Re: What about a Slam Dunk approach to Icepick?

[Bruce Moomaw]

----- Original Message ----- From: LARRY KLAES To: europa Sent: Thursday, October 31, 2002 8:06 AM Subject: What about a Slam Dunk approach to Icepick? Remember the plans for the CRAF probe over a decade ago that was going to send a spike-shaped probe into a comet to penetrate its surface and study the interior of an ancient iceball?    Would it be possible to design something similar for Icepick? If we find a relatively thin area of Europa's crust, perhaps one of the cracks or those upwellings just in the news, we could literally use a hardened protective cone to smash through the ice and deposit the Icepick Hydroobot into the liquid ocean.  Or at the least slam it deep into the ice so we would not have to melt/drill/dig so far?   My hope for this is to reduce the amount of power and such to get through the ice crust so we can focus more resources on the Hydrobot.  Could the Hydrobot be designed to survive such an impact?    Well, no matter how fast you ram a penetrator into Europa's ice, it won't go deeper than a few meters -- and we're talking about a vehicle that has to melt its way through KILOMETERS of ice.  If Richard Greenberg's theory that there are some water-filled cracks running almost all the way to the surface is correct, a penetrator Cryobot might be able to smash down a substantial part of the distance through their ice covering -- but you'd have to locate such a place very precisely, and the penetrator would have to be extremely precisely targeted to hit it.  (On top of that, the evidence for Greenberg's model -- as opposed to Pappalardo's thick-crust model of Europa's ice -- seems to be extremely weak, including the fact that ice is ductile enough that the pressure even a few km down probably causes it to flow and seal up any such cracks quickly.  The total thickness of Europa's ice crust may be very uniform from place to place.)   This does prove again that a radar sounder on Europa Orbiter is worthwhile to try to locate relatively thin spots in the ice, such as Greenberg's cracks (or even isolated near-surface water pockets, which are far more likely) as high-value possible landing sites for later Europa missions.  But it's a safe bet that virtually all of a Cryobot's downward progress through the ice layer must be done by melting.