Via researchgate.net
In September 2019, NASA and the European Space Agency (ESA) announced that they plan to shoot their Double Asteroid Redirection Test (DART) spacecraft directly into an asteroid by 2024 to see if it has any effect.
The logic behind that mission is to see if there is some way to deflect an asteroid heading towards Earth and prevent a disaster of gigantic proportions.
In August 2019, as NASA was preparing for the asteroid ‘Colossal God of Chaos’ – which could strike Earth in the year 2068 – none other than Elon Musk said, currently have no defense. “
That makes this latest news from JAXA, the Japanese equivalent of NASA, about their Hayabusa2 mission to the asteroid Ryugu a bit daunting.
Revealed in a virtual presentation at the Lunar and Planetary Science Conference on March 15 by planetary science professor Gaku Nishiyama of the University of Tokyo, Japan’s Hayabusa2 spacecraft fired a 5.5-pound high-speed bullet using an explosive. propellant charge of 10 pounds and the asteroid didn’t even flinch.
The bullet was supposed to perform an artificial impact crater operation, ie generate an artificial impact crater, which enabled JAXA to conduct a seismic experiment on Ryugu.
What actually happened was that the bullet, a Small Carry-on Impactor (SCI), left a crater about 10 meters wide, but instead of sending shock waves through Ryugu, the asteroid just about shrugged.
“Significant movement of boulders was expected,” said Nishiyama. “But such a large rock movement has not been observed.”
Related: Check out the largest ‘potentially dangerous’ asteroid to pass Earth in 2021
Extensive surface modification was expected to be induced by the impact-induced seismic waves; however, boulders remained in almost the same location.
We perform seismic wave propagation simulations to resolve this apparent discrepancy and to understand Ryugu’s physical properties. We show that surface changes are highly dependent on a shallow subsoil.
Our results suggest that the conversion of collision energy into seismic waves is less efficient than previously thought. The weakness of powdery regolith can limit surface asteroid quakes.
Based on this hypothesis, we propose a formula for how the surface moves on asteroids that takes into account the unclear properties of regolith. The lack of seismic shaking is consistent with the mysterious discovery that boulders remain unstable on other boulders.
Basically what JAXA is saying is that the surface dust on Ryugu dissipates the energy of seismic waves much better than they expected.
The daily star reports …
… That leaves the question of what flattens Ryugu’s smaller craters. It has no atmosphere, no seismic activity of its own, and now it appears that the space rock cannot be shaken by external influences.
Images from Hayabusa2’s cameras show that Ryugu has fewer small surface craters than expected for an asteroid this size, suggesting that something dust is moving in the craters to fill them.
As one of the members of NASA’s Double Asteroid Redirection Test (DART), Professor Alan Fitzsimmons of Queen’s University Belfast’s Astrophysics Research Center said in December 2019, “We will one day have a serious asteroid impact. It may not be during our lifetime, but Mother Nature determines when it will happen. We will have to do something about it. We’ll have to move that asteroid so it misses us and doesn’t hit us. “
It looks like we need a bigger DART spacecraft.