Under the watchful eye of astrophysicists since 2004, Apophis, the “god of Chaos”, is a very special asteroid. Representing a possible threat to the Earth, it should not, according to calculations, hit it when it approaches it very closely in 2029. However, what will happen to the asteroid during its approach from Earth or after it goes back into space? A study published by the journal The Planetary Science Journal and currently available on the preprint server arXiv answered these questions.
Apophis, a rock studied closely
If we humans have our eyes glued to the sky in search of potential threats coming from above, it is to avoid the terrible misadventure that the dinosaurs experienced 66 million years ago.
It is therefore due to a perfectly justified fear of potentially seeing Humanity being exterminated from the planet by an unexpected collision, that Apophis was discovered in 2004 by astronomers from the Peak National Observatory in Arizona (USA). First classified as “one of the most dangerous asteroids likely to collide with Earth”, as NASA points out, this is no longer the case today.
Indeed, calculation after calculation, scientists were able to estimate that the trajectory of Apophis should not directly cross that of the Earth during the next hundred years. However, even though it is no longer a threat, it remains studied. Several missions led by NASA and the European Space Agency (ESA) aim to analyze the consequences of an approach on the brushing of the Earth by such a large asteroid.
As part of the planetary defense program, ESA will therefore send Ramses (Rapid Apophis Mission for Space Safety), a probe which will accompany the asteroid before it passes “only” 32,000 kilometers from Earth in 2029. NASA, for its part, will use its OSIRIS-APEX probe (Origins, Spectral Interpretation, Resource Identification and Security – APophis EXplorer) which will follow the space rock after its passage to study the consequences of such an approach.
How will the asteroid react when it approaches Earth and afterward?
Apophis, whose name is a reference to the “god of Chaos” in Egyptian mythology, is not expected to cause any problems for Earth in 2029. However, there is no indication that the same will be true for him after his approach to our planet. planet or during.
Thus, scientists led by Ronald Ballouz from the applied physics laboratory of the Johns Hopkins University in the United States have looked into this question. Not knowing the shape of Apophis, scientists based themselves on that of another asteroid: 25143 Itokawa, which is roughly shaped like a potato.
Considering their model, 99942 Apophis should therefore experience two main consequences as it approaches Earth:
- The asteroid should experience multiple earthquakes, relatively short, but powerful enough to be detectable using instruments from Earth. This would be due to a direct consequence of its approach to Earth: gravity or at least the gravitational force which will pull the asteroid between two choices: continuing its course or crashing into Earth.
- The asteroid should see its rotation change throughout its course around the Sun
There remains only one point of doubt, will the surface of the asteroid be modified because of its approach?
An asteroid that could hit Earth if…
Although all threats of a collision in the near future have been ruled out by the calculations of Apophis researchers, it remains the exception. This is called “the unexpected” and its probability of happening has also been calculated.
Indeed, on August 26, 2024, a study published by Canadian astronomer Paul Wiegert in The Planetary Science Journal highlighted that Apophis could still touch Earth. But for this to happen, a chain of events would have to occur:
- The asteroid encounters a smaller rock with which it collides
- Apophis deviates from its initial trajectory
- And disaster could happen
However, given the immensity of space and the probabilities, it has been estimated that such a scenario would have less than a one in 2 billion chance of happening. It’s low, but it’s not absolute zero.
Source : ScienceAlert
