A review published in Space: Science & Technology presents the 2029 encounter as a major opportunity for planetary science and planetary defense. Led by Li Jianyang of the School of Atmospheric Sciences at Sun Yat-sen University, the study brings together radar measurements, optical light curves, and spectral observations to assess what is currently known about Apophis and what researchers may be able to learn during its passage. The review also examines possible changes to the asteroid’s orbit, rotation, surface, internal structure, and dust environment. Because Apophis will be visible to powerful observatories and accessible to spacecraft during a limited period, the authors argue that the event should be treated as a coordinated international campaign rather than as an isolated flyby.

Apophis first attracted worldwide attention after its discovery in 2004, when early calculations indicated a possible future collision with Earth. Improved observations have since eliminated the predicted impact risk for the foreseeable future, but the asteroid remains classified as potentially hazardous because of its size and orbit. Current measurements indicate that Apophis is an elongated, asymmetric body with a slightly bifurcated appearance. Radar-based shape models suggest a complex object rather than a smooth, monolithic rock. Its spectral classification is Sq, a category associated with ordinary-chondrite-like materials and broadly similar to the composition inferred for the asteroid Itokawa. This makes Apophis especially important for testing whether small near-Earth asteroids are commonly made of loosely bound fragments rather than solid stone.

The physical data summarized in the review point toward a fragile “rubble-pile” interior. Apophis is estimated to have a density of about 1.95 grams per cubic centimeter and a porosity near 55 percent, meaning that a substantial fraction of its volume may consist of empty space between rocks and grains. It rotates in a non-principal-axis state, sometimes described as tumbling, with a principal rotation period of approximately 30.6 hours. Such a configuration complicates predictions because the asteroid’s response to gravity depends not only on its shape and mass, but also on how its rotation axis moves through space. Small errors in the estimated mass distribution, surface topography, or spin state could therefore produce large differences in forecasts of what will happen during the encounter.

Earth’s gravity is expected to alter Apophis’s orbit substantially. Before the flyby, the asteroid follows an Aten-type orbit, whose orbital period is shorter than Earth’s. The gravitational encounter will transfer it into an Apollo-type orbit, with a longer period and a different relationship to Earth’s path around the Sun. The flyby will also amplify uncertainties in the asteroid’s future trajectory. According to the review, the predicted orbital uncertainty could grow from roughly one kilometer before the encounter to approximately 6,000 kilometers one year afterward. This does not mean that Apophis will suddenly become an impact threat, but it demonstrates how a close planetary encounter can magnify small uncertainties in position, velocity, and nongravitational forces such as thermal emission.

The asteroid’s spin may change just as dramatically. Modeling cited in the study predicts that the rotation period could shift by between approximately minus 7.6 hours and plus 14.4 hours, depending on the asteroid’s internal structure, orientation, and exact tidal response. Earth’s gravity will exert torques across Apophis, pulling more strongly on the side closest to the planet than on the far side. This differential force can accelerate or slow the asteroid’s rotation and may alter its tumbling motion. By comparing pre-encounter and post-encounter light curves, radar images, and spacecraft measurements, scientists could reconstruct changes in the body’s spin and infer how its mass is distributed. The results may provide one of the clearest observational tests yet of the mechanical behavior of a rubble-pile asteroid.

The flyby is not expected to tear Apophis apart, but it could rearrange parts of its surface. Numerical simulations indicate that local movement may affect roughly one percent of the asteroid’s surface, with displacements potentially reaching several times the maximum radius of individual surface particles. The predicted changes are generally at centimeter-to-decimeter scales, small by terrestrial standards but significant on a 340-meter asteroid. Boulders could shift, loose regolith could slide, and previously buried material might become exposed. These changes could produce measurable variations in color, brightness, and infrared spectra, allowing researchers to identify fresh material and compare it with weathered surfaces altered by long-term exposure to solar radiation. Such observations would help determine how easily small bodies reshape themselves during planetary encounters.

Apophis will also cross several regions of Earth’s near-space environment, including the magnetosheath, magnetotail, and magnetosphere. The review examines the possibility that its weak surface gravity could allow fine particles to escape if they are disturbed by tidal forces, rotational changes, electrostatic effects, or other processes. Particles smaller than roughly 50 micrometers may be especially vulnerable to ejection. Once released, some dust could be influenced by Earth’s magnetic and electric environment, potentially creating high-speed particle streams and electromagnetic signals detectable by spacecraft. Whether a substantial dust cloud will form remains uncertain, because it depends on the asteroid’s surface cohesion, particle size distribution, and exact response to the encounter. Even a non-detection would be scientifically valuable by placing limits on the strength and mobility of Apophis’s surface material.

The encounter has already prompted plans for an international fleet of observers. NASA’s OSIRIS-APEX, the repurposed spacecraft formerly known as OSIRIS-REx, is planned to rendezvous with Apophis in June 2029 and study the asteroid after its closest approach. The European Space Agency’s RAMSES mission has been proposed to arrive before the flyby, enabling it to monitor the asteroid as Earth’s gravity acts upon it. Japan’s DESTINY+ mission is also associated with Apophis exploration efforts, while Chinese researchers have proposed concepts including ARS and CROWN/Apophis. Mission studies reviewed in the paper show that different launch windows can support rendezvous, flyby, sample-return, and impactor architectures. In some cases, relatively small launch vehicles could reach the asteroid, particularly when trajectories are designed to minimize launch energy and encounter velocity.

Ground-based astronomy will provide another essential layer of observation. During the flyby, Apophis is expected to be resolved by several 10-meter-class telescopes, allowing astronomers to track its changing brightness, rotation, shape, and surface properties. Radar facilities will be able to refine its orbit and search for changes in topography. China’s planned Fuyan radar could potentially achieve meter-level imaging and detect surface deformations at sub-centimeter precision, depending on the final observing geometry and system performance. Together, these observations could transform Apophis into a continuously monitored laboratory, linking measurements taken before, during, and after the encounter. Researchers may be able to see not only where the asteroid travels, but also how its surface and internal dynamics evolve in response to a planetary flyby.

The scientific value of Apophis is closely tied to planetary defense. Under the International Asteroid Warning Network, the encounter is expected to function as the first major global coordination exercise involving a potentially hazardous asteroid that poses no immediate impact threat. Observatories, spacecraft teams, radar operators, data analysts, and emergency-planning organizations can test how rapidly they share measurements, update predictions, coordinate missions, and communicate results to the public. The exercise will expose practical weaknesses before they matter during a real emergency. The review compares the importance of the event with landmark episodes such as the Voyager missions and the international observation campaign for Halley’s Comet in 1986. By combining scientific discovery with operational practice, Apophis could become a defining moment for asteroid research—and a rehearsal for humanity’s response to the next object that truly comes our way.

Subject of Research: The physical properties, tidal response, orbital and spin changes, surface activity, dust environment, exploration opportunities, and planetary-defense significance of near-Earth asteroid Apophis during its 2029 Earth flyby.

Article Title: The Apophis Encounter in 2029: A Rare Opportunity for Planetary Science and Defense

News Publication Date: 22 July 2026

Web References: https://doi.org/10.34133/space.0505

References: Li Jianyang et al., “The Apophis Encounter in 2029: A Rare Opportunity for Planetary Science and Defense,” Space: Science & Technology.

Image Credits: Space: Science & Technology

Keywords: Apophis, near-Earth asteroid, asteroid flyby, planetary defense, OSIRIS-APEX, RAMSES, asteroid science, rubble-pile asteroid, tidal forces, space missions, International Asteroid Warning Network

The flyby is extraordinary not simply because Apophis will come close, but because an asteroid of this size is not expected to make a comparable passage again for thousands of years. Statistical estimates suggest that an object of similar dimensions passing Earth at such a small distance occurs, on average, only once every 7,500 years. The encounter therefore offers a rare opportunity to observe a potentially hazardous asteroid under intense tidal stress while it remains accessible to ground-based observatories and robotic spacecraft. The review, led by Jianyang Li of Sun Yat-sen University’s School of Atmospheric Sciences, brings together radar measurements, optical light curves, spectroscopy, orbital calculations and mission studies to assess what scientists may learn before, during and after the passage.

Apophis has been watched closely since its discovery in 2004, when preliminary orbital calculations identified a possible future collision risk and triggered worldwide public concern. Improved observations have since ruled out an impact with Earth for at least the next century, but the asteroid remains classified as potentially hazardous because of its size and orbit. Current measurements indicate a rotation period of approximately 30.6 hours, a density near 1.95 grams per cubic centimeter and a porosity of about 55 percent. Those properties suggest that Apophis may be a rubble-pile asteroid: a gravitationally assembled collection of rocks, boulders and dust held together more by weak self-gravity than by solid material strength.

Radar-derived shape models show an elongated, asymmetric body with a slightly bifurcated appearance. Spectroscopic observations classify Apophis as an Sq-type asteroid, a category whose surface properties resemble those of ordinary chondrite meteorites. This connection is scientifically important because ordinary chondrites are among the most common meteorite materials found on Earth. Apophis may therefore provide a relatively accessible example of the primitive rocky bodies that populate near-Earth space. Yet its internal arrangement remains uncertain. Scientists do not know how much of the asteroid is made of large boulders, how tightly its components are packed, or whether strong internal zones might resist the gravitational disturbances expected during the flyby.

Earth’s gravity will alter Apophis in several measurable ways. The encounter will redirect the asteroid from an Aten-type orbit, whose average path lies largely inside Earth’s orbit, into an Apollo-type orbit that spends more time outside Earth’s orbital path. The gravitational interaction will also magnify uncertainties in the asteroid’s future trajectory. According to the review, the uncertainty in its position could grow from approximately one kilometer before the encounter to nearly 6,000 kilometers a year afterward. That does not mean Apophis will become unpredictable in a dangerous sense, but it illustrates how a close planetary encounter can amplify small errors in measurements and models.

The asteroid’s rotation could change even more dramatically. Tidal forces act differently across the near and far sides of a passing body, producing torques that can accelerate or decelerate its spin. Current projections indicate that Apophis’s rotation period could change by roughly minus 7.6 to plus 14.4 hours. Because the asteroid is already in a non-principal-axis rotation state—meaning it does not rotate around its simplest, most stable axis—its motion may become especially complex. Carefully timed measurements of its brightness, shape and surface orientation could reveal changes in its angular momentum and help scientists reconstruct the distribution of mass inside the asteroid.

The flyby is not expected to tear Apophis apart, but it could rearrange parts of its surface. Numerical simulations cited in the review suggest that tidal forces may mobilize material across approximately 1 percent of the surface, with individual displacements generally limited to about three times the maximum particle radius used in the models. Even small movements could have major scientific value. A shifted boulder, newly exposed patch of regolith or altered slope could reveal how rubble-pile asteroids respond to external stress. Freshly exposed material might also change the asteroid’s spectral signature, allowing telescopes and spacecraft to compare the surface before and after the encounter.

Apophis will also pass through several regions of Earth’s space environment, including the magnetosheath, magnetotail and magnetosphere. Its exceptionally weak surface gravity means that very small particles—potentially those smaller than 50 micrometers—could be detached or expelled during the gravitational disturbance. Some of this dust may become temporarily influenced or captured by Earth’s magnetic environment, forming fast-moving streams capable of interacting with spacecraft and instruments. Whether such particles will be directly detected remains uncertain, but even a non-detection would help constrain the asteroid’s surface cohesion, particle size distribution and response to tidal forces. Dust observations could become one of the most unexpected scientific highlights of the encounter.

The event is already shaping an international campaign of robotic and ground-based exploration. NASA’s OSIRIS-APEX, the spacecraft formerly known as OSIRIS-REx after its successful sample-return mission from asteroid Bennu, is expected to rendezvous with Apophis in June 2029. The European Space Agency’s RAMSES mission has been designed to arrive before the flyby and monitor the asteroid through the encounter, although its final implementation depends on mission approval and funding. Japan’s DESTINY+ has also been associated with Apophis exploration, while Chinese researchers have proposed concepts including ARS and CROWN/Apophis. Mission studies reviewed in the paper include rendezvous, rapid flyby, sample return and impactor architectures. Calculations of launch energy, or characteristic energy C3, and encounter velocity indicate that some launch windows could be accessible even to relatively small launch vehicles. One example trajectory could approach Apophis at a low relative velocity of about 1.88 kilometers per second in January 2029, increasing the time available for observations.

Earth-based facilities will be equally important. During the closest approach, several telescopes in the 10-meter class may resolve surface-scale features that are normally impossible to distinguish on a distant near-Earth asteroid. Radar observations can measure the body’s shape, rotation and motion with exceptional precision, while repeated light-curve measurements can detect subtle changes in brightness caused by shifting orientation or newly exposed material. China’s under-construction Fuyan radar could potentially achieve meter-level imaging and detect surface deformations smaller than a centimeter under favorable conditions. Coordinating these measurements across continents will be essential because Apophis will be visible from different locations for only limited periods, and many of the expected changes may occur rapidly.

For planetary defense, Apophis represents a rehearsal with no immediate threat attached. Observatories, space agencies, navigation teams, communication networks and emergency-response organizations will have the opportunity to practice how they would coordinate observations and mission decisions during a real asteroid warning. Under the International Asteroid Warning Network, the campaign could become the first worldwide joint exercise centered on a naturally occurring close approach rather than an impending impact. The review argues that the experience will improve rapid-response mission design, clarify how scientific uncertainty should be communicated to the public and strengthen cooperation between countries. It may also support broader efforts associated with an International Year of Planetary Defense.

The significance of Apophis extends beyond one asteroid and one date. Its passage will test models of rubble-pile structure, tidal reshaping, spin-state evolution, dust release and asteroid–magnetosphere interactions in a single event. It will also provide a practical demonstration of how quickly the international community can organize to study a changing object in near-Earth space. Like the Voyager launches of the late 1970s and the multinational observations of Halley’s Comet in 1986, the 2029 encounter could become a defining moment in space science. What was once viewed mainly as a potential danger is now emerging as a rare scientific opportunity—one that may influence future asteroid exploration, resource utilization and the technology used to protect Earth.

Subject of Research:
The physical properties, tidal response, exploration opportunities and planetary-defense significance of near-Earth asteroid Apophis during its 2029 close flyby of Earth.

Article Title:
The Apophis Encounter in 2029: A Rare Opportunity for Planetary Science and Defense

News Publication Date:
22 July 2026

Web References:
https://doi.org/10.34133/space.0493

References:
Li Jianyang et al., “The Apophis Encounter in 2029: A Rare Opportunity for Planetary Science and Defense,” Space: Science & Technology, DOI: 10.34133/space.0493.

Image Credits:
Space: Science & Technology

Keywords:
Apophis, near-Earth asteroid, planetary defense, asteroid flyby, rubble-pile asteroid, tidal forces, asteroid exploration, OSIRIS-APEX, RAMSES, radar observations, dust ejection, planetary science

Chandrayaan-3, which successfully landed near the lunar south pole, has provided unprecedented direct temperature readings that challenge and refine our understanding of lunar surface conditions. The atmosphere on the Moon is incredibly thin, and the lack of substantial insulation means that surface temperatures can fluctuate starkly between day and night. The team, led by Durga Prasad, utilized the ChaSTE temperature probe, an advanced instrument designed to measure temperatures both at the surface and at a depth of 10 centimeters. The data yielded from this probe is invaluable for assessing the thermal environment of the lunar polar regions.

One of the most striking results from the mission is the remarkable temperature variation observed at the landing site, located on a sun-facing slope. The temperature peaked under direct sunlight at an astonishing 355 Kelvin, which translates to about 82 degrees Celsius during the day. Conversely, during the harsh lunar night, the temperatures plummeted to a frigid 105 Kelvin. This stark contrast underscores the Moon’s extreme thermal environment, which poses challenges for both exploration and potential habitation.

Interestingly, the research uncovered that a mere meter away from the lander, in a flat region, the temperature was considerably lower. This location registered a peak temperature of 332 Kelvin, or 59 degrees Celsius, highlighting how critical topographical features like slope angle can significantly affect temperature readings. This data serves as a launchpad for research into how lunar geography and topology influence environmental conditions, which is essential for identifying locations amenable to ice formation.

The implications of these temperature measurements extend far beyond simple scientific inquiry. They provide critical insights into the areas where ice might accumulate close to the surface. The study indicates that slopes facing away from the sun, particularly those with angles exceeding 14 degrees, might possess cooler temperatures conducive to ice aggregation. This revelation is particularly exciting in light of current plans for manned missions to the Moon, notably NASA’s Artemis program, which aims to establish a human presence in the lunar south pole region.

Previously, the understanding of surface temperatures on the Moon was primarily based on the Apollo missions data, which was limited in scope as it focused primarily on equatorial regions. As a result, the opportunity to study the polar regions—where ice’s potential for formation has significant implications—was largely unexplored. The recent results from Chandrayaan-3 signify a pivotal shift in lunar science, allowing for a more nuanced understanding of the temperature dynamics at play over different regions of the Moon.

Understanding where ice may reside beneath the lunar surface is not just a matter of scientific interest; it has practical ramifications for future lunar missions. Water is vital for sustaining human life, and if future explorers can locate or even extract ice, it could serve as a key resource for drinking water, oxygen production, and even fuel. Thus, the potential habitats identified through this research could essentially lay the groundwork for sustainable exploration and habitation on the Moon.

The data also allows researchers to create refined models of lunar temperature variations, which are crucial for understanding the thermal behavior of the surface in different lunar locales. With this model, there comes an enhanced predictive capability regarding where future landers and crewed missions could operate effectively in a way that optimizes safety and resource utilization. This aspect of the research can directly influence mission planning for agencies like NASA, ESA, and ISRO as they explore the Moon’s intricate environments.

The significance of the findings cannot be overstated. They fuel the dreams of a more profound human connection to our celestial neighbor in a way that transcends simple exploration. The prospect of utilizing lunar resources—specifically ice—as a life-supporting material paves the way for establishing long-term operations that could, in turn, facilitate missions beyond the Moon, including journeys to Mars and beyond. Each finding acts as a breadcrumb in the quest for human expansion into our solar system and beyond.

Moreover, the study serves as a reminder of the collaborative potential among international space agencies. The ability to share findings and insights from missions like Chandrayaan-3 can foster a community-wide push towards expanding our understanding of extraterrestrial environments. As scientists build upon this research, further investigations will be needed to confirm the extent and accessibility of lunar ice deposits, and to explore the technology required to utilize these resources.

In conclusion, the groundbreaking findings from the Chandrayaan-3 mission have significantly altered the landscape of lunar research, pivoting our understanding of temperature variations and ice presence on the Moon. The continuing exploration of the Moon promises not only to enrich scientific understanding but also to serve as a stepping stone towards mankind’s ambitions of interplanetary exploration and habitation.

As space exploration continues to advance, the discoveries made through missions like Chandrayaan-3 remain essential. They hold the keys to understanding not only the Moon’s environment but ultimately our own survival, as we look to the stars to answer some of humanity’s most profound questions about life’s possibilities beyond Earth.

Subject of Research:: Analysis of temperature variations and potential ice locations in lunar polar regions
Article Title:: Higher Surface Temperatures Near South Polar Region of the Moon Measured by ChaSTE Experiment On-board Chandrayaan-3
News Publication Date:: 6-Mar-2025
Web References:: http://dx.doi.org/10.1038/s43247-025-02114-6
References:: Not specified in the provided content
Image Credits:: Not specified in the provided content

Keywords

Moon, polar ice, Chandrayaan-3, lunar exploration, surface temperature, water, Artemis missions, extraterrestrial habitation, space research, ice accumulation

Credit: West Virginia University