For roughly the last three billion years, half of the Moon has been hiding. Earth’s gravity caught the Moon early in its existence and slowed its spin until the same face was permanently turned toward us — a process called tidal locking, completed somewhere between three and four billion years ago, which left every human civilisation that ever existed staring at the same single hemisphere of the same single satellite for the entire duration of human history. No human being saw the other half until 7 October 1959, when the Soviet Luna 3 probe transmitted the first photographs from a flyby trajectory. No human or human-built object touched the far side until 3 January 2019, when China’s Chang’e-4 mission soft-landed Yutu-2, a small rover, into Von Kármán crater. No spacecraft of any nationality had ever collected and returned physical material from the far side to a laboratory on Earth — until 25 June 2024, when the return capsule of Chang’e-6 parachuted into the grasslands of Inner Mongolia carrying 1,935.3 grams of lunar soil and rock fragments scooped and drilled from the South Pole-Aitken Basin.

According to a comprehensive reference summary of the Chang’e-6 mission architecture and operational sequence, the mission’s four-component spacecraft — a lander, an ascent vehicle, an orbiter, and an Earth-return capsule — launched from Wenchang Space Launch Site on Hainan Island aboard a Long March 5 rocket on 3 May 2024. The spacecraft entered lunar orbit on 8 May, then spent approximately three weeks mapping potential landing sites and refining its trajectory. On 1 June, the lander and ascent vehicle separated from the orbiter and descended autonomously toward the surface, communicating with mission control in Beijing through the Queqiao-2 relay satellite that had been launched into a high lunar halo orbit in March 2024 specifically to bridge communications between far-side surface operations and Earth. Direct radio contact with the far side is impossible — the lunar mass itself blocks the signal — and every far-side mission, beginning with Chang’e-4 in 2019, has required a dedicated communications relay positioned to see both Earth and the lunar surface simultaneously.

Where the lander touched down

Chang’e-6’s landing site was within the Apollo Basin, a 538-kilometre-wide impact crater that sits inside the much larger South Pole-Aitken Basin — the largest, oldest, and deepest confirmed impact structure in the entire solar system. As reported by Scientific American’s coverage of the Chang’e-6 sample return and the scientific significance of the landing site, the South Pole-Aitken Basin stretches approximately 2,500 kilometres across the lunar surface and reaches depths of approximately 8 kilometres below the surrounding terrain. The basin was formed approximately 4 billion years ago, in the period of intense bombardment that followed the formation of the solar system, by an impact substantial enough to potentially have excavated material from the Moon’s mantle and brought it to the surface. If true — and the question of whether SPA Basin ejecta actually includes mantle material has been an open scientific question for decades — then samples from the basin would represent the first physical material from beneath the lunar crust that humans had ever held in a laboratory.

The lander spent approximately 49 hours on the surface, using a robotic scoop to collect material from the immediate surface and a drill to extract samples from up to two metres below ground. Per the Planetary Society’s overview of the Chang’e-6 surface operations and sample-handling sequence, a small 5-kilogram rover named Jinchan (“Golden Cicada”), which had been kept secret during the launch preparations, was deployed from the side of the lander and photographed the spacecraft from a distance of several metres — producing the first close-up image of a lunar far-side lander taken from the lunar surface. The collected samples were transferred into a sealed container inside the ascent vehicle, which lifted off from the top of the lander on 3 June at 23:38 UTC, rendezvoused with the orbiter in lunar orbit on 6 June, transferred the sample container into the Earth-return capsule, and was subsequently crashed back into the lunar surface. The orbiter and return capsule then began the journey back to Earth, with the return capsule separating from the orbiter shortly before atmospheric entry and executing a skip-reentry trajectory — bouncing off the upper atmosphere once to shed velocity before completing the descent — to a soft landing in Inner Mongolia on 25 June. Total mission duration was 53 days.

Why far-side samples matter

The asymmetry between the lunar near side and far side is, by every available scientific measure, one of the larger unsolved problems in planetary science. The near side — the half of the Moon humans see from Earth — is covered for approximately 30 percent of its surface by basaltic maria, the dark plains of solidified ancient lava that the early astronomers mistook for seas. The far side has almost none. As detailed in a planetary scientist’s analysis of what the Chang’e-6 samples could reveal about lunar history, less than 1 percent of the far side is covered by maria. The far side’s crust is substantially thicker than the near side’s. The far side contains substantially lower concentrations of the geochemically distinctive elements collectively known as KREEP — potassium, rare earth elements, and phosphorus — that dominate the near-side surface chemistry. Why the two halves of the same body should differ so dramatically in their geological and chemical composition has been a subject of active research and unresolved theorising since the first far-side photographs were transmitted by Luna 3 in 1959.

Initial analyses of the Chang’e-6 samples have already begun producing scientifically substantial results. As covered in a November 2024 paper in Science by Cui et al. of the Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, fragments of volcanic basalt from the samples have been dated to approximately 2.83 billion years old — substantially younger than most far-side material had been expected to be, suggesting that volcanic activity persisted on the far side for far longer than existing models predicted. A parallel analysis led by Zhang et al. at the Institute of Geology and Geophysics, published in Nature the same month, produced essentially the same age estimate using a different sample fraction. Earlier work led by Wang et al. on volcanic glass beads from the Chang’e-5 mission to the lunar near side had identified evidence of unexpectedly recent volcanism dated to approximately 120 million years ago. Whether comparably young volcanism occurred on the far side remains an open question that the continued analysis of Chang’e-6 samples may eventually address. The far-side basalts that have been dated so far contain substantially lower concentrations of radioactive heat-producing elements than near-side basalts of comparable age, which raises a new puzzle: if the far-side magma source was as chemically cool as the analyses suggest, what kept it molten long enough to produce volcanism extending into the relatively recent geological past? The current working hypothesis, which the analysis of the remaining samples over the coming years will substantially refine, is that the thin crust beneath the South Pole-Aitken Basin allowed mantle material to remain partially molten and to erupt through the comparatively thinner overlying rock long after the rest of the far side had cooled.

The 1,935 grams of lunar soil in a laboratory in Beijing now represent the only physical samples humans have ever recovered from a hemisphere of the Moon that, for the entire duration of human civilisation and for billions of years before it, has been permanently hidden from view. The next missions in the series — Chang’e-7 in 2026 and Chang’e-8 in 2028 — will focus on the lunar south pole, searching for water ice and testing in-situ resource utilisation in preparation for the International Lunar Research Station that China plans to begin building by 2035. The same techniques that produced the Chang’e-6 sample return will be used, with modifications, for the Tianwen-3 Mars sample return mission scheduled to launch in 2028 — a mission that, on its current schedule, will deliver the first samples from the surface of another planet to Earth in approximately five years.

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Imagine throwing a refrigerator at a mountain travelling 135,000 kilometres per hour through deep space, after a ten-year flight, and asking the refrigerator to land softly enough to keep ten scientific instruments intact. This is, in essential respects, what the European Space Agency attempted in November 2014, and remarkably it almost entirely worked. The mother spacecraft, Rosetta, had launched from Kourou in French Guiana on 2 March 2004, carrying Philae folded against its side, on a trajectory that would take both vehicles past Earth three times and Mars once for gravity-assist accelerations, past two asteroids (21 Lutetia and 2867 Šteins) for scientific flybys, and across approximately ten and a half years of continuous deep-space travel — much of it in deliberate hibernation, with most systems powered down to conserve energy across the long stretches between gravity assists. The original target had been a different comet entirely, Comet 46P/Wirtanen, but a failure of an Ariane 5 rocket in late 2002 had delayed the launch and forced the European Space Agency to select a different target. The new target was Comet 67P/Churyumov-Gerasimenko, a 4-kilometre-wide irregular ice-and-dust body in a 6.5-year orbit between Jupiter and the inner solar system, named after the two Soviet astronomers who had discovered it in 1969. Rosetta and Philae arrived at the comet on 6 August 2014. Rosetta became the first spacecraft in history to enter orbit around a comet. Philae’s planned descent followed three months later.

According to the European Space Agency’s official announcement of the Philae touchdown, the descent itself began at 08:35 UTC on 12 November 2014, when Philae separated from Rosetta at a distance of approximately 22.7 kilometres from the comet’s centre. The lander then drifted slowly toward the surface for approximately seven hours at a relative velocity of about one metre per second — roughly the pace of a brisk walk. The plan, on touchdown, was for two harpoons fired from the bottom of the lander to anchor it to the comet’s surface and for a small thruster on the top of the lander to push it down against the recoil. The combined gravitational pull of the comet on the 100-kilogram lander was approximately one-hundred-thousandth of Earth’s surface gravity — so weak that any upward force on Philae’s body would, without the anchoring systems, simply send it bouncing back into space. The first touchdown occurred at 15:34 UTC at a site the mission team had named Agilkia, after the Egyptian island where the original Philae obelisk now sits.

Why the lander bounced

The anchoring systems did not work. The harpoons did not fire. The top-mounted thruster did not fire. The ice screws built into the landing legs could not penetrate the unexpectedly hard surface material of the comet — which, contrary to the team’s expectations of soft snow-like consistency, turned out to be more like solid water ice. The result was that Philae, on contact, behaved exactly as a 100-kilogram object behaves when it touches a surface at one metre per second in essentially zero gravity with no anchoring of any kind: it bounced. The first bounce sent the lander approximately one kilometre back up into the comet’s tenuous atmosphere, where it drifted slowly for nearly two hours before falling back to the surface for a second bounce, and then a final, much smaller bounce, before coming to rest at 17:31 UTC at a location the team named Abydos — about a kilometre from the originally planned landing site, against the wall of a cliff, in a position where direct sunlight reached the lander’s solar panels for only approximately 1.5 hours per 12.4-hour comet rotation period, rather than the 6 to 7 hours per rotation that the mission team had planned for.

The science programme proceeded anyway. As reported in a comprehensive reference summary of the Philae mission and its scientific operations on the comet, all ten of the lander’s onboard scientific instruments were operated at least once during the approximately 57 hours that Philae remained active on the comet’s surface — drawing on the energy stored in the lander’s primary battery, which had been charged on the journey out and was not dependent on solar power for the initial science sequence. The instruments captured the first photographs ever taken from the surface of a comet, performed the first in-situ chemical analysis of cometary nucleus material, detected organic compounds including the amino-acid precursor glycine, measured the magnetic and thermal properties of the surface, and characterised the dust environment in the immediate vicinity of the lander. At 00:08 UTC on 15 November 2014, the primary battery was exhausted. The lander entered hibernation. The mission team’s hope was that as the comet’s orbit took it closer to the Sun in the subsequent months, additional sunlight on the solar panels might allow the secondary battery to recharge sufficiently to wake the lander up. This hope was substantially realised — Philae communicated sporadically with Rosetta between 13 June and 9 July 2015 — but the contact never stabilised into the sustained science operations the team had hoped for, and after 9 July 2015 no further signals were received.

What the mission found

Per National Geographic’s overview of the scientific discoveries that emerged from the Rosetta and Philae mission across the subsequent years of analysis, the combined results from the orbiter and the lander substantially revised the existing scientific understanding of cometary composition and the role of comets in the early solar system. The water on Comet 67P, as measured by Rosetta’s mass spectrometers, has a deuterium-to-hydrogen ratio approximately three times higher than the water in Earth’s oceans — which substantially weakened the long-standing hypothesis that the bulk of Earth’s water was delivered by comet impacts during the early bombardment of the inner solar system. Cometary water, in 67P at least, does not match Earth water. Asteroids or another source must have supplied the difference. The mission also identified complex organic molecules in the comet’s outgassing material, including molecular oxygen (a finding the team had not predicted and could not initially explain), glycine, methylamine, ethylamine, and other carbon-based compounds that are precursors to the building blocks of biology. The two-lobed “rubber duck” shape of Comet 67P, photographed at high resolution by Rosetta’s cameras, turned out to be the result of two separate cometesimals having gently merged in the early solar system rather than a single body having been eroded into the irregular form.

As described in the comprehensive reference on the broader Rosetta mission and its final operational disposition, the orbiter itself was deliberately crashed into the comet on 30 September 2016, after the comet’s outbound orbit had carried it too far from the Sun for Rosetta’s solar panels to continue generating sufficient power. Philae’s exact landing location was identified in photographs taken by Rosetta’s high-resolution camera less than a month before the orbiter’s own demise — the lander wedged into a dark crack on the comet’s smaller lobe, its three legs visible in the image, exactly where the bounces had carried it on the afternoon of 12 November 2014. The two spacecraft now sit on the surface of Comet 67P together, accompanying it through its 6.5-year orbits around the Sun for the foreseeable astronomical future, the first human artefacts ever to permanently reside on the surface of a comet.

The post A small European spacecraft called Philae became the first machine in human history to soft-land on a comet — bouncing twice in near-zero gravity before settling in a shadowed crevice on Comet 67P — after a 10-year, 6.4-billion-kilometre journey across deep space, where it transmitted scientific readings home for roughly 60 hours before its batteries finally died appeared first on Space Daily.

A growing body of evidence suggests that leaving Earth may do far more than challenge the human body. According to a new study, the absence of gravity itself could temporarily reshape consciousness, loosening the brain’s most strongly ingrained assumptions and opening the door to altered perceptions, expanded awareness, and even experiences that resemble some aspects of psychedelic states.

As humanity prepares for longer stays on the Moon, commercial space tourism, and eventual missions to Mars, researchers contend that understanding what happens to the mind in microgravity may be just as important as understanding the engineering that gets astronauts there. According to them, gravity may not simply keep people anchored to the ground—it may also help anchor human consciousness itself.

In a new paper published in Frontiers in Psychology, researchers Dr. Annahita Nezami and Dr. Elisa Raffaella Ferre of Birkbeck, University of London, explored decades of neuroscience, psychology, and spaceflight research to propose that Earth’s gravitational pull acts as a deeply embedded “super-prior” within the brain. By disrupting this ancient reference point, microgravity may trigger widespread changes across neural networks that underpin perception, self-awareness, and emotional regulation.

“Human consciousness has evolved under the constant pull of terrestrial gravity, yet its role in shaping perception and awareness has received limited theoretical attention,” researchers write. “As spaceflight transitions from short missions to long-duration habitation, understanding how consciousness responds to non-terrestrial gravity becomes increasingly urgent.”

Every human brain evolved under the constant force of Earth’s gravity. From before birth onward, sensory systems constantly rely on gravity cues to determine which way is up, where the body is in space, and how to interpret movement.

Researchers argue that this constant exposure has made gravity one of the brain’s most reliable assumptions. In the language of predictive neuroscience, the brain constantly generates expectations about the world and updates them using incoming sensory information. Gravity, they say, functions as a basic expectation—a “1G super-prior”—that helps stabilize consciousness.

Remove that constant, and things begin to change.

In orbit, vestibular signals from the inner ear become unreliable. Visual, proprioceptive, and balance information no longer align as the brain evolved to expect. The resulting mismatch generates anticipation errors, forcing widespread recalibration.

Those changes are already well documented among astronauts. Space travelers commonly experience spatial disorientation, altered body perception, sleep disturbances, mood swings, and, in some cases, feelings of depersonalization or derealization—states in which individuals feel separated from themselves or perceive their surroundings as unreal.

Astronauts have also reported more positive and profound experiences. Many describe feeling “unmoored,” “expanded,” and deeply interconnected with humanity, or overwhelmed by awe while viewing Earth from orbit. This phenomenon, known as the Overview Effect, has been associated with lasting shifts in values, increased environmental concern, and enhanced feelings of oneness.

The study suggests that these experiences might originate from the same neurocognitive processes triggered when gravity’s stabilizing role is weakened.

“By perturbing the most stable embodied reference – gravity itself – spaceflight offers a rare window into how fundamental expectations shape consciousness,” researchers write. “The loosening of perceptual boundaries in microgravity has been proposed as a neurocognitive foundation for the Overview Effect.”

Brain imaging studies lend support to the idea. MRI scans of astronauts before and after extended-duration missions have revealed structural changes, including fluid redistribution, enlargement of brain ventricles, and gray matter remodeling. Functional MRI studies have also found changes in connectivity among vestibular, sensory, and default mode network regions involved in awareness and the combining of internal and external information.

Especially intriguing are changes observed in the default mode network, a system involved in introspection, self-referential thought, and consciousness. Activity inside this network appears to diminish after spaceflight, with some changes persisting for months after astronauts return to Earth.

Electroencephalography studies have likewise detected reductions in alpha-wave activity during and after missions, another sign that brain function is being reorganized in response to microgravity.

These neural changes led the researchers to an unexpected comparison.

Many of the same large-scale patterns recorded after spaceflight resemble effects previously documented under psychedelic compounds such as psilocybin and LSD. In both situations, highly organized brain networks appear to loosen, while communication between previously separate regions increases.

Researchers stress that the mechanisms are entirely different. Psychedelics act through serotonin receptors, whereas microgravity represents an environmental disruption rather than a pharmacological one. Yet both seem to converge by weakening the brain’s highest-level assumptions and increasing the combination of sensory information.

According to researchers, this convergence phenomenon suggests that spaceflight could provide scientists with a natural, drug-free model for studying transformative states of consciousness.

The researchers argue that terrestrial gravity, microgravity, and psychedelic states may represent different conditions along a spectrum defined by the strength of the brain’s deeply ingrained “1G super-prior.” As that stabilizing role weakens, top-down constraints relax, potentially increasing neuroplasticity and mental flexibility.

The implications go beyond astronaut health. Understanding how consciousness changes in unfamiliar environments may provide new clues to the neural foundations of self-awareness. It could also prove increasingly important as private citizens spend more time in space and human settlements expand away from Earth.

Researchers suggest that microgravity offers scientists something that cannot be replicated on Earth—a chance to observe what happens when one of evolution’s oldest assumptions suddenly disappears.

“By situating consciousness in an environment for which evolution offers no precedent, spaceflight positions microgravity as a powerful natural neurocognitive catalyst for transformative experience,” researchers write. “In stepping beyond Earth’s gravity, we gain a unique vantage point from which to examine the contingent foundations of human awareness and the conditions under which it can be fundamentally transformed.”

Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan.  Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com 

On my way to Tash Rabat from Son-Kul, both in Kyrgyzstan, sitting on the comfortable seats of a minibus, I had to pinch myself just to realize that it wasn’t a dream. I could see green valleys on one side of the road and the rugged brown Pamir Plateau on the other. As someone whoContinue reading "Capturing the night sky in Kyrgyzstan"

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