For the last 20 years NASA has claimed to be searching for signs of water on Mars - because where you find water you usually find life. But the American space agency has avoided landing a Rover near liquid water to begin that search. Why?
The reason given is because the places where liquid water is known to exist are called "Special Regions" and Planetary Protection rules forbid entry into a Special Region unless the Rover has been sterilised to the highest standard possible to avoid contamination of Martian water by Earthly microbes.
The last Lander to be sterilised to this degree was the Viking Astrobiology Mission back in 1976, and NASA has not sterilised a craft to this degree since, to include the new mission in 2020. With no ability to enter a Special Region where liquid water exists, how can NASA claim to be searching for life? Planetary scientists are left frustrated:
"If we're looking for life, we should really go where life is most likely to be." (Nilton Renno) 
“It seems pointless to send missions to search for life into non-Special regions, if the Special Regions are the regions that are of interest for possible life.” (Chris McKay)
So the question remains:
Why won’t NASA sterilise a Rover so it can go into a “Special Region” and investigate the water?
Until they do so, can they seriously claim to the world that they are searching for life on Mars?
M J Craig
 Quotes from C. McKay and N. Renno http://www.popsci.com/we-should-probably-check-for-life-on-mars-before-we-send-astronauts-there