July 5: the day the world was due to end
On 5 July 2025, a catastrophic event was set to wipe out much of Japan.
The rumour had started with the manga “私が見た未来” (The future I saw), which was based on the dreams of the author. The manga predicted a major disaster would strike Japan on the 5 July 2025, creating a flutter of gossip across the country.
But if a disaster were imminent, would we be prepared?
Natural disasters take many forms and are notoriously difficult to predict. But while Japan is no stranger to seismic events, the JAXA Planetary Defense team studies the threat of a celestial impact.
Research into protecting our planet from a collision with an incoming asteroid is an international endeavour. Starting two weeks before the 5 July deadline, our Planetary Defense team gave a rundown on social media of projects worldwide designed to protect the Earth.
The ESA Risk List
What is the probability of a celestial small body striking the Earth tomorrow? Published by the European Space Agency (ESA), the publicly available “Risk List” is a catalogue of all known objects that have a non-zero chance of hitting the Earth.
The list can be shuffled by the reader to sort by different properties including the probability of impact, the date and time of the possible impacts, and the diameter of the approaching celestial body. At the time of positing, the next potential impact is due to occur on 15 July, but with a probability of only 1 in 7 billion of actually hitting the Earth. That is a chance smaller than winning the lottery with one ticket! Conversely, the most likely impact is currently from asteroid 2017 WT28, which has a 1 in 147 chance of collision in 2104. This is a fairly comfortable 80 years away, and the size of the asteroid is not large enough for a major disaster.
How accurate is the ESA Risk List? The answer is related to the number of observations that have been made of a particular small celestial body. If the observational data is small, then the predicted orbit will be very uncertain. This will lead to an equivalent uncertainty in the chance that the small body will impact the Earth.
The NASA Jet Propulsion Laboratory (JPL) also host a catalogue showing the probability of impact from known near-Earth asteroids. When only a few observations have been made, the ESA and NASA estimates for the resulting orbit and closest approach will often disagree. However, more observations increase the accuracy of both estimates and the discrepancy between the ESA and NASA lists dissolves.
For accurate predictions for potential impacts, observations therefore need to be collected from all observatories all around the world. This is the task of the IAU Minor Planet Center.
The IAU Minor Planet Center
When a new observation is made of an asteroid, the position at the time of observation is measured and reported to the IAU (International Astronomical Union) Minor Planet Center (MPC).
The first observation of an undiscovered asteroid can only identify the current direction to the asteroid. This single snapshot is not sufficient to reveal the direction that the asteroid came from, or where it is heading. However, collecting together multiple observations from observatories imaging the asteroid over different nights reveals its path and allows an accurate prediction of where it will head in the future.
By collecting observations from observatories worldwide, the MPC provides an global collaborative database that allows the most accurate predictions of the orbit of a small body to be estimated.
The Vera C. Rubin Observatory
On the website for the Center for Near Earth Object Studies run by NASA JPL is a bar chart showing the number of discoveries of near-Earth asteroids made each year. Sections of each bar are also coloured to show which observatory made the discovery. Every time a new facility is opened, the number of newly detected asteroids jumps.
The opening of a new observatory does not result in the Solar System manifesting more asteroids to throw towards the Earth. Instead, the hike in detections represents improvements in observational performance that allows smaller asteroids to be discovered. The number of near-Earth asteroids over 1 km in size has changed very little over the last twenty years. However, current statistics suggest we know less than 7% of near-Earth asteroids with diameters over 50m. To put this in terms of risk, an asteroid of about 50m is thought to be the cause of the 1908 Tunguska Event that flattened 2150 square kilometres of forest, an area equivalent to that of Tokyo.
To detect and map these city-killer asteroids is therefore key to protecting our planet. And this brings us to the opening of the Vera C. Rubin Observatory.
Perched on the top of the Cerro Pachón mountain in central Chile, the Rubin Observatory hosts the 8.4m Simonyi Survey Telescope equipped with the largest digital camera in the world. Funded by the National Science Foundation and Department of Energy in the USA, the observatory is named for astronomer Vera C. Rubin who provided compelling evidence for the existence dark matter. One of the primary goals of the Rubin Observatory is indeed to study dark matter and dark energy, however the observatory’s unique capabilities make it an incredible asteroid hunter.
Rubin will scan the entire southern sky once every three nights, a cadence so frequent that moving objects such as asteroids and other small bodies in our Solar System can be rapidly identified and have their orbits mapped. When the first observations with Rubin were released on June 23, the observatory had detected 2104 new asteroids in just seven nights, seven of which were near-Earth objects.
The Rubin observatory is anticipated to detect more asteroids during the first year of observations than all previous telescopes combined.
The Asia-Pacific Asteroid Observation Network
One challenge faced by even the Rubin Observatory is that asteroid hunting is a nighttime activity. To allow continuous monitoring of the heavens, observatories are needed in both the northern and southern hemispheres and all around the globe. At present, many observatories are concentrated in the USA, South America and Europe, with a dearth of facilities in the Asia-Pacific.
To tackle this problem, the JAXA Planetary Defense team is supporting APAON: the Asia-Pacific Asteroid Observation Network. The goal of APAON is to boost observations of small celestial bodies in the Asia-Pacific region by both observatories and amateur observers.
NEO Surveyor
Even if complete observatory coverage around the globe could be achieved, asteroids could still sneak up on the Earth. As any tennis player will tell you, a small body approaching from the direction of the Sun cannot be seen.
To spot asteroids approaching from this blind spot, NASA is developing the Near-Earth Object (NEO) Surveyor to observe asteroids from space using highly sensitive infrared sensors. Not only will NEO Surveyor be able to spot asteroids typically missed from the ground by the glare of the Sun, the telescope will also be sensitive to dark asteroids that emit little visible light but glow in the infrared as they are heated by sunlight.
The NEO Surveyor website shows an interactive real-time visualisation called “Eyes on Asteroids” that marks every known near-Earth object. A notable near-Earth asteroid is “Apophis” which will approach very close to the Earth in 2029. Until recently, it was suspected that there was a small probability to Apophis hitting the Earth. However, more observations were able to confirm that the Earth will not be in danger, although there remains a small possibility of a few percent of a collision with the Moon.
Visiting asteroids
What could we do to avoid an asteroid on a collision course with Earth? The best course of action will depend on accurate information about the shape, size, and surface environment of the asteroid. These properties govern the fate of the asteroid as it hits the Earth’s atmosphere, and how it might be deflected from its current trajectory.
As asteroids are usually no more than point sources even through powerful ground-based telescopes, missions to conduct close-up observations and return samples for laboratory study of their composition are required.
In 2020, the JAXA Hayabusa2 mission retuned to Earth with a sample from the C-type asteroid Ryugu. While the primary goal of the Hayabusa2 mission was to understand the formation of planets and habitable environments, the returned detailed images and samples will be invaluable if humanity needs to deflect an asteroid of this class. Similarly, studies and samples of the S-type asteroid Itokawa and B-type asteroid Bennu by the Hayabusa and NASA OSIRIS-REx missions have greatly expanded our knowledge of the structure and strength of the celestial bodies we may have to deflect.
Hayabusa2 is now on an extended mission dedicated to planetary defence. The Hayabusa2# mission will perform a rapid flyby of asteroid 2001 CC21 in 2026, and rendezvous with asteroid 1998 KY26 in 2031, a class of asteroid never previously visited with a diameter of 30m.
Under development at ISAS JAXA is the DESTINY+ mission, which will perform a flyby of asteroid Phaethon and other small celestial bodies approaching the Earth to boost our information about their nature. DESTINY+ will demonstrate the flyby technique, and the use of the Earth’s gravity to enable the spacecraft to visit multiple small bodies, without needing to carry high quantities of fuel.
July 5, 2025
On 5 July 2025, the Planetary Defense social media posts fell silent.
Unlike other natural disasters, the international effort to observe the sky allow us to predict the time and location of an asteroid impact. This prediction can usually be made earlier for larger and more dangerous asteroids.
It was therefore unlikely that an asteroid impact would be the cause of a sudden disaster on the 5 July. Moreover, we can be certain that no asteroids over 1km in size that would cause a global-scale catastrophe are likely to hit the Earth in the next 100 years.
However, there are areas of planetary defence where more research is needed. The low density of observatories in the Asia-Pacific Region reduces the power of our early warning system. There is also a lack of recourse in the event an asteroid on a collision path is identified. While an impact from an asteroid capable of destroying a city will not happen this week, such a collision will almost certainly happen in the future. At present, we would expect to anticipate the impact and arrange evacuation but more proactive measures such as deflection to prevent the impact require a greater understanding of asteroids.
An international collaboration to observe the close approach of Apophis in April 2029 is currently underway. The asteroid is expected to pass within 32,000 km of the Earth, over a factor of ten closer than the Moon. The close pass will provide a rare opportunity to examine an asteroid without having travel long interplanetary distances, and also observe how the asteroid changes when pulled by the Earth’s gravity. This data will be vital if the next approach by an asteroid is on a collision course.
But despite Apophis being discovered in 2004, plans to observe the asteroid during the approach to Earth are only now proceeding at pace. As we develop our planetary defence activities, responding quickly to celestial events that might harm the Earth or provide opportunities to better protect our planet should improve.
In April 2024, JAXA gathered a team of specialists to officially form the agency’s Planetary Defense team. The JAXA Planetary Defense logo centres on a wolf howling at the night sky. The wolf represents the acronym “Watching of Life’s Future”, however it is also reminiscent of the Aesop Fable of “The boy who cried wolf” in which a wolf eats a flock of sheep and their shepherd boy because the villagers do not come to the boy’s aid after repeated false alarms (admittedly intentionally triggered by the boy). The image reminds us to stay vigilant, and take every opportunity to study near-Earth asteroids so that we have the information to protect our planet when that time comes.
The Planetary Defense team completed their social media posts on 6 and 7 July.
The 5 July 2025 had passed without a catastrophic incident. But, we remain ready.
Further Information:
ESA Risk List (external site)
IAU Minor Planet Center (external site)
NASA NEO Surveyor website (external site)
Vera C. Rubin Observatory (external site)
Hayabusa2 mission website
DESTINY+ mission website
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