Spam filters test your Ph.D

Spam filers are getting more and more confusing. They question your sight asking you to write down muddy and blurry letters. They test your Maths skills asking you to calculate and put down how much is 7 plus 5.

So now that is something new. They think you care about astronomy! Today while submitting a link I got this:

Please answer the following test question, which has been set in order to discourage automatic submissions to this form:

Which planet is closest to the sun, Mercury or Jupiter?

I do not get it.