists, famous astronauts and NASA brass all showed up to witness the historic test. More than six years after the agency officially kicked off its Artemis programme to return humans to the Moon, it felt as if the Artemis Moon landing was becoming real.
If NASA manages to pull off an Artemis III landing, it will have taken some US$100 billion to develop the rockets, crew capsule, landing system and other equipment. As with the Apollo 11 landing in 1969, in which Neil Armstrong and Buzz Aldrin became the first people to set foot on the Moon, the Artemis III landing aims primarily to get astronauts there and back safely.
But science is an integral part of the Artemis programme, according to NASA. The agency has ramped up its astronaut training to incorporate more field geology, so that crew members can learn how to explore the lunar landscape and determine which rocks to pick up, as well as how to deduce the area’s geological history.
Such training paid off during the final three Apollo missions, when each astronaut had roughly 1,000 hours of science training, says Dean Eppler, a lunar geologist who has retired from JSC. “We look at Apollo as the way to do it because it was very successful,” he says. On Apollo 15 in 1971, for instance, two former test pilots spotted and brought home a gleaming fragment of what turned out to be primordial lunar crust. That sample, nicknamed the Genesis Rock, helped geologists to understand how the Moon solidified from a molten magma ocean more than four billion years ago.
In the 2000s and 2010s, NASA trained astronauts to observe Earth from the International Space Station. Now, through visits to places such as asteroid craters and volcanic terrain, astronauts experience what it will be like on the Moon. “That way they know, when you get to the surface of the Moon — if things are not quite the way you had them in your mind, that’s OK,” says Cynthia Evans, a geologist at JSC who leads astronaut geology training.
The harsh light at the Moon’s south pole means that astronauts must prepare to work in a strangely illuminated landscape.Credit: NASA/Josh Valcarcel
Artemis III will visit a part of the Moon that has never been explored by astronauts, the lunar south pole. Because of the region’s high latitude, the illumination will be harsh and at a steep angle relative to the surface as the Sun circles the horizon. The contrast between brightly lit regions and deep shadows will make it difficult for astronauts to work in the environment.
Ground zero for the recent exercise in extravehicular activities (EVAs) was the San Francisco volcanic field north of Flagstaff, Arizona, where NASA and the US Geological Survey (USGS) trained Apollo astronauts in the 1960s. This month’s test, known as JETT5 for Joint EVA and Human Surface Mobility Test Team, took place on private land near a cinder cone known as SP Crater. (SP stands for ‘shit pot’, because the crater and its associated lava flow look as if someone tipped over a chamber pot and the contents flowed out onto the landscape.)
A satellite view of SP Crater in Arizona shows the volcanic crater and lava flow that serve as a simulated Moon landscape for astronauts in training.Credit: NASA/GSFC/METI/ERSDAC/JAROS, and US/Japan ASTER Science Team
Last year, USGS geologists mapped the test area and handed those maps to the researchers who gathered at JSC in a ‘science back room’ during the training exercise. The researchers drew up four simulated moonwalks, each of which ventured from a landing site to explore lava flows, gorges and other geology in the area. “This is very relevant to exactly what we’ll be doing for Artemis,” says Lauren Edgar, a geologist at the USGS in Flagstaff who is co-leader of the JETT5 science team.
During the third of the four moonwalks this month, Rubins and Douglas climbed into spacesuits that mimic what the Artemis team might wear on the Moon. They ‘disembarked’ from their ‘lander’ by walking through a set of orange poles strung with tape — and they were suddenly on the lunar surface, albeit one riddled with ant hills and cow dung.
Rubins and Douglas took photographs and began collecting rocks, radioing their observations back to mission control. They were so efficient at working through their carefully scripted checklists that they were soon running ten minutes ahead.
Some 1,600 kilometres away in Houston, their speed caught the attention of Brett Denevi, a planetary geologist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, who was serving as leader of the science back room for the evening.
Planetary geologist Brett Denevi consults with other researchers about what NASA astronauts should do during their simulated moonwalk.Credit: Michael Starghill Jr for Nature
Looking for ideas, Denevi asked the science scrum — the informal name for the team members sitting around a map-strewn table. Among them were four scientists, each of whom represented one of JETT5’s main science goals: the study of the area’s surface processes; age relationships between its rocks; its volcanic history; and whether there could be volatile elements frozen in the soil in this simulacrum of the Moon’s south pole. The scrum decided to ask whether the astronauts could collect a drive tube of eroded sediments.
Drive tubes are metal cylinders that allow geologists to collect core samples of soft sediments. During the Apollo era of lunar exploration from 1969 to 1972, NASA astronauts gathered tubes of lunar soil that revealed how cosmic rays pummel the Moon’s surface. Now, Denevi and her team wanted a sample of sediments that had eroded off a nearby rock outcrop. It was a big ask that would require the astronauts to divert from other tasks they had planned.
Each decision during the test had to be justified in real time and carefully documented. “We can’t just say we want that rock,” said José Hurtado, a geologist at the University of Texas El Paso who was Denevi’s deputy for the evening. “We have to elucidate why we want that specific rock and why it ties back to our priorities.”
Denevi walked over to a man wearing a communications headset and passed him a note. “We want to do a single drive tube,” she told him. “Here are the coordinates.”
The scientists’ request was relayed to mission control, which agreed; flight controllers then told the astronauts to go ahead and collect the requested sample. The science back room clocked that as a big win for the evening and erupted in cheers. “We did that!” said one of the scientists at the map table, pumping her arm in triumph. Soon, a series of clinking sounds filled the mission audio feed as Rubins hammered the drive tube into the ground.
Locating astronauts in real time on the lunar surface is one of the challenges that NASA is working to overcome.Credit: Michael Starghill Jr for Nature
Not everything went smoothly during the night-time EVA. The flight-operations team deliberately built in some challenges, including dropping video communications with the astronauts any time they travelled too far from the lander. An artificial, 20-minute delay on downloading imagery meant that the science team often couldn’t see real-time photos of the rocks the astronauts were picking up.
At one point, Rubins, who is a microbiologist, joked about collecting a piece of cow manure and putting it in a geological sample bag, given that it is ever-present on the Arizona ranch land.
The science back room hummed with activity on multiple audio loops and virtual chats. In addition to the scrum, another group of researchers set up at a neighbouring table to analyse images from the moonwalk, while two other scientists kept track of where the astronauts were.
Real-time videos from the ‘moonwalking’ astronauts in Arizona appear on display screens at NASA’s Johnson Space Flight Center in Houston, Texas. Scientists at the centre discuss what the astronauts should do during the training.Credit: Michael Starghill Jr for Nature
To mimic the lighting conditions at the lunar south pole, JETT5 organizers built a ‘Sun cart’ — essentially a giant spotlight wheeled onto the landscape. To Rubins and Douglas, the light looked like the distant Sun hovering just above the horizon.
The astronauts carefully navigated their way across the dim landscape, relying on a few personal lights to aid their work. Rubins in particular was thrilled to have a handheld light that she could direct where she wanted, in addition to the helmet-mounted lights that pointed only in the direction in which she was looking. “I’m going to call a light that illuminates the area near my feet totally necessary,” she told mission control — feedback that could help astronauts when they reach the Moon.
The point of JETT5 was to develop tools and procedures that will work for Artemis III astronauts on the lunar surface. But many of NASA’s challenges are much greater than working out which rocks to pick up. The Artemis programme has less funding than Apollo did — that programme and its precursors spent more than $300 billion in today’s dollars between 1960 and 1973 — and the planned cadence of Artemis missions is accordingly slower.
Artemis I, an uncrewed test of the heavy-lift rocket and crew capsule to be used for astronauts, was a 25-day space flight that orbited the Moon in late 2022. Artemis II, which will send four astronauts around the Moon without landing, is scheduled for no earlier than September 2025 and the Artemis III landing would be no sooner than September 2026. Artemis IV, another crewed mission to the surface, is pencilled in for 2028. Meanwhile, China has announced its own plans to send humans to the Moon by 2030.
Lift off! Artemis Moon rocket launch kicks off new era of human exploration
NASA has been collaborating with other space agencies on its Artemis plans. Rubins, for instance, has done extra field geology training with the European Space Agency, including at an impact crater in Germany.
“You really want to get your astronauts best acquainted with what they will come across in space in an environment on Earth that you can control and they can learn from,” says Samuel Payler, who helps to lead astronaut science training at the European Astronaut Centre in Cologne, Germany.
At the end of the evening’s moonwalk, Denevi and her team got a surprise of their own. “I forgot to tell you something super-important,” Rubins told mission control as she and Douglas were wrapping up for the night. “I found a really cool rock and I didn’t tell you about it!”
The mystery rock piqued the interest of the science back room. Rubins said it was about the size of a softball, but gave no further clues. The scientists then had to work out how to account for it in their planning, including how much it might consume of the allotted weight of rocks they were able to bring back from the ‘Moon’ during the exercise.
Mock spacesuits and a tool cart mimic the equipment that Artemis astronauts might use on the surface of the Moon.Credit: NASA/Josh Valcarcel
The next night, during the final stage of JETT5, the astronauts pulled off their longest simulated moonwalk yet, at nearly four hours. They had collected about 38 kilograms of rocks and soil, and met their main goals. As the astronauts stowed their Moon tools in Arizona, the science back room in Texas suddenly got a lot more crowded as the flight operations team joined the room for a debriefing session.
Flight controllers described how JETT5 went from their perspective, and the science back room was relieved to hear that the process worked well. “Thank you for allowing us to advocate for science — I think it was powerful to see that happen,” Cherie Achilles, a mineralogist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-leader of the science team, told the room.
Soon, the scientists were planning for a more extensive debriefing the next day. After that, there would be spreadsheets to finish, documents to finalize and papers to write up.
NASA isn’t planning another big exercise like JETT5 any time soon, but there will be smaller efforts to test specific tools for lunar exploration. If NASA is going to make its Artemis dreams come true, there’s a lot of work to be done.
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Nature, Published online: 23 May 2024; doi:10.1038/d41586-024-01401-0
A colossal object called Dracula’s Chivito, referring to an well-stuffed sandwich popular in Uruguay, is the chunkiest planetary nursery known.
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Nature, Published online: 22 May 2024; doi:10.1038/d41586-024-01357-1
A phenomenon that affects the magnetic fields of rotating bodies could be involved in recurring changes in the Sun’s behaviour, which are related to a periodic flipping of its field. The proposal is a fresh take on this strange effect.
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Stunning photographs of the northern and southern lights, seen at much lower latitudes than usual, saturated social media on Friday and Saturday. For space-weather scientists, the auroras, created by a raging solar storm, were long-expected but dramatic evidence that the Sun is nearing the peak of its 11-year cycle of activity.
Satellite operators, electrical-grid managers and others who maintain crucial technological infrastructure are still assessing the impacts of this historic event — the severest geomagnetic storm since 2003. But most major systems seem to have weathered the blast.
That’s encouraging, because more storms are likely: the most powerful geomagnetic storms of a solar cycle can occur after the ‘solar maximum’, which is expected later this year. Nature explains what happened over the past few days and what solar physicists are anticipating next.
The immediate cause is a cluster of sunspots, known as active region 3664, that appeared below the Sun’s equator on the side currently facing Earth. The cluster is around 17 times as wide as Earth, and is probably the largest and most complex sunspot region observed during the current solar cycle, which began in 2019, says Shawn Dahl, a space-weather forecaster at the US National Oceanic and Atmospheric Administration’s Space Weather Prediction Center in Boulder, Colorado.
Starting around 8 May, active region 3664 sent at least seven blasts of magnetized plasma, or coronal mass ejections, racing in Earth’s direction at speeds of up to 1,800 kilometres per second. Along with waves of charged particles and other solar debris, the coronal mass ejections swamped space-weather detectors. The experience was “hypnotic”, says solar physicist Ryan French of the National Solar Observatory in Boulder — first in watching the data flood in, and then later with the “raw awe” of witnessing the aurora.
The Sun unleashed blasts of magnetized plasma (one seen at lower right in this ultraviolet image) during a ferocious solar storm that began around 8 May.Credit: NASA/SDO
Huge — by a number of measures. It was ‘extreme’ on the five-tiered scale that describes geomagnetic storms, and a ‘superstorm’ according to an index of changes in Earth’s magnetic field.
And then there were the auroras. Earth’s magnetic field shields humans and other life from the effects of solar storms by redirecting harmful particles around the planet. But when the material from coronal mass ejections slams into the magnetic field, it dumps energy into Earth’s upper atmosphere. Chemical elements there, such as oxygen and nitrogen, become ionized and glow in various colours, creating auroras. The lights are usually seen near Earth’s poles, but on 10 May, because of the intensity of the solar storm, auroras were seen at remarkably low latitudes, including in Mexico.
“Unforgettable,” says Steph Yardley, a space physicist at Northumbria University in Newcastle-upon-Tyne, UK. The auroras were so active that she had to look south, rather than north, from her viewing point in Scotland to see it.
The solar storm interrupted radio and GPS communications across the globe. The broadband internet connection provided by Starlink, a division of the aerospace firm SpaceX — a service that relies on more than 5,000 satellites — reported some temporary degradation in the quality of its signals. That could be because of communications disruptions or because the storm changed the density of Earth’s atmosphere and created drag on the satellites, space-weather physicist Tamitha Skov posted on the social-media platform X (formerly Twitter).
Staring at the Sun — close-up images from space rewrite solar science
In anticipation of the extreme solar activity, electrical-grid operators had taken protective measures — geomagnetic storms can induce extra electrical currents in the grid, causing power cuts. New Zealand’s electrical-transmission service temporarily turned off some circuits around the country to prevent equipment damage.
NASA said on 10 May that it foresaw no threat to the four US and three Russian astronauts aboard the International Space Station. Three people are aboard China’s Tiangong space station, but there have been no reports of precautionary actions taken there either.
Some satellites did stop making scientific observations. For instance, NASA’s Chandra X-ray Observatory temporarily ceased gathering astronomical data as a precaution before the storm and stowed its instruments to protect them from radiation blasts. And during the storm, NASA’s ice-measuring ICESat-2 satellite automatically stopped doing science when it experienced unexpected rotation, most likely from increased atmospheric drag, an agency spokeswoman said.
There might be fresh insights to come. The European Space Agency’s Solar Orbiter probe is nearly behind the Sun with respect to Earth, giving it a different view of the storm. Active region 3664 is now rotating off of the side of the Sun seen from Earth and into the field of view of Solar Orbiter. “We should get a better idea in the next few days if this sunspot intends to keep packing the punches on the other side of the Sun,” says David Williams, the spacecraft’s instrument operations scientist. NASA’s Parker Solar Probe — which is in the middle of a series of dives through the Sun’s outer atmosphere — happens to be at the outermost part of its looping orbit around the Sun and could be able to provide an extra perspective, but the data might take some time to reach Earth.
Researchers expect a coronal mass ejection to slam into Mars in the next few days, says Shannon Curry, a planetary scientist at the University of Colorado in Boulder. That collision could be observed by NASA’s MAVEN spacecraft, which is orbiting the red planet.
At any time. Scientists expect the current solar cycle to peak some time this year, owing to the number of sunspots they are observing. The biggest storms typically happen months to years after this official peak. Furthermore, as the solar cycle progresses, sunspots tend to appear closer to the Sun’s equator, increasing the chances of coronal mass ejections that will head directly for Earth rather than out into space, Dahl says.
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The planet 55 Cancri e (artist’s impression) orbits very close to its star.Credit: Mark Garlick/Science Photo Library
Astronomers say that they have used the James Webb Space Telescope (JWST) to detect for the first time an atmosphere surrounding a rocky planet outside the Solar System1. Although this planet cannot support life as we know it, in part because it is probably covered by a magma ocean, scientists might learn something from it about the early history of Earth — which is also a rocky planet and was once molten.
Finding a gaseous envelope around an Earth-like planet is a big milestone in exoplanet research, says Sara Seager, a planetary scientist at the Massachusetts Institute of Technology in Cambridge who was not involved with the research. Earth’s thin atmosphere is crucial for sustaining life, and being able to spot atmospheres on similar terrestrial planets is an important step in the search for life beyond the Solar System.
The planet investigated by JWST, called 55 Cancri e, orbits a Sun-like star 12.6 parsecs away and is considered a super-Earth, a terrestrial planet a little bigger than Earth — in this case, with about twice Earth’s radius and more than eight times as heavy. According to a paper published today in Nature1, its atmosphere is probably rich in carbon dioxide or carbon monoxide and has a thickness that is “up to a few per cent” of the planet’s radius.
Another reason that 55 Cancri e is uninhabitable is that it is very close to its star — around one sixty-fifth of the distance from Earth to the Sun. And yet, “it’s perhaps the most studied rocky planet”, says Aaron Bello-Arufe, an astrophysicist at the Jet Propulsion Laboratory (JPL) in Pasadena, California, and a co-author of the paper. Its host star is bright in our night sky, and because it is large for a rocky planet, it’s easier to study than other planets outside the Solar System. “Every telescope or instrument that you can think of in astronomy has pointed to this planet at some point,” Bello-Arufe says.
55 Cancri e was so well studied that after JWST launched in December 2021, engineers pointed the observatory’s infrared spectrometers towards it for testing. These instruments can detect the chemical fingerprints of gases swirling around planets as they absorb infrared wavelengths from starlight. Bello-Arufe and his colleagues then decided to dig deeper to confirm whether the planet had an atmosphere.
Before the latest observations, astronomers had changed their minds about 55 Cancri e myriad times. The planet was discovered in 20042. At first, researchers thought it was probably the core of a gas giant similar to Jupiter. But in 2011, the Spitzer Space Telescope observed the planet as it passed in front of its star3, and researchers found that 55 Cancri e is in fact a lot smaller and denser than a gas giant, making it a rocky super-Earth.
55 Cancri e is a little bigger than Earth, but much smaller than the Solar System’s giant planets, such as Neptune.Credit: NASA, ESA, CSA, Dani Player (STScI)
Some years later, researchers noticed that 55 Cancri e was cooler than it should have been for a planet so close to its star, indicating that it probably has an atmosphere4. One hypothesis was that the planet is a ‘water world’ enveloped by supercritical water molecules; another was that it is surrounded by an expansive, primordial atmosphere composed mainly of hydrogen and helium5. But these ideas were eventually disproved.
A planet so close to its star would be bombarded by stellar winds and have a hard time holding on to volatile molecules in its atmosphere, says Renyu Hu, a planetary scientist at JPL and a co-author of the latest study. Two possibilities remained, he says. The first was that the planet is completely dry, with an ultrathin atmosphere of vaporized rock. The second was that it has a thick atmosphere composed of heavier, volatile molecules that do not bleed away easily.
The latest data indicate that 55 Cancri e’s atmosphere contains carbon-based gases, pointing to option two. The team collected bona fide evidence of an atmosphere, Seager says, but more observations are needed to determine its full composition, the relative quantities of gases present and its precise thickness.
Laura Schaefer, a planetary geologist at Stanford University in California, is interested in learning how 55 Cancri e’s atmosphere interacts with materials beneath the planet’s surface. It’s still possible that the atmosphere is being eroded by stellar winds, the study’s authors say, but the gases could be getting replenished by the melting and outgassing of rocks in the magma ocean.
“Earth probably went through at least one magma-ocean stage, maybe several,” Schaefer says. “Having actual present-day examples of magma oceans can help us understand the early history of our Solar System.”
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Onboard this Long March 5 rocket, Chang’e-6 is waiting to lift off from the Wenchang Space Launch Centre on Hainan Island, southern China.Credit: Xinhua/Shutterstock
China has successfully launched its historic Chang’e-6 mission.The 53-day odyssey will be the most complex and challenging Moon mission China has carried out. If all goes according to plan, scientists will be examining the first rocks from the Moon’s far side by late June.
The 7.2-metre-tall, eight-tonne spacecraft lifted off aboard a Long March 5 rocket on Friday afternoon local time, piercing through a tropical rainstorm from the Wenchang Satellite Launch Centre on Hainan Island. Just over one hour into the flight, the China National Space Administration (CNSA) announced the launch “a complete success”, after the craft separated from the rocket and entered the designated Earth-Moon transfer orbit.
Quentin Parker, an astrophysicist at the University of Hong Kong, hails the launch as “flawless”. “China’s accomplishments in space exploration over the past few years are without precedent. If successful, this mission will be another science bonanza,” he says.
The lunar far side, which always faces away from us because the Moon is tidally locked to Earth, could not be more different than its near side, says planetary scientist Bradley Jolliff at Washington University in St Louis. Most of the ancient volcanic activity on the Moon happened on the near side, while the far side remained quieter under a thick and heavily cratered crust. “You would hardly know that they are from the same body by comparing the two sides,” Jolliff says.
What China’s mission to collect rocks from the Moon’s far side could reveal
A total of 10 missions, manned or unmanned, have brought back Moon rocks for analysis — all from the near side. Landing on the Moon’s far side requires, among other things, a communications satellite to relay signals with Earth.
This is why China launched the Queqiao-2 satellite in March, which is equipped with a 4.2-metre-diameter radio antenna — the largest of its kind used in deep space exploration — to orbit the Moon and wait for the arrival of Chang’e-6.
After arriving at the Moon early this week, the spacecraft will gradually lower its orbit and prepare for landing in one of three pre-selected areas within the South Pole-Aitken basin (SPA). The SPA is the largest and oldest impact basin on the lunar surface, and samples from there will provide clues to the Moon’s two-face mystery and the early history of the solar system.
In early June, the spacecraft will drop a lander, which aims to drill and scoop up two kilograms of soil and rocks. Then an ascender will blast off from the lander and ferry the samples back to the orbiter for the trip back home. Thanks to Queqiao-2, the spacecraft and Earth will remain in contact during the mission’s critical moments, such as the 15-minute descent and touchdown, two-day sampling, and 6-minute ascent.
“The geological conditions on the far side are less clear. Whether we’ll actually be able to scoop up or drill down, all remains to be seen when the sampling begins,” Pei Zhaoyu, a senior CNSA official and chief designer of China’s upcoming Chang’e-8 mission, told China Central Television during the launch livestream.
Scientists hope Chang’e-6 will also return material from beyond its landing site, such as rock fragments thrown over to the landing site from far distant locations during powerful impacts, Jolliff says. The material collected at the Chang’e-6 site “will be like a treasure chest”, he says. “The samples collected will be analysed for decades to come, and hopefully with access provided to the international research community,” he says.
Chang’e-6 is expected to return to Earth around June 25. If successful, the precious samples will land at the Siziwang Banner Landing Site in Inner Mongolia and be retrieved within 48 hours, according to CNSA.
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The fate of the Universe might not be as dark and empty as cosmologists have long suspected. That’s one potential implication emerging from an innovative project that has produced some of the biggest maps ever made of the Universe.
At a meeting of the American Physical Society in Sacramento, California, in early April, researchers released initial results from the Dark Energy Spectroscopic Instrument (DESI), based at the Kitt Peak National Observatory near Tucson, Arizona. DESI started mapping the Universe in 3D in 2020 and was designed to measure the elusive force, known as dark energy, that is pushing galaxies apart.
The surprising early results suggest that dark energy could be weakening over time.
Could JWST solve cosmology’s big mystery? Physicists debate Universe-expansion data
“That’s really a hint that something could be happening,” says cosmologist Nathalie Palanque-Delabrouille at Lawrence Berkeley National Laboratory in California, who is DESI’s spokesperson.
Although the study was based on only the first of the five years planned for data collection, it is already one of the largest maps ever made of the Universe, and it reveals the effects of dark energy across an unprecedented 11 billion years of cosmic history (DESI collaboration. Preprint at arXiv https://doi.org/mtqw; 2024).
If confirmed, the hints that dark energy might be weakening would bring the first substantial change in decades to the generally accepted theoretical model of the Universe. And if dark energy is not constant, that would hold implications for theories of how the Universe has evolved and for what its future might hold.
But researchers say that the evidence for changes in dark energy is still very uncertain. That was the overwhelming sentiment at a gathering of cosmologists on 15–16 April at the Royal Society in London. The standard cosmological model remains strong, most cosmologists agree — and has been working better and better as the years go by.
Wendy Freedman, an astronomer at the University of Chicago in Illinois, calls the hints of a weakening “tantalizing”, but says it will require a lot more data to see if they pan out. “Time will tell if they stand the test of time.”
At the largest scales, the cosmos is ruled by gravity, and Einstein’s general theory of relativity allows for gravity to be repulsive as well as attractive. Whereas ordinary forms of energy — which includes the mass of matter — result in an attractive force, general relativity also predicts that some more-exotic forms of energy could produce repulsive gravity.
Dark energy was discovered in 1998, when two teams of astronomers used supernova explosions in distant galaxies to measure how the rate of cosmic expansion has changed. Their results indicated that the rate has accelerated over time, pushed by some unseen repulsive force that would later be dubbed dark energy. The name was intended to echo the equally mysterious entity known as dark matter — which is invisible but can be measured by its gravitational influence on galaxies.
The 1998 data that led to the discovery of dark energy had large error bars, and they were consistent with the simplest possible assumption: that dark energy is spread uniformly across space, earning it the name cosmological constant, or Λ. A consensus emerged around a theory called Λ cold dark matter (ΛCDM), in which cosmic history is largely the result of a struggle between the pull of dark matter and the push of dark energy.
A section of a map of the Universe based on observations made by DESI shows patterns in the arrangements of galaxies.Credit: Claire Lamman/DESI collaboration; custom colormap package by cmastro
Save for small deviations that remain unexplained, all of the evidence cosmologists have collected so far has strengthened this ΛCDM model. The gold standard was set in 2013 by the Planck space mission of the European Space Agency (ESA), which mapped the relic radiation from the early Universe, called the cosmic microwave background. The data from that mission are in “exquisite” agreement with the model, says senior Planck researcher George Efstathiou, a cosmologist at the University of Cambridge, UK. The current Universe, Planck found, is about 70% dark energy, 25% dark matter and 5% ordinary matter — the stuff of stars, planets and people.
The standard assumption of ΛCDM is that the expansion of the Universe will continue to accelerate, and that most galaxies would ultimately disappear from view. But theorists have developed hundreds of other models of dark energy; many posit that dark energy could be getting slowly diluted, and the Universe’s expansion will start to slow down. Another possibility is that dark energy is getting stronger and will ultimately rip galaxies apart.
For a long time, the hints from observations were too vague to answer even the most basic questions about dark energy: exactly how strong is it, and is it constant or slowly changing? DESI is the first in a new generation of experiments aimed at providing some answers. Others include ESA’s Euclid mission, which launched into space last year; the massive, 8-metre telescope of the Vera C. Rubin Observatory nearing completion in the Chilean Andes; and NASA’s Nancy Grace Roman Space Telescope, scheduled to launch in 2027. Another telescope, called eROSITA, part of a Russian–German space mission, has mapped the Universe in the X-ray spectrum.
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“There’s a whole slew of projects that are about to start taking data or have just started,” Palanque-Delabrouille said at the Royal Society meeting. “This is really unique in the history of cosmology.”
All of these efforts rely on mapping the distribution of matter in the Universe over vast distances, which — because of the time that light takes to reach Earth — also means over vast stretches of time. DESI does not take pictures of the sky in the way that an ordinary telescope camera does, but instead collects light from selected locations in its field of view. It does so by pointing optical fibres at objects — typically galaxies or quasars — with its 5,000 robotic arms, and routing that light to sensitive spectrographs. The spectrum of each object reveals its distance, because the farther away the object is, the faster it moves away, and the more its spectrum has ‘redshifted’ towards longer wavelengths.
To reconstruct the history of cosmic expansion from its 3D data, the DESI team uses one of the most well-established techniques in cosmology. It looks at the relic of what used to be sound waves in the primordial Universe.
As space expanded and matter cooled over time, the waves became frozen in the distribution of protons and neutrons (known collectively as baryons) across the Universe. That imprint, called baryon acoustic oscillations, or BAO, is still detectable today in how galaxies are scattered across space.
The BAO features are the largest structures in the Universe. “If we could see them individually, we would see a shell,” Palanque-Delabrouille explains. “It’s like when you throw pebbles in a lake. If you throw just one pebble, you can see its waves expanding out,” she says. “If you throw too many pebbles at once, all the ripples they produce will overlap with one another.”
DESI doesn’t just see the BAOs in the current Universe. Its 3D map stretches back in time, and by measuring how the average size of the features has grown over time, cosmologists can reconstruct the rate of expansion — and from that, the strength of dark energy. The instrument’s results are in principle still compatible with all the options — a dark energy that is constant, weakening or even strengthening.
At the most basic level, the DESI results provide solid confirmation of the original discovery, says Ofer Lahav, a cosmologist at University College London who is part of the DESI collaboration. “To me, it’s spectacular that you can confirm that the Universe is accelerating, and more or less get the same value people have claimed 25 years ago,” he says.
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“The instruments, data and measurements are spectacular,” says Marc Kamionkowski, a theoretical cosmologist at Johns Hopkins University in Baltimore, Maryland.
Kamionkowski says that he is cautious about interpreting the results as indicating that dark energy is weakening. He says that they could be an effect of the particular type of analysis the team did. Pedro Ferreira, a theoretical physicist at the University of Oxford, UK, agrees, pointing to a study he published last year with his colleague William Wolf, which called for cosmologists to change how they interpret dark-energy data (W. J. Wolf and P. G. Ferreira Phys. Rev. D 108, 103519; 2023). Ferreira adds that he is pessimistic that even the coming high-powered studies together will be able to pin down a theoretical model for dark energy.
But researchers hold out hope that the extra data will point in new directions.
The standard model was created as the simplest possible theory for the Universe, but the actual physics of its contents is probably more complicated, says Eleonora Di Valentino, a cosmologist at the University of Sheffield, UK. “I don’t believe that ΛCDM can be the final answer,” she says.
Cosmologist James Peebles — a chief architect of the standard model that helped to earn him a Nobel Prize in 2019 — agrees. “I find it very difficult to imagine that ΛCDM is the end of the story,” says Peebles, who is at Princeton University in New Jersey. “It’s too simple.”
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