Most earthquakes occur when a geological fault, fractures within the earth’s crust, slip and release energy. Individual faults, some of which form the tectonic plate boundaries, build up strain over decades and centuries to eventually break in large earthquakes.
It basically it takes four things to make a waterfall.
We could send humans to Mars whenever we want to. We have the technology to do it today, though we would need to build new rockets that use that technology.
2016 is a leap year, meaning we insert an extra day, February 29, into the calendar. We do this once every four years in order to keep our calendar aligned with the Earth’s seasons.
The short answer to the question is that we don’t know. The closest planets to Earth are located millions of miles away, so it’s very difficult to go off and find evidence directly.