Disappearing Martian Canals

http://en.wikipedia.org/wiki/Image:Karte_Mars_Schiaparelli_MKL1888.png 

This image comes from the 4th edition of Meyers Konversationslexikon (1885-90). The copyrights have expired and this image is in the public domain  

Back in 1877 the canal system on Mars was observed by  the Italian astronomer (mentioned by H G Wells in War of the Worlds) Giovanni Schiaparelli, these observations were later confirmed by others and the Irish astronomer Charles E. Burton made drawings of the canal system.

If they could see them with the instruments available over 100 years ago why can’t they see them now, another conspiracy