For example from the Mars 2020 mission (Perseverance rover) landing site selection: https://marsnext.jpl.nasa.gov/scieng_plantary.cfm https://marsnext.jpl.nasa

For example from the Mars 2020 mission (Perseverance rover) landing site selection: https://marsnext.jpl.nasa.gov/scieng_plantary.cfm https://marsnext.jpl.nasa.gov/scieng_plantary.cfm > A Special Region is defined as a location where the temperature could exceed -28° Celsius (-18.4° Fahrenheit) and water activity is at least 0.5. Water is key to life as we know it, and water activity considers the availability of water and water vapor as a potential support for life processes. > The Mars 2020 mission is restricted from landing in, entering, or creating, a Special Region on Mars [...] > Thus, the Mars 2020 mission is also restricted from landing in sites where scientists suspect water, brine, or water ice could be present, or could be induced, within 5 meters (about 16.4 feet) of the surface