With Monday's announcement of the likelihood of water flowing on Mars, the Red Planet is a hot topic this week. This new discovery leads to the question of how we can further understand the nature of Martian water. Also, since there has been no first-hand witnessing of H2O on the Red Planet, water on Mars is only strongly suspected, but not confirmed.
Scientists know where water most likely is, however, so the most obvious solution would be to point the current Mars rovers in the direction of the recurring slope linea (RSLs) where briny water is suspected to be flowing. At these sites, the rovers could take liquid samples and report the data back to Earth.
This will not happen, unfortunately, at least not by the current Curiosity or Opportunity rovers. This is because the rovers are deemed too dirty for the task. Since the rovers originated from Earth, they are likely carrying microbes that would contaminate the pure Martian water. Also, during they rovers' 140 million mile journeys, they could have picked up other dust or germs from space. So, it is hard to know exactly how contaminated these rovers might be.
Exposing the rovers' germs to Martian H2O would compromise a study of the water's composition. We could falsely discover "life on Mars" is in reality just life from Earth that stowed away through space. This would cause confusion and potentially many setbacks in the scientific world.
There are also legal reasons why Curiosity and Opportunity cannot investigate the water. One of those reasons is international space law. The U.S. signed the Outer Space Treaty in 1967, which puts limitations on what astronauts or objects sent to celestial bodies are allowed to do.
Also, Mars is protected under additional stipulations provided by the Committee on Space Research (COSPAR)'s Planetary Protection Policy. The policy states that certain "Special Regions" on the Red Planet where life is more likely to be present are protected from potential harm or contamination. This harm or contamination could come from the introduction of the microbial-carrying rovers. So, Mars may have water, but it also has a lot of slippery legal slopes.
There have been a few proposed but quickly nixed solutions. Sterilizing Curiosity and Opportunity to a degree that it would be safe enough to send them to the RSLs would also damage the rovers' equipment. Perhaps future rovers like ExoMars 2018 or Mars 2020 could be engineered to be self-cleaning upon arrival to Mars. Whether or not these rovers will be clean enough to be permitted to Mars' Special Regions is still up for debate among scientists and their legal counterparts.
Another solution, suggested by Science Alert, is that perhaps a robotic probe could be sent to Mars that could 3-D-print other robots. These minted-on-Mars robots would be less likely to be carrying harmful contaminants and could potentially investigate the Martian water without risking its purity.
Scientists will be clamoring to come up with solutions to this problem in order to protect Mars' resources. We could potentially see contention and/or evolution in future space law. For now, though, Curiosity and Opportunity will have to remain curious about the opportunity of water — from afar.