A possible answer to a scientific question that can be tested is a

The key to a good and manageable investigation is to choose a topic of interest, then ask what is called a “testable question.” Testable questions are those that can be answered through hands-on investigation by the student.

Mars and earth have quite a few things in common. both are  terrestrial planets, both are located within the sun’s  habitable zone, both have  polar ice caps, similarly  tilted axes, and similar  variations in temperature. and according to some of the latest scientific data obtained by rovers and atmospheric probes, it is now known that mars once had a  dense atmosphere  and was covered with  warm, flowing water.