Re: "How would you justify it?" Hmm,
Same questions were raised when the Pioneers were sent [in the first place].
<warning, corny/cheesy comments below>
I never liked the dark, Bowser. I've found that it's really true what they say (esp. since seeing Hubble's deep field photos) that you can see the light at the end of a tunnel. It may take man as long as it will take those probes, or the task may be as endless as this universe seems for both man and machine, but it's good to try... better than staying in the dark.
Cheers,
Marcia