I see that escape velocity on 67P/Churyumov–Gerasimenko is 0.64 m/s. (Contrast Earth's 11,186 m/s.) With such light gravity I imagine any material kicked up would take hours to land, or orbit indefinitely. The thing seems covered in sand and fine particles, in line with the rubble pile model of cometary nuclei.

Have precautions been taken with the landing of Philae and harpooning its anchor to lessen kicking up dust? Are we likely to see landing dust in photographs?

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    $\begingroup$ I don't know, but I may be in the control center when it happens, so if you don't have an answer by then, and I remember, I will ask. $\endgroup$ Aug 25, 2014 at 12:01
  • $\begingroup$ The comet is expected to have no atmosphere when Philae lands, thus there is no inertia of gases to kick up the dust. $\endgroup$
    – dotancohen
    Sep 1, 2014 at 12:33
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    $\begingroup$ It'll be known soon enough. The comet is already outgassing at a rather surprising rate considering its distance to the Sun. One other thing to note is that the two harpoons will only fire once two of Philae's three legs touch ground, so most of kicked up dust should hit its belly. And the Agilkia landing site's ("J site") topmost dusty layer is likely electrostatic since it interchangeably enters sunlight and shadow as the comet rotates. We'll see. $\endgroup$
    – TildalWave
    Nov 12, 2014 at 0:43

2 Answers 2


I did some research, and according to this source, Philae has only one, upward-pointing, thruster, the "Active Descent System". It has no downward-facing thrusters that could kick up dust. This thruster will likely only be used when Philae is already on the ground to keep it there while it anchors itself, not for course correction.

Rosetta contains a mechanism to eject Philae with an adjustable force, in order to send in on the right path. However, if that mechanism fails, there is also a backup mechanism to eject Philae with a fixed pre-defined force. If that method is used, they may need the cold gas thruster to adjust the course.

I suspect they will be careful not to point it at the comet.


The two harpoons fire into the dust at 300 feet/s (100m/s) on touchdown. http://www.designnews.com/author.asp?section_id=1365&doc_id=274752 That is bound to kick up some dust. I have not found more info about this specific issue. http://www.dlr.de/dlr/presse/en/desktopdefault.aspx/tabid-10308/471_read-6556/year-all/#/gallery/9154


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