As we all know, water is the source of life. Where there is water on earth, there must be life. But now, we have found liquid water 1.5km underground on Mars. Does this mean that we will also find life on Mars. Exploring the underground lakes of Mars will certainly be put on the agenda, but how to ensure that there are no microbes that can pollute the lakes from the earth's drill bits is an unsolvable problem at present. To overcome this difficulty, human efforts are needed. The discovery of liquid water on Mars not only means that there may be life on Mars, but also means that Mars is a suitable planet for human‘s survival (compared with other planets). If Earth people will immigrate to Mars in the future, it will be much more convenient to break a 1.5km ice sheet than to spend a lot of energy transporting pure water to Mars.