Whooosh, boom!


This is what NASA does. They launch stuff to smash into asteroids, and I’m here for it. Here’s a video of the final seconds of the DART space probe, before it smashed into the asteroid moonlet Dimorphos (Dimorphos orbits a larger asteroid, Didymos). Wheee!

That video ends abruptly, as you’d expect. The probe launched a separate camera to record the collision, though, and that looks like this:


Why was this collision so strange? In 2022, to develop Earth-saving technology, NASA deliberately crashed the DART spacecraft into the asteroid moonlet Dimorphos. The hope was that this collision would alter the trajectory of Dimorphos around its parent asteroid Didymos and so demonstrate that similar collisions could, in theory, save the Earth from being hit by (other) hazardous asteroids. But analyses of new results show that the effects of the collision are different than expected — and we are trying to understand why. Featured here is the time lapse video taken by the ejected LICIACube camera LUKE showing about 250 seconds of the expanding debris field of Dimorphos after the collision, with un-impacted Didymos passing in the foreground. In 2026, Europe’s Hera mission will reach the asteroids and release three spacecraft to better study the matter.

Very pretty. All those rocks and dust streaming out of the moonlet…

It’s since been acting a bit weird, although more accurately, we ought to say that it acted unpredictably. The moonlet exhibited a slight slow deceleration for a prolonged period.

The DART team has since confirmed that Dimorphos did indeed continue slowing in its orbit up to a month after the impact — however, their calculations show an additional slowdown of 15 seconds, rather than a full minute. A month after the DART collision, the slowdown plateaued.

What caused Dimorphos to slow steadily for a month, before reaching equilibrium? A swarm of space rocks could be to blame: Recent observations of the asteroid have revealed a vast field of boulders — likely shaken loose from Dimorphos’ surface during the impact — strewn about the area. It’s possible that some of the larger boulders fell back onto Dimorphos within that first month, slowing its orbit further than anticipated, DART team member Harrison Agrusa told New Scientist.

I guess we have another reason to think the movie Armageddon was schlock. We can’t calculate the ultimate outcome of space collisions — there are just too many parameters.

Comments

  1. StevoR says

    See also :

    the entire shape of the asteroid (Dimorphos -ed) has changed, from a relatively symmetrical object to a ‘triaxial ellipsoid’ – something more like an oblong watermelon.”

    Source : https://www.nasa.gov/missions/dart/nasa-study-asteroids-orbit-shape-changed-after-dart-impact/

    Plus see the follow up ESA Hera mission page here :

    https://www.esa.int/Space_Safety/Hera

    Which has already photographed a couple of small asteroids in the asteroid belt and, if all goes well, will reach its target next year :

    The Hera mission to follow-up on the aftermath of NASA’s DART asteroid crash has caught sight of two other asteroids in an important test of its camera ahead of its rendezvous its main target: the double space rock system of Didymos and Dimorphos.

    …(Snip)…

    ..The asteroids they chose were (1126) Otero and (18805) Kellyday, neither of which are particularly well known. Both are also very distant and very faint. However, imaging them would mimic the conditions in which Hera’s Asteroid Framing Camera will first spot Didymos and Dimorphos.

    Source : https://www.space.com/astronomy/asteroids/spacecraft-headed-to-dart-asteroid-crash-site-images-2-faint-space-rocks-to-boost-planetary-defense-tactics

  2. chrislawson says

    Dimorphos did not follow the calculated trajectory after impact? It must be an alien craft!

  3. unclefrogy says

    that they got there and then hit one of them hard enough to get results is impressive.
    that asteroid looks very little like the ones in the movies always seem to look. barely sorted rocky debris held together by very low gravity. first try at hitting one not bad. If we can keep that sort of thing going that is the question currently if not the U.S. A. I hope the data and the research results will be shared with other less anti-science flat earthers then are presently in power here.

  4. StevoR says

    @ ^ unclefrogy : Yup.Seems a lot of asteroids including Didymus are “rubble pile”‘ ones, loose groupings of larger and smaller rocks. Think a bank of gravel floating through space – except also tumbling and spinning as it is pushed by the pressures of light and gravity from occassional encounters with planets and the odd impact with other asteroids. Seems they can spin fast enough to throw off rocks that then become moons of their own – as noted in this clip – Dimorphos Is Probably A Piece Of Didymos plus in much more detail by this technical paper here :

    Here we investigate the possible origin of Dimorphos. Using 1D models of ring/satellite interactions, we study the evolution of material lost from Didymos’ surface and deposited as a ring at its equator. We find that due to viscous spreading, the ring spreads outside the Didymos’ Roche limit forming moonlets. A fraction of the mass will form Dimorphos and a set of objects near the Roche limit, while most of the ring’s mass falls back on Didymos.

    879

    https://www.sciencedirect.com/science/article/abs/pii/S0019103523000052

    As Phil Plait, the Bad Astronomer, notes this process occurs for other asteroids and asteroid moons too :

    We see lots of solid asteroids spinning faster than this “breakup” speed, held together because they’re solid. But a rubble pile cannot spin faster than that because then it starts to fling rocks off its surface. The fact that Kleopatra is so close to but not faster than its breakup rotation rate again implies it’s a rubble pile.

    Also, both moons orbit in the same plane as Kleopatra’s spin, which is very interesting. Asteroids can be spun up faster by the force of sunlight. But if it spins too fast it loses matter, which takes away angular momentum, so it slows. That may be what happened here: Sunlight spun up Kleopatra, it started “mass shedding”, flinging material off the main body that coalesced into a moon, and slowed its spin a bit. Sunlight spun it up again and it formed another moon. It may be near that point once again.

    Source : https://www.syfy.com/syfy-wire/kleopatra-may-be-a-dumbbell-shaped-metallic-rubble-pile

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