It’s official. NASA scientists have found evidence of present-day liquid water on Mars. But before you start thinking about a second home there, know this: that water isn’t drinkable. It’s chock full of salts called perchlorates that can be toxic to humans. Several states, including California and Massachusetts, have issued limits on the amount of perchlorates that can be in drinking water, because it can cause thyroid problems and harm the gastrointestinal tract, skin, breast tissue and the placenta.