Results 1 to 4 of 4

Thread: How deep can a “rubble pile” planetary surface be?

  1. #1
    Join Date
    Feb 2010
    Posts
    707

    How deep can a “rubble pile” planetary surface be?

    As in small asteroids rubble pile. So the depth of sand dunes, or pulverized rock (due to planet quakes, slides, meteor impacts).

    Or, how deep do you have to go before all is solid rock, no cracks etc (but tiny pores OK)?

    Doesn’t make sense for gas planets, or moons like Europa with subsurface oceans.

  2. #2
    Join Date
    Aug 2006
    Posts
    3,322
    Depends on the size of the body.

    A small asteroid has precious little gravity, so the rubble layer will be much deeper than a moon- or planet- sized body, and may even go all the way to the centre.

  3. #3
    Join Date
    Sep 2004
    Location
    South Carolina
    Posts
    2,558
    For a true rubble-pile asteroid (not planet), you can go down only 5 km by definition before reaching the center of the largest possible one. See paper below. Bigger than that, the core becomes solid through, I assume, gravitational pressure and compression.


    https://arxiv.org/abs/1810.01815

    Rubble Pile Asteroids

    Kevin J. Walsh (Submitted on 3 Oct 2018)

    The moniker rubble pile is typically applied to all solar system bodies with Diameter between 200m and 10km - where in this size range there is an abundance of evidence that nearly every object is bound primarily by self-gravity with significant void space or bulk porosity between irregularly shaped constituent particles. The understanding of this population is derived from wide-ranging population studies of derived shape and spin, decades of observational studies in numerous wavelengths, evidence left behind from impacts on planets and moons and the in situ study of a few objects via spacecraft flyby or rendezvous. The internal structure, however, which is responsible for the name rubble pile, is never directly observed, but belies a violent history. Many or most of the asteroids on near-Earth orbits, and the ones most accessible for rendezvous and in situ study, are likely byproducts of the continued collisional evolution of the Main Asteroid Belt.
    There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
    — Mark Twain, Life on the Mississippi (1883)

  4. #4
    Join Date
    Feb 2010
    Posts
    707
    Thanks.

    5 km seems quite small; I’d’ve thought a mid-sized crater could create rubble at least that deep, especially on a smaller world. Time for me to check Ries, for example.

    Also, I didn’t mean to imply only rocks; we know at least some comets have a lot of void space, and that the surface of Titan is sorta “rocky” in the multiple ice boulders way.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •