Through researchgate.net
In September 2019, NASA and the European Space Agency (ESA) announced that they plan to launch their DTA (Asteroid Redirection Test (DART) spacecraft directly into an asteroid in 2024 to see if it has any effect.
The logic behind this mission is to see if there is any way to divert an asteroid heading towards Earth and avoid a disaster of throaty proportions.
In August 2019, as NASA was preparing for the asteroid “Colossal God of Chaos”, which could reach Earth in 2068, no more and no less than Elon Musk said: on Earth and we currently have no defense against it. “
Which makes the latest news from JAXA, the Japanese equivalent of NASA, about its Hayabusa2 mission to the asteroid Ryugu is a bit daunting.
Revealed in a virtual presentation at the March 15 lunar and planetary science conference by Tokyo University professor of planetary science Gaku Nishiyama, the fact that the Japanese space probe Hayabusa2 fired a high-velocity bullet was revealed of 5.5 pounds with 10-pound explosive propellant charge and the asteroid did not even flinch.
The bullet was supposed to perform an artificial impact cratering operation, i.e. generate an artificial impact crater, which allowed JAXA to conduct a seismic experiment at Ryugu.
What really happened was that the bullet, a Small Carry-on Impactor (SCI), left a crater about 33 feet in diameter, but instead sent shock waves through Ryugu, the asteroid he almost shrugged.
“Significant stone movement was expected,” Nishiyama said. “Still, no such movement of stones has been observed.”
Related: Look at the largest ‘potentially dangerous’ asteroid that passed through Earth in 2021
Impact-induced seismic waves were expected to cause extensive surface modification; however, the stone blocks were housed in almost the same place.
We perform seismic wave propagation simulations to resolve this apparent discrepancy and understand Ryugu’s physical properties. We show that surface changes depend largely on a shallow subsoil.
Our results suggest that the conversion of impact energy into seismic waves is less efficient than previously thought. Weakness of the regulated powder can limit asteroid earthquakes on the surface.
Based on this hypothesis, we propose a formulation of how the surface moves on asteroids that considers the unclear properties of regolith. The lack of seismic shocks coincides with the mysterious discovery that pebbles remain unstable in other pebbles.
Basically, what JAXA says is that Ryugu’s surface dust dissipates the energy of seismic waves much better than they had anticipated.
The Daily Star reports
… this leaves the question of what is flattening Ryugu’s smaller craters. It has no atmosphere, no seismic activity of its own, and now it seems that the space rock cannot be shaken by external impacts.
Images from Hayabusa2’s cameras reveal that Ryugu has fewer small craters on the surface than was expected for an asteroid of its size, suggesting that something makes dust move in the craters to fill them.
As one of the members of NASA’s Dual Asteroid Redirection (DART) test, Professor Alan Fitzsimmons of the Queen’s University Center for Astrophysics at Belfast, said in December 2019: “Will we ever have a severe impact of asteroids. It may not be in our lives, but Mother Nature controls when this will happen. We will have to do something about it. We have to move this asteroid so that we miss it and don’t hit us. “
Looks like we’ll need a bigger DART probe.