DART, the mission to protect the planet against an asteroid will have a different outcome than expected

sarahjay1 (69)memberin Popular STEM • 2 years ago

(NASA/Johns Hopkins, APL/Steve Gribben https://go.nasa.gov/3upI9b0)

The mission to “protect the planet from an asteroid” found out that the impact of the DART probe with the asteroid Dimorph will not have the expected outcome.

Instead of forming an ordinary crater, the impact will shift and eject away some of the material of the asteroid leading to a global change in its shape.

The DART (Double Asteroid Redirection Test) project is the first attempt to experimentally test one of the planetary defense methods.

The intention of the mission is to impact the small asteroid Dimorph, which is part of the binary system (65803) Didim.

If the controlled ramming changes the orbital period of the asteroid by 4-7 minutes, this would be interpreted as a success.

The impact attempt is scheduled for October 2, 2022, and in 2027 the Hera station will reach Dimorph, and examine the system in detail to confirm the change in Dimorph's orbit.

Now, a team of researchers from the University of Bern have published simulations of the impact of a DART object with small spherical and ellipsoidal asteroids.

The astronomers Sabina D. Raducan and Martin Jutzi wanted to assess the possible outcome of DART’s impact.

The couple knew that the magnitude of the change in the orbit of an asteroid strongly depends on the properties of its surface and interior.

And asteroids with a diameter of less than 50 kilometers are the result of the decay of a larger parent body.

Such objects can be "piles of rubble", agglomerates held together only by their own gravity or small cohesive forces, like Ryugu or Bennu.

The team used an impact model based on the hydrodynamics of flattened particles and considering the behavior of geological materials and compaction of porous matter upon collision.

The impactor body in the model was a sphere with a mass of 500 kilograms, a density of about 1000 kilograms per cubic meter, and moving at a speed of 6 km/s.

Raducan and Jutzi also considered the evolution of the asteroid within 2 hours after the impact.

The researchers found that collision events where the size of the impactor is less than 1/150 the size of the target can still significantly deform poorly connected asteroids.

The lower the cohesive strength of the asteroid's material, the more material will move (up to 20%) or be ejected away (up to 3%) at a speed faster than the escape velocity.

The authors believe that the strength of Dimorph is less than 50 Pascals, and if it is at the level of 10 Pascals, then the DART impact may not lead to the formation of a classic crater.

The impact, instead, will lead to a global change in the shape of the asteroid.

At the same time, the DART impact angle on Dimorph will probably not have a significant impact on the whole process.

Source: