It’s been a little over two months since moment of impact probe-kamikaze DART on the asteroid Dimorph. The purpose of the mission was a practical assessment of the kinetic impact on the asteroid to change its trajectory. The result exceeded expectations and even came as a surprise – the orbital period of the asteroid following the collision with the probe shrunk not for a minute or two, as calculations showed, but for 32 minutes. What happened scientists learned only recently.
System of Didymus and Dimorph through 2 months following collision (November 30).Source: Magdalena Ridge Observatory/NM Tech
The first and relatively detailed information regarding the event was obtained thanks to the Italian cubesat LICIACube. The cubesat was dropped from the DART 15 days before the collision. It followed the probe and flew past Dimorph three minutes following impact. A bright flash and a plume of debris – both cubestat cameras transmitted enough data to make a fairly accurate assessment of the force and consequences of the collision. In addition, by the strength of the reflection of light from the debris, scientists were able to assess the composition of the rocks and the structure of the asteroid.
It turned out, in particular, that Dimorph has the same structure as the huge asteroid Didim, around which it revolves. Earth and space telescopes are not sensitive enough to see the Dimorph in detail from such a distance. Almost all the light reaching the terrestrial devices was reflected from Didyma. The cubestat cameras finally made it possible, even in a halo of debris, to see the true light reflected by a small asteroid.
Thus, the scientists found out two things. Firstly, the structure and composition of Dimorph and Didim are the same. Secondly, Dimorph is not a monolithic body, but a set of stone blocks linked together. This became clear following the formation of a huge tail of debris behind it. Two months of observation of this trailing debris from several angles – from terrestrial observatories and from space telescopes, including even the James Webb – made it possible to estimate the volume of rocks knocked out during the collision with the probe.
According to the most modest estimate, DART knocked out regarding 1000 tons of rock from the asteroid into space. According to the most daring scale, up to 10,000 tons of debris flew into space. If we set the momentum transfer coefficient to unity in the case of a successful head-on collision of the probe with the asteroid surface, then calculations show that the real effect turned out to be more than three times stronger. The estimated coefficient was 3.6. Hence the incredible change in the period of the orbit, which is up to 25 times higher than the lower limit of the calculated value. Rock flying into space acted on the asteroid as a jet engine, greatly slowing down its movement in orbit.
Images from the LICIACube cubesat regarding 3 min following the collision. Image Source: ASA/NASA
“This is very good news for the kinetic impact method, Andy Cheng, head of the DART research group at the Laboratory of Applied Physics, said at a press conference. John Hopkins. “At least in the case of DART, the kinetic impact on the target was really effective in changing the target’s orbit.”
This observation of the consequences of an asteroid impact does not end there. Scientists will continue to collect data on its behavior. For the most accurate assessment of the consequences of the collision, a research probe will be sent to the asteroid Hera European Space Agency, which is scheduled to launch in 2024. But now there is hope that earthly science has obtained a result on the basis of which it makes sense to build a planetary defense to protect once morest dangerous asteroids – the orbits of these celestial bodies can indeed be changed and even unexpectedly strong.
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