Through researchgate.net
In September 2019, NASA and the European Space Agency (ESA) announced that they plan to blow up the Double Asteroid Redirection Test (DART) spacecraft directly into an asteroid in 2024 to see if it has any effect.
The logic behind that mission is to see if there is any way to deflect an asteroid heading for Earth and prevent a giant-sized distractor.
In August 2019, as NASA was preparing for the asteroid “Colossal God of Chaos” – which could actually erupt on Earth in 2068 – none other than Elon Musk said: “A large rock will touch the Earth in we still have no defense. “
Which makes this latest news from JAXA, the Japanese equivalent of NASA, about their Hayabusa2 mission to the asteroid Ryugu a little daunting.
Revealed in a virtual presentation at the March 15 Lunar and Planetary Science Conference by Tokyo University Professor of Planetary Science Gaku Nishiyama, it was the fact that the Japanese spacecraft Hayabusa2 launched a 5.5-pound high-speed bullet using a 10-pound explosive propellant charge and the asteroid didn’t even startle.
The bullet was to perform an artificial impact crater operation, ie to generate an artificial impact crater, allowing JAXA to perform a seismic experiment on Ryugu.
What actually happened was the bullet, a Small Carry-on Impactor (SCI), which left a crater measuring about 33 feet, but instead of sending shock waves through Ryugu, the asteroid raised quite a bit of shoulders.
“A significant movement of the boulders was expected,” Nishiyama said. “However, such a large boulder movement was not observed.”
Related: Watch the largest “potentially dangerous” asteroid pass by Earth in 2021
Extensive surface modification was expected to be excited by impact-induced seismic waves; however, the boulders remained almost in the same location.
We perform seismic wave propagation simulations to resolve this apparent discrepancy and to understand the physical properties of Ryugu. We show that surface changes are strongly dependent on a surface area.
Our results suggest that the conversion of impact energy into seismic waves is less efficient than previously thought. Weakness of regular dust can limit asteroid earthquakes to the surface.
Based on this hypothesis, we propose a formulation of how the surface moves on asteroids that takes into account the unclear properties of regolith. The lack of seismic tremor agrees with the mysterious discovery that the boulders are unstable on other boulders.
Basically, what JAXA says is that the surface dust on Ryugu dissipates energy from seismic waves much better than anticipated.
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 seems that the space rock cannot be shaken by external impacts.
Images from Hayabusa2’s cameras reveal that Ryugu has fewer small craters on its surface than he expected for an asteroid of its size, suggesting that something is moving dust into craters to fill them.
As one of the members of NASA’s Double Asteroid Redirection (DART) test, Professor Alan Fitzsimmons of the Queen’s University Astrophysics Research Center in Belfast, said in December 2019: It may not be in our lives, but Mother Nature controls when that will happen. We will have to do something about it. We will have to move that asteroid so that we miss it and it doesn’t hit us. “
Looks like we’re going to need a bigger DART spaceship.