It took Christopher Columbus (who wasn’t the first to discover North America) about 2 months and some odd days to reach that shore. He did not know, of course, that he would reach anything since he was only surmising that the world was a round globe but that had not yet been proven.
Vasco de Gama was the first to sail around Africa (November 1497) and reach India (May 20 1498).
Many endeavors since the beginning of explorations of first man meant no return to the original start, or that they would even survive the journey at all. Yet all of them went. Some never did return.
Colonizing Mars or any other planet or asteroid will be many years in the making however. Too many platforms have to be addressed before any kind of journey can be considered such as providing endless oxygen, suitable medical supplies, the ability to grow food, creating and managing habitats that can endure extremes in both heat and cold, water etc. By the time these are concrete, there will also be transport options even if the time span forward and back will still be long.
Very likely, before such journeys will become reality, we will have already created subterranean colonies under our seas since that kind of habitat would more nearly mirror those on other planets.