It appears that we underestimated comet 67P's mass significantly (see What was known about 67P/C-G's mass before the arrival of Rosetta?) during the initial planning. I wonder if this contributed to:

  1. Stronger-than-expected gravity;
  2. Helped Philae to finally settle on the surface despite failure of its thrusters and harpoon?
  • 2
    $\begingroup$ Remember that Philae was landing on a ballistic trajectory, i.e. no propulsion. Idea was to use the harpoons and a small cold gas thruster as soon as two of its legs touch ground, but that didn't happen, so Philae was landing completely passively. If the comet was less massive, it would also reduce the velocity with which the lander hit it (both vertical due to smaller gravity and horizontal due to smaller required orbital speed for Rosetta) and less of impact's kinetic energy would be reflected back, due to which it bounced a couple of times before settling down on the comet. $\endgroup$
    – TildalWave
    Commented Nov 16, 2014 at 13:07
  • $\begingroup$ @TildalWave - thanks for your comments. So would it be reasonable to say it made practically no difference due to kinetic energy / potential energy trade off ( as both energy equations involve first power of mass) ? $\endgroup$
    – pat_nafs
    Commented Nov 16, 2014 at 13:43
  • 2
    $\begingroup$ Well, probably as long as the initial nudge from the Rosetta to send Philae into ballistic trajectory wouldn't be too strong and it would end up in an even higher orbit or reach escape velocity, I'd say yes. Comet's outgassing wouldn't be a problem either since the lander is far denser than any outgassing products. But if the comet was far less massive, it might have meant that its also less compact, with softer, more loose surface dust and the lander might have sunk into it on impact. So in that sense, considering it's a tired comet with many perihelions, I guess larger mass did help. $\endgroup$
    – TildalWave
    Commented Nov 16, 2014 at 13:50


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